Solar Building Design...By Stephen Heckeroth by SUSB


									E NERGY W ORKS
                                    May/June 2000 Backwoods Home Magazine

    A practical review of four projects

      By Stephen Heckeroth                   • A barn roof with an integrated
                                           three kilowatt photovoltaic (PV) array

              olar building design has     that satisfies the energy needs of a sin-
              been used since ancient      gle family home and loft apartment on
              times. In the more recent    a five-acre ridge-top homestead.
              past, it has been more or      • A 2,000-square-foot house that
              less ignored as impracti-    combines the use of passive solar
cal, complicated, or too expensive.        design with thermal collectors to satis-
Incorporating the sun’s energy into the    fy heating needs and a roof-integrated
design of the built environment, how   -   PV system for electricity generation.
ever, is practical, simple, and afford-
able.                                      Caspar Point house
  Ancient civilizations knew that ori-       The 3,000-square-foot Caspar Point
entation to the sun was an important       home is located in northern California
factor in the layout of their cities and   on a rugged point of land jutting out
homes. As the knowledge and technol-       into the Pacific. It incorporates south-
ogy of using solar, wind, and water        ern exposure, sun spaces, thermal
sources evolves, owner-builders and        mass, insulating envelope, earth cou-
building professionals alike will have     pling, and thermosiphon solar-heated
a greater opportunity to incorporate       water for domestic hot water and radi-
energy-conserving strategies into any      ant floors. The solar heating strategies
project.                                   have maintained comfortable indoor
                                           temperatures in an extremely harsh
Introduction:                              climate without the use of fuel since
  Following are four projects designed     the home was completed in 1991.
by the author that illustrate passive        The indoor temperature has been
solar design strategies, introduce a       maintained above 65 degrees
new building-integrated photovoltaic       Fahrenheit in this relatively cool loca-
roofing material, and show how inte-       tion. Opening windows and ventila-
grating energy systems lowers overall      tion tunnels protect the house from
cost. Examples include:                    overheating. The electricity needs are
   • An award-winning passive solar        about 1/10th that of a conventional
home on the northern California coast      home. This is accomplished by using
that offers all the comforts of modern     energy efficient appliances and
living but uses only solar energy for      fixtures along with solar strategies.
heating and the prevailing wind for        The $93 per-square-foot construction
cooling.                                   cost was $30 less per square foot
  • A five-story solar-heated tower        compared to other custom homes
house nestled in the redwoods with a       in the area.
roof-top, solar-heated hot tub.

May/June 2000 Backwoods Home Magazine

                                           Thermal mass and                            it by reaching for the sky. The passive
                                           insulating envelope                         solar design concepts used in the
                                                                                       Caspar Point house are repeated but
                                             Thermal mass within a building
                                                                                       adapted to a different setting by ori-
                                           regulates interior temperatures. The
                                                                                       enting the building vertically. The sun
                                           mass absorbs heat on sunny days and
                                                                                       is the only energy source necessary to
                                           prevents overheating. At night, the
                                                                                       heat the five-story tower in the win-
                                           stored heat is radiated into the build-
                                                                                       ter. Overhangs prevent overheating
                                           ing. The thermal mass at Caspar
                                                                                       by the high summer sun. The house
                                           Point consists of 100 yards of struc-
                                                                                       works as a cooling tower when win-
                                           tural concrete. The insulating enve-
                                                                                       dows are opened by venting hot air
                                           lope extends to below grade on exte-
                                                                                       out of a hatch on the roof deck. This
                                           rior walls to integrate the founda -
 The Caspar Point house is unique                                                      pulls cool air into the lower floors.
                                           tion’s structural function with its abil-
 in that it uses no fuel for space         ity to store heat. At Caspar the slab is
 heating or cooling throughout
                                                                                       Solar gain
                                           insulated from the earth with R-11
 the year.                                                                               The south side is open to the sun
                                           insulation, the exterior walls are
                                                                                       with an attached greenhouse on the
                                           wrapped with R-19 insulation, and R-
                                                                                       lowest level and large windows that
 Orientation                               30 was used in the ceilings to create
                                                                                       let in the winter sun but are shaded
                                           an insulating envelope.
   Buildings incorporating passive                                                     from the high summer sun.
 solar design rely on the sun, wind,       Solar heating                               Photovoltaic (PV) panels are mount-
 and the earth to maintain comfortable                                                 ed above flat plate collectors on
                                             Flat plate solar collectors mounted
 indoor temperatures. Proper orienta-                                                  either side of the sun space/green-
                                           on south elevations can be used to
 tion accounts for more than 80% of                                                    house to run pumps which distribute
                                           provide solar heated liquid for space
 the success of passive solar design.                                                  heated liquid through radiant floor
                                           and domestic water heating. Two
 The prevailing wind should be used                                                    pipes embedded in the floor slab.
                                           large flat plate collectors are integrat-
 for cooling and ventilation. Earth                                                    Heated air rises naturally through the
                                           ed into the south-facing roof above
 berms can protect the house from                                                      house, controlled by the opening and
                                           the stairwell. The heated liquid ther-
 cold winds.                                                                           closing of doors at various levels.
                                           mosiphons into a tank. The heat
   The Caspar Point house is built into                                                  Flat plate collectors are also
                                           stored in the tank is then pumped
 the earth on the north and west sides                                                 installed on the shed roof over the
                                           through pipes embedded in the slab
 to protect it from the prevailing wind.
                                           floor to place the heat where
 The berms also increase the depth of
                                           it does the most good. A
 the house’s connection with the earth
                                           heat exchanger in the solar
 to take advantage of the more con-
                                           tank is used to provide
 stant below-grade temperatures. Two
                                           domestic hot water.
 stories of glazing open the house to
 the south for solar gain and a view of    A tower house
 the ocean. The exposed greenhouse
                                             The Sterling-Norris tower
 acts as a heater where tomatoes thrive
                                           house, located four miles
 through the year.
                                           inland on a ridge just south
   The sun enters the building through
                                           of Albion, CA., responds to
 the greenhouse entry, a sunspace off
                                           the redwoods that surround
 of each bedroom, and large view win-
 dows in the main living spaces.
 Overhangs are sized to shade the win-              This tower house
 dows in the summertime while letting            takes full advantage
 the sun’s rays fully penetrate in the                  of winter sun.
 winter, ensuring maximum direct                   Shading keeps out
 gain in thermal storage walls and          the summer sun. Venting
 concrete floors.                             the hot air helps pull in
                                                            cooler air.

