How to Make Cellulose Insulation

You could even have Jesse J. Savell (See Building Passively Heated and Cooled Houses) put up one of his energy-miser dwellings for you.

R Rating of Insulation Materials

• Fiberglass bait R-3.33
• Mineral wool R-3.33
• Sawdust R-2.44
• Loose fill fiberglass R-2.22
• Vermiculite R-2.08
• Wood R-1.25

What if You Can’t Afford a New Energy-Efficient Home?

“Well, that’s all very nice,” a number of you have recently told us, “and we certainly thank MOTHER for bringing these new breakthroughs in energy-efficient housing to our attention. But we can’t afford a place like that just now. We’re going to have to stay where we are for a while. And we aren’t even sure we can afford that! What can we do right now to cut the amount of energy we’ll have to use to keep our current home warm this winter? And don’t tell us to have insulation installed . . . because we can’t afford a bill for $300 or $400 or more for that either and, besides, most of the contractors who install insulation have a backlog of orders as it is.”

You Can Make and Install Your Own Insulation!

But who says you have to pay today’s outrageous prices for insulation? (One contractor we know hiked his prices three times in the month of August alone!) And who says you have to put your name in the pot and then patiently wait days or even weeks until an insulating firm can get to you?

Nobody, that’s who! Not when you can quickly, safely, and easily manufacture one of the best insulations ever devised. Not when you can make that insulation to equal or far exceed the specifications (fireproofing, vermin-proofing, etc.) of any manufacturer in the field. And not when you can do it all by yourself in your spare time and for just one-fifth or less of the out-of-pocket cost of what a probably inferior insulation would set you back if you hired a contractor to install it for you.

Yeah, sure. This all sounds too good to be true. But that’s only because you’ve spent your whole life being brainwashed into The Perfect Little Consumer. And that’s not your fault. Nowadays, even the mechanics and shop magazines (which, 30 years ago, would have given you exactly the sort of information that MOTHER is now gonna lay on you) maintain the polite — and, for you, expensive! — fiction that insulation somehow isn’t actually insulation unless it comes in a trademarked bag and a “real” contractor installs it for you.

Homemade Insulation Works

Well, folks, that particular myth just ain’t true. There may well be a bewildering selection of insulations on the current market. And some of them definitely are more fireproof . . . or more vermin-proof . . . or more water resistant . . . or easier to install in new construction … or easier to blow into old walls . . . or more this or less that than any of the others. But when it comes to downright cost effectiveness (even at contractor’s prices), all-around availability, ease of installation under almost any conditions, minimum toxicity, and absolute minimum use of the planet’s resources in a highly “natural” way . . . the all-time winner and champion always has, still is, and probably always will be . . . plain ole cellulose fiber.

Yep. Cellulose fiber. Which is nothing but old newspapers, cardboard boxes, and other kinds of waste paper . . . ground up fine . . . and treated with some readily available and inexpensive chemicals to make it self-extinguishing and vermin-proof.
It’s hard to think of a more readily available, a simpler, or a less costly insulation . . . yet the “R” factor (the higher the “R”, the better) of each inch of cellulose fiber is a very respectable 4. Even when you buy it ready-made, then, this is an extremely cost-effective insulation. And when you make it yourself your savings can really skyrocket!

How to Make Cellulose Insulation

That “makin'” is not in the least complicated either. as MOTHER’s researchers recently proved to themselves. It mainly consists of [1] gathering together enough bone-dry scrap cardboard or old newspapers, [2] running them through a farm-type hammermill set for its finest possible grind, [3] mixing in — either before or after the cellulose is ground enough fireproofing and vermin repellent to protect it, and [4] putting the finished insulation where you want it.

The only “complication” we’ve found about this whole do-it-yourself project is that nothing less than a real, live, genuine hammermill will handle the grinding of the cellulose the way it should be handled. Little garden mulcher-type “shredder grinders” simply won’t chew either paper or cardboard into the fluffy, fuzzy mass of fibers that makes the best insulation. (Rule of thumb: If you can still read whole words on your ground newsprint, it wasn’t ground finely enough.)

