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					                Solar Energy for
                Buildings
                Introduction: Solar Design Issues
                By Keith Robertson and Andreas Athienitis

Abstract:
Solar Energy for Buildings presents basic information on solar                    THE PRINCIPLES OF
building design, which includes passive solar heating, ventilation                  SOLAR DESIGN
air heating, solar domestic water heating and shading. The article
suggests ways to incorporate solar design into multi-unit residential         Benefits of solar energy
buildings, and provides calculations and examples to show how                 For both new and retrofit projects,
early design decisions can increase the useable solar energy.                 solar energy can substantially
                                                                              enhance building design.
This Introduction to Solar Design Issues, presents basic notions of
                                                                              Solar energy offers these advantages
solar design and describes different passive, active and hybrid               over conventional energy:
systems and the solar aspects of design elements, which include
                                                                              s   Free after recovering upfront
window design, cooling and control, and water heating.                            capital costs. Payback time can
   Upon reading this article, the reader will understand:                         be relatively short.
                                                                              s   Available everywhere and
   1. The benefits of solar energy in building design.                            inexhaustible.
   2. The difference between passive, active and hybrid solar technologies.   s   Clean, reducing demand for fossil
                                                                                  fuels and hydroelectricity, and
   3. The design opportunities available for multi-unit residential               their environmental drawbacks.
      buildings (MURB).
                                                                              s   Can be building-integrated,
                                                                                  which can reduce energy
                                                                                  distribution needs.
Solar Energ y for Buildings




The amount of energy that reaches earth’s           Passive, active and hybrid solar                                           An active solar system uses mechanical
upper atmosphere is about 1,350 W/m2—                                                                                          equipment to collect, store and distribute
                                                    Solar buildings work on three principles:
the solar constant. The atmosphere reflects,                                                                                   the sun's heat. Active systems consist of
                                                    collection, storage and distribution of the
scatters and absorbs some of the energy. In                                                                                    solar collectors, a storage medium and a
                                                    sun’s energy.
Canada, peak solar intensity varies from                                                                                       distribution system. Active solar systems
about 900 W/m2 to 1,050 W/m2,                       A passive solar building makes the greatest                                are commonly used for:
depending on sky conditions. Peak solar             use possible of solar gains to reduce energy
                                                                                                                               s    Water heating;
intensity is at solar noon, when the sun is         use for heating and, possibly, cooling. By
due south.                                          using natural energy flows through air and                                 s    Space conditioning;
                                                    materials—radiation, conduction,
Energy from the sun reaches earth as direct,                                                                                   s    Producing electricity;
                                                    absorptance and natural convection.
reflected and diffuse radiation.
                                                                                                                               s    Process heat; and
                                                    A passive building emphasizes passive
Direct radiation is highest on a surface
                                                    energy flows in heating and cooling. It can                                s    Solar mechanical energy.
perpendicular to the sun’s rays (angle of
                                                    optimize solar heat gain in direct heat gain
incidence equal to 0 degrees) and provides                                                                                     Hybrid power systems combine two or more
                                                    systems, in which windows are the
the most usable heat.                                                                                                          energy systems or fuels that, when integrated,
                                                    collectors and interior materials are the
                                                                                                                               overcome limitations of the other, such as
Diffuse radiation is energy from the sun            heat storage media.
                                                                                                                               photovoltaic panels to supplement grid-
that is scattered within the atmosphere by
                                                    The principle can also be applied to water                                 supplied or diesel-generated electricity.
clouds, dust or pollution and becomes
                                                    or air solar heaters that use natural
non-directional. On a cloudy day, 100 per                                                                                      Hybrid systems are the most common, except
                                                    convection to thermosiphon for heat
cent of the energy may be diffuse radiation;                                                                                   for the direct gain system, which is passive.
                                                    storage without pumps or fans.
on a sunny day, less than 20 per cent may
be diffuse.

The amount of the sun’s energy reaching
                                                                                                 S o la r E n e r g y o n a V e r t ic a l P l a n e
the surface of the earth also depends on
cloud cover, air pollution, location and the                      7 .0 0
time of year. Figure 1 shows the solar
                                                                  6 .0 0
energy available in five Canadian cities at
                                                                  5 .0 0                                                                                       Ha lif a x
different times of the year.
                                                     kWh/m2/day




                                                                                                                                                               To r o n to
                                                                  4 .0 0
The amount of solar energy reaching a                                                                                                                          Ed m o n t o n
                                                                  3 .0 0
tilted collector significantly changes the                                                                                                                     Yell ow kn i f e

                                                                  2 .0 0
result. Figure 2 shows the amount of solar                                                                                                                     V anc ouv er

energy received by a horizontal collector,                        1 .0 0

such as window, for a passive solar design.                       0 .0 0
Note that even Yellowknife receives a                                      Jan   Fe b   Ma r   A pr   Ma y   Ju n    Ju l   A ug   Sep     Oc t   No v   Dec

significant amount during part of the
heating season.                                                                                                     Source: RETScreen1
                                                    Figure 1 – kWh/m /day on a ver tical surface, for selected Canadian cities
                                                                                        2




1
 RETScreen is free energy assessment software that assesses renewable energy options against a base building model. Software modules are available at
http://www.retscreen.net/ang/menu.php


    2    Canada Mortgage and Housing Corporation
                                                                                                                                            Solar Energ y for Buildings




Glossary
                                                                         S o l a r En e r g y o n a H o r iz o n t a l S u r f a c e
Absorptance—The ratio of absorbed to
                                                               7 .0 0
incident radiation.
                                                               6 .0 0
                                                                                                                                                             Halifax
Active solar—A solar heating or cooling                                                                                                                      Montréal
                                                               5 .0 0
system that operates by mechanical means




                                                 kWh/m 2/day
                                                                                                                                                             Toronto
                                                               4 .0 0
such as motors, pumps or valves to sort                                                                                                                      Winnipeg
                                                               3 .0 0
and distribute the sun's heat to a buidling.                                                                                                                 Edmonton
                                                               2 .0 0                                                                                        Yellowknife
Energy rating (ER)—A rating system that
                                                               1 .0 0
                                                                                                                                                             Vancouver
compares window products for their
heating season efficiency under average                        0 .0 0
                                                                        Jan   Feb   Mar   A pr       May   Ju n   Ju l   A ug   Sep   Oct    No v   De c
winter conditions.

Evacuated tube collectors—Solar                  Figure 2 – kWh/m2/day on a south-facing horizontal surface, for five Canadian cities
collectors that use individual, sealed                                                                              Source: RETScreen
vacuum tubes surrounding a metal
absorber plate.

Flat-plate collectors—The most common            R-value (imperial), RSI-value (metric)—                                  Solar south—180 degrees from true or
type of solar collector. Can be glazed or        A measure of resistance to heat flow                                     grid (not magnetic) north.
unglazed.                                        through a material or assembly—a
                                                                                                                          Solarwall®—A proprietary system that
                                                 numerical inverse of the U-value.
Hybrid power systems—Combines active                                                                                      uses perforated metal panels to pre-heat
and passive solar power systems or involves      Solar balcony—An enclosed balcony that                                   ventilation air.
more than one fuel type for the same device.     acts as a solar collector.
                                                                                                                          Switchable glazing—Glazing materials
Latent Heat—Also called heat of                  Solar constant—1,350 W/m —The                   2
                                                                                                                          that can vary their optical or solar
transformation. Heat energy absorbed or          average amount of solar energy reaching                                  properties according to light (photochromic),
released by a material that is changing state,   the earth’s upper atmosphere.                                            heat (thermochromic) or electric current
such as ice to water or water to steam, at                                                                                (electrochromic).
                                                 Solar Domestic Hot Water (SDHW)—A
constant temperature and pressure.
                                                 supplement to traditional domestic hot                                   Thermosiphon solar collector —A system
Low-emissivity (low-e)—Coatings applied          water heating. The most common system                                    in which the circulation of hot water in the
to window glass to reduce inside heat loss       uses glazed, flat-plate collectors in a closed                           loop is based only on buoyancy.
without reducing outside solar gain.             glycol loop.
                                                                                                                          U-value—A measure of heat flow through
Passive solar—A solar heating or cooling         Solar Heat Gain Coefficient (SHGC)—                                      a material or assembly. Measured in
system that operates by using gravity, heat      Equal to the amount of solar gain through                                Watts/m2/°C.
flow or evaporation to collect and transfer      a window, divided by the total amount of
                                                                                                                          Warm-edge spacers—Separate a window's
solar energy.                                    solar energy incident to its outside surface.
                                                                                                                          glazing layers with thermal break or a low-
Photovoltaic (PV) system—System that                                                                                      conductivity material.
onverts sunlight into electricity. Can be
autonomous or used with another energy
source. (Can be connected to the main
power grid, for example).




                                                                                                                   Canada Mortgage and Housing Corporation                 3
Solar Energ y for Buildings




Building design issues                               What is design                                       not use the building enclosure as part of
                                                                                                          an integrated energy system in which
Careful solar design can:                            integration?                                         the components fit together well.
s       Maximize possible solar transmission and     The most important factor for a successful           Collaboration between architects and
        absorption in winter to minimize or reduce   solar building is “integration.” This                engineers is increasing, but the traditional
        to zero the heating energy consumption,      concept includes not only the integration            working relationships between architects,
        while preventing overheating.                of design professionals at the project’s start,      engineers, property managers and other
                                                     but also the integration of those who are            professionals do not foster an integrated
s       Use received solar gains for                                                                      design approach.3
                                                     responsible for the systems operation. This
        instantaneous heating load and store
                                                     potential for synergy is usually overlooked          A preferable approach is to consider the
        the remainder in embodied thermal
                                                     because architects and engineers                     building and its HVAC system as one
        mass or specially built storage devices.
                                                     traditionally do not explore the concepts            energy system and to design them together,
s       Reduce heat losses using insulation and      together closely enough to truly integrate           taking into account possible synergies such
        windows with high solar heat gain factors.   systems, and they infrequently discuss new           as electricity generation, thermal storage
                                                     concepts with property managers, except              and control strategies.
s       Employ shading control devices or
                                                     when auditing a building failure.
        strategically planted deciduous trees to
        exclude summer solar gains that create
        additional cooling load.

s       Employ natural ventilation to transfer
        heat from hot zones to cool zones in
        winter and for natural cooling in the
        summer; use ground-source cooling                                                        Direct
        and heating to transfer heat to and                                                      Gain
        from the underground, which is more
        or less at a constant temperature, and                 Solar Facade
        utilize evaporative cooling.

