McMullen County is in IECC Climate Zone 2A (Hot - Humid). Get accurate Manual J load calculations with official ASHRAE design temperatures for McMullen County.
McMullen County, Texas is classified under IECC Climate Zone 2A (Hot - Humid), a cooling-dominated region with humid moisture conditions. With 2 ZIP codes and 1 communities, every HVAC installation in McMullen County must use the ASHRAE design temperatures of 35°F (99% winter heating) and 102°F (1% summer cooling) for accurate Manual J load calculations.
As a cooling-dominated zone, controlling solar heat gain is essential in McMullen County. Windows must have an SHGC of 0.25 or lower, along with R-13 wall and R-30 ceiling insulation. Proper sizing prevents oversized AC systems that short-cycle and waste energy.
Minimum insulation R-values and window performance for Climate Zone 2A in McMullen County, TX.
| Building Component | Minimum Requirement | Unit |
|---|---|---|
| Ceiling / Attic Insulation | R-30 | R-value |
| Wall Insulation | R-13 | R-value |
| Floor Insulation | R-13 | R-value |
| Window U-Factor | 0.4 | BTU/hr-ft²-°F |
| Window SHGC | 0.25 | Coefficient |
| Air Infiltration | 0.25 | ACH50 |
Climate Zone 2A requires precise load calculations. Upload your McMullen County blueprint and get a professional Manual J report in 60 seconds— first report is FREE. Pre-loaded with McMullen County's exact design temperatures (35°F winter / 102°F summer).
Enter your ZIP code to confirm it's in McMullen County and get climate zone details.
Official ASHRAE design temperatures for McMullen County, TX, used for accurate Manual J load calculations.
Minimum insulation and window requirements for McMullen County per IECC 2021 energy code.
Climate Zone 2A: Hot - Humid - Cooling-dominated with hot, humid summers and mild winters. Significant cooling loads with moderate heating needs.
1 cities and communities in McMullen County share Climate Zone 2A requirements.
Compare climate zones with other counties in Texas. Different zones require different HVAC equipment sizing.
Upload your McMullen County blueprint and get a professional Manual J load calculation using official Zone 2A design temperatures. First report is FREE.
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