Homemade Cellulose Insulation

John Landers

It probably never occurred to you that you can make your own cellulose insulation. The process is fast, safe and relatively easy. The insulation is just as good as or better than insulation you buy on the market. It is fire retardant and resists insects and rodents.

You will follow the same basic procedures for installing this type of insulation. Like you would with other insulation products, make sure that the application area is air- and watertight. Use spray foam and sealant as necessary to seal any openings or cracks


Cellulose insulation is made out of newspapers, cardboard containers and other paper waste products ground up into fine slivers of paper fibers. The fibers are treated with some safe chemicals, which make it fire-resistant and resistant to vermin.

The R-value, which is the measurement of an insulation resistance to heat loss, is favorable to fiberglass batt insulation. Cellulose has an R-value of 3.1 compared to an R-value at 3.2 for fiberglass batt. Cost-wise, cellulose insulation has always been very reasonable. If you decide to manufacture the insulation yourself, you will spend 20 percent or less what you would pay to have cellulose insulation installed by a contractor.

The Process

Wear a respirator as you work. There are fine paper particles and other dust particles, which may be airborne during the manufacturing process. To grind the paper into a fine fibrous product, you will need a hammermill. A hammermill is a machine that consists of a rotating steel drum with hammers secure to the mechanism. The drum rotates at a very high speed; as paper is feed into the hopper, the hammers strike down on the product simultaneously shredding the paper and forcing it through specially sized screens.

Some people try using garden variety mulching machines, but the machine is not capable of chomping and crushing the cardboard and paper scraps into the shriveled mass of paper fibers, which are the hallmark of the insulation. As a general rule, the print on the shredded materials should not be readable.

It is essential that the paper products and cardboard scraps that you feed into the machine be totally dry. Take care to keep the material dry from the manufacturing process to the actual installation. If the material gets wet, your homemade insulation project will transform into a homemade “compost endeavor.”

The most common product mixed with cellulose to make it fire retardant is boric acid. As you know, boric acid is often prescribed for use as an eye wash. It may be difficult to find enough for you homemade cellulose insulation project. An alternative to boric acid is borax. Borax is a key ingredient in many of the mass-market laundry soaps.

Use aluminum sulfate to make the homemade cellulose insect and rodent resistant. If you are installing the insulation in recreational vehicles or metal buildings, use a 50/50 mixture of aluminum sulfate and lime. The lime will nullify the corrosive affect of aluminum sulfate to the metal. Feed the chemicals into the hammermill so that the ingredient mixes with the paper and cardboard scraps as it is going through the shredding process. This completes the homemade cellulose insulation process. The insulation is ready for installation into the designated wall or floor cavities.