Mississippi spans 2 IECC climate zones. Find your exact zone, design temperatures, and get free Manual J load calculations for any Mississippi location.
Mississippi spans 2 IECC climate zones (Zone 2A, Zone 3A), which means insulation requirements, design temperatures, and equipment specs vary significantly depending on location. The primary zone, Zone 2A (Hot - Humid), is cooling-dominated, with winter design temperatures as low as 32°F and summer highs reaching 95°F. HVAC contractors working across Mississippi 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 Mississippi.
| Component | Zone 2A | Zone 3A |
|---|---|---|
| Ceiling / Attic | R-30 | R-30 |
| Walls | R-13 | R-20 |
| Floor | R-13 | R-19 |
| Window U-Factor | 0.4 | 0.32 |
| Window SHGC | 0.25 | 0.25 |
Source: IECC 2021 Table R402.1.2. Requirements shown are for residential construction. Mississippi 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 Mississippi homes. The winter 99% value represents the coldest temperature expected, while the summer 1% value represents the hottest.
Hot - Humid
Warm - Humid
Based on Climate Zone 2A (Hot - Humid), here are typical HVAC equipment specifications for Mississippi installations.
Annual Fuel Utilization Efficiency for Mississippi furnaces
Seasonal Energy Efficiency Ratio for Mississippi AC systems
Mississippi's climate zone data ensures proper equipment sizing. No more callbacks from oversized or undersized systems.
Mississippi building departments require IECC-compliant Manual J calculations. Our tool uses official Mississippi climate data.
Right-sized systems based on Mississippi climate data reduce energy costs for homeowners and improve your reputation.
Upload your Mississippi blueprint and get a professional Manual J load calculation with official climate zone data. First report is FREE.
Join 10,000+ Mississippi contractors who trust AutoHVAC for permit-ready load calculations
Get detailed climate zone information for major cities
Need Mississippi HVAC permit forms and building department contacts?
View Mississippi Permit Directory