HOW TO MAKE AND INSTALL YOUR OWN INSULATION...FOR 5? OR LESS A SQUARE FOOT!

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The aluminum sulfate listed here as a rodent and insect repellent can best be put into perspective when you realize that it's one of the chemicals generally called "alum" (even though the term is more accurately descriptive of a double sulfate of ammonium or a univalent metal-such as sodium or potassium-and of a trivalent metal, such as aluminum, iron, or chromium). The chemical, in short, is an astringent and, as such, may be safely handled without gloves (although we do recommend keeping its dust out of your lungs and away from your mucous membranes). Do bear in mind, however, that aluminum sulfate is highly corrosive to most metals ... and, for this reason, an equal weight of ordinary lime (which neutralizes the alum) should be substituted for half the aluminum sulfate when your treated insulation will be used in metal buildings or mobile homes.

THE PRICE IS RIGHT

As the first chart reproduced here indicates, MOTHER's researchers ground up and tested six batches of cellulose fiber ... each of which contained a different percentage of vermin repellent and fireproofing. After trying to ignite all the test mixes with a propane torch and observing the results (see chart) , we recommend that a minimum of 25 pounds of aluminum sulfate (or half aluminum sulfate and half lime) and 12 pounds of borax be mixed into every 100 pounds of ground newsprint or cardboard.

This figures out to a total chemical cost (at $8.50/100 pounds for aluminum sulfate and $15.00/100 pounds for borax) of less than $4.00 per 100 pounds of paper that is treated ... or 5¢ a square foot when an attic is filled with a 6"-deep layer of the cellulose fiber (which produces a total "R" factor of 24, and that's very good). This compares quite favorably to the 24-1/2¢ a square foot that a local contractor charges to fill an attic space with only 5" of a commercially manufactured cellulose fiber. On a 1,300-square-foot house, that's an immediate saving of $253.50 right there ... and you're getting one-fifth more insulation to boot!

The chemicals were mixed into our first six test batches by shaking them onto the paper as it was fed into our hammermill. This is exactly the method used by the commercial manufacturers of cellulose fiber insulation that we've visited ... but it does have a minor drawback: The chemicals do tend to settle out of the mix as it's handled and, if some care isn't taken, more of the fire retardant than we like to see will wind up at the bottom of any space filled with this insulation.

For this reason we tried grinding some cellulose all by itself, putting it in a pile, and then sprinkling controlled amounts of borax and aluminum sulfate across the surfaces of the fiber. We were figuring, of course, thatsince flames burn up-it would take less of the chemicals to fireproof the pulverized insulation if those chemicals were put on top of the cellulose, instead of being allowed to sift to its bottom.

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