Cellulose, and Airkrete foam are a couple of the most common types of blown- and sprayed-in insulation materials in the retrofit market in. And it is worth it. Retrofitting insulation into existing walls and attic space can achieve a 20 to 30 percent savings on heating bills. The learning curve and the inconvenience factor make most other blown-in applications impractical for a homeowner, and spray-in insulation should be left to the pro.
Cellulose is composed of up to 85 percent recycled newsprint. The remaining content is commonly a mixture of borate and ammonium sulfate that functions as a fire retardant. These chemicals also deter rodents, insects, and mold. Avoid materials containing formaldehyde and mineral fibers. Dry cellulose is very popular for blown-in insulation applications. Cellulose’s small particles fill voids and corners well as the material is shot into the walls. Dry cellulose offers an “itch free” installation, but respirators and safety goggles must be worn during the process. Cellulose dust is fine and tends to take a long time to settle.
Airkrete cementitious foam is a magnesium-based product that is derived from seawater. Because of its consistency, foam is the most effective product for retrofitting into existing walls. Foam will work its way around any obstacle, providing a near-100 percent wall fill (cellulose, for example, may not fill completely around bundles of wires or pipe runs and leave random voids). Unlike bottled foam insulation used to seal small gaps around pipes and wiring, it does not shrink or expand. Airkrete cementitious foam is the most costly insulation to retrofit, but is the most benign in regards to indoor air quality; when it is being applied into a wall there is no dust.