16 inches (40 cm) thick and 10 feet (3 m) tall. Several tons of rebar went into the concrete.

The back wall is two stories tall, with the second story walls 12 inches (30 cm) thick. An 8 foot (2.4 m) wide by 12 foot (3.6 m) long by 8 foot high room at the second floor level provides a rear exit. Total concrete in the house came to 130 cubic yards (98.4 m3).

After the walls were poured, they were waterproofed on the outside with Thoroseal, a cement sealing mixture, and insulated to R-16 with 4 inches (10 cm) of closed cell foam. The ambient earth temperature here is 55°F (13°C). Four mil plastic sheeting was placed against the insulation, and held in place by 3/8 inch (10 mm) reject particle board.

A 4 inch drain pipe was placed at the base of the walls on the outside, and covered with drain rock. This French

The steel I-beams arrived by truck, and were hoisted into place by a crane.

drain ensures that water going down the outside wall is directed away from the building to prevent seepage and hydrostatic problems. Soil fabric was placed over the drain rock. This fabric is permeable to water, but keeps soil from clogging the drain pipe. The drain pipe is placed around the perimeter of the walls below the footing, and diverts the water away from the walls to where the pipe emerges in the daylight on either side. The ends of the pipe are covered with screen to keep rodents out.

The walls were then backfilled with the dirt and rock from the house excavation. Huge, junk, earthmover tires, filled with rock, act as riprap to hold the west wall's backfill. On the east end, we stacked huge boulders to create a retaining wall to hold the backfill in place. For an amateur backhoe operator, this was a bit tricky.

Roof Construction

The peaked roof is held up with four, huge, steel I-beams, with three center posts in the house and five steel uprights across the front. The span across the front of the house is 30 feet (9.1 m). The span from front to rear is 40 feet (12.2 m). Our engineer, Phillip B. McCulloch of Medford, Oregon, specified the placement of the beams after calculating the roof loads. He assumed 25 pounds per square foot for snow load, and a saturated earth load of 140 pounds per cubic foot.

The ends of the I-beams were welded to steel plates embedded in the tops of the walls. Bolted to the top of the I-beams are 2 by 12 (5 cm x 30 cm) Versa-Lam purlins (made from fingerjointed, laminated Douglas-fir veneers). Next, we glued and nailed 11/8 (2.9 cm) inch tongue and groove plywood to the purlins as roof sheathing. Then came 30 pound felt and 12 inches (30 cm) of closed cell foam insulation (R-36), glued in place. The 12 inches of insulation was necessary

Roof layers—shown are the roof felt and closed cell foam over tongue and groove plywood.

The steel I-beams arrived by truck, and were hoisted into place by a crane.

Roof layers—shown are the roof felt and closed cell foam over tongue and groove plywood.

because, according to the building department, "Dirt has no insulating quality."

This was confirmed by Ralph Smoot, a builder of earth-sheltered homes in Austin, Texas. Basically, the benefit of an earth-sheltered home is that the earth moderates the temperature swing by storing heat. So, he recommends that you first find out what your yearly average daytime temperature is, and use the following guidelines:

• 3 feet (0.9 m) of dirt covering will yield a plus or minus 9°F (5°C) variation from the average;

• 9 feet (2.7 m) of dirt covering will yield plus or minus 5°F (3°C) variation; and

The finished roof in full bloom—with weather vane and chimney.

• 27 feet (8.2 m) of dirt covering will keep the temperature constant.

Ralph says that if your area gets frost, the structure needs to be insulated (high density foam) and waterproofed, again! Adding insulation helps prevent stored heat from escaping. (For an article about earth-sheltered homes, see HP29, page 22.)

After the insulation, two, 50 by 20 foot (15 m x 6 m) sheets of EPDM rubber roofing came next. Each sheet weighed 450 pounds (204 kg), and was very difficult for two people to handle. The EPDM was placed on

The house's open interior, looking toward the north exit.

both slopes and overlapped by two feet at the center. Contact cement was used to glue the overlaps. A sudden rainstorm while we were gluing proved that contact cement really won't hold when wet. Tempers got short, and cooling off, drying out, and regluing were in order.