s       Integrate building envelope devices
        such as windows, which include                                                                 Collector-storage
        photovoltaic panels as shading devices,                                                        Wall
        or roofs with photovoltaic shingles;
        their dual role in producing electricity
        and excluding thermal gain increases         Figure 3 – Two major options for thermal mass placement in passive solar
        their cost-effectiveness.                    design: direct gain and Trombe wall, or collector-storage wall

s       Use solar radiation for daylighting,2
        which requires effective distribution
                                                     The architect may design the building                Passive solar heating systems (thermal) are
        into rooms or onto work planes, while
                                                     envelope to passive solar design principles          separated into two broad categories, direct
        avoiding glare.
                                                     while the engineer designs HVAC to                   gain and indirect gain (see Figure 3). An
s       Integrate passive solar systems with         extreme design conditions, ignoring the              indirect passive system insulated from the
        active heating–cooling/air-conditioning      benefits of solar gains and natural cooling.         heated space is an isolated system.
        systems in both design and operation.        The result is an oversized system that does

2
    See Daylighting Guide for Buildings at: http://www.cmhc.ca/en/inpr/bude/himu/coedar/coedar_001.cfm
3
    See Integrated Design Process Guide at: http://www.cmhc.ca/en/inpr/bude/himu/coedar/coedar_002.cfm


    4        Canada Mortgage and Housing Corporation
                                                                                                                 Solar Energ y for Buildings




Depending on climate and building             The key aspects of passive solar design are            s    sensible—such as concrete in the
function, certain heating/cooling systems     interlinked, dependent design parameters:                   building envelope with exterior
are more compatible with passive systems.                                                                 insulation, or
                                              s   Location and orientation of a building;
For example, the thermal mass in a floor
                                                                                                     s    latent such as phase-change
may store passive solar gains and act as a    s   Fenestration area, orientation and type;
                                                                                                          materials.
floor-heating system. This is a control
                                              s   Thermal massing and envelope
challenge that must be carefully planned if                                                      The ultimate objective of design integration
                                                  caracteristics;
it is to achieve acceptable thermal comfort                                                      is to minimize energy costs while
for the occupants.                            s   Amount of insulation;                          maintaining interior comfort. A larger
                                                                                                 thermal mass within a building can delay
                                              s   Shading devices—type, location
                                                                                                 its response to heat sources such as solar
                                                  and area;
                                                                                                 gains—the thermal lag effect. This thermal
                                              s   Effective thermal storage insulated from       lag can avoid comfort problems if taken
                                                  the exterior environment, as well as           into account in selecting the thermal mass,
                                                  amount and type;                               choosing appropriate control strategies
                                                                                                 and sizing the heating–cooling system.




                                                                              Source: CMHC, at http://www.cmhc-schl.gc.ca/en/imquaf/himu/buin_018.cfm

Figure 4 – Sixteen of the 42 units in this apar tment building in Amstelveen, the Netherlands, take advantage of solar
energy from the atrium as an air pre-heating system. Solar domestic hot water panels provide about half the building’s
domestic hot water energy.




                                                                                             Canada Mortgage and Housing Corporation              5
Solar Energ y for Buildings




Design procedure                                   Building orientation                            Generally, buildings with long axes running
                                                                                                   east and west have greater solar-heating
The initial design steps in solar design are to:   Orientation is crucial since it can provide     potential if their window characteristics are
                                                   free savings from the concept stage. There      chosen accodingly. For MURBs with a
1. Set performance targets for energy
                                                   is a difference between true north and          typical double-loaded corridor, this means
   sources and uses.
                                                   magnetic north. The deviation between           half the units face south and half face
2. Minimize heating and cooling loads              magnetic north and true north—magnetic          north. A partial solution could be a
   through orientation, massing, envelope          declination—varies between east and west        south-facing central atrium or solar heater
   and landscape design.                           coasts. In Nova Scotia, the compass             that pre-heats and delivers air for the
                                                   points west of true north; in B.C.,             north-facing units.
3. Maximize solar and other renewable
                                                   east of true north.
   energy to meet the building load, then                                                          Buildings with east-and west-facing
   to design efficient HVAC systems                The maximum difference (as a percentage)        orientations have greater potential for
   that are integrated with the building           between south-facing and 30ºE (or W)            overheating in the non-heating season and
   envelope performance characteristics.           orientations occurs when the sun is lowest      get little solar gain in winter. In figure 5 the
                                                   and the days shortest (Dec. 21). When solar     Foyer hongrois in Montréal angles the
4. Use simple energy simulation tools and
                                                   facades or roofs generate photovoltaic          windows to the south creating a sawtooth
   detailed simulations in evaluating
                                                   electricity that is sold to the grid at time-   plan, to avoid east-and west-facing
   options at the early design stages and
                                                   of-day rates, these rates may change the        windows.
   later to assess alternatives.
                                                   optimal orientation if their peak value is
                                                   not at noon.

                                                   Further information about magnetic
  Generally, deviations up to ±30º                 deviation and a calculation routine is
  from due south reduce solar gains                available at
  by up to about 12% and are thus
  acceptable in solar building design,             http://www.geolab.nrcan.gc.ca/geomag/ma
  providing significant freedom in                 gdec_e.shtml
  choice of form.




  6      Canada Mortgage and Housing Corporation
                                                                                                                    Solar Energ y for Buildings




                                                                                                      Although differences in assumptions and
                                                                                                      input data make comparisons difficult, a
                                                                                                      study of a Toronto building produced
                                                                                                      different results. RETScreen’s passive solar
                                                                                                      energy module was used for the Toronto
                                                                                                      building. The RetScreen model of a 110 m2
                                                                                                      (1,184 sq. ft.), south-facing suite in
                                                                                                      Toronto with 7.2 m2 (75 sq. ft.) of windows
                                                                                                      (similar to the suites in Halifax) gave the
                                                                                                      following results. (Increases in cooling load
                                                                                                      were not calculated, as this was assumed to
                                                                                                      be an unconditioned building.):

                                                                                                      s   Increasing the glass Solar Heat Gain
                                                                                                          Coefficient (SHGC) from .45 to .65
                                                                                                          saved 1,100 to 1,200 kWh annually.

                                                                                                      s   Doubling window area and increasing
                                                                                                          the SHGC gave a slight annual energy
                                                                                                          loss in a low-mass (wood-frame)
                                                                                                          building and a slight saving in a high-
                                                                                                          mass (concrete-frame) building.

Figure 5 – Foyer hongrois in Montréal. South angled windows on a building with a                      s   Increasing the glass R-value and
long nor th-south axis. Sunshades shadow these windows in the summer time.                                maintaining a high SHGC saved about
                                                                                                          900 kWh annually.
Building Conditions                                 s   High insulation levels.
                                                                                                      s   The best results came from increasing
NRC’s EE4 software4 was used to model                                                                     the R-value, increasing the mass,
                                                    Simulation Results
the energy use of a Halifax MURB, and                                                                     increasing the window area, and
showed modest energy reductions from                s   Using a higher Solar Heat Gain                    maintaining a high SHGC.
orientation, window performance and                     Coefficient (SHGC) glazing reduced
                                                                                                      These results are expected from basic solar
window size. The advantage of energy                    the total annual heating cost by three
                                                                                                      design principles. Increasing the resistance
reductions due to orientation is that they              to four per cent.
                                                                                                      of windows to thermal loss (low-e glazing)
are free, and the savings continue for the          s   Orienting the building along the long         while admitting high solar gains reduces
life-time of the building. Note also that               east–west axis instead of north–south         heating energy consumption if the building
these energy simulation results are specific            axis reduced annual heating cost by           is well insulated and there is enough thermal
to a particular location. The MURB had                  about one per cent.                           mass to store the solar gains and prevent
the following characteristics:                                                                        overheating. Obviously, the thermal
                                                    s   Increasing the window area on the
s    Four-storey, double-loaded corridor,                                                             performance of windows cannot be
                                                        south-facing suites reduced annual
     wood-frame.                                                                                      separated from solar gains, which relate to
                                                        heating cost by less than one per cent.
                                                                                                      form, orientation and solar transmittance.
s    Window-to-wall ratio: 19 per cent on           s   Increasing the interior mass reduced          Optimizing requires rigorous energy
     primary facades.                                   annual heating cost by about two per          modelling and project-specific analysis.
s    Double-glazed, low-e vinyl windows.                cent.


4
    EE4 is the software developed for NRCan’s Commercial Building Incentive Program to check for compliance to its program requirements.

                                                                                                  Canada Mortgage and Housing Corporation         7
Solar Energ y for Buildings




More details on the design of windows and             approximately equal to the amplitude of the         Obstructions to sunlight
glazing selection are presented in Selection          cyclic heat flow into the mass divided by its
                                                                                                          Obstructions can have a significant effect
and Commissioning of Window Installations5            surface temperature amplitude or swing.)
                                                                                                          on solar potential. For low- to mid-rise
The analytical tool selected depends on               A good design strategy for building                 buildings, obstructions are usually
the detail required. For basic energy flows,          orientation is to “tune” windows to admit           buildings, terrain or trees. For larger
an analysis based on solar heat gain                  or exclude solar energy based on their              buildings, obstructions are usually other
coefficients and thermal conductance                  orientation. Generally, south-facing                large buildings.
provides an approximate estimate of the               windows should admit winter solar gain
                                                                                                          Obstructions can be identified on the sun
net energy transfer across the building               and east- and west-facing windows should
                                                                                                          path chart in figure 8. East and west
envelope. The calculations can be                     exclude low-angle solar gain. Window
                                                                                                          obstructions can reduce solar gain in the
performed in MathCAD, Matlab or a                     design strategies are discussed in more
                                                                                                          summer and admit energy in the winter,
spreadsheet-based program such as                     detail later.
                                                                                                          when the sun rises in the southeast and sets
RETScreen.
                                                      Another approach is control of solar gains          in the southwest.
To determine room-temperature swings                  with motorized blinds, which are widely
and associated thermal mass response,                 used in airports, atriums and some
more detailed simulation tools are needed.            commercial buildings in Europe. Along
However, even for the calculation of                  with other control technologies, such as
temperature swings and the effectiveness              electrochromic coatings, motorized blinds
of thermal mass, simplified models exist              may soon become cost-effective. If active
which are based on thermal admittance                 solar control is taken into account in sizing
calculations.6 “Thermal admittance” is                cooling systems, there may be significant
essentially a dynamic U-value and is                  savings from reduced energy consumption
typically calculated for a daily cycle. (It is        and reduced equipment sizing.




5
    See http://www.cmhc.ca/en/inpr/bude/himu/coedav/upload/Article_Design_Aug31.pdf
6
    Athienitis A.K. and Santamouris M., 2002. Thermal analysis and design of passive solar buildings, James and James, London U.K..




