Texas Insulation Requirements: IECC Code Guide for Contractors

Published July 3, 2026 · Prestige Insulation

Texas spans three IECC climate zones — zone 2, zone 3, and a small portion of zone 4 in the Panhandle — and each has different minimum R-value requirements for walls, attics, and floors. Here's what contractors need to know.

Texas climate zones

Zone	Cities	Description
2A	Houston, San Antonio, Corpus Christi, McAllen, Beaumont	Hot-humid
3A	Dallas, Fort Worth, Austin, Waco, Tyler	Mixed-humid
3B	El Paso, Midland, Odessa, Lubbock	Mixed-dry (high desert)
4A/4B	Amarillo, parts of the Panhandle	Cold (small area)

Zone 2A requirements (Houston, San Antonio area)

Assembly	IECC 2021 Minimum	Common Spec
Above-grade walls (2×4)	R-13	R-13 kraft-faced
Above-grade walls (2×6)	R-19	R-19 or R-21
Attic floor	R-30	R-30 or R-38 (recommended)
Floor over unconditioned	R-13	R-13 or R-19
Basement wall	Not required (zone 2)	—

Zone 3A requirements (Dallas-Fort Worth, Austin area)

Assembly	IECC 2021 Minimum	Common Spec
Above-grade walls (2×4)	R-13 + R-3.75 ci OR R-15	R-15 HD (most common)
Above-grade walls (2×6)	R-19	R-21 HD
Attic floor	R-38	R-38 to R-49
Floor over unconditioned	R-19	R-19 or R-30

Note: Zone 3A wall requirements changed significantly from IECC 2018 to 2021. If your jurisdiction has adopted 2021, you need R-15 or continuous insulation for 2×4 exterior walls — R-13 alone is no longer sufficient.

Zone 3B requirements (El Paso, West Texas)

Zone 3B (dry/arid) generally mirrors zone 3A for wall and attic requirements under IECC 2021 — R-15 for 2×4 walls, R-38 for attic floors. The dry climate means vapor management differs (no kraft facing typically needed).

Texas adoption status

Texas adopted the 2015 IECC statewide. Individual cities and counties may have adopted later versions — Austin, for example, has adopted stricter local amendments. Always verify with the local jurisdiction before specifying. Many Texas contractors err on the side of the more recent code.

What to order for Texas projects

• Houston / San Antonio (Zone 2A): R-13 walls (2×4), R-19 walls (2×6), R-30 or R-38 attic
• DFW / Austin (Zone 3A): R-15 HD walls (2×4), R-21 attic batts (2×6), R-38 attic floor
• All Texas projects: Unfaced attic batts, kraft-faced or unfaced wall batts depending on assembly

Delivering to Texas

We deliver insulation to contractors throughout Texas — Houston, Dallas, San Antonio, Austin, Fort Worth, and surrounding areas. Same-day quotes, next-day delivery on stocked product. See our Texas delivery page →