   E NERGY W ORKS                                                            May/June 2000 Backwoods Home Magazine

south-facing 4th and 5th floor win-       reduce water usage. Many of the           Power generation
dows. These roof-integrated panels        Mendocino water towers this home            The 700 square feet of thin-film
heat water for domestic use and a hot     imitates have survived over 100 years     amorphous laminated-glass panels
tub built into the roof deck.             on less substantial foundations. This     produce a steady 3 kW for 7 to 8
  The first floor is buried to take       home should last at least as long.        hours in the summer and an average
advantage of the earth’s more con-                                                  of 1.5 kW for 4 to 5 hours in the win-
stant temperature. The walls were         Energy savings
                                                                                    ter. This is enough energy to run all
wrapped with R-19 rigid insulation          The solar strategies added only         the appliances in the house and loft
above and below grade, and R-11           minor costs to this custom home but       apartment year around, and charge an
insulation was used underneath the        resulted in substantial energy cost       electric car and an electric tractor on
slab in order to prevent the heat         savings over the life of the building.    sunny days. Thin-film amorphous sil-
stored in the thermal mass from           The utility bill averages $20 per         icon panels are 6-10% efficient in
escaping to the outside.                  month which is about one-fifth that of    their conversion of sunlight to elec-
                                          the average 2,500-square-foot home.       tricity, compared to 10-14% of crys-
Resource efficiency                       Free solar space heating and cooling      talline panels. But amorphous panels
  The top soil excavated from the         and water heating account for over        have the advantage of performing
building site was spread on the sur-      50% of energy savings. Good insula-       well in high-temperature and shaded
rounding gardens to enrich the soil.      tion and efficient appliances further     conditions. The roof, including the 4
Runoff from the roof is collected in a    add to the energy savings. The con-       kW synchronous Trace inverter and
reflecting pond immediately south of      struction cost was $84 per square foot    battery pack, cost $15,000 and will
the house. The pond is used to irri-      which is 30% below the $125 per           pay for itself in 10-15 years.
gate terrace gardens further down the     square foot which is typical for cus-
south slope.                              tom homes in the area.
  The foundation was designed to
form retaining walls instead of bury-     A barn re-roofing
ing the required 50 yards of concrete       The replacement of a south-facing
underneath the house. As a result, the    leaking metal roof with photovoltaic
structural concrete serves the multiple   panels turned an old barn roof into a
functions of foundation, thermal          power generator for the author’s
mass, and earth connection. With the      homestead located three miles inland
addition of a skylight, it further pro-   from the Pacific Coast in Albion, CA.
vides 300 square feet of comfortable      Using solar panels over the roof
living space at almost no extra cost.     framing saves the cost of roofing and
  The house was framed and trimmed        a mounting structure that would be
with resawn, recycled redwood tim-        necessary to support the panels.
bers salvaged from a local mill. The 2    Skylights were also integrated into
x 6-foot T&G fir flooring used            the new roof to provide daylighting,
throughout the house is supported by      and a flat plate collector was added to
exposed redwood beams and also            supply domestic hot water to a barn
serves as the ceiling of the floor        loft apartment.
  Like the Caspar Point                                                             Above: A shed dormer transforms
house, energy efficient                                                             the loft apartment into a warm
appliances and fixtures                                                             and sunny place.
help lower the overall
energy consumption.                                                                 Left: Author replaces an old
Full-spectrum capsule                                                               roof with dormers, PV modules,
fluorescent lights are                                                              solar water-heating panels, and
used, requiring one                                                                 skylights. The finished roof is
quarter of the energy of                                                            revealed in the opening photo of
incandescent lightbulbs.                                                            this article, and on the cover of
Low-flow plumbing fix-                                                              this issue.
tures were installed to

