Callahan County is in IECC Climate Zone 3B (Warm - Dry). Get accurate Manual J load calculations with official ASHRAE design temperatures for Callahan County.
Callahan County, Texas is classified under IECC Climate Zone 3B (Warm - Dry), a mixed-climate region with dry moisture conditions. With 4 ZIP codes and 1 communities, every HVAC installation in Callahan County must use the ASHRAE design temperatures of 22°F (99% winter heating) and 101°F (1% summer cooling) for accurate Manual J load calculations.
With balanced heating and cooling loads, Callahan County homes require well-rounded insulation — R-20 walls, R-30 ceilings, R-19 floors — and windows with both U-factor 0.32 and SHGC 0.25 to handle both winter lows and summer highs.
Minimum insulation R-values and window performance for Climate Zone 3B in Callahan County, TX.
| Building Component | Minimum Requirement | Unit |
|---|---|---|
| Ceiling / Attic Insulation | R-30 | R-value |
| Wall Insulation | R-20 | R-value |
| Floor Insulation | R-19 | R-value |
| Window U-Factor | 0.32 | BTU/hr-ft²-°F |
| Window SHGC | 0.25 | Coefficient |
| Air Infiltration | 0.15 | ACH50 |
Climate Zone 3B requires precise load calculations. Upload your Callahan County blueprint and get a professional Manual J report in 60 seconds— first report is FREE. Pre-loaded with Callahan County's exact design temperatures (22°F winter / 101°F summer).
Enter your ZIP code to confirm it's in Callahan County and get climate zone details.
Official ASHRAE design temperatures for Callahan County, TX, used for accurate Manual J load calculations.
Minimum insulation and window requirements for Callahan County per IECC 2021 energy code.
Climate Zone 3B: Warm - Dry - Warm climate with low humidity, hot summers and cool winters. Moderate heating and cooling loads.
1 cities and communities in Callahan County share Climate Zone 3B requirements.
Compare climate zones with other counties in Texas. Different zones require different HVAC equipment sizing.
Upload your Callahan County blueprint and get a professional Manual J load calculation using official Zone 3B design temperatures. First report is FREE.
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