    8      Canada Mortgage and Housing Corporation
                                                                                                                            Solar Energ y for Buildings




Direct-gain passive solar
techniques
                                                                                                               Outdoor temperature




                                                            Air temperature
Pure passive solar design uses the sun’s
energy directly, without mechanical                                                                            Light timber-framed building
intervention. In its simplest form, the sun
                                                                                                               Heavy building with
shining through a window directly heats
                                                                                                               external insulation
the space. Thermal mass within the
building can absorb some of the heat                                                                           Heavy building set into and
and release it at night.                                                                                       partially covered with earth

Internal thermal mass reduces temperature                                     Time of day
swings within a space. In a properly
designed passive solar system, thermal                 Figure 6 – Effect of internal mass on internal temperature swings
mass absorbs solar energy during the day,
preventing the building from overheating,
and releases the energy at night. Thermal              Mass is known to be able to reduce peak               It can be calculated as a percentage of the
mass is most effective when it can gain                cooling load when night temperatures are              total area of the south-facing exterior
energy directly from the sun. An ideal                 cooler than day temperatures. Exterior and            wall—of limited use because it is not
thermal mass for passive solar heating has             interior masses cool down at night and                affected by what goes on beyond the
high heat capacity, moderate conductance,              reduce peak cooling demand while also                 wall—or as a percentage of heated floor
moderate density and high emissivity.                  delaying the time of the peak solar gain              area—which accounts for the volume of
Additional cost is negligible if the material          during the day. However, the effectiveness            the building.
is also structural or decorative. Concrete             of thermal mass is proportional to the
                                                                                                             A typical passive solar-heated building may
and masonry are good thermal mass                      allowable room temperature variation over
                                                                                                             have south-facing glazing equal to 10 to 15
materials. (Plaster, drywall, and tile are also        a day.
                                                                                                             per cent of the heated floor area. As the
useful in this respect, but calculations are
                                                                                                             area of south glass increases, the amount
needed to determine if they have sufficient            Windows
                                                                                                             of mass inside must also increase. The
mass, as was done in the Halifax study.)               Window orientation, layout and                        Advanced Buildings Technologies and
Passive solar design in single-family                  performance are important in passive solar            Practices website, at
residences shows that operational energy               design. The goal is to provide an                     http://www.advancedbuildings.org,
can be reduced by 30 to 50 per cent                    appropriate amount of window area in the              recommends a window-to-exterior wall
through window sizing and thermal mass                 right place. Where there is no fenestration,          area ratio (WWR) of 25 to 35 per cent,
storage. A recent study of MURBs in                    a conventional insulated wall is a solar              similar to a typical MURB.
Sweden reported that operational energy                barrier, transmitting little energy to the
                                                                                                             WWR may increase with proper control of
use in a heavy structure is only slightly              inside.
                                                                                                             solar gains (for example, with motorized
lower than in a similar, lightweight
                                                       Window sizing                                         shading) and transfer of excess energy to
structure.7 The additional energy used to
                                                                                                             north-facing zones. This could possibly
build the heavy structure outweighed its               There are two ways to quantify a building's           approach 50 per cent when a large atrium
operational advantage in a lifecycle analysis          south-facing glass.                                   is included with adequate thermal storage
of costs.




7
    Stahl, Fredrik, The effect of thermal mass on the energy during the life cycle of a building, presented at Building Physics 2—6th Nordic Symposium




                                                                                                       Canada Mortgage and Housing Corporation           9
Solar Energ y for Buildings




capacity. Utilization of double facades with
blinds in the cavity, or exterior controlled
shading reduces cooling loads during summer.
(Figure 4 – Urban Villa, Amstelveen)8

Glazing

This section describes some the most
important parameters of window and
glazing design.

Solar heat gain coefficient (SHGC)

The Solar Heat Gain Coefficient (SHGC) is
a useful measure of a window's ability to
admit solar energy. SHGC is the amount
of solar gain a window allows, divided by
the amount of solar energy available at its
outside surface, a number between zero
                                                    Figure 7 – Double-glazed, low-e window
(solid wall) and one (open window).

SHGC can be measured for the window                     help retain heat by reducing longwave           A recent glazing development is switchable
unit, including the frame, or the glazed                (infrared) radiation losses. This is very       glazing. These can vary their optical or solar
area. The higher the SHGC, the better the               helpful from a passive solar heating            properties according to light (photochromic),
window will perform as a solar collector. If            point of view.                                  heat (thermochromic) or electric current
overheating is a concern, low-SHGC                                                                      (electrochromic). Initial computer simulations
                                                    s   There are reflective coatings that block
windows exclude solar energy to reduce                                                                  show that electro chromic glazing has the
                                                        unwanted solar gain (reduce the SHGC)
cooling loads.                                                                                          most promise for improving comfort. These
                                                        to reduce the cooling load. There are many
                                                                                                        are prototype systems. They will likely be
A single pane of clear glass facing the sun             types of spectrally selective glazings that
                                                                                                        able to reduce cooling loads and glare and
will admit most of the visible solar radiation,         block out selective wavelengths that can
                                                                                                        improve visual comfort if high solar
some of the infrared and very little ultraviolet        change the SHGC and levels of visible
                                                                                                        transmittance is not needed. Switchable
and have the highest heat loss from inside              light transmittance.
                                                                                                        glazings may have poorer optical properties
to outside. Ways to modify windows to
                                                    s   Evacuating the space between the                and not be suitable in residential buildings.
enhance their performance include:
                                                        panes, using an inert gas such as argon
s    Adding a second or third layer of glass,           or krypton, or transparent insulation,          Visible light transmittance
     which can dramatically lower the                   can reduce heat loss by conduction and          Visible light transmittance (VT) measures
     U-value (increase the R-value), while              convection. Because gas-fills perform           the visible spectrum admitted by a window.
     maintaining a large SHGC. Additional               well and are low cost, they should be           Typical daylight strategies require windows
     layers of glass also permit thin, low-             used whenever a low-e coating is used           with a high VT. A low SGHC is also desirable
     emissivity (low-e) coatings to be                  in a glazing unit.                              where heat gain is a concern. Reflective
     applied onto a protected glass surface.                                                            glass is not recommended for daylighting.
                                                    High-performance windows may make it
     Low-e coatings still allow solar gain
                                                    possible to move heating outlets further from       Table 1 shows typical values for light
     (short wavelength radiation) and they
                                                    windows to eliminate ducting or piping.             transmittance and SHGC of common
                                                                                                        glazing systems.
8
  See Innovative Buildings Case Studies — “Atrium, Solar shading and ventilation for residents’ confort”, Amstelveen :
http://www.cmhc.ca/en/inpr/bude/himu/inbu_001.cfm#CP_JUMP_58686

    10    Canada Mortgage and Housing Corporation
                                                                                                                     Solar Energ y for Buildings




    Table 1 – Visible Light Transmission–solar heat gain coefficient (per cent)
    Glazing system (6 mm glass)                                 Clear                Blue-green            Grey                  Reflective
    Single                                                      89–81                75–62                 43–56                 20–29
    Double                                                      78–70                67–50                 40–44                 18–21
    Double, hard low-e, argon                                   73–65                62–45                 37–39                 17–20
    Double, soft low-e, argon                                   70–37                59–29                 35–24                 16–15
    Triple, hard low-e, argon                                   64–56                55–38                 32–36                 15–17
    Triple, soft low-e, argon                                   55–31                52–29                 30–26                 14–13
    Source: ASHRAE Fundamentals 1997,Table 11, page 29


Frames                                               Warm-edge spacers use low-conductivity            hours before solar noon. East and west
                                                     materials, rather than aluminum, and are          facades receive maximum solar gain in the
Frames are often the weakest thermal part
                                                     important in reducing heat loss through           summer; a south-facing surface receives its
of a window. Although frames (sash and
                                                     the window. By reducing the likelihood of         annual maximum in the late fall or winter.
mullion assemblies) are only 10 to 25
                                                     condensation on the glass surfaces, they
per cent of window area in commercial                                                                  Figure 8 shows a sun path chart for latitude
                                                     can also influence daylighting performance.
buildings, they can account for up to half                                                             44ºN. The sun’s path varies by a project’s
                                                     The low cost and good performance of
the window heat loss and be the prime site                                                             latitude. The X-axis gives the direction of
                                                     warm-edge spacers make them suitable for
for condensation.9                                                                                     the sun; the Y-axis the sun’s angle above the
                                                     all window systems and should be
                                                                                                       horizon. The curved lines show the arc of
Thermal performance of frames is improved            considered mandatory whenever low-e
                                                                                                       the sun across the sky on the 21st day of
either by using a low-conductivity thermal           coatings and inert gas fills are used.11
                                                                                                       each month. The dashed lines show the
break in metal frames or a frame of a low-
                                                     Window orientation                                time of day. An accurate location of the
conductivity material, such as wood, vinyl
                                                                                                       sun can be determined by plotting the time
or fibreglass. Low-conductivity window               The greatest amount of solar energy is            of day and month.
frames reduce energy consumption in all              generated at noon on any given day in the
types of buildings. For MURBs the                    year. The greatest amount of energy               Obstructions are also plotted to show when
designer should note that Canadian fire              received through a window is when the sun         a building will be shaded. Sun charts for
codes state that the area of windows with            is perpendicular to the window and 30 to          any latitude can be generated through a
combustible framing materials must be less           35 degrees above the horizon. South, east         University of Oregon online program at
than 40 per cent of the building wall area           and west windows receive about the same           http://solardat.uoregon.edu/SunChartProgr
and that non-combustible materials must              annual maximum of solar radiation. The            am.html
separate windows.10                                  time and date that the maximum energy is          Figure 9 shows the intensity of solar energy
                                                     received depends on the building’s latitude       striking a vertical surface facing the sun. The
Spacers
                                                     and wall orientation. The earth rotates           maximum energy entering a window occurs
Spacers separate panes of glass in a sealed          15 degrees an hour; when a window is              when the sun is 30 to 35 degrees above the
window to prevent the transfer of air and            oriented 30 degrees east of south, the            horizon and directly in front of the window.
moisture in and out of the glass cavity.             maximum heat gain will be about two

9
     Website: Advanced Buildings: Technologies and Practices http://www.advancedbuildings.org/_frames/fr_t_building_low_conduct_window.htm
10
     Website: Advanced Buildings: Technologies and Practices http://www.advancedbuildings.org/_frames/fr_t_building_low_conduct_window.htm
11
     Website: Advanced Buildings: Technologies and Practices http://www.advancedbuildings.org/_frames/fr_t_building_warm_edge_windows.htm