May/June 2000 Backwoods Home Magazine

 Embodied energy                           coil of pipe located in the solar tank
   The thin-film amorphous panels can      acts as a heat exchanger to provide
 recuperate the energy it took to man-     domestic hot water.
 ufacture them in six months of use as
                                           Integrated PV roofing
 compared to up to 3-5 years for crys-
 talline panels. Thin-film technology        A 2-kW PV array bonded to archi-
 uses 300 times less silicon feedstock     tectural standing-seam metal roofing
 and produces virtually no waste com -     is the first of its kind on a single-fam-
 pared with cutting crystalline cells.     ily residence. The array, made by           Plastic tubing embedded in concrete
 Embodied energy is also saved with a      Uni-Solar of Troy, MI, was installed        insulated from the ground makes for
 roof of multiple functions: shelter,      in three hours. This equals the time it     a warm floor in winter.
 power generation, water heating, and      would have taken to install regular
 daylighting.                              standing-seam metal roofing. The            in material needed to build a support-
                                           flexible PV material is bonded to           ing structure. They also add insula-
 A PV roof house                           metal panels 16 inches wide and 18-         tion to the wall. While it is relatively
   The McMillan residence is a 2,000-      20 feet long. Each panel requires only      expensive to buy new flat plate col-
 square-foot, three-bedroom home that      two electrical connections, easily          lectors, the initial cost is quickly
 shows how solar strategies can be         accessible under the ridge cap. Each        recuperated. When compared to elec-
 incorporated into a traditional design.   panel generates 128 watts of power.         tric water and space heating, the
 The home is located three miles           The installation involves just one          initial cost can be recovered in as lit-
 inland on a sunny plateau just south      roof penetration under the ridge cap.       tle as three years. After that,
 of the town of Mendocino, CA. The         It channels the wires to a combiner         hot water and warm floors are
 main glazing on the building is ori-      box near the batteries and inverter.        almost free.
 ented south for solar gain. Flat plate    Here the 24Vdc power is inverted
                                           to 110Vac.                                  Conclusion
 collectors provide heated liquid for
 domestic h o t water a n d radiant                                                      In the past, solar components were
                                           Cost savings                                regarded as unconventional and visu-
 floors. An integrated P V roof makes
 electricity.                                 The PV roof costs $5.50 per watt         ally unpleasing additions to build-
                                           which is approximately equal to the         ings. When solar components are
 Solar gain                                cost of a non roof-integrated PV            integrated into the skin of a building,
   Arbors and overhangs protect the        panel in need of a mounting structure       they eliminate the need for the mate-
 south facing glazing from the high        or tracker. Orienting the PV roof to        rial they replace and blend in with the
 summer sun while exposing the tile        the south is the only requirement           structure. New solar materials can
 floors to the low winter sun.             for efficient operation. The value          enhance the aesthetics of both tradi-
   Flat plate collectors are mounted on    of energy production over the 50-year       tional and contemporary structures
 the south wall between windows and        life expectancy of the roof more than       while providing a clean and self-
 doors. By mounting these solar col-       justifies the initial cost which will be    reliant energy supply.
 lectors vertically, twice as much heat    recuperated in 10-15 years of use.            These four projects show that the
 is generated in the winter when it’s         Flat plate collectors used as siding     technologies available to gather and
 needed as in the summer when over-        not only avoid the cost of the siding       conserve energy do not add signifi-
 heating can be a prob-                    they replace but also save the expense      cantly to initial expense but do lower
 lem. The heated liquid                                                                the long-term cost.
 is stored in solar tanks
                                                                                         (Stephen Heckeroth, 30151 Navarro Ridge
 in the attic and circu-                                                               Road, Albion, CA 95410. Phone: 707-937-
 lated through hydronic                                                                0338; e-mail:;
 heating pipes embed-                                                                  Website: ∆
 ded in the floor slab. A
                                                                                         Alternative Power, 104 N. Main, Viroqua, WI 54665
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 form part of the                                                                          DC Refrigerators, Composting Toilets, Trace
                                                                                         Inverters, Batteries, DC Everything, Catalog $3.
 roof of this 2,000-                                                              , (608)637-2722
 square-foot home.                                                                  


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