THERE'S A SOLAR HEATED HOUSE ALIVE AND WELL IN PRESCOTT ARIZONA

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The "Prescott Solar House", as it's come to be known, wasn't originally planned to be a solar-heated structure at all. The residence was initially designed as more or less a "conventional" dwelling by local architect George Allan for Mr. and Mrs. Robert Grieve.

The idea of heating the building with solar energy was raised only after the structure's design was "set". At that time, the Grieves asked 'us-a group of solar energy enthusiasts-to conduct a feasibility study on their house. That study convinced us that although it was located on steep mountain terrain-the home's orientation and structure did seem to favor retrofitting a solar space-heating system to the residence. In addition, Prescott's climate seemed almost ideal for the operation of a sun-powered furnace. We decided to give the idea a try.

The Grieve's house is sited on steep terrain that slopes southeasterly. The residence is oriented 40 degrees east of south and the largest area of the roof-which has an 11-degree pitch faces southeast. Due to the constraints of the site and our construction budget, we decided to locate the building's collector on its roof. This was not an ideal choice for at least two reasons: Solar collectors make best use of the sun when they're

[1] faced full south or southwest and
[2] set up at an angle of approximately 60 degrees. The roof on which we proposed to locate our flat-plate collectors was a long way from either of those optimum conditions but installation simplicity and low cost won out over operating economics. In short, the cost of orienting the collector for maximum efficiency would have been prohibitive, so we settled for a "second best" that was guaranteed-in advance-to cut the effectiveness of our collection panels by approximately 40%.

The rooftop collector is made up of four bays, each eight feet wide and thirty-two feet long (with a one-foot-wide walkway between bays for maintenance). The area covered with glass totals out to 1,024 square feet and the panes are placed on a typical greenhouse frame module of wooden 2 X 4's-set on 16-inch centers which run to the roof's ridge. The pieces of glass are overlapped like shingles and closed at each joint with tube caulking. Greenhouse bar cap. caulking (which comes in rolls) and aluminum bar caps are used to seal the glass to the 2 X 4's.

The heat-absorbing surface in the bottom of the collector is actually laid directly on the roof of the Grieve house. The roof itself is made up of typical wood frame construction covered with a one-half-inch-thick plywood deck. Two 40-pound base sheets of roofing with a 120-pound black cap sheet form the roof's "real" surface and two layers of metal (plastering) lath, painted black, act as the absorber.

At the time this article was written, we had operated the Prescott solar home's collector for four full months with no glass breakage and no apparent weathering of any of the flat-plate furnace's components.

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