Spray Insulation Foam vs Gap Filler Foam: Key Differences, Uses & Cost

Which is better for sealing and insulating your home—spray foam insulation or gap filler? Both have their merits, but the differences in their composition, application, and long-term benefits make the choice significant. Spray foam insulation boasts an R-value of up to R-8 per inch, offering energy savings and comprehensive coverage for large areas. In contrast, gap fillers excel in sealing smaller, more precise spaces, making them an ideal choice for minor DIY projects. This blog dives deep into these two options, exploring their insulation properties, uses, cost, and more to guide you in making an informed decision.

What Is Spray Insulation Foam?

Spray foam insulation is a polyurethane-based material that expands upon application to create an airtight thermal barrier. It reduces heat transfer, lowers energy loss, and improves indoor comfort. Two main types exist: open-cell and closed-cell spray foam.

Key Attributes of Spray Insulation Foam

• Material: Polyurethane foam

• Function: Thermal insulation, air sealing

• R-Value: R-3.5 to R-6.5 per inch

• Durability: 20+ years

• Application: Walls, attics, crawl spaces

What Is a Gap Filler Foam?

A gap filler is a foam or caulk-based product used to seal small cracks or voids, designed for sealing small gaps up to 3 inches wide. It prevents air leakage and blocks moisture, but does not provide significant insulation. Common forms include expanding foam sealants and silicone-based fillers.

Key Attributes of Gap Fillers

• Material: Polyurethane or silicone-based

• Function: Seal gaps, block drafts

• R-Value: Minimal (not designed for insulation)

• Durability: 5–10 years

• Application: Around windows, doors, and small holes

Although it offers lower R-values compared to spray foam insulation, gap filler foam excels in air sealing capabilities, potentially reducing energy consumption by up to 30% by minimizing drafts. This makes it particularly useful for DIY enthusiasts tackling small-scale projects that require precise sealing without the complexity of mixing components. You can find the use cases and effectiveness of the gap filler in this table.

What Are the Main Differences Between Spray

Insulation Foam  and Gap Fillers?

The primary difference lies in their purpose and performance. Spray foam insulation provides both thermal resistance and air sealing, while gap fillers mainly block drafts and moisture without significant insulation.

Which One Is Better for Energy Efficiency?

Spray foam insulation is better for energy efficiency because it provides a continuous thermal barrier. Gap fillers only seal localized gaps and cannot significantly reduce heat loss in walls or attics.

When Should You Use Spray Foam Insulation?

Use spray foam insulation for large areas that require thermal resistance and airtightness, such as:

• Attic floors and roof decks

• Exterior walls

• Crawl spaces and basements

• Large retrofits for energy savings

When Should You Use a Gap Filler?

Use a gap filler for small voids that allow air or moisture penetration, including:

• Window and door frames

• Electrical penetrations

• Plumbing entry points

• Small cracks in walls

Can Spray Foam Be Used as a Gap Filler?

Yes, spray foam can fill gaps, but it is costlier than traditional gap fillers. For minor sealing tasks, a dedicated gap filler is more practical.

Cost Comparison: Spray Foam vs. Gap Filler

Spray foam insulation, while more expensive initially, presents a compelling case for investment due to its material and professional installation costs. The price for open-cell spray foam ranges from $0.44 to $0.65 per board foot, with closed-cell foam ranging from $1 to $1.50 per board foot. These costs reflect the superior insulation properties and the specialized equipment needed for application. Professional installation ensures optimal coverage and performance, which is crucial for maximizing the insulation's long-term benefits. Although the upfront cost is higher, the potential for significant energy savings over time makes spray foam a valuable option for large-scale insulation projects.

Read more: 'How Much Does Spray Foam Insulation Cost to Install?' 

Gap fillers, on the other hand, offer a more economical solution for smaller sealing tasks. Their cost-effectiveness is attributed to their lower price point and ease of application, often requiring only a simple aerosol can for usage. While gap fillers do not provide the same level of thermal resistance as spray foam, their ability to seal air leaks in smaller areas can still contribute to energy savings. This makes them a practical choice for DIY enthusiasts and homeowners looking to improve energy efficiency cost-effectively.

Pros and Cons of Spray Foam Insulation

Pros

• High R-value

• Air and moisture barrier

• Long lifespan

Cons

• High upfront cost

• Requires professional installation

• Difficult to remove

Read More: 'Types of Insulation: A Comprehensive Guide'

Pros and Cons of Gap Fillers

Pros

• Low cost

• Easy to apply

• Ideal for small repairs

Cons

• No significant insulation value

• Shorter lifespan

• Limited coverage

FAQs

Q: Can spray foam reduce energy bills?

Yes, by up to 40% due to better thermal performance.

Q: Is gap filler waterproof?

Some formulations are water-resistant but not vapor barriers.

Q: Can you paint over spray foam?

A: Yes, after full curing. For nore information, read our blog about 'Can You Paint Spray Foam Insulation?'

Q: Where should expanding foam not be used?

Avoid using expanding foam near electrical boxes, open flame sources, and highly combustible areas. It's crucial to follow manufacturer guidelines for safe application.

Q: Why might spray foam be considered a red flag for lenders?

Some lenders see spray foam as a concern due to potential off-gassing issues, complicating future property sales and inspections. Proper installation and ventilation can mitigate these risks.