IECC Climate Zone 2 — Hot HVAC Guide
IECC Climate Zone 2 (Hot) covers regions with summer design temperatures of 90–110°F and winter design temperatures of 24–38°F. Moisture regime subzones: A (Moist) + B (Dry). Cooling is the dominant HVAC load.
Zone Overview
| Parameter | Value |
|---|---|
| IECC Climate Zone | 2 |
| Climate Type | Hot |
| Moisture Regime Subzones | A (Moist) + B (Dry) |
| Summer Design Temperature (1%) | 90–110°F |
| Winter Design Temperature (99%) | 24–38°F |
| Heating Degree Days (HDD) | < 3,500 |
| Cooling Degree Days (CDD) | 3,500 – 5,000 |
| Dominant Load | Cooling Dominant |
Typical Cities in This Zone
- Houston, TX
- Phoenix, AZ
- Tampa, FL
- New Orleans, LA
HVAC Design Priorities
- Oversized AC is a common mistake — proper Manual J sizing is critical
- Humidity control important in Moist (A) subzones, less so in Dry (B)
- Heat pump with auxiliary heat strips covers most heating needs
- Solar heat gain coefficients (SHGC) below 0.25 for east/west windows
- Duct leakage testing recommended for energy code compliance
IECC Building Envelope Requirements
| Parameter | Value |
|---|---|
| Wall R-Value (min) | R-13 |
| Ceiling R-Value (min) | R-38 |
| Floor R-Value (min) | R-13 |
| Fenestration U-Factor (max) | 0.4 |
| SEER Minimum | 14 |
Climate Zone Comparison
| Zone | Summer Design Temperature (1%) | Winter Design Temperature (99%) | Wall/Ceiling R | Dominant Load | Typical Cities |
|---|---|---|---|---|---|
| Zone 1 — Very Hot | 88–95°F | 40–55°F | R-13/R-30 | Cooling | Miami, FL, Honolulu, HI |
| Zone 2 — Hot | 90–110°F | 24–38°F | R-13/R-38 | Cooling | Houston, TX, Phoenix, AZ |
| Zone 3 — Warm | 88–100°F | 16–32°F | R-20/R-38 | Cooling | Atlanta, GA, Dallas, TX |
| Zone 4 — Mixed | 84–95°F | 6–22°F | R-20/R-49 | Heating | New York, NY, Washington, DC |
| Zone 5 — Cool | 80–92°F | -4–14°F | R-20/R-49 | Heating | Chicago, IL, Boston, MA |
| Zone 6 — Cold | 78–90°F | -12–2°F | R-20/R-49 | Heating | Minneapolis, MN, Burlington, VT |
| Zone 7 — Very Cold | 74–86°F | -30–-8°F | R-20/R-49 | Heating | Fairbanks, AK, Duluth, MN |
| Zone 8 — Subarctic | 68–80°F | -50–-20°F | R-20/R-60 | Heating | Utqiaġvik (Barrow), AK, Deadhorse, AK |
Frequently Asked Questions
What climate zone is my city in?
Climate Zone 2 covers cities like Houston, TX, Phoenix, AZ, Tampa, FL. To find your exact climate zone, check the IECC climate zone map or use your ZIP code with the DOE Building Energy Codes Program lookup tool.
What insulation R-value do I need in Climate Zone 2?
IECC 2021 requires minimum R-13 walls, R-38 ceilings, and R-13 floors in Climate Zone 2. Fenestration (windows) must have a maximum U-factor of 0.4.
What HVAC system works best in Climate Zone 2?
In Hot climate (Zone 2), cooling is the primary concern — a high-efficiency AC or heat pump is recommended. Always size equipment using Manual J calculations for your specific home.