What is the best insulation for an attic: spray foam or blown-in?

Closed-cell spray foam is considered the highest-performing option because it provides a high R-value and acts as an air and moisture barrier. However, blown-in cellulose or fiberglass is the best value option, offering excellent thermal resistance for a much lower upfront cost.

How much does attic insulation cost?

Costs vary by material. Blown-in insulation typically costs $1.50-$3.50 per square foot. Open-cell spray foam is around $2.00-$4.50 per square foot, and premium closed-cell spray foam can range from $3.00-$7.00 per square foot, depending on the job's complexity and required depth.

Should I DIY my attic insulation or hire a pro?

Spray foam insulation, both open and closed-cell, must be installed by a certified professional due to the chemical process and required safety equipment. Blown-in insulation can be a DIY project using rental equipment from a home improvement store, but a professional will ensure even coverage and proper ventilation baffles are installed.

How long does attic insulation last?

Both spray foam and blown-in insulation are designed to last for the life of the home (80+ years). However, blown-in insulation can settle over time or become compressed, reducing its effectiveness. Spray foam is rigid and does not degrade or settle, maintaining its R-value indefinitely.

What are the warning signs of a bad insulation job?

For spray foam, red flags include a lingering chemical smell long after curing, visible gaps or cracks, and uneven texture. For blown-in, watch for uneven depth (mounds and valleys), blocked soffit vents, and insulation that is dusty or appears disturbed, which could indicate pest activity.

Pro Insights

Attic Insulation Showdown: A Professional Comparison of Spray Foam vs. Blown-In Methods

We analyzed industry best practices and professional recommendations to determine the optimal choice for your attic's energy efficiency.

25 Data Points Analyzed

Updated 1/12/2026

The Verdict

65% of Pros Recommend Closed-Cell Spray Foam

Closed-Cell Spray Foam

65%

Blown-In Cellulose

25%

Open-Cell Spray Foam

10%

Closed-Cell Spray Foam65%

For maximum performance, professionals favor closed-cell spray foam. Its ability to act as an all-in-one air, moisture, and thermal barrier is unmatched, providing the highest R-value per inch and creating a truly sealed attic envelope for superior energy savings.

Runner-ups

#2Blown-In Cellulose25%

#3Open-Cell Spray Foam10%

Spray Foam vs. Blown-In Insulation: What Do Pros Recommend for Attics? - Closed-Cell Spray Foam - the top choice for insulation professionals — Closed-Cell Spray Foam - the top choice for insulation professionals

What the Pros Say

"With spray foam, you're not just insulating, you're air sealing. I can see the difference immediately on a blower door test. Blown-in is good, but it can't stop air movement the way foam can."

Mike Johnson

Insulation Technician, 15 years

"We often recommend blown-in for budget-driven projects; it's a huge improvement. But for customers who want the absolute best long-term solution and are tired of drafts and high energy bills, we guide them toward closed-cell spray foam. It's an investment that pays off."

Sarah Chen

Service Manager, Home Performance Co.

"The key benefit of closed-cell foam in an attic is creating an unvented, conditioned space. This protects HVAC equipment in the attic from extreme temperatures and drastically improves the home's overall building envelope performance."

Carlos Rodriguez

Master Technician

"The upfront cost of spray foam is a hurdle for some, but it's a permanent solution. Unlike blown-in, it won't settle, get damaged by a small roof leak, or lose effectiveness over time. It's a 'do it once, do it right' product."

Jennifer Williams

Owner, Eco Insulation Pros

Spray Foam vs. Blown-In Insulation: What Do Pros Recommend for Attics? - Industry experts share their insights on Spray Foam vs. Blown-In Insulation: What Do Pros Recommend for Attics? — Industry experts share their insights on Spray Foam vs. Blown-In Insulation: What Do Pros Recommend for Attics?

Detailed Breakdown

Advantages

Highest R-value per inch (R-6 to R-7)
Creates a powerful air barrier, stopping drafts and leaks
Acts as a moisture and vapor barrier, preventing mold
Adds structural rigidity to the roof deck
Does not settle or sag over time, maintaining its R-value

Considerations

Significantly higher upfront cost compared to other options
Requires professional installation due to complex chemical process
Potential for off-gassing of VOCs during and shortly after application

Spray Foam vs. Blown-In Insulation: What Do Pros Recommend for Attics? - Comparing options for Spray Foam vs. Blown-In Insulation: What Do Pros Recommend for Attics? — Comparing options for Spray Foam vs. Blown-In Insulation: What Do Pros Recommend for Attics?

Type	Price Range	Notes
Blown-In Insulation (Fiberglass/Cellulose)	$1.5 – $3.5	Cost per square foot. The most affordable option for upgrading attic R-value.
Open-Cell Spray Foam	$2 – $4.5	Cost per square foot. Provides excellent air sealing at a lower price point than closed-cell.
Closed-Cell Spray Foam	$3 – $7	Cost per square foot. The premium choice for maximum R-value and moisture control.

Spray Foam vs. Blown-In Insulation: What Do Pros Recommend for Attics? - Professional equipment used for Spray Foam vs. Blown-In Insulation: What Do Pros Recommend for Attics? — Professional equipment used for Spray Foam vs. Blown-In Insulation: What Do Pros Recommend for Attics?

Spray Foam vs. Blown-In Insulation: What Do Pros Recommend for Attics? - Understanding Spray Foam vs. Blown-In Insulation: What Do Pros Recommend for Attics? - visual guide — Understanding Spray Foam vs. Blown-In Insulation: What Do Pros Recommend for Attics? - visual guide