Reduce Heat Loss With Thermal Panel Window Insulation

Two simple, inexpensive ways to cover large windows.


| January/February 1984



Pop In Shutter Airtight Corner

A completed, airtight corner.


MOTHER EARTH NEWS STAFF

You may recall that in The Homemade Thermal Shade we presented three varieties of fabric thermal shades, all of which rang in at about $10 a window. (In case you missed that heat-saving advisory, we should tell you that the price is very modest: Commercial window insulators can cost $90 or more!) Well, in this installment, we're going to present two other methods of thermal panel window insulation that are particularly good for covering large expanses of glazing. And in keeping with our previous models, these heat-holding panels can be made for little more than $10 a window.

Our shutters are primarily composed of expanded polystyrene insulation, a foamlike material that comes in 4' X 8' sheets and is often used in the building trades. "Beadboard", as it's known, is rigid yet light in weight and easy to work with. It makes a durable, inexpensive, and simple-to-install thermal shutter. Polystyrene is rated at R-4 to R-5 per inch (so in the case of the 1 1/2"-thick pop-in shutters detailed below, the insulative value would be about R-7).

The MOTHER EARTH NEWS thermal panels are pretty much of the "generic" variety, but you can fancy up these no-frills shutters with paint, fabric, or wallpaper if you like. The foam panels may be left in the windows to forestall heat loss both day and night . . . or you can remove the cover-ups (which obviously do block out light) to let in the sun's rays during the day. If you decide to keep the shutters in the windows for long periods of time, you should check occasionally for mold or mildew caused by condensation of moisture. Wiping off window surfaces with a dry cloth and dabbing diluted chlorine bleach on the sills can help prevent such problems.

Pop-in Shutters 

Our first thermal project this go-around was designed for a 3' by 7' expanse of glass that included one 32" X 36" unit and two 23" X 36" windows. To cloak these panes, we decided to make three pop-in shutters . . . beadboard blocks lodged in a wooden frame and wedged in the window. The sills and casings we worked with had adequate depth to accommodate our shades, but you could insert the panels in a window without a casing—such as those found in a mobile home or on a brick or stone-veneered wall—if you mounted an exterior frame around the window first.

For the three window coverings, we purchased five 8' lengths of 1 X 2 fir (at a total cost of $9.60) and two sheets of 3/4" polystyrene at $8.29 per sheet. Thus, the cost of the basic materials came to $8.73 per window . . . and there was enough lumber and headboard left over to cover at least one more window. We also used four 2 1/2" inside corner braces ($1.79 per package of four) and one tube of Quick Bond Panel and Foam Adhesive ($1.39) to complete each window. (Of course, you can use a different kind of glue than the one we chose. If you do, be sure to spot-test it first on some polystyrene to make certain it doesn't damage the beadboard.) That brought the total cost for each of the three thermal shutters to $11.91.

It took us a little less than two hours to put together our first insulative panel, but—with some experience—you could easily shave time off that figure.





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