All About Insulation

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Polyiso offers superior insulation properties—the highest of the rigid foam insulation materials—with an average R-value between R-6.5 and R-8 per inch. Its various facings, such as plastic or aluminum, further increase its resistance to heat.

Like other forms of insulation, polyiso suffers from thermal drift, a gradual deterioration of R-value over time. Out of the mold, polyiso foam boards are rated about R-9 per inch, but within two years the R-value declines to its stable insulation value, about R-7 per inch. (Foil facing adds about R2 to the insulation.)

Polyurethane/Spray Foam Insulation. In the '70s and `80s, rising heating prices motivated homeowners to retrofit their homes with insulation. Many people injected polyurethane foam into wall cavities through holes drilled in the finished walls. However, polyurethane foam soon began to cause problems. Formaldehyde, which was used as a binding agent in the foam, outgassed from the walls, causing a host of health problems ranging from sore throats to skin rashes.

Polyurethane products also relied on a blowing agent known as CFC-11, a potent ozone-destroying chemical. And many found that the foam offered incomplete protection, as it failed to fill cavities evenly, resulting in uninsulated regions in walls.

Today, manufacturers use carbon dioxide gas as the blowing agent. One of the leading polyurethane insulation products is Icynene. It is applied by a trained installer and is sprayed in a paint-thin layer into open wall cavities.

Icynene adheres readily to all surfaces it contacts and quickly expands to approximately 100 times its original volume, filling cavities. Excess can be trimmed off with a handsaw. Although Icynene is typically sprayed into open cavities before wallboard or paneling is applied, it can be applied in closed wall cavities. A carefully measured amount is poured into the cavity through a small opening in the wall. The product expands from the bottom up, filling the voids.

Icynene provides about R-3.6 per inch. Because it forms an airtight seal and also is resistant to water vapor, Icynene eliminates the need for vapor barriers in standard stick-frame construction. Further adding to its benefits, Icynene does not settle, sag or shrink. Unlike most other insulation materials, Icynene's R-value does not decline over time. Additionally, its production uses no CFCs or HCFCs, the foam does not outgas harmful chemicals and it offers no nutritive value to termites.

Introduced in the late 1970s, Air Krete, a cementitious foam product containing magnesium oxide, is one of the few insulation products that chemically sensitive individuals seem to tolerate. Like other spray-in foam insulation materials, Air Krete is stable and does not shrink or settle after being applied. It supplies about R3.9 per inch, but must be applied by people trained in its application.

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