The Best Insulation for Your Home
(Page 2 of 3)
November/December 2006
By Susan Lahey
The more environmentally sound versions are low density, meaning they also have a lower R-value, closer to the range of 3.2 to 4.5 per inch rather than the 6 or 7 R-values found in denser, more toxic varieties. Because they actually block air flow much more than other types, however, the R-value is only part of the reason to consider foam insulation. Another drawback is that during installation foam insulation outgases toxic chemicals. Once it cures, it becomes inert.
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Another type of foam insulation, polyisocyanurate, is a rigid foam good for exterior retrofitting, often on roofs, with an R-value of 6 to 7.5 per inch. "Polyiso," as it's called, was formerly created with ozone-depleting HCFCs as blowing agents, but the new "green polyiso" uses hydrocarbons that don't emit greenhouse gases.
Cementitious foam-a nonflammable, extremely stable insulation-is made of magnesium oxide derived from seawater. When dry, it's inert and should have no impact on chemically sensitive people.
Cotton: The insulating fabric
Cotton insulation is made from remnants that denim manufacturers and other textile plants otherwise would have thrown away. It's sold either as loose fill or in batts, like fiberglass, but without chemical or respiratory irritants. Like other textile products, cotton insulation is treated with boric acid as a fire retardant, pest repellent and an antifungal agent. Unlike most pest repellents and antifungals, boric acid is fairly nontoxic.
Cellulose: Read all about it
Cellulose insulation consists of 80 to 90 percent post-consumer recycled newsprint, cardboard and paperboard. It's sometimes applied by making it into a wet newspaper mush and spraying it into open wall cavities; sometimes it's shredded dry and used in attics as loose fill. Like cotton, cellulose insulation is often treated with boric acid.
Although cellulose insulation is earth friendly and benign, some chemically sensitive people are bothered by outgasing from the newsprint ink. Because it's made of wood fiber, cellulose can absorb more moisture than most other types of insulation. If the wall insulation gets wet often or is unable to dry out, the boric acid could leach out and mold could grow.
5 INSULATION TIPS
When weighing insulation options, consider where you're going to use it and how R-value might be affected, advises Joel Hirshberg, president of Green Building Supply in Fairfield, Iowa.
1. If insulation isn't installed properly, most manufacturers won't guarantee the promised R-value. That means savings you gain from doing it yourself could cost you in energy savings.