Is Spray Foam Waterproof?

Spray foam insulation has become a popular choice in commercial buildings due to its energy efficiency.

But one question we often get is: Is spray foam insulation waterproof?

The short answer? It depends on the type of foam.

At GIDEON, we've been working with spray foam roofing for over 20 years, and in this article, will explain exactly when spray foam is waterproof and when it's not. We'll also talk about why waterproofing is so critical, particularly when it comes to energy efficiency.

Table of Contents

• What Is Spray Foam Insulation?
• How Spray Foam Is Used
• The Benefits of Spray Foam
• Is Spray Foam Waterproof?

What Is Spray Foam Insulation?

Spray foam insulation, or SPF (Spray Polyurethane Foam), is a unique and versatile insulation material that has gained popularity in both residential and commercial applications. Unlike traditional insulation materials (like rigid foam boards) SPF is a liquid that is sprayed onto surfaces, where it expands and hardens.

How does spray foam work? Well, it is composed of two chemicals that are heated and sprayed simultaneously from a spray foam gun. As the chemicals mix, they react with each other, expanding rapidly to form a foam that fits snugly in wall cavities and fills cracks.

How Spray Foam Is Used

Spray foam insulation is used in a wide array of applications, ranging from insulating walls, ceilings, and floors to sealing gaps around windows and doors. It provides excellent thermal insulation and also plays a vital role in air sealing, thus reducing energy loss.

Walls and Ceilings: SPF creates an effective barrier against heat and cold, enhancing the energy efficiency of the building.

Roofing Applications: The closed cell type is commonly used in roofing for its waterproofing abilities. It is typically combined with an elastomeric coating when used in roofing. 

Sealing Gaps: Its expandable nature makes it perfect for filling voids and preventing drafts.

Specialized Applications: Some unique applications include soundproofing and flotation for boats.

The Benefits of Spray Foam

The Most Energy Efficient Insulator in the World

Spray foam insulation has the highest R-value (a measurement of a material's ability to prevent heat transfer) of any insulating material currently available. Most SPF clocks an r-value of 6.5-7.0, substantially higher than other common insulators, like rigid foam board.

Where spray foam really overperforms, however, is in the U-value. U-value measures the capacity of an entire building element (like a wall assembly or roof assembly) to conduct heat. It takes into account gaps between materials (like seams between insulation boards), as well as the thermal conductivity of additional materials like metal fasteners.

Because spray foam is a monolithic material, that is, it doesn't require metal fasteners (which can conduct heat) and it eliminates gaps, it significantly outperforms materials like foam board.

Can Pay for Itself with Reduced HVAC Costs

Because of it's superior thermal resistance, spray foam can reduce HVAC costs substantially, with a study conducted by Texas A&M concluding a spray foam roof can pay for itself in just 5 years.

Easy To Maintain

When used as a roofing system, spray foam is easy to maintain because it's typically installed with an elastomeric coating, which provides excellent protection from the elements and can be easily reapplied every 10-20 years. There are also no seams, joints, or fasteners - all of which can wear out and cause leaks.

Is Spray Foam Waterproof?

The short answer is yes, it can be waterproof, but it depends on the type and density of foam.

Open Cell Spray Foam Insulation vs Closed Cell Foam Spray Foam Insulation

Spray foam is composed of millions of tiny cells, and spray foam insulation can be broken down into two types, based on the nature of the cells: closed cell spray foam and open cell spray foam.

Open Cell Foam: This type of foam is softer and more flexible. It's open cell structure allows water and moisture to penetrate. It typically has a lower density, around 0.5 pounds per cubic foot.

Closed Cell Foam: In contrast, closed cell foam is composed of cells that are completely closed and sealed off from one another. This mean that, even if one cell is broken, water will not flow into the other cells. It is denser (often 1.75 pounds per cubic foot or more), water-resistant, and can be fully waterproof at higher densities.

Why Waterproof Insulation Is So Critical

When it comes to roofing, the importance of waterproofing is obvious: the primary purpose of your roof is to prevent water intrusion.

But waterproofing is also critical from an energy-efficiency standpoint, because water conducts heat better than air. If the air pockets within the spray foam become saturated with water, the material loses much of it's ability to insulate, becoming a "heat sink".

The Upshot

In conclusion, whether spray foam insulation is waterproof depends on the type of foam, its density, and its application. Closed cell foam offers robust waterproofing capabilities suitable for many applications, while open cell foam does not. Understanding the specific needs of a project and the differences in R-value and U-value between these two types of foam is crucial for choosing the right material.

Now that you’ve learned about the waterproofing capabilities of spray foam roofing, reach out to us at GIDEON for a free 30 minute consultation. Every building and situation is unique, and we can offer tailored advice to help you get the solution that’s right for you.