spray polyurethane foam, health and safety

Insulating Foam Sealant for Do-It-Yourself (DIY) Projects

Do-It-Yourself (DIY) projects around the home can include small weatherization jobs using a convenient insulating foam sealant product in an easy to use, small can (typically 12-24 oz.).

Insulating foam sealants (also known as “foam in a can” or “one-component foam”) are a type of spray polyurethane foam product and are readily available at home improvement stores.  These products are intended for use in a “bead type” application for air sealing or adhering.  Their small volume, ease of use, and portability make them ideal for smaller projects, such as sealing gaps and crevices, tackled by the DIYer.

This website addresses insulating foam sealants.  It does not address another kind of product called low pressure two-component spray polyurethane foam (SPF), sold in kits or refillable cylinders (often used by weatherization professionals and SPF contractors). This product is typically used on larger scale insulation projects and is available to trained weatherization contractors and professional installers of spray foam. 

Some DIYers occasionally express an interest in installing low pressure two-component foam themselves.  For more information, see our section for weatherization contractors/professionals.  This section discusses a number of key issues, including training and personal protective equipment, including respirators, to consider before attempting to pursue a low pressure two-component SPF installation project yourself.  Note that some product manufacturers may limit the use of this product to spray foam professionals, or may also have specific training or other requirements to be met before these products can be used.

When to consider hiring a professional
Typical uses for insulating foam sealant
Insulating foam sealant ingredients
Guidance on using insulating foam sealant
Post-spraying guidance
Storage and disposal


When to consider hiring a professional

Insulating foam sealant products are sold in aerosol cans (typically 12-24 oz.) and designed for DIYers (and professionals) to fill smaller gaps and cracks around the home. They are not intended to be used as insulation for larger areas or projects. There are other types of spray polyurethane foams designed for mid-to larger size insulation projects. (See "Types of SPF insulation and how it’s applied").

For mid-size projects, there are low pressure two-component kits that may require further training and specialized personal protective equipment, to use them properly and safely. These low pressure kits are primarily used by weatherization professionals and spray polyurethane foam contractors to insulate and seal small to mid-size areas around the home, such as attics, crawl spaces, and rim joist. Refer to the section for Weatherization contractors/professionals for more information.

High pressure two-component SPF systems are more often used when insulating larger areas, such as walls and roofs on new construction or major renovations. These products are not for DIYers and are designed for professional use. These systems require special training and the use of specialized personal protective equipment (PPE), including respirators. When high pressure two-component spray polyurethane foam insulation is needed, an SPF contractor having the proper training, equipment and personal protective gear to handle these large-scale projects should be hired.

For more information about selecting a professional SPF contractor, check the Consumer section of the website or see the “Selecting and Working with Your SPF Contractor” guidance.

You also may consider hiring a trained SPF or weatherization professional to get an energy audit and full assessment of where insulation should be used throughout your home to further reduce energy bills.

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Typical uses for insulating foam sealant

Many home improvement centers and hardware retailers sell insulating foam sealant products in 12-24 oz. cans. These products are useful for small DIY projects such as sealing holes, gaps and crevices around your home where air leakage could occur. There are different grades of insulating foam sealants for different uses. Refer to the product label for information on appropriate product uses and check with the product manufacturer if you have questions about its intended use.

Some possible areas to consider sealing include around:

Seal gapping baseboardsSeal window and door framesSeal around electrical boxes

Living spaces (see above): Seal gapping baseboards, window and door frames, wire and pipe penetrations, air vents, and around the sides of (not inside) electrical boxes.

Sink plumbing Sink plumbing: Seal by filling the gap between the wall and the pipe. 
Dryer vents Dryer vents: Seal from either the interior or exterior of the penetration, depending on which has easier access.
Sill plate Sill plate: Seal around the wood framing of the walls of an unfinished basement where the wood 2” X 4” or 2” X 6” meets the poured concrete foundation wall.
Attic Hatch HVAC penetrations (attic registers): Seal between the penetration and duct work from the attic to the ceiling registers on the top floor of the house.

Other typical uses:

  • Attic Hatch: Seal the attic hatch door from the living space by going into the attic and filling the gap between the frame of the attic hatch door and the attic floor.

  • Basement/Attics: Seal pipe and duct penetrations, plumbing shafts and stacks, wall cracks, sill plates and floor/wall junctions.

  • A/C wiring: Seal the gap between the pipe and the wall where the cooling line from the A/C condenser (look for a copper pipe) enters the basement from the outside of the house. It can be found near where the air conditioning unit sits on the ground.

  • HVAC penetrations (floor registers): Seal between the gap around the floor registers and duct work in the basement.

Exterior uses

Insulating foam sealant is also effective for some exterior uses, such as:

  • Where siding meets the foundation

  • Electrical, gas and air conditioning penetrations

  • Garage ceiling and wall joints, and

  • Around outdoor faucets and vents

It can even be uses in some landscaping applications, such as stone wall repair (image below).

Stone Wall Repair

  • Securing landscape blocks, as well as for

  • Pond and waterfall fillers and repair

Follow the manufacturer’s instructions for application.  It can be helpful for exterior applications to paint the surface to be treated with black paint (appropriate for outdoor use and the surface selected) to help prevent UV degradation and discoloration of the foam.