The house's open interior, looking toward the north exit.

Two layers of horse fencing (road wire) were laid down on top of the EPDM to act as reinforcement, and 3 inches (8 cm) of concrete was poured on the roof. We hired a concrete crew that specialized in sidewalks to complete this stage. Working on the steep pitch of a roof proved to be a challenge for these guys, and provided a bit of comic relief.

We placed 3/8 (10 mm) inch reject particle board on the concrete to act as a cushion, and to protect it from damage during backfilling. About 3 feet (1 m) of dirt was then placed on the roof. A 3 foot parapet across the front and back of the roof keep the dirt from spilling over the ends. This spring, wildflowers were in full bloom up there.


The floor of the house is a 4 inch (10 cm) concrete slab, covered with 14 inch square (35 cm) floor tiles. We chose a tile that varies from light color to a medium dark. This gives good heat absorption from sunlight without making the house seem dark

The loft's view—the passive solar design includes a The kitchen, Russian masonry heater, and wood window-to-floor ratio of about one to eight. cookstove that doubles as a hot water heater.

The loft's view—the passive solar design includes a The kitchen, Russian masonry heater, and wood window-to-floor ratio of about one to eight. cookstove that doubles as a hot water heater.

inside. We did not insulate under the slab because we temperature year-round is 68° to 74° F (20-23°C). The were afraid that the house would overheat. ratio of window to our floor area is about one to eight.

Water System

When we decided on our domestic water system, we went with one that had proven adequate for our needs in our last two houses. Collection of rainwater in storage tanks provides all of our domestic water. Our rainwater has no minerals, while some local wells have arsenic and heavy concentrations of other minerals.

The collection system consists of a galvanized shed roof over two, 1,300 gallon (5,000 l) drinking-water-grade, black tanks. The rainwater is collected from the shed roof and channeled through a screen and into the tanks. Once a year, during a heavy rain, we put 1/4 teaspoon or so of chlorine bleach into the intake. The heavy water input mixes with the bleach, which prevents any bacterial or algae buildup.

The water tanks are located about 150 feet (46 m) higher than the house, so we have plenty of water

Rainwater, collected in these tanks, provides all of Colin and Christine's domestic water.

Rainwater, collected in these tanks, provides all of Colin and Christine's domestic water.

The walls inside have a thin coat of plaster, floated to a sand finish. The back wall of the bedroom loft is covered with cedar we milled ourselves.

The layout of the interior is open, with the bedroom loft overlooking the great room. Under the loft, is our library, with a bathroom off the side. Also under the loft is a pantry, opening off the kitchen area. Upstairs, at the rear of the loft, a closet-lined hallway serves as the second-story egress. Additional storage space is located under the eaves.

Dominating the great room is a Russian masonry heater and its chimney. We had lost the plans we had gotten from a friend for this heater, but since it was the same as the one in our last house, we were able to build it from memory. The heater is seldom used because of the solar gain we get in the house. If the heater is needed, a couple of armfuls of wood, burned at a high temperature, heat the stove's five tons of mass. The outside of the stove never gets too hot to touch, and will stay warm for two to three days.

The front of the house is all windows, which provide lots of light, as well as solar heating. The windows are regular, double pane glass. Pleated shades are used to keep excess summer and fall heat out and winter nighttime warmth in. We use an antique wood cookstove for fall, winter, and spring meals. This also adds heat to the house, so in the summer, we use solar ovens and a small, two-burner, propane stove.

The total area of the house is about 1,800 square feet (167 m2). If a passive solar house is too large, it will usually not maintain an even temperature, and if too small, will likely overheat. We have a very good ratio of window area to thermal mass to house volume. The

The underside of the PV rack showing its homemade mounts.

McCoy/Reising System Loads

Watts Hrs./Wk.

Watts Hrs./Wk.


VestFrost fridge, 12 cu. ft.

Renewable Energy 101

Renewable Energy 101

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.

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