When it comes to insulating your attic, there’s no shortage of options — but two of the most commonly compared are blown-in insulation and spray foam insulation. Each has its own strengths, weaknesses, and ideal use cases, and the right choice often depends on your home’s structure, your climate, and your long-term energy goals.
Blown-in insulation is known for being cost-effective and easy to install, especially in hard-to-reach attic spaces. Spray foam, on the other hand, is a premium product praised for its high R-value and strong air-sealing capabilities — though it comes with a higher price tag and more complex installation requirements.
In this article, we’ll break down the differences between spray foam insulation vs blown-in insulation, including cost, efficiency, durability, and installation.
1. Material and Installation: Spray Foam vs Blown-In Insulation
The most fundamental difference between spray foam insulation and blown-in insulation lies in how they are made and how they’re installed.
Blown-In Insulation
Blown-in insulation — typically made from fiberglass, cellulose, or rock wool — is installed using a machine that distributes the loose-fill material across attic floors or into wall cavities. It’s especially effective for covering irregular spaces, filling gaps, and topping off existing insulation.
- Non-invasive and quick to install
- Ideal for retrofitting attics without major construction
- Does not require curing or long dry times
- Cost-effective for large surface coverage
Spray Foam Insulation
Spray foam insulation is a two-part chemical mixture that expands on contact to fill cavities and seal air leaks. It’s applied as a liquid and then hardens into a solid foam.
- Available in open-cell and closed-cell varieties
- Provides insulation and air sealing in one step
- Requires professional application due to chemical handling
- Takes longer to apply and cure compared to blown-in
2. R-Value and Energy Efficiency
One of the most important factors when comparing spray foam insulation vs blown-in insulation is the R-value — a measure of thermal resistance. The higher the R-value, the better the material insulates your home from heat and cold.
Blown-In Insulation
Blown-in insulation typically offers an R-value of R-2.3 to R-4.3 per inch, depending on the material used. Fiberglass and cellulose are the most common types used in attics, and they’re effective at reducing heat loss when applied in sufficient depth. However, blown-in insulation does not provide an air seal on its own — air leaks around vents, light fixtures, and attic hatches can still impact overall performance if not sealed properly.
Spray Foam Insulation
Spray foam delivers significantly higher R-values:
- Open-cell foam: ~R-3.7 per inch
- Closed-cell foam: up to R-6.7 per inch
Because spray foam expands and hardens into a dense barrier, it not only insulates but also seals air leaks. This double function can significantly improve a home’s energy efficiency, especially in extreme climates. It’s been shown to reduce energy costs by up to 40%, depending on how well the home was previously sealed.
3. Durability and Lifespan
When choosing between blown-in insulation and spray foam, it's important to consider how long each material will maintain its insulating properties over time.
Blown-In Insulation
Blown-in fiberglass and cellulose can provide effective insulation for 20 to 50 years, depending on installation quality, ventilation, and moisture exposure. However, these materials are prone to settling over time, which can reduce their effectiveness unless topped off or maintained. In humid or leaky attics, moisture can degrade cellulose faster, leading to mold or reduced performance.
Spray Foam Insulation
Spray foam is more stable over the long term. Closed-cell spray foam can last 80 to 100 years without sagging or shifting. It’s also resistant to moisture, air infiltration, and pests. Because of its rigid structure, spray foam holds its form and insulation value with minimal maintenance, making it a longer-term solution for homeowners looking to insulate once and not revisit it for decades.
4. Cost and Installation Complexity
Budget and project scope often play a major role in deciding between spray foam insulation vs blown-in insulation, especially when insulating a large attic.
Blown-In Insulation
Blown-in insulation is generally more affordable and quicker to install. On average, the cost ranges from $0.50 to $2.30 per square foot, depending on the material (fiberglass or cellulose) and attic conditions. It’s also less labor-intensive and safer to install, making it a common choice for both homeowners and contractors looking for a cost-effective solution that delivers reliable results.
Spray Foam Insulation
Spray foam comes at a higher price point. Material and professional installation can range from $1.30 to $3.10 per square foot for closed-cell foam, with open-cell foam being slightly less expensive. Due to chemical handling and equipment needs, spray foam must be applied by trained professionals. The process also takes longer and requires curing time before the attic can be safely re-entered.
While spray foam offers stronger performance, the higher initial investment may not be suitable for all projects — particularly when budget is a concern.
5. Environmental and Health Considerations
In addition to performance and cost, homeowners often weigh the environmental impact and health implications when deciding between spray foam insulation vs blown-in insulation.
Blown-In Insulation
Blown-in insulation — particularly cellulose — is considered one of the more eco-friendly options available. Cellulose is made from recycled paper products, and fiberglass options often contain a significant percentage of recycled glass. These materials are non-toxic, don’t emit harmful gases, and can be safely installed with minimal protective gear. However, blown-in insulation is more vulnerable to moisture absorption, which can lead to mold if the attic is not properly ventilated.
Spray Foam Insulation
Spray foam insulation is petroleum-based and involves the use of chemical compounds that expand and harden during application. While the foam is inert after curing, the installation process releases fumes that require full protective gear and ventilation. Some formulations may emit volatile organic compounds (VOCs), especially during application, which is why professional installation is essential. From an environmental standpoint, spray foam has a higher carbon footprint due to its production and chemical composition.
Choosing What’s Right for Your Attic
Both blown-in insulation and spray foam insulation have their advantages. Spray foam offers higher R-values, excellent air sealing, and long-term durability — but it comes at a significantly higher cost and requires specialized installation. Blown-in insulation, while more affordable and easier to install, still provides reliable thermal performance and is a proven solution for attics, especially when combined with proper air sealing or heat-reflective barriers.
At Affordable Attic Insulation, we focus on what delivers the most value and efficiency for homes in the Houston and Katy area. That’s why we install Blown-In Fiberglass Insulation — a dependable, cost-effective choice for improving comfort and reducing energy costs.
For added summer performance, we also offer Spray-On Radiant Barrier Paint, a highly effective solution that reflects up to 75% of radiant heat from the roof. When used together, these two systems help create a well-insulated attic that keeps your home cooler, reduces strain on your A/C, and improves year-round energy efficiency — all without the high cost of spray foam.
Ready to improve your attic’s insulation?
Contact us today for a free estimate and let’s make your home more efficient, one layer at a time.