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Insulating foam sealant ingredients

A can of insulating foam sealant contains a group of chemicals referred to as polymeric methylene diphenyl diisocyanate (pMDI) and a resin blend that may contain a mixture of polyols, catalyst (primarily amines), hydrofluorocarbon or hydrocarbon propellant, surfactants and flame retardants.  See the manufacturer’s label for specific product contents since they may vary slightly depending on the type of insulating foam sealant.  When these chemicals combine, a reaction occurs to create the foam. Before the foam has sufficiently hardened, there may be potential for exposure to these chemicals. Therefore, it’s important to follow the safety precautions and wear the protective gear (glasses/goggles, gloves and full- coverage clothing) as described on the product label.

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Guidance on using insulating foam sealant

Here are a few key considerations when using insulating foam sealant:

  • Follow instructions on the product label: Just read and follow all instructions on the product label carefully.

  • Provide ventilation: Provide plenty of ventilation to avoid breathing vapors and mist until the foam has hardened.

  • Wear appropriate protective gear: It is important that you wear protective gear often referred to as “personal protective equipment” (PPE) when applying insulating foam sealant. Wear the clothing and eye protection recommended by the product manufacturer on the label. This can be safety glasses or goggles, full-coverage clothing, e.g., long sleeves; and gloves. Avoid getting foam on your skin or in your hair. (The foam is highly adhesive and very difficult to remove).

  • Keep children and pets away while spraying: Keep children and pets away from the area where you are applying the product.

  • Shut off ignition sources: Be thoughtful about addressing potential combustion risks. Extinguish heat sources, sparks and open flames in the spray area, adjacent rooms and behind neighboring walls. This includes pilot lights to gas stoves, dryers, furnaces and water heaters. Keep area free from ignition sources until fumes have dissipated.
    Refrain from smoking while spraying the foam.

  • Avoid spraying in high heat areas: The unreacted chemical constituents in the can may be combustible, so you should carefully read the instructions on the product label and follow them with respect to avoiding installations in areas exposed to high heat, such as around fireplaces, heaters, radiators, heat lamps, recessed lighting, bare copper wires, or inside electrical boxes. 

    Note: Insulating foam sealants typically contain flame retardants and when installed properly, are designed to meet all applicable building and fire code regulations  Installed cured product is combustible and will typically begin to thermally degrade at temperatures above 240ºF/116ºC.

  • Clean up the work area, including any foam trimmings: Insulating foam sealants generally do not need trimming, because the product is applied in a narrow “bead.”  However, if you wish to trim the applied product, it is good practice to wait until the foam has cured or hardened before attempting to trim it. Consult the product label and instructions for trimming information and cure times. Cured or “hardened” foam trimmings may be disposed of as you would other household wastes. Be sure to thoroughly clean up the work area after the job is completed.

    Note: Generally, it is considered acceptable to leave cured or “hardened” insulating foam sealant exposed when it is used to seal small gaps and cracks. However, in the unlikely event that it is used for larger area applications (e.g., greater than about 2 square feet), consider a consultation with your local building code official, or work with a professional weatherization or spray foam contractor, who understands local building code requirements for foam plastics.

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Post-spraying guidance

Generally, people can reenter the area when the insulating foam sealant has hardened to the point where it is considered “tack free” (no longer wet or sticky on the surface). Typically, it can take between 5 and 60 minutes for the foam to become tack-free. Consider wearing appropriate protective gear (for example, eye protection, full-coverage clothing and gloves) when checking the foam’s hardness or “tack-free” state.

The amount of time it takes for a foam to cure or harden varies depending on the product-specific formulation, temperature, humidity, the amount of foam being sprayed, and other variables. Typically, insulating foam sealants cure quickly at moderate temperatures and humidity. The foam surface cures first, and then gradually cures inside of the foam body. The thicker the foam is applied, the longer it takes to cure throughout. Spraying a mist of water on the substrate or/and between layers of foam can speed up the curing process. Full cure may be reached in a time range of about 8 to 24 hours, depending on the product and site conditions. Consult the product label and instructions regarding cure times.

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Refer to the product label for first-aid instructions. Keeping the instructions on the product label unobstructed (clearly readable) at the project site helps in the event that first-aid guidance is needed.

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Storage and disposal

Empty cans may be disposed of as non-hazardous household waste. 

For full or partially used cans of insulating foam sealant, follow the product label instructions regarding storage and disposal.  The ingredients in the can are pressurized, so upright storage of the can at room temperature consistent with the manufacturer’s recommendations is important (avoiding freezing or hot temperatures). Remember that the temperatures in a parked vehicle in the summer can rapidly reach very hot temperatures, so plan your purchase and transportation of the insulating foam sealant accordingly.

After initial use, a partially used can of insulating foam sealant may be re-used for a limited time (typically up to 15 days) if stored in cool and dry conditions.

Disposal of full or partially used insulating foam sealant cans must be in compliance with all federal, state/provincial and local laws and regulations. Regulations may vary in different locations.  Call the product manufacturer for instructions.

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