                                                                                                  Canada Mortgage and Housing Corporation          11
Solar Energ y for Buildings




Superimposing Figure 9—Solar energy             North-facing windows provide consistent            North, the sun is at a low angle in the sky
intensity – over the sun path chart shows the   indirect light with minimal heat gains, but        during winter, when sunlight is most
effect of window orientation on solar gain      can also create heat loss and comfort problems     needed to contribute to heating. This is
                                                during the heating season. South-facing            when south-facing clerestory windows have
Figure 10 aligns the solar intensity chart to
                                                windows provide strong direct and indirect         an advantage over horizontal roof glazing.
south on the sun path chart. This shows
                                                sunlight that varies during the day. Controlling   However, the sun also creates glare.
that the maximum solar gain occurs at
                                                heat gain can be a problem during the              Overhangs over south windows may need
noon in October and February.
                                                cooling season. Shading is easily done with        to be large to prevent this. Also, when the
To indicate the solar gain on a west            horizontal shading devices in these windows.       sun is low, buildings and trees can create
window, align the solar intensity chart with                                                       shade, which is desirable in some seasons.
                                                East- and west-facing windows can create
west on the Sun path chart, as shown in
                                                more problems with glare and heat gain             Note that south-facing surfaces receive
Figure 11. This clearly shows how window
                                                and are more difficult to shade because the        more energy in the winter and less in the
orientation affects the time of day and the
                                                sun is closer to the horizon. In Canada’s          summer than east- and west-facing
time of year of maximum solar gain.
                                                                                                   surfaces. A strategy to control overheating

 Adapted from Edward Magria “The Passive Solar Energy Book”




Figure 8 – Sun path char t
                                                                    Figure 10 – Energy striking a south window for latitude 44ºN




Figure 9 – Solar energy intensity
                                                                     Figure 11 – Energy striking a west window for latitude 44ºN
 12      Canada Mortgage and Housing Corporation
                                                                                                                     Solar Energ y for Buildings




is to maximize window area on the south           s   Maximize southern exposure.                     Shading
and use less on the east and west. For
                                                  s   Optimize northern exposure.                     Shading may be exterior, interior, fixed,
mainly cloudy regions, where overheating
                                                                                                      motorized or between an exterior glazing
is less of a problem, interior spaces benefit     s   Minimize western exposure when the
                                                                                                      and an interior facade in double-facade
from larger windows (including the north              sun is lowest and most likely to cause
                                                                                                      systems. Figure 12 shows some examples
facade) that allow more light into a                  glare and overheating. Windows
                                                                                                      of shading systems. A good shading system
building. There can be a trade-off between            themselves can be oriented differently
                                                                                                      permits lower levels of artificial illumination,
allowing more daylight and increasing heat            from the plane of the wall in a
                                                                                                      because the eye can accommodate itself
loss. In mainly clear regions, glare and heat         “sawtooth” arrangement.
                                                                                                      without strain to function within a wide
gain are more problematic. In direct
                                                  Larger window areas increase the risk of            illumination range.
sunlight, smaller windows can provide
                                                  glare, overheating in summer and heat loss
adequate daylight. Direct sunlight can also                                                           Exterior shading devices are the most
                                                  in winter. For areas with direct sun,
be reflected or diffused, or both, with                                                               effective at controlling solar gain. Interior
                                                  shading needs to reduce transmittance to
window shading.                                                                                       window shading allows much of the solar
                                                  10 per cent or less to prevent glare.
                                                                                                      energy into the building and allows more
Window performance and tuning                     Glare from windows can occur when the               heat, sometimes an unwanted partner
Window orientation, size, layout and              incoming light is too bright compared               of daylight, to enter the building. Light-
performance are important in passive solar        with the general brightness of the interior.        coloured interior shading will reflect some
design. Proper glazing and frame selection        Punched windows can create strong                   of this energy back through the window.
can enhance daylighting and energy                contrasts from the interior between                 However, a minimum of about 20–30 per
performance. General rules for tuning             windows and walls. Horizontal strip                 cent of incident solar radiation will come
window orientation include:                       windows provide more even daylight                  indoors as transmitted or be absorbed and
                                                  distribution and, often, better views. This         re-emitted as heat when interior blinds
s   Determine the window size, height             article discusses other interior design             are used. Exterior blinds collect dust and
    and glazing treatments separately for         guidelines later.                                   may be difficult to maintain and clean.
    each facade.                                                                                      One solution is to place reflective blinds
                                                                                                      between the two glazings and possibly
                                                                                                      to have airflow within the cavity—a
                                                                                                      double-facade.




             Overhang                           Louvred Overhang                         Lightshelf                            Vertical Fins

Figure 12 – Common types of exterior shading




                                                                                                 Canada Mortgage and Housing Corporation           13
Solar Energ y for Buildings




South-facing windows are the easiest to          Energy Rating—ER                              Because the ER relies on an average solar
shade. Horizontal shading devices, which                                                       gain, it cannot be used to compare actual
                                                 Energy Rating (ER) is a rating system
block summer sun and admit winter sun,                                                         performance for a specific location
                                                 developed by the Canadian Standards
are the most effective. East- and west-                                                        orientation and window size. Further
                                                 Association and the window industry. It
facing windows are best shaded with                                                            calculations can determine the Energy
                                                 compares window products for their
vertical devices, but these are usually harder                                                 Rating Specific (ERS). This determines a
                                                 heating season efficiency under average
to incorporate into a building and not                                                         specific ER value for a window based on
                                                 winter conditions. The ER is the value of
limit views from the window. On lower                                                          the climate of a particular location, the
                                                 energy gained or lost in watts per square
buildings, well-placed deciduous trees on                                                      window-to-floor area ratio and the window
                                                 metre (W/m2). RSI value is a misleading
the east and west reduce summer                                                                orientation on the building.
                                                 measure of energy efficiency because it
overheating and allow desirable winter
                                                 often only accounts for the heat loss         Both the ER and ERS are part of CSA-
solar gains. Some practioners are testing
                                                 through the centre of the glass. The ER       A440.2 Energy Performance of Windows
vines hung on metal lattices to reduce
                                                 considers all the energy flows through the    and Other Fenestration Systems standard.
overheating. Interior shading is most
                                                 window, the total glass R-value, the frame
effective at controlling glare and can be
                                                 R-value, air infiltration and average solar
controlled to suit the occupants.
                                                 gain. The solar gain is an average of the
                                                 four orientations.




Figure 13 – Double facade in a residential building,                    Figure 14 – Glazed solar pacade from the outside of
Klosterenga, Oslo, Norway                                               Klosterenga




 14      Canada Mortgage and Housing Corporation
                                                                                                                         Solar Energ y for Buildings




Solar cooling                                        compared to that of a compressor in a                Solar balconies
                                                     conventional electric air conditioner or
Traditionally, passive solar cooling is                                                                   Glazed, stacked balconies can also work as
                                                     refrigerator. This system is not yet efficient
associated with much warmer climates than                                                                 passive collectors. They passively re-radiate
                                                     enough for conventional buildings and
Canada’s. In Canada, the most effective                                                                   heat or actively ventilate to the rest of the
                                                     requires a large, upfront investment.
method is to exclude solar gain through                                                                   unit or to the outside.
fenestration design, window glazing                  Desiccant cooling uses a desiccant, a
                                                                                                          An effective method is to inset the balcony
selection and shading devices. Another               chemical drying agent, in contact with the
                                                                                                          into the building envelope. This simplifies
common strategy is to use the mass of the            air to be cooled. The air becomes so dry
                                                                                                          the building envelope and eliminates the
building, which cools down at night to               that moisture can be injected into it
                                                                                                          need to separately support or cantilever the
mitigate overheating by absorbing solar              without affecting comfort. The moisture
                                                                                                          balcony. It also reduces the amount of
energy during the day.                               droplets evaporate and cool the air. The
                                                                                                          thermal bridging across the envelope, but
                                                     drying agent is regenerated by hot air that
Harnessing the stack effect, that is the                                                                  may require additional shading devices if
                                                     is heated through solar air collectors or a
upward movement of warmer, more buoyant                                                                   the room is to be occupied regularly or if
                                                     coil connected to liquid-based collectors.12
air, is possible if a building is designed to                                                             temperature fluctuations are not desirable.
capture solar heat and exhaust it at roof            The Rankine-cycle cooling process is a               Of course, the balcony becomes less
level. This warm air can be released to the          vapour compression cycle similar to that of          effective as a solar collector as it is oriented
outside, drawing cooler ground-level air             a conventional air conditioner. Solar                away from south. An enclosed balcony
into and up through the building. An                 collectors heat the working fluid, which             partially or entirely projecting from the
atrium can act as a solar chimney with               has a very low vaporization point, which             exterior allows solar gains in units without
motorized windows to harness the stack               then drives a Rankine-cycle heat engine.             direct southern exposure.
effect and help the natural ventilation              This technology is mainly experimental
                                                                                                          In the CMHC study of renewable energy
process. Using thermal mass in an atrium             and not used often because it needs a large
                                                                                                          at the building envelope, energy modelling
helps prolong the chimney effect well into           system size to do any meaningful amount
                                                                                                          of a six-storey MURB in Halifax predicted
the night to draw cool air into the                  of cooling.13
                                                                                                          that solar balconies would reduce energy
building. In Europe, cool night air is
                                                                                                          consumption by about four per cent.
passed (using fans) through hollow core              Overheating
floors to store coolness. During the day,                                                                 A Dutch study14 looked at solar balconies
room air is recirculated through the cool            Overheating tends to occur more from                 in renovating post-war, multi-family
floor to provide free cooling.                       unshaded west-facing windows and, to a               residential buildings with aged and failing
                                                     lesser extent, east windows. Late summer is          envelopes. The study showed that the new
Absorption cooling involves high-                    often the most crucial time of year. Design          solar elements were a cost-effective way to
temperature solar collectors connected to            strategies include minimizing the amount             upgrade while reducing energy
an absorption chiller operating at around            of east- and west-facing glass, selecting            consumption by about 35kWh per square
100°C (212°F). The device uses a solar               glazings with a low SHGC to exclude                  metre. Optimizing thermal, glazing and
collector to evaporate a pressurized                 heat and provide shading. Thermal mass               ventilation parameters and using simple
refrigerant from an absorbent–refrigerant            inside the building can also have the                venting and solar shading enhanced
mixture. Absorption coolers require little           effect of reducing the peak-cooling load             occupant comfort.
electricity to pump the refrigerant                  in some climates.



