DIY Solar Heating with the Heat Grabber

Build this DIY solar heating collector, the Heat Grabber is a "window box" solar collector you can fabricate in under an hour.

| September/October 1977

You can build this super-simple and super-effective DIY solar heating collector in just one hour!

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 south facing 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" DIY solar heating 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 inches to 1-7/8 inches. 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 south facing solar collector (in the Northern Hemisphere) or a north-facing collector (in the Southern Hemisphere) is your latitude plus 10 degrees. This adds up to 45 degrees for MOTHER EARTH NEWS North Carolina offices (which are situated 35 degrees 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.

1/22/2015 8:08:34 AM

Wow, what a great idea. I've been reading about electric underfloor heating mats on I wonder if this would generate enough power to run some matting in small bathroom? Either way, this is a fantastic way to get into solar and start saving on your energy bills - without the initial expense. Brilliant, keep up the good work!

12/22/2014 5:14:53 PM

Does this not leave the window easy to open by intruders? Anyway, our windows here in Denmark are hinged at the top and open out. So not sliding onto this construction, but leaving an opening at the sides.

8/23/2014 10:25:29 PM

Hello! I'm in process of building a window mounted solar heat grabber as per MotherEarth news... I'm adding a middle heat collector plate on top of my 'foamboard' divider and I'm planning on putting 'baffles' in... These baffles would go on top of the divider and raise the metal heat collector (aluminum printing plate (0.008" thick)) about 3/4"-1" (another plan using this metal plate uses (3/4") but I was thinking of using a (1") space - not sure what the difference would cause)... My question is: my box is going to be about 27" wide and about 66" long - with a 4" space at the bottom the metal plate will be about 27" wide and about 62" long... I'm not sure how wide to make each baffle, how many baffles to use, how long across the face to make each baffle (which would say - how long an opening at the end of each baffle)... I am also thinking of putting baffles on top of the metal plate and making them the opposite of the baffles under the plate and then using your idea of putting weather stripping on top of these to seal better with the glass... Also, I've read where you can attach a Solar Fan to the hot-air outlet to increase the consistency of hot-air output flow... I'm wondering what 'fan' is the better/best to use for this purpose and where to find one, ie. Walmart, etc (Or make you own from a computer fan - how would this be done)...?? Any Suggestions/Ideas would be greatly appreciated...

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