Is polyurethane foam insulation safe?

Larry from New York asks:

A contractor is suggesting we install a spray-on polyurethane insulation. What are the health and environmental factors to consider, and are there better alternatives?

The Green Guide replies:

Spray foam has several practical advantages for building insulation, making it a popular choice: it is injected between interior and exterior walls, sealing cavities in otherwise unreachable locations. Several varieties of spray insulation require flame retardants in order to meet fire safety standards. Unfortunately, Penta-BDEs, or penta-brominated diphenyl ethers -- a type of brominated flame retardant frequently used in polyurethane foam products -- pose a recently recognized and worrisome concern. Although the human health effects of penta-BDEs are unclear, scientists are concerned about studies showing rising levels of the chemical in human breast milk. Studies by Health Canada and Environment Canada have found that penta-BDE levels in breast milk in North America have increased by 15 times over the last ten years. In research on animals, penta-BDEs have been shown to damage the liver, harm developing brains, and lower thyroid hormone production. While penta-BDEs have been voluntarily banned in Europe, polyurethane foam made in the U.S. typically comprises as much as 25% penta-BDEs. Moreover, it is possible for deca-BDE's, another kind of brominated flame retardant, to degrade into 2 penta-BDE molecules, posing yet another brominated flame retardant risk.

According to Judy Marzula, an engineer at Underwriter's Laboratory, polyurethane spray foam insulation may use either brominated flame retardants or phosphorus-based varieties. Unfortunately for the consumer, no labeling exists to indicate what kind of flame retardants have been used in insulation. It's easy, according to John Bower of the Healthy House Institute, to seal a building properly (with caulking, airtight insulation barriers, and gaskets), thus keeping insulation materials from leaking into the home air and environment. However, looking into the far future, it is likely that any penta-BDEs in insulation will migrate into the environment (through building demolition, for example). For this reason, we urge you to avoid products that may contain or produce penta-BDEs. In the absence of labels, you will have to ask specific manufacturers about the flame retardants in their polyurethane foam products.

There are alternatives to polyurethane foam. Air Krete, a frothy non-toxic mineral spray made of air, water and cement, provides excellent insulation, and was used in The Audubon Society's New York headquarters. Unfortunately, it comes with a higher price tag. Cellulose and ground-up newspapers, are environmentally-friendly insulation choices; however, these materials are very dusty and can cause breathing problems if walls aren't carefully sealed with an airtight barrier.

Carefully sealing and insulating your home is a penny-wise and environmentally responsible thing to do, as it will cut your heating bills and reduce your fossil fuel consumption and greenhouse gas emissions. Make sure, however, that your house is adequately ventilated, as insulation not only keeps cold out but also keeps indoor air pollution in. See the EPA's The Inside Story: A Guide to Indoor Air Quality for more information and ventilation suggestions.