Cellulose

Although the broad category of cellulose insulation includes a variety of products such as granulated cork, hemp fibers, straw, and grains, the most common and readily available cellulose insulation is made almost entirely from recycled newspapers, cardboard, waste paper, and wood pulp. Cellulose insulation is perhaps the best example of a significant recycled product in widespread use. Most is approximately 90% post-consumer recycled waste paper, with fire-retardant chemicals and, in some products, acrylic binders added.

“Mineral fiber materials take at least 25 to 30 times more energy to make than cellulose of equivalent R-value,” says Daniel Lea, executive director of the Cellulose Insulation Manufacturers Association, citing cellulose’s low-intensity manufacturing process and high recycled content.

Nowadays, blown cellulose is applied dry or merely damp, eliminating the extended drying times required for older, “wet” applications. Because of its relative high density and fire suppressants, this recycled newsprint product increases the fire resistance of building assemblies by 22% to 55%, per the Canadian National Research Council. It also provides a better air seal than fiberglass because of its higher density and slight dampness when applied, which tend to push the material into framing member penetrations.

As with cotton and wool, cellulose is an organic and flammable product that requires added biocides and flame retardants, usually borate and ammonium sulfate. Most cellulose installations are done by contractors using special equipment, but loose fill is also available that anyone can simply pour out of a bag. As with all other insulation products, installers should wear proper respirators as recommended by the manufacturer, especially since some people have sensitivity to newsprint ink.

Foam

Although R-values remain close to equivalent across all insulation products, expanding foam has an added benefit because of the excellent air seal it provides. Foams are two-part products that are mixed through a blowing mechanism and sprayed into the framing cavity. The two chemicals react and expand. As the foam expands, it fuses tightly around all pipes, ducts, and wires, creating an airtight seal that yields much higher thermal performance than R-value alone would suggest.

The adhesive quality of foam offers another benefit rarely associated with insulation: High-density foam insulation provides improved structural integrity that helps make a building a little stronger.

Nowadays, most foams use HCFCs as blowing agents, which are less destructive to the ozone layer than the old, and now banned, CFCs but still considered environmentally detrimental.

Foams that do not use ozone-depleting blowing agents include Icynene, which uses carbon dioxide and water; Air Krete, a foam produced from magnesium oxide (derived from sea water) and compressed air; and BioBased, which uses compressed air.

As a builder of low-cost houses, I look for the least expensive option to achieve the best possible results. For this reason, I often use high-density fiberglass batts coupled with an excellent sealing job. But when my company set out to build a LEED for Homes–certified demonstration house, we chose BioBased insulation as a high-performance alternative.