At Evergreen, we use the best insulation product for the job. In attics and sidewalls, that's usually cellulose. In basements, it's often spray foam - a product some homeowners have questions about.

We don't always use spray foam insulation, but when we do, we insist on these best practices:

Sparing, targeted use;

Expert installation and thorough ventilation;

and thermal protection.

We're also transitioning to products with low global warming potential (GWP) as they become available.

Wonder why? Read on...

What is SPF?

Spray Polyurethane Foam is a heat-activated plastic that is sprayed into place and serves as both an air barrier and an insulator. SPF is a mixture of two liquid chemical components and a blowing agent. As the ingredients react, the liquid turns foamy, expands, and hardens in place. This curing process can take anywhere from a few hours to a few days, depending on the type and thickness of spray foam, the temperature and humidity, and the technique of the installer. The finished product can be one of two types: closed-cell or open-cell. Closed-cell foam is more expensive than the open-cell variety, but it also offers a higher R-value, more rigid support, and greater resistance to water vapor.

Is SPF safe?

Spray foam insulation is a chemical product. Although the ingredients are potentially toxic and the mixture off-gasses while it cures, testing indicates that the final product is inert. However, if the mix of chemicals is off, there may be lingering odors and prolonged off-gassing. Since some people have reported health problems attributed to SPF, the EPA has issued information to make consumers aware of potential health risks, particularly during installation.

Is SPF environmentally friendly?

Spray foam’s high insulating and air sealing value has earned it a reputation as a green building material. However, even foams identified as soy- or castor-based include fossil-fuel-based materials. The installation of most closed-cell spray foam products depends on hydrofluorocarbon (HFC) blowing agents with high carbon dioxide content, which have negative global warming and ozone depletion potentials.

Fortunately, spray foam is getting more environmentally friendly. One manufacturer recently introduced a spray foam system incorporating a new blowing agent that offers the performance of HFCs but dramatically reduces the ozone depletion potential and global warming potential. Widespread adoption of this foam could save the equivalent of 60 million metric tons per year of carbon dioxide.

How does Evergreen maximize safety and minimize problems associated with SPF?

For both health and environmental reasons, Evergreen recommends these best practices when using spray foam insulation:

Sparing, targeted use:
Most issues with SPF occur when a problem with the chemical mixture goes unnoticed, either because it’s hidden in wall cavities or buried in a thick layer of foam. Evergreen only recommends foam on the foundation walls of existing homes, where it can be easily inspected, and at a 2” thickness, so it can cure completely.

Expert installation and thorough ventilation:
Most of the health and safety concerns about spray foam are focused on the installation period. Any installer should wear appropriate protective equipment (including respirators) and run a fan to vent the vapors generated during SPF installation. Evergreen takes this standard a step further, ventilating for the entire curing period (up to 72 hours) and maintaining a pressure difference that keeps basement air downstairs to ensure that off-gassing does not compromise the air quality of your living space. Based on EPA recommendations, Evergreen strongly advises that homeowners make plans for their families and pets to be out of the house overnight on the day of application.

Thermal protection:
Like other petrochemical products, spray foam is highly flammable. To ensure home safety, we coat fully cured foam with fireproof intumescent paint. This step is time-consuming but essential and required by Maine State fire safety codes, as it creates the same 15-minute fire barrier provided by drywall.

Transitioning to low GWP products:
Evergreen will transition to the new low GWP spray foam system as soon as it is reliably available. We look forward to this foam’s enhanced insulating properties, improved yield, and environmental benefits­, and will continue to recommend its use when it is the best available option.