Is spray foam a sealant?

Author: Prof. Terence Cruickshank  |  Last update: Tuesday, March 25, 2025

One component spray foam is dispensed as a liquid. It expands and cures into solid foam insulation and sealant. One component foam is used to fill and seal small cracks and gaps (i.e., around door frames, window frames, and electrical devices) where air leakage and energy loss occur.

What is the difference between spray foam and sealant?

Spray foam sealant is designed to create airtight and watertight seals in gaps, cracks, and joints. Spray foam insulation on the other hand is designed to provide thermal and acoustic insulation mostly for larger areas, such as walls, ceilings, and floors.

Does spray foam create a watertight seal?

Closed cell spray foam is water-resistant, meaning it won't absorb moisture, and it can help protect your home from water damage by creating a barrier. However, it's essential to understand that no insulation material is completely waterproof.

Why is spray foam a red flag for lenders?

Spray foam insulation is one of those many factors that can throw up a red flag to a mortgage lender. For a lender, your insulation matters because it affects crucial metrics such as the home's saleable value and energy efficiency rating.

Why is it hard to sell a house with spray foam insulation?

Some Buyers May Be Uncertain Of Spray Foam Insulation.

If they don't know the contractor who installed it, they may worry that the foam was installed by people who didn't know what they were doing. Other buyers have heard negative stories about spray foam insulation.

Everything You Need to Know About Spray Foam

Why do insurance companies not like spray foam insulation?

The chemical aspect of spray foam makes it very hard for standard insurance companies to provide coverage. Most standard lines insurance carriers want to write the risks with no liability not spray foam contractors that manufacture plastic every day in the field.

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.

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.

How long does spray foam sealant last?

Both types of spray foam insulation can last anywhere from 80 years to 100 years, with closed cell spray foam having a slight edge in terms of durability. For most families, this represents the lifetime of the house and then some!

What does spray foam not adhere to?

If you spray foam on a surface with a moisture level of more than 20%, the foam won't stick. The surface has to be paintable for the foam to adhere.

Does WD-40 remove expanding foam?

Yes, WD-40 will remove cured expanding foam by softening the foam residue for easy removal. Typically, WD-40 is applied to dissolve residue after removing a large chunk with a scraper or saw.

Can I use spray foam around water pipes?

You can have spray foam insulation installed around or on your water pipes. The chemical reaction and its byproduct of heat will not ruin or damage the pipes. Spray foam will also not increase the chances of a water leak.

When 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.

Is expanding foam a sealant?

Some of the main benefits of using expanding foam are insulation - they provide thermal insulation by filling open areas, reducing heat and energy loss. Sealing - they create an airtight and watertight seal, preventing drafts, moisture and also stop pests such as wasps etc. from entering buildings.

Do you need vapor barrier over spray foam?

Home » FAQs » Do I need a vapor barrier with spray foam insulation? Usually no. Closed cell foam is a vapor barrier. Open cell foam is a vapor retarder, but its moisture permeability properties in our climate are sufficient for most structures.

What is the downside of using expanding foam?

While spray foam insulation can make a home more energy efficient, its downsides often out-weight its benefits. If spray foam insulation isn't installed correctly or is used in the wrong setting, it can cause all sorts of problems, from reducing ventilation to rotting wooden roof beams.

How long will expanding foam last?

On average, fire rated expanding foam can last anywhere from 10 to 20 years, depending on the conditions mentioned earlier. Fireproof expanding foam that is well-maintained and installed correctly in a stable environment will typically last longer.

Is spray foam 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.

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.

Will expanding foam stop mice?

In fact, expanding foam products have been developed that bond to most common building materials while also including an olfactory deterrent to help prevent pest incursion. One such foam is specially formulated to block mice, birds, bats, tree squirrels, and other pests such as ants, roaches, and spiders.

What happens to expanding foam if it 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.

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

Independent chartered building surveyor, Geoff Hunt said due to government initiatives open cell spray foam has gained popularity in recent years. But he called for 'caution and refusals on higher-risk applications' as mortgage lenders struggle to assess spray foam.

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.

What is better than spray foam insulation?

While both types of insulation are great choices for home insulation, fiberglass insulation is generally considered to be safer than spray foam insulation. This is because spray foam contains a special type of chemical called isocyanate, which is toxic when inhaled.

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