Oklahoma spans 2 IECC climate zones. Find your exact zone, design temperatures, and get free Manual J load calculations for any Oklahoma location.
Oklahoma spans 2 IECC climate zones (Zone 3A, Zone 4A), which means insulation requirements, design temperatures, and equipment specs vary significantly depending on location. The primary zone, Zone 3A (Warm - Humid), is a mixed climate, with winter design temperatures as low as 22°F and summer highs reaching 94°F. HVAC contractors working across Oklahoma need to verify the exact climate zone for each job site — using the wrong zone data leads to oversized or undersized equipment, failed inspections, and unhappy homeowners.
Minimum insulation R-values and window specifications required by the 2021 International Energy Conservation Code for Oklahoma.
| Component | Zone 3A | Zone 4A |
|---|---|---|
| Ceiling / Attic | R-30 | R-49 |
| Walls | R-20 | R-20 |
| Floor | R-19 | R-19 |
| Window U-Factor | 0.32 | 0.32 |
| Window SHGC | 0.25 | 0.4 |
Source: IECC 2021 Table R402.1.2. Requirements shown are for residential construction. Oklahoma contractors must use the zone that corresponds to the job site location.
These ASHRAE design temperatures determine how Manual J load calculations size heating and cooling equipment for Oklahoma homes. The winter 99% value represents the coldest temperature expected, while the summer 1% value represents the hottest.
Warm - Humid
Mixed - Humid
Based on Climate Zone 3A (Warm - Humid), here are typical HVAC equipment specifications for Oklahoma installations.
Annual Fuel Utilization Efficiency for Oklahoma furnaces
Seasonal Energy Efficiency Ratio for Oklahoma AC systems
Oklahoma's climate zone data ensures proper equipment sizing. No more callbacks from oversized or undersized systems.
Oklahoma building departments require IECC-compliant Manual J calculations. Our tool uses official Oklahoma climate data.
Right-sized systems based on Oklahoma climate data reduce energy costs for homeowners and improve your reputation.
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