New Hampshire is in IECC Climate Zone 6A (Cold - Humid). Get accurate Manual J load calculations with official design temperatures and IECC requirements.
New Hampshire falls entirely within IECC Climate Zone 6A (Cold - 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 -9°F and a summer 1% design temperature of 89°F, New Hampshire HVAC contractors must size systems for a 98°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 New Hampshire.
| Component | Zone 6A |
|---|---|
| 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 New Hampshire homes. The winter 99% value represents the coldest temperature expected, while the summer 1% value represents the hottest.
Cold - Humid
Based on Climate Zone 6A (Cold - Humid), here are typical HVAC equipment specifications for New Hampshire installations.
Annual Fuel Utilization Efficiency for New Hampshire furnaces
Seasonal Energy Efficiency Ratio for New Hampshire AC systems
New Hampshire's climate zone data ensures proper equipment sizing. No more callbacks from oversized or undersized systems.
New Hampshire building departments require IECC-compliant Manual J calculations. Our tool uses official New Hampshire climate data.
Right-sized systems based on New Hampshire climate data reduce energy costs for homeowners and improve your reputation.
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