Ohio is in IECC Climate Zone 5A (Cool - Humid). Get accurate Manual J load calculations with official design temperatures and IECC requirements.
Ohio falls entirely within IECC Climate Zone 5A (Cool - Humid), making it a heating-dominated state where furnace capacity and insulation R-values are the primary sizing concerns. With a winter 99% design temperature of 0°F and a summer 1% design temperature of 91°F, Ohio HVAC contractors must size systems for a 91°F temperature swing between extreme winter and summer conditions. Proper Manual J load calculations using these design temperatures are essential for code-compliant, right-sized installations that avoid callbacks and comfort complaints.
Minimum insulation R-values and window specifications required by the 2021 International Energy Conservation Code for Ohio.
| Component | Zone 5A |
|---|---|
| Ceiling / Attic | R-49 |
| Walls | R-20 |
| Floor | R-30 |
| Window U-Factor | 0.3 |
| Window SHGC | 0.4 |
Source: IECC 2021 Table R402.1.2. Requirements shown are for residential construction.
These ASHRAE design temperatures determine how Manual J load calculations size heating and cooling equipment for Ohio homes. The winter 99% value represents the coldest temperature expected, while the summer 1% value represents the hottest.
Cool - Humid
Based on Climate Zone 5A (Cool - Humid), here are typical HVAC equipment specifications for Ohio installations.
Annual Fuel Utilization Efficiency for Ohio furnaces
Seasonal Energy Efficiency Ratio for Ohio AC systems
Ohio's climate zone data ensures proper equipment sizing. No more callbacks from oversized or undersized systems.
Ohio building departments require IECC-compliant Manual J calculations. Our tool uses official Ohio climate data.
Right-sized systems based on Ohio climate data reduce energy costs for homeowners and improve your reputation.
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