Understanding SPF

As an indoor air quality professional, I have investigated some very problematic SPF installations in the last 10 years. Some 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, say such odors give them headaches. One couple who built their dream house in Florida for their retirement was so sickened by the odor they moved—leaving their clothing, furniture, and other belongings behind.

SPF insulation must be installed in the correct ratio and thickness and under the recommended conditions or unpleasant odors can result. But what can cause such odors?

To answer this question, I have to lean on my education as an organic chemist.

KINDS OF FOAMS

There are two 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, in a solid foam, the liquid surrounding the bubbles must solidify to contain the gas.

Most injected insulating foams are formed by mixing 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 sprayed onto a surface or into a cavity. Depending on the components of the two parts, the foam can 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, creating bubbles that cause the foam to expand. A catalyst is required to facilitate these reactions. This catalyst may contain nitrogen; many organic compounds that contain nitrogen belong to a class of organic chemicals related to ammonia called amines.

WHAT ARE AMINES?

Many amines have a strong ammonia-like or 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 a heating system. 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.

INSTALLATIONS & REMOVALS

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 they want to remove the insulation. The chemicals causing this odor may be from chemical reactions or from contaminants in the B side like dioxane and dioxolane, according to the National Institute of Standards and Technology.

• 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 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 foam was only visible and accessible in the eaves, where the odor was very strong. A contractor had to remove all the roof shingles and sheathing to retrofit the insulation.
• In a third situation, a contractor purchased a home with a strong chemical odor in the attic due to SPF insulation. To get rid of the odor, he replaced the roof structure.

Attic SPF with intumescent paint and a hole for a core sample

EFFECTS BEYOND ODOR

My concerns about SPF go beyond the odors that could result from improper SPF installations and have to do with the potential effects SPF installations could have on human health.

Part A of the foam contains isocyanates—a highly reactive and potentially deadly chemical. Exposure to isocyanates may cause “skin, eye and lung irrigation, asthma, and sensitization,” according to the EPA. The EPA also says direct skin contact can cause marked inflammation, and exposures to isocyanates should be minimized.

Once isocyanates react with moisture or Part B of the foam they are no longer a threat. Still, exposure is a concern for those installing the foam as well as for people in the building while the foam is being installed. Occupants should not be present during the installation; they should be away from the property for at least a day or two after installation is complete.

There is a longer-lasting threat, however, due to exposure to SPF dust particles and spheres. I have seen very small spheres in air samples I’ve taken in buildings where SPF insulation was installed. The spheres even appeared in air samples I took in rooms adjacent to, below, or above where the foam was installed. The spheres are small enough to be aerosolized by foot traffic, to remain airborne for extended periods of time, and to be inhaled. And the dust could be disturbed by foot traffic or even airflows and then be inhaled.

SPF spheres and dust contain all of the chemicals in the foam, including fire retardants (such as TCPP), exposure to which over time may affect neurological development and reproduction, and may possibly be carcinogenic, according to the EPA. After SPF has 
been installed it’s extremely important that all surfaces in the work area be cleaned of all dust. Note that the 
large overspray droplets that adhere to surfaces 
do not pose much of an exposure risk, because they are not aerosolized by airflows or foot traffic.

Adhered SPF drops

A micrograph of SPF spheres (stained pink)

All the white dust consists of SPF dust. This photo was taken in a newly constructed home.

I think SPF insulation is a great product, but care must be taken during and after its installation to protect occupants’ health. When my clients are considering having SPF insulation installed, I always recommend they work with a contractor who has been installing this product for at least 10 years. Some clients or their contractors even hire an SPF consultant to oversee the installation.

PHOTOS COURTESY OF MAY INDOOR AIR INVESTIGATIONS LLC