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IECC R402 — Building Thermal Envelope (Residential)

Updated Mar 25, 2026
Residential envelope: wall, ceiling, floor insulation and window performance by climate zone.

IECC 2024 Residential Table R402.1.2: CZ3 ceiling R-38, wall R-20/13+5ci, floor R-19. CZ4 ceiling R-49, wall R-20/13+10ci. CZ5 ceiling R-49, wall R-20+5ci. Windows: CZ1=U-0.40, CZ4=U-0.30. Air leakage: max 3 ACH50 (CZ3-8). Mandatory blower door test. Air sealing at penetrations, plates, rim joist.

TAGS
IECCresidentialinsulationair-sealingblower-door
DETAILS
code year
2024
code section
R402
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