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IECC 2024 — Residential Building Envelope Requirements

Updated Mar 25, 2026
Minimum insulation R-values and window U-factors by climate zone. Zone 3: R-20 walls, R-49 ceiling, U-0.30 windows. Zone 5: R-20+5ci walls, R-60 ceiling, U-0.28 windows. Air barrier required all zones.

The International Energy Conservation Code sets minimum energy efficiency for residential buildings. Key envelope requirements by climate zone: Zone 1-2 (Miami, Houston): R-13 wall, R-38 ceiling, U-0.40 windows, SHGC 0.25. Zone 3 (LA, Atlanta): R-20 or 13+5ci wall, R-49 ceiling, U-0.30 windows. Zone 4 (NYC, Seattle): R-20 or 13+5ci wall, R-49 ceiling, U-0.30 windows. Zone 5 (Chicago, Denver): R-20+5ci or 13+10ci wall, R-60 ceiling, U-0.28 windows. Zone 6-8 (Minneapolis, Anchorage): R-20+10ci wall, R-60 ceiling, U-0.28 windows. Air barrier required in all zones — maximum 3 ACH50 for zones 3-8, 5 ACH50 for zones 1-2. Blower door test required. Compliance paths: prescriptive, total UA alternative, simulated performance, ERI (Energy Rating Index).

TAGS
energyieccinsulationenveloper-valueu-factorclimate-zoneair-barrier
DETAILS
chapter
4 - Residential Energy Efficiency
severity
prescriptive
code year
2024
code system
IECC
building types
["residential_single","residential_multi"]
section number
R402
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