Debunking Common Myths About Spray Foam Insulation: What Builders Need to Know

By Mickel Maalouf, Building Science Manager at Huntsman Building Solutions

Despite its widespread use in both residential and commercial construction, spray polyurethane foam (SPF) insulation continues to be the subject of persistent myths. For builders and contractors striving to meet increasingly stringent energy codes and client expectations, these misconceptions can lead to hesitation – if not outright avoidance – of a material that offers well-documented benefits.

From concerns about fire performance to misunderstandings regarding moisture behavior and environmental impact, misinformation about SPF can influence sound decision-making. By separating fact from fiction, construction professionals are better equipped to confidently consider polyurethane-based insulation as part of durable, high-performance envelope assemblies.

Myth #1: Spray foam is a fire hazard

A common concern among builders is that spray foam insulation is inherently flammable and therefore compromises a building’s fire safety. In truth, the idea that spray foam is exceptionally dangerous in fires is misleading. All organic materials – including items like sofas, curtains, and furniture– are combustible and will emit toxic smoke if ignited. SPF, like many other construction materials, will burn under certain conditions, but it is not uniquely hazardous when properly installed.

Modern SPF products are engineered with fire-retardant properties and must meet stringent fire performance standards, including those set by the National Building Code of Canada (NBC). These building codes permit the use of combustible insulation materials – such as SPF – in both combustible and non-combustible buildings, if they are protected by a thermal barrier or meet specific fire tests, depending on the application. 

Beyond compliance, SPF can enhance fire safety in some assemblies. Its ability to form a continuous fully adhered air barrier helps prevent air movement through gaps and joints – pathways that otherwise accelerate flame spread. By limiting air leakage, SPF can reduce the movement of hot gases and smoke, thereby helping to slow fire progression and protect adjacent materials from ignition.

Builder takeaway: When installed in accordance with national code and protected by a compliant thermal barrier, SPF is not a fire hazard. On the contrary, its air-sealing capabilities may contribute to improved fire safety by slowing flame and smoke spread within the building envelope. 

Myth #2: Spray foam traps moisture and causes mold problems

Moisture control is fundamental to the longevity and health of any building envelope. A persistent myth suggests that SPF, particularly closed-cell varieties, can trap moisture within wall assemblies, leading to mold growth, rot, or structural decay. In truth, many of the moisture issues attributed to SPF arise from installation errors, poor detailing, or inadequate ventilation – not the material itself.

In fact, closed-cell SPF also acts as a continuous air barrier and a code-compliant vapour barrier, addressing key causes of moisture-related failure such as air leakage and vapor diffusion. Because air barriers are significantly more effective than vapour barriers at controlling condensation, closed-cell SPF’s ability to expand and fully adhere to substrates – including concrete, masonry, and timber – ensures it fills gaps, joints, and irregularities that would otherwise permit air and moisture intrusion. This seamless application eliminates air channels and voids where condensation and mold could develop, making SPF particularly valuable in basements, crawl spaces, and older homes with irregular foundation walls.

Builder takeaway: SPF does not inherently trap moisture or cause mold problems. In fact, when properly specified and installed, it can prevent many of the conditions that lead to moisture damage. Its ability to simultaneously insulate, air-seal, and control vapour diffusion makes it a valuable tool in comprehensive building envelope design – especially in Canadian climates where temperature swings and humidity levels vary dramatically.

Myth #3: Spray foam has a high environmental impact

SPF has historically been criticized for its petroleum-based composition and high embodied carbon, particularly due to the past use of high-global-warming-potential (GWP) blowing agents. However, this view is increasingly outdated; recent regulatory changes in Canada have significantly improved the environmental profile of SPF, making it a much more sustainable insulation option today.

As of January 2021, Canadian environmental regulations ban the use of HFC-based blowing agents in SPF due to their extremely high GWPs which typically ranged from 1,000 to over 3,000. These were replaced with hydrofluoroolefin (HFO) blowing agents, which have a GWP of just 1 – on par with carbon dioxide. This change has resulted in an 80% reduction in the carbon footprint of SPF insulation, making modern formulations far more climate-responsible than their predecessors.

Beyond its chemistry, SPF supports environmental performance through material consolidation. It acts as a high-performance thermal insulator, an air barrier, a vapour retarder, and a sealant – all in one product. This multifunctionality means fewer products need to be manufactured, transported, and installed, which reduces both material waste and construction site impact. These benefits make SPF-based systems among the lowest environmental impact building envelope assemblies available today.

SPF also offers exceptional durability, particularly in moisture-prone areas. Closed-cell SPF is the only insulating material recognized by FEMA as Class 5 highly flood-resistant, meaning it can remain intact and bonded to the substrate even after flooding. Unlike batt insulation, which often must be replaced after water exposure, SPF maintains its performance – reducing both material waste and renovation frequency over the building’s lifetime.

Builder takeaway: Modern Canadian SPF is not only low in embodied carbon – it also replaces products, reduces waste, and delivers long-term resilience, making it one of the most sustainable options for high-performance building envelopes, as demonstrated by the products EPD (Environmental Product declaration)

Myth #4: Spray foam off-gasses indefinitely and Is unsafe for occupants

One of the most frequently cited concerns about spray foam insulation is that it continues to emit harmful chemicals – so called ‘off-gassing’ – long after installation. This misconception stems from a misunderstanding of how SPF cures and the nature of volatile organic compounds (VOCs).

In reality, professionally installed SPF undergoes a rapid chemical reaction and cures fully within about 24 hours. This period allows the foam to cure adequately and ensures any residual chemicals have dissipated, promoting a safe environment for occupants. Once cured, the foam becomes inert, structurally stable, and non-emissive. 

Modern SPF systems are rigorously tested and are often certified under GREENGUARD Gold or similar programs, making them suitable for sensitive environments such as healthcare facilities, schools, and residential settings. The VOC emissions of SPF products are also regulated by the Canadian standard for SPF products.

Builder takeaway: When installed by certified professionals under the right conditions, SPF does not pose an ongoing off-gassing risk. Proper curing ensures indoor air quality is preserved.

Conclusion: Informed builders build better

Spray foam insulation has been the subject of skepticism since its introduction, but the building science behind it has never been more robust. As energy codes tighten and clients demand better performance, SPF offers a compelling combination of thermal insulation, air sealing, and moisture management.

Builders and contractors who take the time to understand the real facts about SPF – beyond the myths – can deliver buildings that perform better, last longer, and cost less to operate. With the right information and expert partners, spray foam insulation can be a powerful tool in any builder’s toolkit.

By confronting these myths directly, builders can look forward to more informed and confident use of SPF in Canadian construction, where performance, durability, and occupant comfort are non-negotiable.