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ARCH-TECH TIP EDITION 1 / SPRING 2009

Horizon Archi-Tech Tips

Tip #3. Polyurethane vs. soy-based sprayed foam alternatives

If properly installed, 2 lb. closed-cell polyurethane foam insulation is a safe, practical technique for insulating a home. While sprayed foam is considered a very “green” product in terms of its performance capabilities, polyurethane is still derived from chemicals distilled from petroleum. Most building experts consider this a fair trade-off since its benefits far outweigh that fact that oil is required in order to create it.

Secondly, there have also been health concerns raised about flame retardant chemicals used in rigid and sprayed foam insulation and that the off-gassing from this chemical compound may be hazardous to humans. While many building experts and architects now agree that PBDE (polybrominated diphenyl ethers, once commonly used as a flame retardant in closed cell foam insulation) could be hazardous to people over a long periods of exposure, there are now plenty of polyurethane product options that don’t contain PBDEs yet are still fire rated and safe for people.

For those who want an even greener foam insulation option, there are also soy-oil-based spray foam insulation products available. The current soy products perform much better than fiberglass batts, but there are some sacrifices with soy foam in that they don’t insulate as well as closed-cell polyurethane foam. While they are constantly being improved and may someday rate as high as the petroleum based products, current soy-based technology can’t compete on the same level and provide the same density of insulation or R-value as poly.

Other benefits of closed-cell polyurethane are increased density and rigidity to structurally support roofs and walls, plus it’s nearly waterproof. When combined with a membrane cover and laminated right to the foam, sprayed poly-foam will remain watertight and structurally sound for decades.

Many homeowners may still prefer a soy-based foam option and would rather sacrifice some performance in order to reduce the use of petroleum-based chemicals. In the end it’s really a “wash” between the two options—Poly vs. Soy—in the sense that reducing insulation performance is essentially increasing the need to generate more power to heat and cool the home, which in turn creates more CO2

We are leaving out many other green alternatives here that are even less efficient insulators than soy-foam. You can insulate a home with recycled blue jeans or straw bales if you like (and yes, these green product options are available.), but you’ll have to accept the fact that you’re giving up significant performance for a recycled or naturally grown product.

In summary, these are not perfect solutions, but poly-foam is simply the best performing option available. Reducing insulation performance results in higher energy costs for the homeowner and contributes to additional CO2 in our atmosphere.

Upcoming Horizon Archi-Tech Tips editions will include tips on the concept of the “moisture envelope” and other benefits of closed-cell foam insulation, such as leak-free roofing and watertight basement applications.