The Mother Earth News Solar "Heat Grabber"

Image Gallery Once built, the Mother Earth News heat grabber should give years of dependable service. J. WEILAND

Some of the climatologists are predicting that the coming winter could well be colder than the last one. But even if that forecast comes true, you'll be a lot warmer during the clear-but-below-zero sieges ahead than you were during the frigid weather of last January and February, if your house or apartment has one or more unshaded southfacing windows and if you outfit those windows with the Heat Grabber. (See the Image Gallery for Heat Grabber plans or click here for larger plans you can order.)

Believe it or not, this simple and effective "window box" solar collector can be fabricated in just under an hour by an experienced home craftsman (or in less than two hours by the more fumble-fingered among us) for the astonishingly low price of $32.18 (see materials breakdown on next page, prices are from 1977). And once constructed, this sturdy unit should give years of dependable service.

The secret of the Heat Grabber's quick assembly and low cost is a new rigid foam insulation board manufactured by Celotex. This board, trade-named "Thermax TF-610," is impregnated with glass fibers for strength, faced on both sides with heavy aluminum foil, and available in thicknesses ranging from 3/8" to 1-7/8". Celotex actually markets the material as a replacement for the pressed fiber sheathing or "blackboard" now used by contractors in the construction of wood framed houses and does not recommend it for any other purpose. Mother Earth News researchers, however, have run heat and other tests on the insulation board and found it near-ideal for use in quick, easy and low-cost solar collectors such as the Heat Grabber.

Yes, the basic Thermax TF-610 sheet does have a slight disadvantage. Its aluminum foil surfaces can be punctured relatively easily by anyone intent on doing just that. There are, however, at least two remedies for this problem: [1] Substitute Thermax-610/.019 — which is the same foam, but faced on one side with a much heavier layer of aluminum—for the Thermax-610 specified here, or [2] use the Thermax-610 called for in our plans and protect the sides and bottom of the finished collector with a casing of scrap lumber. The second alternative will be less expensive than the first, but, really, neither course of action should be necessary unless you live in a high-vandalism area.

The ideal angle at which to position a southfacing solar collector (in the Northern Hemisphere) or a north-facing collector (in the Southern Hemisphere) is your latitude plus 10°. This adds up to 45° for Mother Earth News' North Carolina offices (which are situated 35° north of the equator) and that's the angle shown on the following plans. Please take this into consideration when making the cuts called for in Steps 3 and 6 in the diagrams in the Image Gallery.