12
     Natural Resources Canada website: http://www.canren.gc.ca/tech_appl/index.asp?CaID=5&PgID=164#desiccant
13
     U.S. Department of Energy website: http://www.eren.doe.gov/consumerinfo/refbriefs/ac2.html
14
     Advanced glazed balconies: Integration of solar energy in building renovation, W/E consultants, The Netherlands, EuroSun'96



                                                                                                      Canada Mortgage and Housing Corporation          15
Solar Energ y for Buildings




Cour tyards, atriums and                                An efficient flat-plate solar hot water heater         project consists of 100 well-insulated units;
common spaces                                           can collect approximately 2GJ of energy                each with 140 m2 (1,506 sq. ft.) heated
                                                        per m2 (550 kWh/m2) of collector area per              area, and assessed configurations of
A south-facing atrium can collect pre-heating
                                                        year in most of southern Canada. Other                 collector area (900 m2 to 1,500 m2) and
air to be circulated throughout the building.
                                                        systems available include thermosiphon                 insulated underground water storage 1,600
This requires airtight construction and a
                                                        systems, common in southern Europe, that               m3 to 6,300 m3 (56,503 cu. ft. to 222,482
high level of insulation. Overheating in the
                                                        eliminate the need for pumps.                          cu. ft.).16
atrium can be avoided with properly sized
and located motorized shades and a passive              Several projects in Europe are working with            In Hamburg, 24 single-family, detached
ventilation system. Architects must                     prototypes of seasonal storage, the “Holy              houses used 3,000 m2 of collector with
recognize the fire safety issues of atriums             Grail” of the solar world. These projects              4,500 m3 (158,916 cu. ft.) insulated
and provide protection for their occupants.             use large solar arrays to collect heat in the          underground water storage. A sister project
This is addressed in a separate article on              summer and store it in large, well-insulated           in Friedrichschafen used 5,600 m2 (60,277
the CMHC website Fire Safety in High-rise               underground water tanks. The heat is                   sq. ft.) of collector with 12,000 m3
Apartment Buildings.15 The difficulty in                extracted from the water during the heating            (423,776 cu. ft.) of storage for
dealing with smoke control and using an                 season. To illustrate the scope of such                570 flats in eight buildings. Both projects
atrium to pre-heat building air becomes                 systems, they use approximately 10 m2 to               anticipate solar energy will cover 50 per
a challenge.                                            20 m2 (107 sq. ft. to 215 sq. ft.) of                  cent of heating and hot
                                                        collector and 20 m3 to 40 m3 (706 cu. ft.              water needs.17
In high-rise and mid-rise apartments, it
                                                        to 1,412 cu. ft.) of storage for every flat or
may be easier to consider common spaces,                                                                       In much of Canada we have clear cold
                                                        house. Performance projections indicate
such as entry and elevator lobbies and                                                                         winters and under these conditions a
                                                        that they would provide from 30 to 60 per
stairwells, as solar space. This makes                                                                         substantial amount of solar energy is
                                                        cent of a buildings’ energy. Planning for a
orientation of individual units more                                                                           available when needed, so short-term
                                                        100-unit solar demonstration housing
flexible and may allow greater variations in                                                                   (1-2 days) storage is more cost effective.
                                                        project in Bavaria assessed systems capable
temperature swings.                                                                                            An equivalent climate in Canada for these
                                                        of providing 60 to 90 per cent of heating
                                                                                                               European examples would be the lower
                                                        using seasonal solar heat storage. The
                                                                                                               mainland of British Columbia.
Solar water heating
                                                                                                                                          The design shown is
Solar domestic hot water heating systems vary                                                                                          an example of a typical
                                                                                                                 Glazing               liquid-cooled collector.
in complexity, efficiency and cost. Modern                                                                                                Air-cooled collector
                                                                                                                           Box
solar water heaters are relatively easy to                                                                                                     design will vary
                                                                                                                                                   accordingly
maintain and can pay for themselves in
energy savings well within their lifetimes.                                                                                                 Tube
                                                          Outlet
In MURBs, they may pre-heat water for                                                                                                                      Inlet
the boiler in hot water heating systems.
This works best in large projects that have
significant system heat losses (when the return
                                                                             Absorber Plate                                                    Inlet
water is cooled sufficiently that solar can re-                                                                                                Header
heat it). For boilers heating water for space              Note: for further information on
                                                           collector design and performance,                                   Bottom Plate
heating and hot water, solar panels may allow                                                           Insulation
                                                           see manufacturers’ specifications
the boiler to be shut down in the summer and
provide hot water from solar energy alone.              Figure 15 – Glazed flat-plate collector


15
     http://www.cmhc-schl.gc.ca/en/imquaf/himu/upload/Fire-Safety-in-High-Rise-Apartment-Buildings.pdf
16
     D. Lindenberger et al., Optimization of solar district heating systems: seasonal storage, heat pumps and cogeneration, May 1999
17
     B. Mahler et al. Central solar heat plants with seasonal storage in Hamburg and Friedrichschafen

 16        Canada Mortgage and Housing Corporation
                                                                                                                               Solar Energ y for Buildings




Unglazed flat-plate collectors are the most            impractical on high-rise buildings. To avoid            Evacuated tube collectors are individually
common North American collectors, as                   heat loss during transit, a glycol collector            sealed vacuum tubes surrounding a metal
measured by area installed per year. They              with a well-insulated circuit may be used               absorber plate. The vacuum minimizes
are used most for warming water up to                  close to the pool. Southern or overhead                 conductive heat loss, like a thermal jug.
30°C (86°F) for outdoor and indoor                     glazing can also provide direct solar energy            These collectors are commonly used in very
swimming pools.                                        and cut conventional lighting costs. Solar              cold climates. Evacuated tube collectors are
                                                       energy can supply between 30 and 100                    able to provide higher water temperatures,
They are inexpensive, simple systems that
                                                       per cent of the required heat, depending                but are also more expensive, with longer
can provide all the heating needs for
                                                       on variables, including location, collector             payback periods. RETScreen calculations
residential outdoor swimming pools,
                                                       angle and orientation, desired pool                     show that an evacuated tube collector can
eliminating both fossil fuel consumption
                                                       temperature, size of pool and use of                    deliver about 1.2 kWh/m2/day in winter
and the capital costs of conventional
                                                       a pool cover.                                           and up to 2.9 kWh/m2/day in June.
heating equipment. They are simple to
install and generally have a three- to six-
year-year payback.18 In Canada, their use is
limited to non-heating seasons.

Simple RETScreen calculations show that
unglazed collectors deliver about 2.0 to
2.4 kWh/m2/day during summer. Outdoor
pools are usually seasonal and in warmer
months a solar blanket can be used, or
solar collectors and pumps can heat the
pool directly. When indoor pools are at
or below grade, rooftop collectors are




                                                                                                                                       Natural Resources Canada

                                                                                 Figure 16 – Unglazed flat-plate collector




18
   Sheltair Group et al, Healthy High-Rise: A guide to innovation in the design and construction of high-rise residential buildings,
(Canada: CMHC, 1996) p. 49




                                                                                                          Canada Mortgage and Housing Corporation           17
Solar Energ y for Buildings




Active solar space heating
                                                             Evacuated tube
SDHW—Solar domestic hot
                                                           Glazing
water systems
Solar Domestic Hot Water (SDHW)
systems supplement traditional hot water
heating. The most common system uses
glazed, flat-plate collectors in a closed
glycol loop. A heat exchanger transfers the                                                                                  Inlet
energy from the glycol to one or more solar
storage tanks. These are usually connected
in series to the hot water system. The
                                                                                                       Outlet
traditional water heater comes on to keep
the water at the required temperature if the
solar heat is not enough.                        Figure 17a – Evacuated tube collectors
                                                                                                      Source: Natural Resources Canada1


      Cross section of
      evacuated tube            Outer Glass Tube
                                Inner Glass Tube
                                Fluid Tube
                                Copper Sheet
                                Evacuated Space

                                                                         Figure 17b – Evacuated tube collectors
                                                                                                    Source: Natural Resources Canada
There are seasonal variations in the energy
they collect, depending on location, collector
efficiency, collector angle and orientation,
ranging from about 0.6 to 1.0 kWh/m2/day
in winter up to about 2.4 kWh/m2/day in
summer. It is easy to get 50 per cent of hot
water energy from the sun. A reasonable
target for fossil fuel displacement is 30 to
40 per cent. This allows the panels to operate
at a more efficient temperature. These
systems are easily integrated into current
hot water systems and have a payback in
the range of 10 years. In Canada, this
varies tremendously, depending on funding
incentives and fuel cost.                        Figure 17c – Rooftop evacuated tube collector
                                                                                              Source: Architectural Graphic Standards




 18      Canada Mortgage and Housing Corporation
                                                                                                           Solar Energ y for Buildings




                                       Anti-Freeze Solution

                                          Solar             Hot
                                         Heated            Water
                                         Water           to House
   Solar
 Collectors
                      Pump
                    Controller                        Gas or
                                     Heat             Electric
                                   Exchanger          Water
                                                      Heater
                    Cold
                   Water in
            Pump                 Solar Storage
                                     Tank
Figure 18 – Solar domestic hot water system
Source: www.AdvanceBuilding.org



 Table 2 – Cost and benefits of solar collectors

                                                                                                     Capital       Energy delivered
   Collector        Typical uses                 Advantages               Disadvantages
                                                                                                    cost $/m2      annually kWh/m2

                                        Economical, efficient at low   Not for freezing                                 210–250
 Unglazed          Swimming pools                                                                    150–350
                                        temperature differentials.     temperatures.                                 (summer only)

                                                                       Needs glycol protection
 Glazed            DHW pre-heat         Economical.                                                  450–750            500–600
                                                                       from freezing.

                                                                       Expensive; needs glycol
 Evacuated tube    DHW pre-heat         Provides hotter water.         protection from              1,100–1,500         800–840
                                                                       freezing.




                                                                                          Canada Mortgage and Housing Corporation    19
Solar Energ y for Buildings




Solar air heating                                   Table 3 – Common elements in solar air-heating systems
The following summary is based on Solar             Collector systems             Storage systems        Control systems          Distribution
Air Systems: A Design Handbook, edited by
S. Robert Hastings and Ove Mørck. The               s    Flat-plate collector     s   Hypocaust          s     Continuous         s   Usually
authors looked at European and North                                                  (ceiling or              performance            through
                                                    s    Window air
American applications. Cost analyses are in                                           floor slab)                                     ducting.
                                                         collector                                       s     Temperature
Canadian dollars, unless otherwise noted.
                                                                                  s   Murocaust                control
                                                    s    Perforated
Six principal solar air-heating systems are                                           (wall)
                                                         unglazed collector                              s     Solar cell
summarized below. All systems consist of the
                                                         (Solarwall®)             s   Rock beds                control
following common elements in one form
or another: collector, distribution system          s    Double facades           s   Water              s     Timer control
(ducting), storage unit and control system.              and double-shell
                                                                                  s   Phase-change
                                                         collector
A total system can consist of any combination                                         material
of the four different components.                   s    Spatial collector
                                                         (atriums,
The applications analyzed in the study
                                                         sunrooms,
were for industry, dwellings (apartments,
                                                         greenhouses)
row and single-family houses), offices,
schools, sports halls and swimming pools.