What you want to do then (if you don’t already have one) is rent or borrow or barter some time on one of the feed-grinding hammermills that many farmers own (the units are very much like the leaf grinders and limb shredders that you frequently see utility line crews using alongside the road).

Take care, too, to see that all the paper and cardboard you feed through the grinder is bone dry and stays that way (moisture can cause the shredded cellulose to “compost”). And always wear a respirator mask to protect your lungs from both paper dust and fine chemical particles as you work.

That last caution, by the way, is by no means meant to suggest that the chemicals used to treat the cellulose are in any way highly dangerous. Boric acid, the fire retardant used by most manufacturers of this insulation, is — as you probably know — so mild that doctors have frequently prescribed it as an eyewash. If this particular fireproofing is in such short supply, MOTHER’s research crew has tested and recommends fireproofing cellulose insulation with borax. And borax, as you’re surely aware, is so safe that it’s the major ingredient in some laundry soaps.

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.

Homemade Insulation: The Price is Right

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, 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 inch-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 inches of 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, that — since 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.

The idea seems to have merit and our propane torch tests indicate that approximately another one cent in chemical costs can be shaved off every square foot of 6 inch-thick attic insulation with no reduction in fireproofing value when this method of distributing the borax and aluminum sulfate is used. That increases the saving on the cellulose fiber’s installation cost for 1,300-square-foot house from $253.50 to $266.50. Not a great additional saving, to be sure, but one that you should know about.

Homemade Insulation Installation

MOTHER’s homemade cellulose proved just as easy — no more and no less — to install as its commercially available counterpart. It’s extremely easy to pour and spread around between the joists and other structures of an attic. And it’s just as easy to add even more later, anytime you wish.

Putting the insulation into walls and other closed spaces is somewhat more difficult. This usually requires that a series of holes be drilled through a house’s exterior siding (or that some of the siding actually be removed) so the material can be forced into the cavities with an insulation blower. Building supply stores sometimes have these blowers for rent . . . and some clever do-it-yourselfers have actually forced their cellulose into walls with a hose attached to the exhaust end of a heavy-duty vacuum cleaner.

One final point: Any cellulose insulation — whether of the store-bought or I-made-it-myself variety — will absorb moisture when exposed to dampness of any kind. This, of course, reduces the material’s “R” value . . . and cellulose fibers should be used to insulate only those attics, walls, crawl spaces, etc., that you know will remain dry.

Chemicals Added during Grinding Burn Test

• First test 10 lbs. paper, .5 lbs. aluminum sulfate, and .25 lbs. borax burned like crazy
• Second test 10 lbs. paper , 1lbs. aluminum sulfate, and .5 lbs. borax burned
• Third test 10 lbs. paper, 1.5 lbs. aluminum sulfate, and .75 lbs. borax burned slowly
• Fourth test 10 lbs. paper, 2 lbs. aluminum sulfate, and 1 lbs. borax burned very slowly
• Fifth test 10 lbs. paper,  2.5 aluminum sulfate, and 1.2 lbs. borax self-extinguishing
• Sixth test 10 lbs. paper,  3 lbs. aluminum sulfate, and 1.5 lbs. borax self-extinguishing

Chemicals Sprinkled on Cellulose After Insulation in Place Burn Test 2

Note: The Insulation used in this test varied from 4″ to 6″ in thickness .

• First test 1 oz. of Borax and 2 oz. aluminum sulfate barley burned
• Second test 2 oz. of Borax and 4 oz. of aluminum sulfate self-extinguishing
• Third test 3 oz. of Borax and 6 oz. of aluminum sulfate self-extinguishing

Originally published as “How to make and install your own insulation for 5 cents or less a square foot” in the 1977 November/December issue.