How to Build A Window Box Solar Collector

If someone told you that you could make a powerful window box solar collector that fits inside an ordinary window and delivers heat without using power, you probably wouldn’t believe it. Now imagine that they also told you that this window box solar collector could be constructed in only an hour for less than $35.

It may sound incredible, but it’s true. What’s more, this passive solar window box collector has been around for several years now. The full instructions can be found at http://www.motherearthnews.com/Do-It-Yourself/1977-09-01/Mothers-Heat-Grabber.aspx, but a quick overview here will give you a sense of why it works, how to do it, and whether it can be useful in your own home.

The window box passive solar collector is made possible by a new rigid foam insulation board manufactured by Celotex called Thermax TF-610. Thermax insulation board is marketed to contractors to use instead of pressed fiber sheathing or ‘blackboard’. Thermax TF-610 is mostly used in new home construction and is sold mainly for commercial use. Most homeowners have therefore never heard of it and have no reason to be interested in its unique properties.

A Thermax TF-610 insulation board is laced with glass filaments for strength and faced on both sides with aluminum foil. Available in 3/8 inch to 1 7/8 inch thicknesses, Thermax boards are extremely efficient at storing heat. Although they are not made or advertised for use for building passive solar collectors, they are excellent for this purpose and there is no harm in using them this way.

To build your window box solar collector you use a sheet of Thermax TF-610 as a divider inside a simple homemade box topped with glass. The top of the box has an open space and a ‘lip’ that faces inside. As the sun shines on the TF-610 divider on a bright winter day, heat inside the box builds up and is released into your room from the inside opening at the top. Basically what you are doing is creating a loop that forces the passive solar heat to rise and be released into your home.

The DIY window box solar collector works best in sun-facing windows and is a good project to combine with thermal shades or drapes. On cloudy cold days you close up the insulated drapes or shades, and then when the sun comes out, you open them and let your window box solar collector do its work. If you have one or two sun facing windows, this passive solar strategy can result in significant home heating saving, and it’s so very simple.

Often the argument made against solar technology is that it is too expensive and inefficient, but this kind of talk usually ignores passive solar, which is powerful, free, and simply requires and bit of planning and ingenuity. People have been using passive solar for affordable alternative home heating for thousands of years. It’s there for the taking. All you have to do is think it through.

For a complete list of materials and simple construction tips, go to http://thearchdruidreport.blogspot.com/.