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How-To & Guides 8 min read • Jun 12, 2026

Spray Foam Insulation in Texas: Open-Cell vs. Closed-Cell Costs & Energy Savings

Comprehensive guide to unvented attic encapsulation and wall insulation in Texas. Comparing open-cell vs. closed-cell foam, R-values, HVAC downsizing, and pricing.

In a typical Texas summer, vented attic temperatures reach 140°F. Encapsulating the underside of the roof deck with spray foam creates an airtight semi-conditioned attic, keeping temperatures within 10 degrees of living areas.

Open-Cell vs. Closed-Cell Comparison

  • Open-Cell Foam (0.5 lb/cu ft): R-3.6 to R-3.8 per inch. Expands 100x to seal every crack. Economical for roof decks and interior walls.
  • Closed-Cell Foam (2.0 lb/cu ft): R-6.5 to R-7.0 per inch. Rigid moisture-impermeable barrier, adds structural shear strength to walls.

Frequently Asked Questions

How much does spray foam insulation cost in Texas?

Open-cell spray foam typically costs $1.50 to $2.20 per board foot (one sq ft at 1" thickness). Closed-cell spray foam runs $2.50 to $3.50 per board foot. Encapsulating a typical 2,000 sq ft Texas attic runs $4,500 to $7,500.

Which is better for Texas attics: open-cell or closed-cell?

Open-cell (0.5 lb) is standard for residential roof deck encapsulation in non-flood zones because it seals air leaks and allows roof leaks to be detected. Closed-cell (2.0 lb) adds structural racking strength and acts as a vapor barrier, ideal for metal buildings and coastal zones.

Why does spray foam require HVAC reconsideration in Texas?

Encapsulating an attic turns it into conditioned space, drastically reducing home cooling load by 20% to 40%. Oversized existing AC units may short-cycle, leading to high indoor humidity unless a dedicated dehumidifier is installed.

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