A Comprehensive Guide to Foam Insulation and Indoor Air Quality

Whether you are renovating or building a home, selecting the right insulation is a crucial decision. This is because the insulation you choose will impact energy efficiency, comfort and indoor air quality. Foam insulation - including spray foam and rigid insulation foam - is popular due to its impressive R-values and air-sealing capabilities. 

This guide provides an overview of different types of foam insulation and how they can influence indoor air quality. You will learn guidelines for selecting foams and best practices for proper installation and ventilation. With the strategies outlined in this guide, you can make the best insulation choice for your project. 

What is the relationship between foam insulation and air quality?

The type of insulation used in a building can have a significant impact on indoor air quality. Overall, foam insulation products can influence air quality in both positive and negative ways. On the positive side, foam insulation provides excellent air sealing which can reduce drafts and the entry of outdoor pollutants. 

However, some types contain blowing agents, flame retardants and formaldehyde. These ingredients can potentially diminish air quality through off-gassing and volatile organic compounds (VOC) emissions. These emissions are highest right after installation but can persist at lower levels.

Proper ventilation and other mitigation strategies are important when using these products. Carefully evaluating the formulation of different foam insulation materials is key to improving energy efficiency through insulation without sacrificing indoor air quality.

Different types of foam insulation

From foam loft insulation to floor foam insulation, it is important to consider how the materials will impact indoor air quality. Below, we provide an overview of the 3 insulation categories and summarise their indoor air quality advantages and considerations. 

1. Spray foam insulation

Spray foam insulation comes in two main types: open-cell and closed-cell. Both offer excellent air sealing capabilities. The foam expands and hardens to fill cracks and gaps in wall, floor and loft applications. This prevents drafts and inadvertent air leakage, which keeps pollutants from the outdoors from entering the indoors. 

Unlike fibreglass batt insulation, foam insulation spray does not require any additional air sealing. Both open and closed-cell spray foam types are also manufactured without blowing agents that can off-gas later. However, proper installation is crucial to prevent moisture issues that could lead to mould growth and other potential spray foam insulation problems.

2. Rigid foam insulation

Rigid foam boards are made of polyisocyanurate (PIR) or extruded polystyrene. They are commonly used on areas such as a wall or roof. The closed-cell structure and dense packing of the foam panel make it difficult for air to pass through. Like spray foam, this air-sealing ability reduces energy losses from drafts and uncontrolled ventilation. 

However, rigid foams also do not support mould growth. The blowing agents used to manufacture some types of rigid foam boards also slowly off-gas for a period after installation. Be sure to look for products made without these chemical-blowing agents if this is a concern.

3. Flexible foam insulation

This type of foam insulation includes polyethylene and polyurethane-based foams used to seal gaps and cracks. Caulk, pipe wrap and weatherstripping products like tape often utilise flexible polyurethane foams. These provide decent air sealing for small openings. 

Nonetheless, flexible foams made without dangerous flame retardants or formaldehyde can minimise exposure to VOCs. Unlike some other insulation materials, flexible foams will not irritate the skin or respiratory system during installation.

How to install foam insulation for indoor air quality

The installation process is important when working with foam insulation products that can impact indoor air quality through off-gassing. By following the best practice techniques below, you can minimise air quality issues for clients.

• Spray on insulation: Follow the appropriate pass (layer) thickness guidelines (25-50mm per pass). You should allow 2 hours between passes for curing. Use edge rolls for cleaner borders. Do not spray if temperatures are below 50°F (10°C).
• Rigid foam: Cut insulated board with score and snap tools such as a utility knife, not saws that generate particulates. Be sure to use canned foam sparingly between gaps. Also, seal all seams and edges with acrylic caulk.
• Mechanical fasteners: Use plastic washers with nails or screws to prevent thermal bridging. Make sure to space fasteners 12-16 inches apart and make sure they are flush with the foam surface.
• Prep work: All leaks should be repaired before work begins. With vapour barriers, install them on the cold side. Clean and dry all surfaces for maximum adhesion and be sure to cover nearby surfaces to protect from overspray.
• Safety gear: Wear PPE at all times, such as respirators, gloves and goggles. Be sure to offer adequate ventilation in work areas. For reassurance, you should follow all manufacturer safety guidelines.
• Moisture prevention: For exterior applications, maintain a 25-50mm gap between foam and soil outside. With inside jobs, do not install directly over concrete or brick. This is because you should allow a drainage gap.
• Curing: Be sure to advise clients not to disturb freshly sprayed foam until fully cured. All HVAC systems supplying sprayed rooms should be switched off during and after installation.

How much maintenance does foam insulation require?

Maintenance is key in the months following installation to minimise impacts on indoor air quality. Here, we offer tips for ideal maintenance of foam insulation products during the first year and beyond.

• Allow time for off-gassing: Most foam insulation sheet off-gassing occurs in the first few weeks after installation. Avoid occupying rooms or enclosed spaces for 72 hours to allow VOC concentrations to dissipate.
• Increase ventilation: Run HVAC fans, open windows and use exhaust fans to dilute VOCs emitted from new foam insulation. You should maintain higher-than-normal ventilation for several weeks.
• Apply foam sealant properly: Use recommended manufacturer techniques to properly seal spray foam and rigid foam insulation board. This prevents air leaks that could offset air sealing benefits.
• Inspect for moisture issues: Look for any dark spots or mould growth indicating moisture accumulation in foam insulation. This is especially important in the first year after installation. You should address water leaks promptly.
• Test indoor air quality: Make sure you use at-home kits or professional monitoring to test indoor air quality after insulation installation. Continue testing periodically to ensure VOC levels remain low.

Whether it is floor or foam cavity wall insulation, annual inspections should be conducted. Look for cracks, gaps, or areas where the insulation may have shifted. If you notice any damage or gaps, address them promptly to prevent potential indoor air quality issues.

Is spray foam insulation damaging to indoor air quality?

Spray foam insulation can potentially have negative impacts on indoor air quality, as mentioned above. This is primarily due to the off-gassing of chemicals during and after installation. Below are some key considerations to take into account.

1. Off-gassing of blowing agents

The blowing agents used to expand closed-cell spray polyurethane foam during application are typically VOCs like hydrofluorocarbons (HFCs) or hydrochlorofluorocarbons (HCFCs). These can off-gas for weeks after installation and continue at lower levels long-term, degrading indoor air quality.

2. Off-gassing during curing

Components of spray foam react and expand rapidly when mixed on-site. VOCs like isocyanates and flame retardants are emitted as the foam cures over 72 hours. Occupying spaces too soon exposes residents to these off-gassed chemicals.

3. Potential for shrinkage and gaps

If the temperature or humidity is out of the specified range during the application, spray polyurethane foam can over-expand and then shrink as it dries. This creates air gaps that allow drafts, moisture and pollutants to penetrate the insulation.

4. Risk of moisture and mould

Spray foam properly seals gaps and cracks when installed correctly. However, any moisture issues during or after application can lead to mould growth within a cavity wall or loft space if unchecked.