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
Want a quick equipment estimate for your Oklahoma project? Use our free BTU calculator or AC tonnage calculator for a rough sizing, or upload blueprints for a professional Manual J report.
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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