Insulation is a crucial part of green building, because it’s key to reducing the energy usage of a structure. This serves both the immediate owner by lowering energy costs and the greater environmental goal of reducing greenhouse gasses. Spray polyurethane foam has been shown to be one of the most efficient insulators on the market and is regularly used in buildings that want to achieve low energy needs.
Yet a growing number of green builders are embracing other insulation options and turning away from spray foam.
Terry Pierson Curtis, an indoor environmental consultant, doesn’t recommend spray polyurethane foam to her clients. Curtis has 20 years of experience and tests roughly 100 homes per year. “Long-term, I don’t think we really know the effects of being in a home,” she said.
Curtis doesn’t doubt that spray foam manufactures have tested their products thoroughly in the lab. She said the real problem is installing the product in an uncontrolled environment, or in other words, real homes. Curtis estimates that five percent of spray foam jobs have problems. “You don’t want that to be your home.”
Passive House Institute U.S., an organization dedicated to architecture that requires minimal energy use, agrees with Curtis. The organization has deemed spray foam unsuitable in green building.
If something does go wrong, spray foam is extremely difficult to remove because it adheres so well to walls and studs. “Removing it is just as dangerous as having it installed in your home,” said Curtis, particularly because the dust may contain unreacted toxins and is difficult to control.
Instead of spray foam, Curtis recommends cotton denim insulation, which is typically made from industrial scraps.
Another option is cellulose insulation, which can be used as a loose filler, a dense pack, or even applied as a spray. Although it has a lower R-value than spray foam, meaning it insulates less efficiently, cellulose is typically made from recycled paper and other green fibers.
Both cotton and cellulose insulation are typically treated with borate-based flame retardants, which are not regarded as harmful to humans as halogenated flame retardants.
Devin O’Brien, the owner of Brooklyn Insulation & Soundproofing, uses both cellulose and denim insulation. O’Brien recommends cellulose insulation because it’s the safest to install and is a good choice for people who want to minimize toxins in their home.
“Anything is better than polyurethane spray foam,” O’Brien said. “It’s a petroleum-based product that’s not sustainable.”
O’Brien said there are still some jobs where spray foam may be the best option. He hopes that one day a truly bio-based foam will be developed. “That would be huge,” he said. “I think it’s the future of the industry.”
For some projects, mineral wool may be a good option. Mineral wool is one of the oldest insulating materials and can be made with up to 90 percent recycled content. The main health concerns is that formaldehyde is used as a binder in the manufacturing process. However, most testing shows that no formaldehyde remains in the final product.
A newer spray-applied product is spray-applied fiberglass. Alex Wilson at BuildingGreen recently wrote about his experience with Spider insulation from John Mansville, which doesn’t require fire retardants and can be used in some projects where spray-applied cellulose would be too heavy. The binder in this fiberglass product is also biobased.
As it stands, there are tradeoffs associated with each type of insulation available on the market and there is no one-size-fits-all answer. For many buildings, choosing an alternative to spray foam will mean giving up either some space or some of the R-value and using a material that does not perform the core function of insulation as well. From an energy-saving point of view, there are few products that insulate as effectively and seal so tightly. It may take more space to get the same insulating value out of other products, but air quality and recyclability are issues that have to be considered in green building as well as energy.
The health costs of those energy savings may be too high for many. Despite the industry insistence that spray foam is inert and doesn’t off-gas, there is evidence that some people are harmed by the continuing outgassing of irritating fumes.
The long-term impact of whatever insulation you choose should also be taken into consideration. No building stands forever. No matter what type of insulation is used, buildings will be torn down, burnt down, or remodeled and that insulation will impact the people living and working in them well into the future.
There is a strong movement in green building to get rid of plastics made from fossil fuels and toxic chemicals. There is an equally strong pushback from the chemical industry that claims their products are safe, effective and an important tool in efforts to reduce energy consumption