Knox County is in IECC Climate Zone 3B (Warm - Dry). Get accurate Manual J load calculations with official ASHRAE design temperatures for Knox County.
Knox 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 Knox County must use the ASHRAE design temperatures of 20°F (99% winter heating) and 101°F (1% summer cooling) for accurate Manual J load calculations.
With balanced heating and cooling loads, Knox 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 Knox 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 Knox County blueprint and get a professional Manual J report in 60 seconds— first report is FREE. Pre-loaded with Knox County's exact design temperatures (20°F winter / 101°F summer).
Enter your ZIP code to confirm it's in Knox County and get climate zone details.
Official ASHRAE design temperatures for Knox County, TX, used for accurate Manual J load calculations.
Minimum insulation and window requirements for Knox 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 Knox County share Climate Zone 3B requirements.
Compare climate zones with other counties in Texas. Different zones require different HVAC equipment sizing.
Upload your Knox County blueprint and get a professional Manual J load calculation using official Zone 3B design temperatures. First report is FREE.
Join 10,000+ Texas contractors who trust AutoHVAC