Spray Foam vs. Blown-In Insulation: Which Is Better for Texas Attics?

Side-by-Side Comparison

Spray foam: R-6 to R-7 per inch (closed-cell), acts as an air and vapor barrier, $2.50–$4.50 per sq ft installed. Best for attic-encapsulation retrofits and cathedral ceilings.

Blown-in cellulose: R-3.6 to R-3.8 per inch, $0.80–$1.50 per sq ft installed. Best for topping up existing attic insulation to R-38 or R-49.

Blown-in fiberglass: R-2.2 to R-2.7 per inch, $0.60–$1.20 per sq ft installed. Cheapest option, best for new construction and easy top-ups.

What Actually Matters in Dallas-Fort Worth

Attic temperatures here regularly hit 140°F+ in July and August. Air sealing matters more than raw R-value at that point — hot attic air leaking into ceiling cavities can undo half of a well-insulated attic. That's the case for spray foam or a spray-foam-and-blown-in hybrid.

For budget projects, blown-in cellulose to R-49, combined with attic-plane air sealing (top plates, wire penetrations, can lights), gets you 80% of the benefit at 40% of the cost.

When to Choose Each

Choose spray foam if: you're building or gutting, converting to an encapsulated attic, dealing with vaulted ceilings, or want the highest possible energy savings.

Choose blown-in if: you're topping up an existing attic, have a tight budget, or your ductwork is inside the conditioned space and doesn't need attic sealing.