The factors affecting system performance
                                                s       Determine ventilation rate through the       s       Determine the collector area.
are type and mass of building, insulation
                                                        solar air collector.
level and climate.                                                                                   s       Size the ducting.
                                                s       Determine if there are restrictions on
                                                                                                     s       Choose a fan.
Design procedure                                        inlet temperature from ventilation
                                                        system.                                      s       Choose diffusers.
The Solar Air Systems design handbook
recommends the following design steps.          s       Investigate if it is appropriate to          Using an integrated design approach will
More technical details can be found in                  include storage in system.                   enable the building design team to better
the guide.                                                                                           consider any possible alternative purposes
                                                s       Define the required control strategy.
                                                                                                     for the various systems, which could help
s    Define necessary basic data about
                                                s       Choose a solar collector.                    reduce the payback time or provide other
     building and climate.
                                                                                                     benefits to the occupants.
                                                s       Investigate if the system may serve
s    Determine if it is possible to obtain
                                                        other purposes.
     enough collector area.




    20    Canada Mortgage and Housing Corporation
                                                                                                                   Solar Energ y for Buildings




                                                                                                     Preheated
                                                                                                   Ventilation Air




                                                      Solar
                                                     Collector




                                                                                                                   System 1
                                     Conserval
Figure 19 – Ouellette Manor, Windsor,
                                                 Figure 20 – System 1, solar air pre-heat system concept
uses Solarwall ® to pre-heat corridor
ventilation air
                                                 small holes. A gap is left between the cladding     technology. In the last 10 years, about
                                                 and the wall so that outside air passes             35,000 m2 (376,737 sq. ft.) of Solarwall®
System 1: Solar heating of                       through the holes in the collector panel.           collector systems have been installed in
ventilation air, such as Solarwall ®             Air is aspirated into the airspace between          buildings, including low-rise and high-rise
                                                 the collector and the wall, is heated, and          residential. Pre-heated ventilation air
This system provides the simplest, and
                                                 rises as a result of the stack effect and the       systems can be integrated into new
usually least costly way to bring solar-
                                                 lower pressure zone above, which is created         construction or as a retrofit (see figure 19).
heated fresh ventilation air into a building.
                                                 by fans moving air through the system to
It uses mainly off-the-shelf components                                                              In the early 1990s, Ouellette Manor, a
                                                 the interior. This pre-heated ventilation air
in its design. Its major disadvantage is                                                             24-storey, 400-apartment seniors residence
                                                 is then incorporated into the building's
that it will reduce cost-effectiveness of the                                                        in Windsor, reclad part of its complex with
                                                 normal distribution system. A recirculation
building’s ventilation heat recovery unit.                                                           Solarwall®. The new Solarwall® had an
                                                 damper controls the mix of air from the
                                                                                                     incremental cost of about $30,000 and the
An example of this type of system developed      collectors and from inside the building to
                                                                                                     energy savings provided a simple payback of
in Canada is Solarwall®, in which a south-       maintain a constant air temperature for
                                                                                                     about six years. There is more information
facing wall is clad with dark metal panels,      distribution. Using the sun to pre-heat air
                                                                                                     about Ouellette on the CMHC website at
typically steel or aluminum, perforated with     for ventilation in this way is a fairly new
                                                                                                     http://www.cmhc-schl.gc.ca/en/imquaf/
                                                                                                     himu/buin_006.cfm
 Table 4 – Solar heating of ventilation air
                                                                                                     Solarwall® is ideally suited for applications
 Benefits                                        Limitations                                         that require large quantities of ventilation air
 Less cost to heat ventilation air               Requires large, south-facing wall area              during the day and has proven effective at
                                                                                                     pre-heating ventilation air in MURBs. In
 Recaptures heat loss through wall               Reduces opportunity for south facing
                                                 glazing                                             new and retrofit situations, it has the benefit
 May replace conventional cladding
                                                 Reduces the cost-effectiveness of                   of offsetting the cost of traditional cladding
 (new construction)
                                                 ventilation heat recovery (because                  materials. As a result, it can have very quick,
 Conceals old cladding (retrofit)
                                                 owner pays less to heat incoming air)               and sometimes immediate, payback.
                                                 Doesn't replace normal heating system


                                                                                               Canada Mortgage and Housing Corporation           21
Solar Energ y for Buildings




System 2: Open collection loop
with radiant discharge storage
In this system, air circulates, either
naturally or mechanically, through the
collector, distribution system, room space
and back to the collector. It can be built
with or without storage, and may require a
separate ventilation system.                                                                  Open Loop
                                                                                             Air Circulation
System 3: Double envelope
(facade) systems
                                                         Solar
In a double-envelope or double-facade                   Collector
solar air system, solar heated air is
circulated through cavities in the building
envelope, surrounding the building with a
layer of solar-heated air. This creates a
buffer space that reduces the building’s                                                             System 2
heating and cooling load. Inner comfort is
                                                     Figure 21 – System 2, without storage
improved because inner surfaces of the
external walls are warmer. The outer
envelope can be made of opaque materials
(traditional cladding materials with an air                    Solar
                                                              Collector
space) or glass. The Klosterenga project in
Oslo, Norway uses the space between
double layers of south-facing windows to
preheat the air. The figures in Table 5 are
for glass-enclosed systems. Questions of
cleaning and maintenance for this type of
system must be addressed.                                 Cavity
This system is versatile and integrates into
                                                          Wall
most existing heating systems, but is
usually much more expensive than other                                               Radiant
                                                                                      Heat
systems. In North America, costs are
reported to be four to five times that of
traditional, low-cost cladding systems,19 but                                                                      Solar Air
the effective cost may drop if the double                                                                         Surrounds
facade reduces energy consumption.                                                                                 Envelope
                                                                                                     System 3a
                                                     Figure 22 – System 3a, double-envelope system with storage



19
     Meyer Boake, Terry et al. Canadian Architect, August 2003, p. 38



 22        Canada Mortgage and Housing Corporation
                                                                                                                     Solar Energ y for Buildings




There are numerous concepts for double
facade. The following example
demonstrates the heating effect of an air-
heating solar collector with a motorized
blind as the surface absorbing the solar
radiation. Major design parameters are the
spacing between the two skins of the                                                                      Open Loop
facade, the air velocity and the properties                                                                   Air
of the blind, which is controlled by the                                                                  Circulation
building automation system, with manual
override and automatic refresh every hour
or so.
                                                          Solar
The blind, even when closed, must allow                  Facade
enough daylight into the space. This
requires a 20 per cent transmittance
depending on window area. The glazing
must be clear. The airflow-window type of
double facade was considered for the
Seville adaptive reuse project in Montréal.20
Each floor may be separate (with box                                                                              System 3b
window types) with individual inlets and
outlets or connected to form one large              Figure 23 – System 3b, double-facade design option
“chimney.” Figure 23 shows double glazing
for the outer skin with low-emissivity
coating facing the skin cavity to reduce
heat losses in winter. However, this coating,
which increases the outlet temperature
by a couple of degrees, may possibly be
excluded as it can deteriorate in this case.
The inner glazing may be operable. The
inlets and outlets of the airflow window
need to be carefully designed.




20
     “Seville Theatre Redevelopment Project Integrated Design Process,” CMHC Technical Series (63175) Research Highlight 03-102




                                                                                                 Canada Mortgage and Housing Corporation     23
Solar Energ y for Buildings




The following results show an example of
the air temperature rise of the solar
collector due to varying the distance
between the two “facades” or skins.
   v=air velocity: 0.1–0.2 m/sec
   w=width of the space=3.6 m,
   Outdoor air temperature of -5ºC
   L= the distance between the two skins;
   Outer glazing, clear double; inner
   glazing single
   low-emissivity coating on inner side of
   outer glazing (double)
   blind solar absorbance: 60 per cent,
   transmittance 20 per cent.
   Height of the space=4 m
Note that the larger the gap width between
the skins, the smaller the air velocity
needed to achieve the required fresh-air
flow rates.                                      Figure 24 – Fresh-air pre-heating in double facade (Klosterenga, Oslo, Norway)
1. For L=20 cm: for v=0.1 m/sec, the
   collector air temperature will rise to
   about 15ºC (rise of 20ºC) when the
   blind is closed with incident solar
   radiation of 600 watts/m2.                          Solar
                                                      Collector
2. For L=30 cm: for v=0.2 m/sec (L=30
   cm), the collector air temperature will
   rise to about 5ºC (rise of 10ºC) when
   the blind is closed with incident solar
   radiation of 600 watts/m2.

System 4: Closed-collection loop
with radiant discharge storage
                                                    Solar
In this system, an air collector is connected      Collector
to the building’s integrated heat storage. The                                    Radiant
air is circulated in a closed loop, normally                                       Heat
with the aid of fan-forced convection, through
the collector to the storage and back to the
collector. The room-facing surface of the                                                                            Closed
storage discharges heat by radiation and
                                                                                            Mass                      Loop
                                                                                                                     Charge
convection to the room space. The collector                                                        System 4
system can be used as part of the building
envelope, with lower extra costs.                Figure 25 – System 4, with storage


 24      Canada Mortgage and Housing Corporation
                                                                                                     Solar Energ y for Buildings




System 5: Closed-collection
loop with open-discharge loop                       Solar
                                                   Collector
This system provides comfort, even in
rooms with high internal and solar gains
and small losses, because it allows
controlled discharge of stored solar energy
to the heated room. This increases the solar
system’s efficiency and reduces the risk of
overheating. It can use existing building
components and can be combined easily            Solar
with existing HVAC systems. It is more          Collector
                                                                             Radiant
expensive than other systems.                                                 Heat                                Open Loop
                                                                                                                  Discharge
System 6: Closed-collection loop
with heat exchange to water
                                                                                       Mass
The closed-loop solar-air system has
advantages over liquid systems, as there is                                                       System 5
no risk of leaking, boiling or freezing. It
                                               Figure 26 – System 5, with storage
might also be chosen for its economy or
for architectural reasons. Solar-air heated
water can provide space heating, domestic
hot water heating or be used for industrial
applications. Apart from the collector, the
system consists of standard HVAC
components. This system can be used for
heating hot water during the summer. It
requires that the air temperature in the
                                                                                              Air to Water
                                                                                              Heat Exchanger
system be hotter than ventilation pre-heat
systems. It is usually bulkier than liquid                                                    Solar Preheated
                                                                                              Water
systems.
                                                   Solar
                                                  Collector
System design

For more technical details, see pp 103-104
of Solar Air Systems: A Design Handbook

s   Step 1-Profile the loads

s   Step 2-Select collector type                                                                  System 6
s   Step 3-Decide on air mass flows            Figure 27 – System 6, with hot-water storage

s   Step 4-Specify the heat exchanger

s   Step 5-Size the storage and determine
    heat loss




                                                                                    Canada Mortgage and Housing Corporation   25
   26
                                                                                                                                                                               Solar Energ y for Buildings




                                          Table 5 – Comparison of six solar-air heating systems

                                                                                                                                                                 System
                                          System                  Advantages                                   Disadvantages                       Cost                                  Saved energy
                                                                                                                                                               performance

