Maryland is in IECC Climate Zone 4A (Mixed - Humid). Get accurate Manual J load calculations with official design temperatures and IECC requirements.
Maryland falls entirely within IECC Climate Zone 4A (Mixed - Humid), making it a mixed-climate state requiring careful balance between heating and cooling equipment sizing. With a winter 99% design temperature of 13°F and a summer 1% design temperature of 91°F, Maryland HVAC contractors must size systems for a 78°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 Maryland.
| Component | Zone 4A |
|---|---|
| Ceiling / Attic | R-49 |
| Walls | R-20 |
| Floor | R-19 |
| Window U-Factor | 0.32 |
| 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 Maryland homes. The winter 99% value represents the coldest temperature expected, while the summer 1% value represents the hottest.
Mixed - Humid
Based on Climate Zone 4A (Mixed - Humid), here are typical HVAC equipment specifications for Maryland installations.
Annual Fuel Utilization Efficiency for Maryland furnaces
Seasonal Energy Efficiency Ratio for Maryland AC systems
Maryland's climate zone data ensures proper equipment sizing. No more callbacks from oversized or undersized systems.
Maryland building departments require IECC-compliant Manual J calculations. Our tool uses official Maryland climate data.
Right-sized systems based on Maryland climate data reduce energy costs for homeowners and improve your reputation.
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