By Jeffrey C. May — from the March 2021 installment of “May’s Ways” in Healthy Indoors Magazine —
One of my clients reported that he and his neighbor saved about 30% on their heating and cooling costs after removing fiberglass floor batts in the attic and installing SPF insulation between the rafters. In the last ten years, I have investigated some SPF installations that were very problematic. Some of these installations have even led to legal disputes between contractors and homeowners.
Some SPF installations can emit a pungent, ammonia-like or fishy odor. Many of our clients, especially those with chemical sensitivities, report that such odors give them headaches. One couple in Florida who built their dream house for their retirement were so sickened by the odor that they moved out, leaving their clothing, furniture, and other personal goods behind. When I inspected the house, there was even food in the refrigerator.
What can cause such odors?
To answer this question, I have to lean on my education as an organic chemist.
There are two different kinds of foams: open-cell and closed-cell. In an open-cell foam, each “bubble” or “cell” is open to adjacent bubbles or cells. Liquids and gases (like water vapor) can pass through an open-cell foam fairly easily. Open-cell foams include sponges and bread. In a closed-cell foam, each bubble or cell is intact and surrounded by other intact bubbles or cells, so there is no communication between individual bubbles or cells. Closed-cell foams include a soufflé and the black tubular insulation made to go around water pipes.
When a foam forms, at least two things must happen. First, gas has to expand to form the bubbles; and second, the liquid has to solidify in order to contain the gas. Most injected insulating foams are formed by mixing together two different liquids, referred to as “Part A” and “Part B.” In the case of SPF insulation, the two parts are heated, mixed together under high pressure in a nozzle, and then sprayed onto a surface or into a cavity. Depending on the components of the two parts, the foam can either be open-cell or closed-cell; this is why some SPF foams are soft (“open-cell”) while others are rigid (“closed-cell”).
SPF is a urethane polymer (a polymer is a long chain of molecules). The chemical reactions that form the urethane polymer produce a lot of heat. These reactions also produce carbon dioxide, thus creating bubbles that cause the foam to expand. To facilitate these reactions, a catalyst is required. This catalyst must contain nitrogen; many organic compounds that contain nitrogen belong to a class of organic chemicals that are related to ammonia and that are called amines.
Many amines have a strong ammonia-like or dead fish-like odor. As is true of most chemical odors, the higher the temperature, the stronger the odor. People who complain about odor coming from SPF installations usually note that the odor is stronger when the insulated area is warmer, either due to the sun or to a heating system.1 Unfortunately, the odor can be permanent because the amine does not combine chemically with any of the other components in the foam and does not degrade over time. SPF insulation must be installed in the correct mixture ratio and thickness and under the recommended conditions, or strong odors can result.
Other improper installations, primarily for open-cell SPF insulation, off-gas chemical odors that some people describe as “sweet.” Some building occupants find this odor so annoying that they want to remove the insulation. The chemicals causing this odor may be from chemical reactions or from contaminants in the B side such as dioxane and dioxolane.2
To help prevent off gassing, the insulation can be covered with foil-backed gypsum board or a foil-laminated radiant barrier. But sometimes the insulation just has to be removed, which can be an expensive venture. In one new home under construction, SPF had been sprayed against the foundation wall in what became a very elaborate finished basement. In order to remove the foam, all the finished walls had to be removed and replaced.
In another home with tongue and groove cathedral ceilings, the contractor had to remove all the roof shingles and sheathing to retrofit the insulation. The only place where the foam was visible and accessible was in the eaves, where the odor was very strong. In a third situation, a contractor purchased a home that had a strong chemical odor in the attic due to SPF insulation. To get rid of the odor, he replaced the roof structure.
Read the full article in the March 2021 USA-Edition of Healthy Indoors Magazine.