A cold-climate heating scheme that makes use of the sun and the earth.
The "sun-earth connection' makes this solar-heated house the next step up the solar evolutionary ladder, claims its designer, Tom Smith. The connection Smith refers to is the continuous air space running from the peak of the south-facing sunroom down to the soil beneath the house.
Intended for cold-winter climates, the design is noteworthy for its simplicity. It does away with some of the solar design features that have become well known in recent years: it has no superinsulation, no additional thermal mass (like trombe walls, rock bins, or water columns), no double-shell construction, and no extensive amount of south-facing glass.
Running the length of the south side, the sunroom both heats and insulates the rest of the two-year-old house. It collects heat through a set of surprisingly small windows, equal in surface area to only 15 percent of the house's total square footage. (Smith calculates that 15 percent is optimum for gaining heat by day without losing too much at night.) A series of windows and doors opens the room to living quarters in the two-story house.
The heat moves from the sunroom to interior spaces by natural convection or with the aid of paddle fans, then stores in the mass of the house itself. At night, with doors and windows closed, heat stays in.
On extremely cold nights, the earth below the crawl space contributes unexpected heat. Because the earth is protected by the house, it remains a fairly stable 50| no matter what the outside temperature drops to. If the air temperature in the sunroom drops below 50|, the heat in the earth begins to convect into the air. Warmer air rises to the sunroom through spaces between the 2-by-6 decking.
Common-sense elements such as minimal windows on the heat-losing north side, appropriate (R-30) insulation for the Lake Tahoe climate, and an air-lock entry kept construction costs reasonable compared to houses with superinsulation and additional storage mass. To reduce heat loss, Smith insulated the exterior of the perimeter foundation; to keep out moisture, he covered the crawl space and underside of the floor joists beneath living spaces with a plastic vapor barrier.
Owners Beth and Barney Lovelace have a woodstove for back-up heating. In the summer, they can draw cool air from the crawl space by opening the top windows in the sunroom.
Photo: Crisp lines of shingled exterior accent south side of house. Limiting amount of glass on this side keeps sunroom from overheating or losing heat too fast. Sketch illustrates flow of heat
Photo: Wood-paneled sunroom has slight spaces between floorboards to allow air movement from the crawl space below. Doors and windows on right open to let heat pass into house
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|Date:||Dec 1, 1984|
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