                                                   Simple, inexpensive                             Decreased performance of heat recording   Solarwall®     600–800 kWh/m2          110–550 kWh/m2
                                                   Low temperature air usable                      unit                                      $194/m2                                (sunny–cold)
                                             1     All collectors usable                           Collector materials must be non-toxic                                            90–300 kWh/m2
                                                   System uses standard components                                                                                                  (cloudy–temperate)




Canada Mortgage and Housing Corporation
                                                   Simple, can be used with or without storage     May require separate ventilation          $200/m2        Payback 25 years        80–200 kWh/m2
                                                                                                                                                                                    (sunny–cold)
                                             2                                                                                                                                      40–75 kWh/m2
                                                                                                                                                                                    (cloudy–temperate)

                                                   High degree of integration possible, even in    Relatively more expensive                 $90–$475/m2    Payback time depends    150–400 kWh/m2
                                                   retrofits                                                                                                on integration          (sunny–cold)
                                             3                                                                                                                                      100–225 kWh/m2
                                                                                                                                                                                    (cloudy–temperate)

                                                   Using collector as part of building envelope    Window collectors may overheat adjacent                  80–240 kWh/m2           100–425 kWh/m2
                                                   lowers extra costs for the solar system         rooms; rocked storage bulky                              (Heating season)        (sunny–cold)
                                             4                                                                                                                                      50–200 kWh/m2
                                                                                                                                                                                    (cloudy–temperate)

                                                   Existing building components used               Furniture can't be placed against walls   $250–$650/m2                           30–150 kWh/m2
                                                   Can combine with heat and ventilation           Increased installation costs because of                                          (sunny–cold)
                                             5     system                                          facade shell                                                                     10–100 kWh/m2
                                                                                                                                                                                    (cloudy–temperate)

                                                   No problem with freezing, boiling and leaking   Bulkier than liquid systems                              175–375 kWh/m2          300–400 kWh/m2
                                                   in collector                                    Risk of freezing in heat exchanger                                               (sunny–cold)
                                             6     Standard ventilation equipment can be used      Overall efficiency reduced due to                                                120–130 kWh/m2
                                                   Can be used to heat hot water in summer         temperature drop over heat exchanger                                             (cloudy–temperate)
                                                                                                                      Solar Energ y for Buildings




Photovoltaic (PV) systems                                                                              The cost of PV technology is now much
                                                                                                       more expensive than traditional electricity
The photovoltaic effect converts solar                                                                 and has a very long payback period. In 2000,
energy directly into electricity. When                                                                 Natural Resources Canada assessed the break-
sunlight strikes a photovoltaic cell,                                                                  even point for PV products in Canada using
electrons in a semiconductor material are                                                              market data from the past 25 years. Based
freed from their atomic orbits and flow in                                                             on annual growth rates of 20 per cent
a single direction. This creates direct                                                                (growth has been closer to 30 per cent for
current electricity, which can be used                                                                 the past six years), the break-even point for
immediately, converted to alternating                                                                  competing with bulk electricity generation
current or stored in a battery. Whenever                                                               was calculated to be between 2020 and
sunlight arrives at its surface, the cell                                                              2030.21 This was based on lowest production
generates electricity. PV cells normally have                                                          cost but does not consider technological
a lifespan of at least 20-25 years; however,                                                           advancements or the advantage of reduced
they usually last longer if frequent                                                                   greenhouse gas production.
overheating—temperatures in excess of
                                                   Figure 28 – PV as window shading
70ºC (158ºF) is prevented.                                                                             Building-Integrated PV systems
                                                   elements (overhangs) at Queen’s
PV systems can be used as a building's sole        University, Kingston                                (BIPVs)
electricity supply or with other sources,                                  Source Kawneer              A more recent trend is the development
such as a generator or a grid connection.                                                              of Building—Integrated Photovoltaics
                                                                                                       (BIPVs). The PV cells are incorporated
Autonomous PV systems include an array of
                                                                                                       into a building element. Currently there is
PV cells and a power conditioner that
                                                                                                       much development in PV roofing, PV
connects to the building's electrical loads.
                                                                                                       shading elements (see figure 28) and PV
To have electricity when there is no sun,
                                                   While autonomous systems can be                     cladding or semi-transparent curtain wall
this system must have storage batteries.
                                                   immediately cost-effective in remote                components (see figure 29). With PV
Battery storage must be sized to the
                                                   locations, they are not likely to be cost-          cladding it is best to have a vented cavity
anticipated load and solar access. A
                                                   beneficial for MURBs.                               behind the panels so as to operate at lower
weakness of the system is that the supply of
                                                   Grid-connected PV systems cancel out the            temperatures. By following such a
solar energy may be intermittent.
                                                   need for onsite generators and batteries and        construction approach one may also
Hybrid PV systems have at least one                                                                    develop an effective rainscreen system
                                                   eliminate the problem of intermittent solar
additional electricity source, such as a fuel-                                                         which hinders rain penetration. PV
                                                   energy. In many jurisdictions it is possible
fired generator or a wind turbine. These                                                               roofing is installed much the same way as
                                                   to supply excess solar-generated electricity
systems can still be off the utility grid and
                                                   to the grid and receive credit from the
can minimize or eliminate the problem of
                                                   power company.
intermittent solar energy.




21
  Ayoub, J., Dignard-Bailey, L. and Filion, A., Photovoltaics for Buildings: Opportunities for Canada: A Discussion Paper, Report # CEDRL-2000-72 (TR),
CANMET Energy Diversification Research Laboratory, Natural Resources Canada, Varennes, Que., November 2000.



                                                                                                  Canada Mortgage and Housing Corporation           27
Solar Energ y for Buildings




conventional roofing and is available in
shingles, tiles and metal standing-seam
roofing (see Figure 30). PV shading can be
effective as a window shading element,
entrance canopy or walkway shading. PV
panels can be opaque, used where no light
transmission is needed, or semi-transparent
for areas where light is wanted, such as
atriums or skylights, but some shading is
needed to reduce cooling loads.




                                              Figure 29 – PV integrated in cur-
                                              tain wall elements at the Mataró
                                              Librar y, Mataró, Catalonia, Spain.
                                              (The facade is also used for fresh
                                              air pre-heating).



                                                                                                   Sol Source Engineering




                                              Figure 30 – BIPV metal-standing seam roof, Toronto




 28     Canada Mortgage and Housing Corporation
                                                                                                                             Solar Energ y for Buildings




Until the use of BIPVs becomes more
widespread, there are barriers to overcome.
                                                           Simplified Analysis
Canadian utilities are often not familiar                  Incident solar                                             heat transfer           heat lost
                                                                                reflected+      electricity+
with small, decentralized energy                             radiation=                                                 to air+              to exterior
production. Consequently, utility                            1,000 W=              100+             100+                  400+                   400
interconnection for BIPVs is a major
barrier to their use. Another barrier is the           grid-connected PV electrical system was                 of thermal power. This gives the following
absence of technical standards and                     decades. By 2004, the cost of panels had                energy balance on the PV panels:
installation codes. Non-technical barriers             fallen to $4.5 per kW-peak (one kW-peak
include the lack of experience among                                                                           This shows that four times more thermal
                                                       is electricity generated with 1,000 W/m2
builders and electrical inspectors; lack of                                                                    energy is generated than electricity. The
                                                       incident solar radiation). Annual electrical
financing for systems with large capital                                                                       electrical efficiency is 10 per cent, while the
                                                       production is generally in the 70-200
costs; additional permit, insurance and                                                                        thermal efficiency is 40 per cent. This gives
                                                       kWh/m2 range, depending on climate.
inspection fees for net-metering systems;                                                                      an overall efficiency of 50 per cent. If
unawareness of potential and long-term                 Consider a simplified analysis of a PV-                 thermal energy is worth half as much as
benefits to system integrators.22                      thermal system—a PV panel with airflow                  electricity, then this system generates about
                                                       behind it (see figure 10, page 12).                     three times the revenue of a simple PV
Photovoltaic hybrid heating                                                                                    system on the facade.
                                                       Assume that 1,000 W/m2 of solar radiation
system (PV-thermal system)
                                                       is incident on the solar panel, which                   This simplified analysis shows why
A typical crystalline silicon PV panel has             converts 10 per cent to electricity to                  PV–thermal applications are the key to
an efficiency of 10–15 per cent. PV solar              produce 100 watts of electricity for one                early, cost-effective use of PV.
panels produce more than four times as                 square metre of panel (a panel costs about
                                                                                                               Integration into MURBs
much heat as electricity. This heat is                 $450 at mid-2004 prices).
normally lost to the environment. A PV                                                                         For MURBs, facades have the highest
                                                       About 5–10 per cent of incident solar
cell can have a stagnation temperature of                                                                      potential for cost-effective BIPVs. In
                                                       radiation is reflected but the rest becomes
50°C (122ºF) above the ambient if the                                                                          facades, they can easily generate thermal
                                                       heat. By bringing in fresh air through an
heat is not removed. The cooler the PV cells,                                                                  energy. Semi-transparent panels can also
                                                       inlet at the bottom and passing it behind
the higher the efficiency. A solar air collector                                                               provide daylighting. There are two main
                                                       the panels the air is heated the same way as
has a typical thermal efficiency of 40–70                                                                      options for using the hot air. Like the
                                                       in a Solarwall® system. The faster the
per cent. Drawing outside air in across the                                                                    Solarwall® system, the PV system can be
                                                       airflow, the more heat is transferred to the
back of panels pre-heats the HVAC supply                                                                       applied in vertical strips with a fan drawing
                                                       flowing air and less is lost to the outside air.
air and also increases the PV efficiency by                                                                    the air into the HVAC system. An
keeping them cooler.                                   Optimal cavity width and air velocity are               alternative is installation into box-type,
                                                       selected by taking into account fan energy,             airflow windows. If they project from the
Combining these two systems produces
                                                       required outlet temperature and fresh air               facade, they need a separate support
both heat and electricity. (This is
                                                       requirements. The PV can extend over                    structure, adding to installation costs.
equivalent to a co-generation power plant.)
                                                       multiple stories, with multiple inlets. In any
Test results show that using PV panels to                                                                      The applications may range from small
                                                       case, if the inside heat transfer coefficient hi
generate both electricity and useful heat                                                                      overhangs to large continuous facade areas.
                                                       is equal to the exterior film coefficient ho
substantially improves the overall efficiency                                                                  Figure 30 shows a double facade with PV
                                                       (about 12 W/m2 for still air), then the                                                    o
(electrical plus thermal). The payback for a                                                                   overhangs, in Freiburg, latitude 48 N.
                                                       flowing air may capture about 400 watts/m2


22
     Ayoub, J., Dignard-Bailey, L. and Filion, A., IBID.




                                                                                                          Canada Mortgage and Housing Corporation          29
Solar Energ y for Buildings




 Table 6 – Description of collector types

 Collector type               Advantages                              Disadvantages            Capital cost $/kW         Efficiency

 Single crystal               High efficiency                         High cost, fragile,          5,000–10,000           11–15%
                                                                      uniform look
 Polycrystalline              High efficiency                         High cost, fragile,          5,000–10,000           10–14%
                                                                      non-uniform look
 Thin-film amorphous          Flexible, can be applied to different   Low efficiency,                                      5–8%
                              types of surfaces                       degrades
 Spheral solar (crystalline   Low cost, flexible, can be applied to   Low efficiency                  4,500                9–10%
 family)                      different types of surfaces.




