Yes, Virginia, There is Free lunch: It's Called the Solar Greenhouse!

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Since I don't use a backup heater, my growhole qualifies as a solar greenhouse (of a rather unsophisticated type). While such a facility has definite advantages, it has some drawbacks as well . . . most notably the fact that some of the heat collected in cold weather is vented outside and wasted. On many a day last winter, when the Ashley heater in our home was consuming firewood by the cord, I regretted that I hadn't built the greenhouse in such a way that it could spill its excess warmth into the house.

Then, at a recent solar energy conference, I met Bill Yanda . . . a man who has pioneered the construction of solar greenhouses in New Mexico, specifically as a means of providing low- and middle-income families with auxiliary heat in winter and with food all year long.

In July of 1974, Bill received a small grant from the Four Corners Regional Commission to construct and supervise the initial operation of 11 greenhouses in various villages of northern New Mexico. These units are located in several different climatic and geographical locations, ranging from altitudes of less than 6,000 to over 8,000 feet . . . from the lowlands around the Rio Grande all the way to the mountain community of El Valle, which has an outdoor growing season of less than 90 days.

The idea behind Bill's greenhouse-shown in Fig. 1-is simplicity itself: An ordinary stud framework is built onto the south wall of a home, and covered with a double layer of Filon or Lascolite greenhouse-grade fiberglass sheeting. (Filon and Lascolite are trade names for products which differ about as much as Fords and Chevrolets. These materials have a life expectancy of up to 20 years, are specifically designed for the spectral requirements of plants, and-unlike glass-are virtually unbreakable.)

The greenhouse is vented into the dwelling through existing doors or windows, or with specially constructed ventilator flaps, and additional vents are included to control the add-on structure's temperature in the summer when the growing area is closed off from the home. Various methods of shading are also provided to keep the summer temperatures from getting out of hand. The accompanying photos give an idea of some of the many possible variations in design.

The fabrication of such a unit is straightforward and simple, within the skill range of even the most inexperienced handyman. Bill estimates that the cost of the average structure comes to about $1.86 per square foot, and quickly adds that the price could be considerably less for experienced scroungers.

Yanda's greenhouses can be found coupled to almost any type of architecture: built against the side of an old adobe house in downtown Santa Fe, or onto an aluminum-skinned mobile home out in the boondocks. Even if your dwelling doesn't have a south-facing wall, a southeastern or southwestern exposure will serve almost as well. About the only ironclad "no-no" is a site that looks north (unless you're interested in raising nothing but shade-loving houseplants).

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