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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
S
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.
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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.
40
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.
below.
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
41
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: steve@renewables.com;
heating pipes embed- Website: www.renewables.com) ∆
ded in the floor slab. A
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