                                                                        Table 7 – BIPV manufacturers

                                                                        BIPV product        Manufacturer–country

                                                                        Sloped roof         Atlantis Solar Systeme AG, Switzerland
                                                                                            Ecofys,The Netherlands
                                                                                            BMC Solar Industrie GmbH, Germany
                                                                                            BP Solar, United Kingdom
                                                                                            Canon Inc., Japan
                                                                                            Lafarge Brass GmbH, Germany
                                                                                            MSK Corp., Japan
                                                                                            United Solar Corp, U.S.A.
                                                                        Facades             Atlantis Solar Systeme AG, Switzerland
                                                                                            Pilkington Solar Inter., Germany
                                                                                            Isophoton Inc., Spain
                                                                                            Saint-Gobain Glass Solar, Germany
                                                                                            Sanyo Solar Engineering Ltd., Japan
Figure 31 – Double facade with PV overhangs in Freiburg,                                    Schuco Int. KG, United Kingdom
Germany
                                                                        Shading             Ecofys, Netherlands
                                                                                            Colt Solar Technology AG, Switzerland
                                                                                            Kawneer, U.S.A.
                                                                        Flat roof           Powerguard, U.S.A.




 30     Canada Mortgage and Housing Corporation
                                                                                                                  Solar Energ y for Buildings




Summary                                            s   Presently, photovoltaics are an              program is being phased out in 2007.
                                                       expensive way to provide electricity and     However the EE4 software and CBIP goals
Passive solar is best for buildings that have          are more cost-effective combined with        are part of the LEED prerequisites.
low internal heat gains and in which direct            heat recovery as well. However, the cost
solar gain is directed to absorbent thermal            of building-integrated PV (BIPV)             Renewable Energy Deployment
mass. The housing market today may object              systems is coming down as competition        Initiative (REDI)
to hard floor surfaces out of concern for              and market share increase.
comfort and impact noise, but increased                                                             REDI provides an incentive of 25 per cent
drywall thickness and concrete ceilings may                                                         of the installed cost of renewable energy
compensate for the lack of hard flooring.          Tools and resources                              systems for space and water heating and
Mass is most effective if it receives direct                                                        cooling. Eligible systems include:
                                                   Canada Mor tgage and Housing
solar gains, i.e. usually on the floor. However,                                                    s   active solar hot water systems
                                                   Corporation
if this is not possible, a concrete ceiling will
absorb much of the energy from air heated          www.cmhc.ca                                      s   active solar air heating systems
by the floor; this air will rise through           key word: Innovative Buildings                   s   highly efficient, low-emitting biomass
buoyancy. Generally, about 5-10 cm of                                                                   combustion systems.
concrete—or equivalent—on the floor                NRCan and CMHC’s Advanced
provides adequate mass.                            Buildings Technologies                           PV systems are not eligible but receive
                                                                                                    accelerated depreciation under Class 43 of
s   The cost of passive solar is minimal,          www.advancedbuildings.org                        the Income Tax Act.
    but must be planned during the initial
    design stages.                                 C2000 Commercial Building                        Natural Resources Canada
                                                   Program                                          RETScreen
s   Orientation in most MURBs provides
    challenges. An effective strategy is to        This is a Natural Resources Canada               RETScreen is free energy-assessment
    tune the selection of glazing based on         demonstration program for design                 software that assesses renewable energy
    the orientation of each facade.                assistance in energy-efficient commercial        options against a base model. RETScreen
                                                   buildings. The goal is 50 per cent less          has specific modules for passive solar, solar-
s   Solar domestic hot water can have a            energy consumption than a building               air heating and solar domestic hot water
    reasonable payback time and is                 constructed to the Model National Energy         heat. Output includes financial analysis,
    relatively easy to install in new              Code of Canada for Buildings (MNECB).            payback periods and energy displaced.
    buildings and retrofits.
                                                                                                    Modules are available at
s   Solar water heating is less likely to be
                                                   Commercial Building Incentive                    http://www.retscreen.net/ang/menu.php
    effective for space heating, except in
                                                   Program (CBIP)
    very large heating systems.                    CBIP is probably the largest federal
                                                   government initiative to reduce energy use
s   Solar water heating for swimming pools
                                                   in commercial buildings. Building owners
    is very effective for seasonally used
                                                   are given a financial incentive of three
    pools, with short payback times.
                                                   times the annual energy savings if the
s   Solar air-heating systems for pre-             predicted building energy use is 25 per
    heating ventilation air can have very          cent below that required by the MNECB.
    short—even immediate—payback.                  Computer simulations are done with
    Their drawbacks are the need for prime         NRCan's EE4 software. This program has
    southern exposure and their industrial         no provision for analyzing PV systems.
    aesthetic. Such considerations need to         Energy from PV is a credit towards
    be part of the architectural design of         meeting the energy target and contributes
    MURB installations.                            to the eligibility of the incentive. The

                                                                                                Canada Mortgage and Housing Corporation        31
   32
                                                                                                                                                                                          Solar Energ y for Buildings




                                          Case studies — visit CMHC website for other examples

                                                                                                                                                                          Project
                                           Project–location       Building description              Technologies used, solar features                 System cost                                   Comments
                                                                                                                                                                           cost

                                          Amstelveen,             42-unit MURB new               Atrium pre-heats ventilation air, solar DHW,                            $152, 386      Energy use: 13 kWh/m2 for space
                                          Amsterdam,The           construction                   heat recovery ventilation, SOcLAR shading of                            Cdn per unit   heating, 15 kWh/ m2 for DHW,
                                          Netherlands                                            some units

                                          Conservation Co-op,     4-storey apartments, new       Thermally isolated balconies; meeting              Incremental cost     $645/ m2       5,320 GJ/ m2 ;
                                          Ottawa                  construction                   room–greenhouse; external shading                  $733 per balcony                    energy savings small but other




Canada Mortgage and Housing Corporation
                                                                                                                                                                                        benefits

                                          Uster Condominiums,     10 units, 4-storey MURB,       Passive solar heating; large thermal mass; 21 m2   200 USD/sq. ft.                     Total energy consumption 112 kWh/
                                          Switzerland             1997 new construction          solar panels for DHW                               construction cost                   m2-35% of typical MURB

                                          Ouellette Manor,        400 units, 24 storeys          336 m2 Solarwall® pre-heats ventilation air        $90/m2 incremental                  Collector delivers 584 kWh/ m2;
                                          Windsor                                                                                                   cost                                6-year payback; 2,000–4,000 Cdn
                                                                                                                                                                                        savings in energy/yr

                                          Quinpool Towers,        232 units, 10 storeys          228 m2 solar DHW pre-heat system                   $93,000 total                       630 GJ/yr solar delivered; 6-year
                                          Halifax                                                                                                   system ($408/m2)                    payback (with incentives)
                                                                                                                                                    before incentive

                                          Chantrelle Inn, North   2-storey inn (9 suites plus    47.5 m2 flat-plate solar collectors heat DHW       $36,700 ($772/m2)                   46 GJ (12,800 kWh) produced each
                                          River, N.S.             common areas)                  with surplus going to radiant slab; 2 PV panels    after incentive                     year—50% of DHW and 25% of
                                                                                                 for pumps; no fossil fuels consumed on site                                            space heat requirements; savings of
                                                                                                                                                                                        $2,660/year—10.5-year payback
                                                                                                                                                                                        (with incentive)

                                          BedZED, U.K.            Carbon-neutral residential     Combined heat and power units (CHP)—waste-                                             60% decrease in total unit energy
                                                                  development                    wood combustion delivers electricity and space                                         demand; 90% decrease in total heat
                                                                                                 heat via centrally located domestic hot water                                          demand
                                                                                                 cylinders; PV array to recharge cars

                                          Gardsten, Gothenberg,   Social housing project,        Greenhouse in common area; space heating           11,589 euros/m2
                                          Sweden                  10,000 residents; “green       from rooftop solar collectors; solar balconies
                                                                  retrofit” of 1970 s building

                                          Klosterenga, Norway     35-unit 6-storey green         218 m2 rooftop solar collectors for radiant slab                                       Part of IEA solar program
                                                                  apartment demonstration        and DHW pre-heating; passive solar double                                              International Energy Agency
                                                                                                 glazed south facade to pre-heat ventilation air;
                                                                                                 summer shading
                                                                                                            Solar Energ y for Buildings




References
Tap the Sun: Passive Solar Techniques and        Sheltair Group, Healthy High-Rise: A
Home Designs (Canada: CMHC, 1998)                Guide to Innovation in the Design and
Canada Mortgage and Housing                      Construction of High-Rise Residential
Corporation (CMHC)                               Buildings, (Canada: CMHC, 1996)

Ayoub, J., Dignard-Bailey, L. and Filion,        Solar Air System: A Design Handbook
A., Photovoltaics for Buildings: Opportunities   Editors S. Robert Hastings, Ove Morck,
for Canada: A Discussion Paper, Report           James & James 2000
# CEDRL-2000-72 (TR), CANMET
                                                 Edward Mazria, The Passive Solar Energy
Energy Diversification Research Laboratory,
                                                 Book, Innovative Building Case Studies,
Natural Resources Canada, Varennes, Que.,
                                                 CMHC website.
November 2000, pp. 56 (plus appendices).




                                                                                           Canada Mortgage and Housing Corporation   33
Solar Energ y for Buildings




Questions
1. Name three benefits of using              4. What is the difference between    7. Name three types of active solar
   solar energy.                                active and passive solar energy      collectors.
                                                systems?
2. Why is passive solar a good                                                    8. What are three pros and three
   choice for new construction               5. What are the main elements of        cons of a Solarwall® type of
   MURBs?                                       a hybrid grid-connected              ventilation air preheat system?
                                                photovoltaic system ?
3. What four window technologies                                                  9. Describe two ways of integrating
   can improve a window’s                    6. What are the main elements of        PV in MURBs and improving
   performance as a solar                       a typical solar domestic hot         their cost-effectiveness
   collector?                                   water system?




 34     Canada Mortgage and Housing Corporation

				
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