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The choice and placement of windows is, Smith says, every bit as important as insulation. Naturally, the south-facing windows are one major consideration, since they're at the "business end" of the house. Double-pane glass is used here (although single-pane glazing would cost less and admit more heat) because the loss of stored warmth through thinner material at night would exceed the slight gain reaped during the day. The east-and west-oriented windows are also double thick, and the north side of the house doesn't have "viewports" at all (though double- or triple-pane glass could be installed if desired).

As a final precaution against the infiltration of cold outside air, the owner used caulking or weatherstripping on everything "openable" . . . including the two doors that constitute the double-lock entry, or vestibule. In this way, all drafts are eliminated, and the "airlock seal" goes a long way toward keeping the house comfortable . . . especially when the outside temperature plummets to below freezing.

STANDARD CONSTRUCTION ... AND REASONABLE COST

Even though the operation and design of the naturally convective heating/cooling system are unorthodox, the construction techniques used in the house are not. Its foundation—aside from the insulation that shields it from the earth—is nothing more than block and poured concrete. And resting on this substructure is a network of piers which not only support the floor of the house, but also hold it several feet above the foundation . . . providing room for the necessary two feet of heat-storing backfill and circulation air space. This setup, then, is no different from a standard crawl space in any conventional dwelling.

Orthodox construction methods were used in the framing, too. The walls of the outer shell are 2 X 6 studs, and 2 X 12 beams are used in the ceiling (to support the heavy snow load). All windows and glass are standard commercial units, as are the prehung doors. The roof of the inner shell is merely fastened to the bottom of the 2 X 12 beams, and the north side of this interior structure is simply an extra 2 X 4 stud frame wall. Actually, then, the "inside layer" isn't load bearing, so it's no more difficult (or expensive) to construct than any other interior wall scheme.

Of course, there are those who will maintain that the cost of the additional materials required for this inner shell outweighs its advantages. Not so, claims Mr. Smith ... he insists that the overall expense is lower because a large saving is realized by the elimination of expensive heating ductwork within the walls of the house.

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