In the realm of insulation, spray foam has emerged as a revolutionary solution, offering unparalleled thermal efficiency and air-sealing capabilities. Homeowners and builders alike have embraced this versatile material for its ability to create a tight, energy-efficient envelope around structures. However, a common question that arises in discussions about spray foam insulation is whether it can withstand exposure to water. In this article, we delve into the intricacies of spray foam insulation and explore the effects of moisture on its performance.

Understanding Spray Foam Insulation:

Spray foam insulation is a polyurethane-based material that, when sprayed onto surfaces, expands and hardens to form a seamless and airtight barrier. There are two primary types of spray foam insulation: open-cell and closed-cell. Open-cell foam is less dense and allows for some air permeability, while closed-cell foam is denser and acts as a superior moisture barrier.

The Structure of Spray Foam:

To comprehend how spray foam reacts to water, it’s essential to understand its structure. Closed-cell spray foam is composed of tightly packed cells, each filled with a gas that enhances the insulation properties. The cell structure is what gives closed-cell foam its rigidity and water-resistant qualities. In contrast, open-cell spray foam has a more open-cellular structure, making it less resistant to water.

Can Spray Foam Insulation Get Wet?

The short answer is that while closed-cell spray foam insulation is relatively resistant to water, open-cell foam can absorb moisture. Closed-cell foam is impermeable to liquid water, preventing it from seeping through. However, it’s crucial to note that no insulation material is entirely waterproof, and prolonged exposure to water or moisture can have varying effects on performance.

Closed-Cell Spray Foam and Water Resistance:

Closed-cell spray foam is often touted for its excellent water resistance. Its dense structure and closed-cell formation create a barrier that prevents liquid water from infiltrating. This characteristic makes closed-cell foam an ideal choice for applications in areas prone to high humidity, potential water leaks, or even in basements, where dampness is a concern.

It’s important to distinguish between resistance and impermeability. While closed-cell foam can resist water, it is not entirely impermeable. In cases of extreme water exposure, closed-cell foam can still be affected, especially if the water is under pressure, such as in the case of flooding.

Effects of Water on Open-Cell Spray Foam:

Open-cell spray foam, due to its less dense and more porous structure, is more susceptible to water absorption. While it may not resist liquid water as effectively as closed-cell foam, open-cell insulation can absorb moisture without compromising its insulating properties immediately. However, prolonged exposure to water can lead to reduced effectiveness over time.

When open-cell foam absorbs water, it can affect its thermal performance and structural integrity. The material may become heavier, and the insulation value may diminish. Additionally, the moisture absorbed by open-cell foam can create a conducive environment for mold growth, posing potential health risks and compromising indoor air quality.

Mitigating the Risks:

To maximize the performance of spray foam insulation in wet or humid environments, proper installation and moisture management are crucial. Installing a vapor barrier can help mitigate the risk of moisture infiltration and safeguard the insulation. Additionally, addressing any existing water leaks or drainage issues in the building is essential to prevent potential damage to the insulation over time.


In the debate over whether spray foam insulation can get wet, the type of foam plays a crucial role in determining its resistance to moisture. Closed-cell spray foam stands out for its remarkable water resistance, making it suitable for various applications where exposure to water is a concern. On the other hand, open-cell spray foam, while not as impervious to water, can still perform well when proper precautions are taken during installation and moisture management.

Ultimately, the key to ensuring the longevity and effectiveness of spray foam insulation lies in understanding its characteristics and implementing best practices during installation. While spray foam insulation can resist water to a certain extent, it is not a substitute for proper building design and maintenance. Homeowners and builders should carefully consider their specific needs and environmental conditions when choosing insulation materials to create energy-efficient and durable structures.