It’s been more than eight years since we reported on the health & safety and risk management issues related to spray polyurethane foams. So, we decided to re-visit the HETI Horizons we published in November 2013 – updating, as appropriate, based on we what we know today.

One of the cutting-edge advances in new construction was the use of spray polyurethane foam insulation for energy conservation. Although the chemistry has been around since the 1940s, the past twenty years have seen the application expand in commercial buildings and high-end homes. The use of spray foam is likely to reach $2.1 billion by 2025, with an annual growth rate of 5%.

Spray foam is applied to the structural elements of a house – typically on the attic roof deck, on the interior of the rim joist and foundation walls, and within exterior wall cavities – to provide insulation, create an air barrier, act as a vapor barrier, add structural strength (closed-cell foam), and reduce noise transmission. While most applications are for newly constructed buildings, spray foam may also be used to retrofit older buildings and homes.

What is Spray Foam?

The end product of spray foam is a rigid foam produced by an exothermic (gives off heat) chemical reaction between a polyol resin, flame retardants, and an isocyanate – typically polymeric methylene diphenyldiisocyanate (pMDI). The insulation expands 30 to 50 times its original volume as it is applied and permanently adheres/bonds to applied surfaces. Spray foam products are either closed-cell or open-cell, depending on the application. Both act as thermal barriers; but closed-cell foam is denser and acts as a vapor barrier, allowing air but not moisture to pass through. Hence, closed-cell foam is a prime choice where there may be vapor migration or water infiltration, such as on a roof deck. Open-cell may be a better option in warmer environments to reduce cooling demand.

Spray foam is costly when compared to more traditional insulation and has a payback period of two to four years. When applied in an attic, spray foam makes the entire attic part of the heated structure – reducing the potential for thermal bridging and condensation. This barrier, using closed-cell foam, provides a high degree of insulation (approximately R-6 for each inch of foam). U.S. Department of Energy studies show that 40% of a home’s energy consumption results from air infiltration. Spray foam eliminates some of the drawbacks of traditional insulation, such as fiberglass or blown-in cellulose, by sealing these air gaps.

Most spray foam products are typically sold through distributors. They are applied by independent installers, often hired by the property owner. With the interest in energy conservation and availability of grant money, a number of weatherization companies have been created to serve this market.

Are Spray Foam Products Hazardous?

Manufacturers state that when the products are properly installed, they become completely inert once they cure. But human errors may occur when installers do not properly maintain their equipment; try to spray too thick a layer of foam, at too high or low a temperature; or do not ventilate the space being sprayed. The foam may not properly cure and may continue to off-gas for months or even years.

There are many factors that affect how quickly the foam cures – including type and thickness of foam, condition of mixing equipment, air temperature and humidity, temperature of the components, and the installer’s training and experience. Questions have been raised about the level of training provided by the manufacturers to distributors or installers who are usually independent contractors.

Companies making foam components urge property owners to ask for proof of qualifications and training from installers when selecting a spray foam installer. Training for installers has improved significantly over the years. The Spray Polyurethane Foam Alliance offers a professional certification program for installers (with training methods certified under ANSI/ISO Standard 17204), as does the Chemistry Council’s Center for the Polyurethane Industry.

In the past several years, concerns have been expressed about the safety and efficacy of spray foam products. The Environmental Protection Agency has taken a special interest in the subject. Their website has a link to information on the products and states “the potential for off-gassing of volatile chemicals from spray polyurethane foam is not fully understood and is an area where more research is needed”. And ASTM (founded as the American Standards for Testing and Materials) has an indoor air subcommittee D2205 to study volatile organic compounds, diisocyanates, oligomeric isocyanates and amine catalysts.

Isocyanates are strong irritants to the gastrointestinal and respiratory tracts. Inhalation of the vapor or particles of foam dust can cause a sensitization reaction, making exposed individuals susceptible to asthma attacks with each subsequent exposure. The cured foam may contain quantities of formaldehyde and other aldehydes, as well as volatile organic compounds.

Does Spray Foam Burn?

In addition to health-related issues, a secondary concern is flame propagation and smoke damage. Most spray foam products contain flame retardants such as 1-chloro-2-propyl phosphate – called TCPP or Tris. The products have to meet strict guidelines for smoke and flame spread. Treated, spray foam products will not ignite per se. But in the presence of an open flame and heat, it may slowly smolder producing copious quantities of acrid black smoke.

Occasionally, when the foam is applied to surfaces too quickly or in too thick a layer, the heat given off by the chemical reaction may be sufficient to cause charring and ignition of structural wood components, resulting in structural fire damage. Some studies have identified certain difficulties in fighting building fires that use green construction techniques such as spray foam.

Managing the Risk

There have been numerous class-action lawsuits filed against spray foam manufacturers and distributors, as well as product liability claims against foam component installers over the past 10-20 years – claiming adverse health effects including chemical asthma and sensitization, as well as chronic odors that make a property unusable. One primary question raised has been who has the liability – the manufacturer, the distributor, the installer, or all three. Very few states have undertaken the development of state regulations, as the topic is very complex.

In cases where there is product failure or improper installation, the remediation options are limited. The cured foam rapidly bonds or adheres to structural framing elements. Where foam has been sprayed into exterior wall cavities, the wall covering must be removed to expose the foam. The cured foam may be scraped out or treated by blasting with dry ice; however this process is expensive and time-consuming and can produce a lot of smaller foam particles that spread through the building and air handling system. A second option is to cut and remove the treated structures, up to and including the entire roof. This requires careful project management to replace the roof and make the building weather-tight.

Since spray foam is a high value-added product, residential properties are likely to be large and expensive…and either of these removal strategies may cost several hundred thousand dollars. In commercial properties, costs are likely to be considerably more.

Of course, these cost estimates do not include contents replacement, interruption in use of the property, temporary housing, business interruption, relocation expenses and personal injury.  Add to this cost, the retention of law firms, hiring of experts, air testing and other expenses, and the potential exposure and liability may be considerable.

HETI: Experienced EHS Professionals

HETI has extensive experience in supporting our clients through a comprehensive range of environmental health & safety (EHS) support services. Our staff of industrial hygienists and environmental scientists can help manage the complexities and risks presented by spray foam…as well as other new and challenging environmental issues.