Insulation plays a big role in keeping your home comfortable and energy efficient. Two of the most popular types of insulation used in homes today are spray foam and fiberglass. Each type has its own benefits and drawbacks, and the right choice depends on your budget, climate, building design, and how long you plan to stay in your home. Below is a detailed comparison of both types, explained in simple terms to help you make the best decision.

What Is Spray Foam Insulation?

Spray foam insulation is made from a liquid chemical mixture that is sprayed onto surfaces like walls, ceilings, and floors. Once applied, the foam expands quickly and hardens, creating a solid barrier that blocks air, moisture, and even sound. There are two main types of spray foam:

• Open-cell spray foam: This is softer and more flexible. It is a good choice for soundproofing the interior of the house because it permits some moisture and air to pass through.

• Closed-cell spray foam: This is denser, stronger, and acts as both an insulator and a moisture barrier. It is often used in areas where moisture control is important, like basements and crawl spaces.

What Is Fiberglass Insulation?

Fiberglass insulation is made from very fine glass fibers and is typically found in batts (pre-cut panels) or rolls. It’s the most commonly used insulation in residential buildings and is usually installed between wall studs, floor joists, and ceilingrafters. 

Fiberglass can also be purchased in loose-fill form, which is blown into attics or wall cavities.

Spray foam insulation’s benefits and drawbacks

Pros:

Superb Air Seal: Spray foam forms a tight seal that stops air leaks by expanding to fill in cracks and spaces. Your heating and cooling systems operate more effectively as a result.

• High R-Value: Spray foam has a higher R-value per inch than most other types of insulation. This means it’s better at resisting heat flow.

• Moisture Barrier: Closed-cell spray foam resists water and can help prevent mold growth.

• Durable and Long-Lasting: Once installed, spray foam stays in place and doesn’t settle or lose shape over time.

• Improves Indoor Air Quality: Because it seals air leaks, spray foam can help reduce the amount of dust, pollen, and other allergens that enter your home.

Cons:

• High Cost: Spray foam insulation is more expensive than fiberglass, both in terms of material and installation.

• Professional Installation Required: It requires special equipment and training, so it’s not suitable for DIY projects.

• Difficult to Remove: If you need to make changes later, it can be difficult to remove spray foam because it is permanent once it is applied and cured.

Pros and Cons of Fiberglass Insulation

Pros:

• Lower Cost: Fiberglass is generally much cheaper than spray foam, making it a good option for large projects or homeowners on a tight budget.

• Easy to Install: It’s simple enough for many homeowners to install themselves with basic tools and safety gear.

• Readily Available: You can find fiberglass insulation at nearly every home improvement store.

• Fire-Resistant: Fiberglass does not burn easily, which can provide added safety in your home.

Cons:

• Less Effective at Air Sealing: Fiberglass doesn’t stop air movement very well unless combined with a separate air barrier.

• Can Lose Performance Over Time: It may sag or shift, especially if not installed properly, which can leave gaps.

• Moisture Issues: If fiberglass gets wet, it loses its insulating ability and may promote mold growth.

• Skin and Lung Irritation: Handling fiberglass can cause irritation if you don’t wear proper protection.

Performance and Energy Efficiency

A major factor when comparing these two types of insulation is how well they prevent heat transfer, which is measured by R-value. The higher the R-value, the better the insulation:

• Spray Foam:

• Open-cell: R-value around 3.5 to 3.6 per inch

• Closed-cell: R-value around 6.5 to 7 per inch

• Fiberglass:

• Batts or rolls: R-value around 2.9 to 3.8 per inch

This means closed-cell spray foam is far more efficient at insulating per inch than fiberglass, especially in smaller wall cavities.

Cost Considerations

Cost is one of the biggest differences between the two. On average:

• Fiberglass insulation may cost around $0.50 to $1.50 per square foot.

• Spray foam insulation can range from $1.50 to $3.50 per square foot for open-cell, and even more for closed-cell.

While fiberglass is cheaper upfront, spray foam can lead to significant savings on energy bills over time, often paying for itself in a few years.

Where Each Type Works Best

Spray Foam:

• Ideal for hard-to-reach areas like attics, crawl spaces, and rim joists

• Great for homes in humid or extreme climates

• Excellent choice when you need both insulation and air/moisture sealing

Fiberglass:

• Good for standard wall cavities and ceilings

• Cost-effective for large or simple projects

• Works well in dry climates or when paired with an air barrier

What We Recommend

If you’re looking for maximum performance and can afford a higher upfront investment, closed-cell spray foam is the best choice. It gives you high insulation, moisture resistance, as well as improved year-round comfort.

Fiberglass insulation is still a dependable and affordable choice, though, if you’re remodeling a simple space, have a limited budget, or are insulating areas that don’t require high-performance sealing. Just make sure it stays dry and is installed correctly.

For the best of both worlds, many homeowners use a mix of both: spray foam in critical areas like basements and attics, and fiberglass in walls and ceilings.

Final Thoughts

Choosing between spray foam and fiberglass insulation is not just about cost. It’s also about long-term energy savings, comfort, and how your home is built. Spray foam gives better performance but comes at a higher price. Fiberglass is budget-friendly and easier to install but may not seal your home as well.

Think about your goals—whether it’s saving on utility bills, controlling moisture, or simply staying warm and cool year-round—and pick the insulation type that fits those needs best.

FAQ For Spray Foam vs. Fiberglass Insulation:

1. Which is better, spray foam or fiberglass insulation?

A. Spray foam is better for energy savings and sealing air leaks, but it’s more expensive. Fiberglass is cheaper and easier to install but less effective at blocking air.

2. What are the pros and cons of spray foam insulation?

A. Pros: Seals air leaks, high R-value, blocks moisture, lasts long.

Cons: Expensive, needs professional installation, hard to remove.

3. What is the biggest problem with fiberglass insulation?

A. It doesn’t block air well and loses performance if it gets wet or shifts out of place.

4. What is the problem with fiberglass insulation?

A. It can sag, allow air leaks, and grow mold if it gets wet. Also, it may cause skin or lung irritation when handled.

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