This earth-covered, passive solar, 1863 sq ft house achieved the very best performance
in a HUD-sponsored energy survey when it was first built in the late 1970's.
For three years after the house was built, it was computer-monitored, and according
to the National Solar Data Network, the SunEarth house out-performed hundreds
of passive solar houses in the country. The house was designed, built, and marketed
by Colorado Sunworks. The furnace was put to rest during its first winter because
the pilot light was wasting natural gas. All of the space heating demand is
supplied by the passive solar system.
The heating system is a direct gain, passive solar system and
drum wall. The south side exposes 300 square feet of glass windows. The windows
are two panes of insulated glass that run floor to roof. Behind the windows
are 54 large, vertically stacked barrels. Sunlight directly warms these 55-gallon
oil drums that are painted with a flat black finish and filled with water. During
the day, the water and interior concrete walls inside the house absorb the sun's
heat. The heat is released slowly after the sun sets.
At night, when temperatures begin to drop, a blower pushes polystyrene
beads between the two panes of glass, providing insulation to keep the daytime
heat inside the home. On winter nights, this moveable Beadwall insulation converts
the large window areas to R20 heat loss barrier. Six vertical skylights are
arranged on the north side of the earth roof. Maximum solar energy takes place
during the winter, and minimum solar energy occurs in the summer.
House interiors are pleasant and attractive. Rooms are arranged in a spacious
manner around the great room. Bright and warm in winter, cool and shaded in
summer, every element of the design works with the changing environment. Skylights
and light floor tiles help bathe all walls with natural light while collecting
solar energy. The centrally located interior garden is colorful and inviting.
Plants supply fresh air and humidity year round.
The South side exposes 300 sq ft of glass windows
to the winter sun-this directly warms large barrels of water about 10 degrees
F. on a clear day. Atrium windows admit sun directly to lightcolored floor tiles
which then reflect the light to interior concrete walls, storing more energy
for night time use. On winter nights moveable insulation (Beadwall) converts
large window areas to R20 heat loss barrier. Other energy conserving features
of the SunEarth House include a garage buffer to the northwest, air-lock entry,
vertical skylights over the north wall, air tight construction, thermal envelope
ceiling for natural heating and cooling, fireplace piped to outdoor air, summer
shading devices, and passive tank type water heaters. The floor plan emphasizes
elongation of the south side of the building for good solar exposure. Rooms
are laid out to aid natural heat flows. Note that the south collector/storage
wall can "see" much of the north wall for effective distribution of
Stored solar heat is released from the water containers as needed. Heat flows
naturally by low temperature radiation and by warm air convection to the north
side of the house, thus balancing comfort zones throughout the living space.
Interior thermal mass is cooled down on summer nights by providing a natural
air now path. Daily heat gains aree rejected by this method through turbine
roof ventilators. The cooled massive house is then closed up on hot summer days
for comfortable living.
The house is constructed with concrete walls
that are insulated on the exterior. Earth is piled up over the north, west and
east walls. One foot of earth with vegetation covers the roof. The weight is
supported by steel bar joists and a concrete deck.
The design begins with concrete wall construction insulated on the exterior.
Concrete walls (secondary thermal mass) are equal in heat capacity to the south
water wall. Wall temperatures rise 3F degrees on sunny winter days, then discharge
heat to the rooms at night. Earth protects wall from outdoor temperatures, but
must be insulated from the concrete.
Parts of the surrounding concrete walls are exposed to air, especially near
windows. Direct contact with outdoor temperature requires R20 insulation to
be placed on the exterior. Tough styrofoam is glued to wall then plastered with
mix of cement and glass fibres.
One foot of earth cover provides patio, garden, and grassy areas on the roof
thus increasing useable outdoor space. Effects of outdoor temperatures are dampened
considerably. Ceiling is suspended from steel joists providing air flow plenum
for natural cooling and heating.
Maximum solar energy is admitted during winter, minimum in summer, by this vertical
arrangement. The bright light wells diffuse strikingly pleasant natural lighting
along interior north house wall. Triple glazing cuts heat loss to tolerable
South glass wall
The south glass is vertical and functions as a solar collector. On winter nights
the 5 inch cavity between tempered glass panes automatically fills up with tiny
styrofoam beads. The insulating value then becomes R20, keeping stored solar
heat inside the house.
Passive water heater
Passive tank heaters inclined at the south wall collect solar energy used for
pre-heating domestic hot water. The cusp reflector directs all the light falling
on the glass to some portion of the tank. Beadwall insulates the glass at night.
The design as presented is how it was originally built. The house
continues to be occupied, and still performs remarkably well, using virtually
no fuel other than the sun during the winter. The beadwall system is no longer
in use, as it developed some problems; however thermal curtains could be used
to insulate the glass at night instead.
The barrels of water could be replaced by a masonry trombe wall that would
be nearly as effective. Alternatively, the barrels of water could be eliminated
entirely, with somewhat reduced thermal performance.