What Is Blown Insulation Made Of?

New foam insulation fills crevices and envelopes odd shapes.

Blown insulation is shredded or recycled materials remanufactured into forms that can be blown through a hose into irregular spaces. Research in older materials provides information so safer, more effective and easier to use materials can be developed.

Traditional Materials

Rock or mineral wool has been used for insulation since 1850. Rock wool uses waste slag from steel furnaces. Some rock wool contains limestone and basalt or diabase, another volcanic rock. Ingredients are heated and spun into fibers, chopped and blown between rafters in roofs and studs in walls. The material looks like clumps of white to gray cotton.

Sustainable Materials

Cellulose insulation is made of recycled newspaper, washed and treated with boron compounds that act as fire retardants and insect repellents. Cementitious foam uses magnesium from sea water. Finely spun perlite, a lightweight volcanic product familiar to gardeners, is used to fill cavities in cement blocks. Blown fiberglass material is made from silica; today's materials use 20 to 30 percent recycled glass.

Foams

Polyurethane foams are new insulating sprays that form their own air and moisture barriers, expanding to fill joints and cavities. Early foams contained HCFCs or formaldehyde, but today's foams are mostly free of these dangerous compounds.

References

• Inspectapedia: What is Rock Wool Insulation?
• Sustainable Sources: Insulation
• Washington State University: Inspecting Attic Insulation
• National Association of Home Builders Toolbase Resources: Insulation Alternatives: Sprayed Foam Insulation
• Home Energy Magazine Online; Cheating -- The Insulation Industry's Dirty Secret; Michael Uniacke; November/December 2000