1,800 (Not-Yet-Finished) Square Feet for $50,000

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HOT WATER

The front (south-facing) surface of the roof has a 12/12 (45°) pitch, allowing the two flushmounted solar water heaters to lie at the optimum sunlight-catching angle for our area. We used Cornell 480s (list price $1,495 each from Cornell Energy, Inc., 4175 S. Fremont, Tucson, AZ 85714). They're commercially made, passive batch heaters-no moving parts! that are guaranteed not to freeze to -40°F. From spring through fall, we can rely on the 480s for all our hot water needs—as long as the weather is sunny. During warm-season cloudy spells, and all through the winter months, the Cornelis prewarm water that's then boosted to "hot" by an electric heater.

We estimate that the two collectors provide 60 to 70% of our hot water, for a saving of about $250 a year. Since Uncle Sam and Aunt North Carolina paid us back a total of 65% of the system's price tag through renewable-energy tax credits, the pair of heaters actually cost us only $1,000 and should thus pay for themselves within four years. And, so far, the collectors have been entirely maintenance-and trouble-free . . . even when the mercury hit -16°F last January! Mind you, that cold did freeze the pipes running across our attic (in spite of their double-layer foam insulation jackets). But since those lines were made of flexible polybutylene, they weren't damaged and worked fine once thawed.

OVERALL PERFORMANCE

We've been quite pleased with the energy efficiency of the house itself. As I mentioned before, it uses less than a third as much wood heat as our last home (which means I spend less than a third as many fall Saturdays chasing firewood!), and it also seems to distribute heat surprisingly well. I was afraid hot air would rise upstairs and overheat the second floor (my fix for that was"going to be a stairwell door). But so far-perhaps because of the first floor's massiveness and the airholding "wells" created by the big exposed ceiling joists—that hasn't been a problem. I'm still not sure if the heat that does reach the second floor will be evenly distributed. (The distribution was good last winter, but that doesn't count; there weren't any walls!) Too much hot air may go up around the chimney openingin which case, it'll just heat up the master closet! If that happens, I'll have to change the framing around the chimney in the second story to redirect the heat to the hall.

Another concern I've had is air quality. We intentionally didn't build the house up to superinsulation standards. It is still tight, though, so indoor air pollution could be a problem. To help avoid that, we were very careful not to use particleboard or other formalde-hyde-emitting materials . . . we employ electricity (not gas) for cooking and backup water heating . . . and we use our oven vent regularly. And, fortunately, our local concrete generally has a low radon content. I can't really be sure our indoor air is healthful without undertaking expensive tests, but it seems all right as far as we can tell. (We framed in wall openings for two air-to-air heat exchangers during construction, just in case.)

Although our primary reason for using Solarsoft's Sunpas/Sunop computer energy analysis program was to compare design options, the house has used about as much backup wood heat as that program predicted. Speaking of options, the computer told us that our residence would have an SSF (solar savings fraction) of 0.24 with conventional glazing . . . 0.32 with Heat Mirror windows (which cut solar gain some but reduce heat loss more) . . . 0.33 with movable insulation . . . 0.29 with a Trombe wall . . . 0.34 with water walls . . . and 0.57 with an attached solar greenhouse. This last estimate, however, is misleading. It assumes the greenhouse would be used solely as an overgrown solar collector—while I'd expect to return some house heat to the greenhouse on cold nights to keep its plants alive. [EDITOR'S NOTE: One source for computerized design analysis is Southeastern Solar Analysis, P.O. Box 1669, Skyland, NC 28776.]

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