A cold-climate heating scheme that makes use of the sun and the earth The “sun-earth connection’ makes this solar-heated housethe next step up the solar evolutionary ladder, claims its designer, TomSmith. The connection Smith refers to is the continuous air spacerunning from the peak of the south-facing sunroom down to the soilbeneath the house. Intended for cold-winter climates, the design is noteworthy for itssimplicity.
It does away with some of the solar design features thathave become well known in recent years: it has no superinsulation, noadditional thermal mass (like trombe walls, rock bins, or watercolumns), no double-shell construction, and no extensive amount ofsouth-facing glass. Running the length of the south side, the sunroom both heats andinsulates the rest of the two-year-old house. It collects heat througha set of surprisingly small windows, equal in surface area to only 15percent of the house’s total square footage.
(Smith calculates that15 percent is optimum for gaining heat by day without losing too much atnight.) A series of windows and doors opens the room to living quartersin the two-story house. The heat moves from the sunroom to interior spaces by naturalconvection or with the aid of paddle fans, then stores in the mass ofthe house itself. At night, with doors and windows closed, heat staysin. On extremely cold nights, the earth below the crawl space contributes unexpected heat.
Because the earth is protected by thehouse, it remains a fairly stable 50| no matter what the outsidetemperature drops to. If the air temperature in the sunroom drops below50|, the heat in the earth begins to convect into the air. Warmer airrises to the sunroom through spaces between the 2-by-6 decking. Common-sense elements such as minimal windows on the heat-losingnorth side, appropriate (R-30) insulation for the Lake Tahoe climate,and an air-lock entry kept construction costs reasonable compared tohouses with superinsulation and additional storage mass. To reduce heatloss, Smith insulated the exterior of the perimeter foundation; to keepout moisture, he covered the crawl space and underside of the floorjoists beneath living spaces with a plastic vapor barrier. Owners Beth and Barney Lovelace have a woodstove for back-upheating.
In the summer, they can draw cool air from the crawl space byopening 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 orlosing heat too fast. Sketch illustrates flow of heat Photo: Wood-paneled sunroom has slight spaces between floorboardsto allow air movement from the crawl space below.
Doors and windows onright open to let heat pass into house