Is Spray Foam Insulation Waterproof?

When researching building materials, you can’t help but wonder how your options measure up in the case of disaster. As nice as it is to know that a product performs well under normal conditions, what if the worst happens? You may be worried about your basement flooding or trying to find a solution so it won’t flood again. Is spray foam insulation the product to put your mind at ease?

South Central Services has installed spray foam insulation in hundreds of projects. One of our responsibilities is informing customers about what spray foam is and is not, as well as the problems it can and cannot solve.

By the end of this article, you will know:

• If spray foam insulation is waterproof
• What happens to spray foam in a flood
• How homes prevent water damage

Don't have time to read right now? Check out everything you need to know at a glance.

Is Spray Foam Insulation Waterproof?

Spray foam insulation is not waterproof, but neither is any other residential insulation on the market. You will not find a waterproof insulation. The role of insulation is to prevent heat transfer, not water transfer.

When spray foam is installed in commercial roofing applications, the product is waterproof. You can read more in-depth about the water repellent properties of roofing foam from our friends at GIDEON.

While it may make sense for all parts of a home to be waterproof, only the assemblies that come in contact with water regularly need to be waterproof. Instead of waterproofing, insulations and other building materials are rated for their vapor permeability. In plain words, insulations may not stop liquid water but can stop water as a gas.

Spray foam insulation can stop water vapor transfer and is also flood-resistant and mold-resistant.

What Does Flood-Resistant Mean?

Closed cell spray foam is considered a flood-resistant product. According to the Federal Emergency Management Agency (FEMA), flood-resistant refers to a material that will not sustain significant damage after 72 hours of contact with flood waters.

Flood-resistant materials do not prevent other materials touching flood waters. You can think of the difference between waterproofing and flood-resistant in the following way. Waterproofing products protect other materials from flood damage, while flood-resistant materials only protect themselves against flood damage.

What Does Mold-Resistant Mean?

Closed cell spray foam is also considered a mold-resistant product. Mold resistance is precisely what it sounds like: products that resist mold growth. Mold resistance does not guarantee that mold will not grow. Instead, mold-resistant materials are less likely to grow mold in humid conditions.

What Happens to Spray Foam When Flooding Occurs?

The outcome of flooding and spray foam insulation depends on which spray foam was installed.

Closed cell foam is the only insulation product classified by FEMA as acceptable in the case of flooding. According to FEMA, closed cell spray foam is a material that “can survive wetting and drying and may be successfully cleaned after a flood to render them free of most harmful pollutants.” Unless damages occurred behind the insulation, closed cell foam may not need to be replaced after flooding as long as it is dried out. Ruined drywall in front of the insulation may be removed and disposed of, but the closed cell foam can be kept if undamaged and able to dry out.

In terms of flood-resistance, open cell foam is classified by FEMA with cellulose and cotton insulations. According to FEMA, open cell spray foam is a material that “cannot survive the wetting and drying associated with floods.” In the case of flooding, open cell spray foam would need to be removed and replaced.

How Homes Prevent Water Damage

The primary way that water damage occurs is water leaking from outside to the inside. Waterproofing products are mainly installed outside the home, not inside the home. For example, waterproofing products may be installed on the roof of a building to stop rainfall from entering. Waterproofing measures may be taken in basements where water seeps in.

The most common products for roof and basement waterproofing are coatings and membranes. These products are liquid-applied by professionals to ensure rainfall rolls off your roof and groundwater stays inside the ground, instead of seeping inside your home.

Homeowners can install these waterproof coatings themselves. Before attempting to install, homeowners should read about necessary personal protective equipment (PPE).

The Bottom Line About Waterproof Insulation

Waterproof insulation does not exist. The role of insulation in a home is to prevent heat transfer, not water transfer. While waterproofing is a vital aspect of home building, waterproofing products are most appropriate for roof and basement applications.

If you are concerned about having to replace your insulation in the case of a flood, consider closed cell spray foam. Closed cell spray foam is the only insulation the Federal Emergency Management Agency recognizes as reusable after flooding.

Interested in other differences between closed cell and open cell spray foam? Read our comparison of open cell and closed cell.

Want to make sure spray foam insulation offers the features you need? Next you should check out these articles to understand spray foam performance.

• Is Spray Foam Flammable?
• Is Spray Foam Insulation Safe?
• Can Spray Foam Insulation Fail?