Can water get through spray foam insulation?

Author: Tabitha Jacobson  |  Last update: Saturday, August 30, 2025

Closed cell spray foam, in particular, is often touted for its ability to resist water and even act as a vapor barrier in certain applications. On the other hand, open cell spray foam and RetroFoam insulation are more permeable, which means they allow water vapor to pass through but still do not retain liquid water.

What happens if spray foam insulation gets wet?

Open-cell spray foam is more porous than closed-cell foam, so it may absorb water if it gets wet. This can lead to decreased R-value and, over time, the potential development of mold or mildew if the moisture is not properly addressed.

Can water go through spray foam insulation?

Does spray foam absorb water? Yes, there are open cell spray foams on the market that will absorb water, but that doesn't mean they all do. The spray foam used here at RetroFoam of Michigan does get wet and water even moves through it, but it doesn't trap moisture indefinitely. This means it will dry out.

Is spray foam insulation waterproof?

Is there a waterproof spray foam? Some spray foam is waterproof, but not all. Specifically, open-cell foam is not waterproof, but it is water-resistant. Closed-cell foam is also water-resistant, but only the higher-density closed-cell foams are truly waterproof.

Does expanding foam let water through?

Expanding foam insulation is known for keeping water out very well. It's perfect for sealing buildings from water damage. Since it makes a tight seal, it protects from moisture problems. This kind of insulation is great for keeping a building safe and dry.

Water Testing Spray Foam Insulation

Can water leak through foam?

Closed-cell foam is a top choice for keeping moisture out of your home. It's different from open-cell foam because it doesn't let air or water through. This makes it great for stopping leaks and preventing water damage. Closed-cell foam is special because of its density and structure.

Where should you not use spray foam?

Directly against electrical wiring or fixtures: Spray foam insulation should not be applied directly against electrical wiring, fixtures, or recessed lighting unless they are rated for contact with insulation. Contact with insulation can cause overheating and pose a fire hazard.

What is the disadvantage of spray foam insulation?

Environmental damage (spray foam insulation isn't recyclable, and it can release greenhouse gases that are over 1,000 times more harmful than carbon dioxide) Ventilation issues (spray foam insulation covers all gaps, which can lead to dampness, condensation and wood rot)

Does great stuff spray foam absorb water?

In contrast, Great Stuff™ is closed-cell foam. It forms a water-resistant outer coating when cured. Latex foam does not expand.

Is spray foam insulation a moisture barrier?

Closed-cell spray foam insulation, on the other hand, is completely moisture-resistant. Because it creates a moisture barrier on its own, there is no need to install a separate vapor barrier as long as a sufficient quantity of insulation has been implemented—typically around 1.5 inches thick.

Can mold grow under spray foam?

Mold and mildew can begin growing behind the insulation which can go unnoticed until it's already become a huge problem. This often happens when the spray foam isn't installed correctly and space is left between the insulation and the wall, which allows moisture in and gives mold the perfect place to grow, unfettered.

What spray foam does not absorb water?

Closed-cell spray is more efficient for waterproof insulation because it is denser and offers a tight cell that retards water. The two types of spray foam insulation offer excellent thermally insulating properties, but the closed-cell spray foam is watertight.

How much water can foam absorb?

Hawaii Construction Foam insulation will absorb a maximum of 2-4% by volume when exposed to the testing specified by ASTM C578. The ASTM C578 water absorption requirement is determined by submerging a 12” x 12” x 1” piece of insulation in water for 24 hours.

Is fiberglass insulation ruined if it gets wet?

Every type of insulation will react differently when it gets wet. Fiberglass insulation will lose its effectiveness as air is displaced by water, causing it to conduct heat instead of insulating your home. Cellulose will begin degrade if it's not dried quickly, and it can start to grow mold.

How long does spray foam take to fully dry?

Open-cell spray foam: Tack-free in approximately 5 to 10 seconds after application; it can be fully cured within 12 to 24 hours. Closed-cell spray foam: Sets to the touch at roughly the same rate but may require up to 48 hours for complete curing.

How much does it cost to spray foam for 1500 square feet?

The cost to insulate an attic is usually between $1.50 and $3.50 per square foot. This price can change depending on the attic's size and how easy it is to get to. For a typical 1,500-square-foot attic, you pay $2,250 to $5,250.

Can water seep through spray foam?

To answer shortly: YES, spray foam can resist water from entering your home. The air-tight sealing it provides helps keep moisture from seeping inside and damaging your property. Many use it successfully for sealing home spaces prone to leaking, including crawlspaces and basements.

What eats through spray foam?

Spray foam is not a food source, but termites can burrow through spray foam insulation. If your property has faced termite infestations in the past, you can still install spray foam in your attic, basement, or crawl space. However, it will be vital to maintain your pest control strategy after insulating.

Does water go through expanding foam?

The short answer is no, spray foam does not absorb water. Whether you're using closed cell spray foam or RetroFoam injection foam, these products are designed to resist water intrusion rather than soak it up like a sponge.

What is the downfall of spray foam insulation?

Spray foam insulation can cause bad smells

There's a pretty unfortunate problem associated with spray foam insulation – bad smells, or more specifically, a fishy odour that seems to hang around for months after installation. Whilst unpleasant, the issue is rare, especially if installed correctly by professionals.

Where not to use expanding foam?

While it is hugely useful, it should not be used to solve all problems. One such example is electrical boxes. Expanding foam shouldn't be used in these locations as it could cause jams that would be expensive to repair. So avoid using it around sockets or light fixtures, or any electrical components in the property.

Why can't you sell a house with spray foam insulation?

Many contractors and homeowners believe that houses need to breathe, and the concern that a house may be made too airtight causes these buyers to avoid spray foam insulation. If these buyers learn that the insulation is spray foam, they may avoid bidding altogether.

Can mold grow behind spray foam insulation?

Spray foam insulation is not a waterproofing product. If spray foam is installed in a basement or an attic that leaks, mold could grow. Another example of improper installation is the use of the wrong type of spray foam.

Can I sleep in my house after spray foam?

Homeowners who have closed-cell spray foam insulation installed should stay out of the house for at least 48 hours. This amount of time will allow all off-gassing to subside and permit the foam to cure fully.

Should you foam around windows?

Foam strips are a good insulator on the exterior around the window. It is easy to install and can cover cracks forming around the sides of the window as well as drafts around the top or bottom of the window sashes.

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