Cellulose

Cellulose spray insulation is our insulation of choice. It is not appropriate for all applications (see section on spray foam) but typically cellulose is the greenest and most cost-effective insulation solution. Cellulose is a blown-in insulation that looks grey and fluffy. We use stabilized cellulose which we install with a little moisture in order to keep the dust to a minimum and to prevent settling.

Cellulose is composed of 85% post-consumer papers (newspapers, yellow pages, etc) with a 15% borate additive. Compare this recycled content to fiberglass which has at most 40% recycled content and foam which has virtually none. Furthermore, cellulose insulation takes less energy to make than any other insulation material. In fact, fiberglass takes 10 time more embodied energy and foam takes up to 64 time more.

The borate that is added to the cellulose acts as an effective fire-retardant. Studies have shown that a house with cellulose insulation in the walls will withstand a house fire much better than a house without insulation. We did our own experiment and tried lighting the cellulose with a blow-torch; as promised the cellulose charred but did not catch fire. Another benefit of the borate mixed with the cellulose is that it acts to inhibit mold and repel rodents. Unlike fiberglass, which rodents love to use for nests, rodents will not borrow through cellulose.

Cellulose blown into an attic is fluffy and has air pockets that slow the movement of heat. Wall insulation is installed very differently so that it has a high density, completely fills the bay and does not settle. This technique is called “dense-pack” wall insulation. In addition to providing excellent thermal protection, dense-pack wall insulation provides significant noise reduction. In fact, cellulose is approximately three times denser then fiberglass and can deaden the sound through walls and between floor levels.