IECC CZ 2A (hot-humid): Houston, New Orleans, Jacksonville, Miami area. Heating degree days: <3500. Cooling degree days: >5000. Design temps: summer 95F/75F wb, winter 28F. Residential envelope: ceiling R-30, wall R-13, floor R-13, windows U-0.40/SHGC-0.25. Air leakage: 5 ACH50. Key challenges: humidity control (dehumidification), condensation, mold prevention, hurricane wind loads (coastal). Vapor retarder: Class III or none (on warm side — different from cold climates). HVAC: cooling-dominated, high-efficiency AC critical, dehumidification. Seismic: SDC A-B. Special: hurricane shutters/impact glass in coastal WBDR.