IECC 2021 CALLS FOR R-20 WALLS THROUGHOUT MOST OF THE U.S.
Many states and jurisdictions refer to the International Energy Conservation Code (IECC) when establishing residential construction energy codes. With its 2021 version, the IECC calls for a U-0.045 (R-20 with a prescriptive approach) for above-grade wood-framed walls for most of the U.S. In addition to California, with its rigorous Title 24 energy efficiency standards, several other states and jurisdictions have already adopted this requirement, and with skyrocketing energy costs, it’s likely we’ll soon see others do the same.
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THE IECC CLIMATE ZONE MAP
2021 IECC RESIDENTIAL PROVISIONS
INSULATIVE REQUIREMENTS AND PRESCRIPTIVE COMPLIANCE OPTIONS
FOR ABOVE-GRADE 2X4 WOOD-FRAMED WALLS
SOLUTION
OX-IS 1.70” R-10
R-13 CAVITY INSULATION +
OX-IS 1.00” R-6
R-13 CAVITY INSULATION +
OX-IS 1.70” R-10
CLIMATE ZONE
REQUIRED ASSEMBLY
U-FACTOR
0.084
0.060
0.045
PRESCRIPTIVE
MINIMUM R-VALUE*
0 + 10 ci
13 + 5 ci
13 + 10 ci
SOLUTION
OX-IS 1.70” R-10
CLIMATE ZONE
REQUIRED ASSEMBLY
U-FACTOR
0.084
PRESCRIPTIVE
MINIMUM R-VALUE*
0 + 10 ci
SOLUTION
R-13 CAVITY INSULATION +
OX-IS 1.00” R-6
CLIMATE ZONE
REQUIRED ASSEMBLY
U-FACTOR
0.060
PRESCRIPTIVE
MINIMUM R-VALUE*
13 + 5 ci
SOLUTION
R-13 CAVITY INSULATION +
OX-IS 1.70” R-10
CLIMATE ZONE
REQUIRED ASSEMBLY
U-FACTOR
0.045
PRESCRIPTIVE
MINIMUM R-VALUE*
13 + 10 ci
ci = continuous insulation such as OX-IS weatherization system
* The first value is cavity insulation. The second value is continuous insulation (ci). Therefore, “13 + 10 ci” means R-13 cavity insulation plus R-10 continuous insulation (ci).
Data in the chart shown above has been gleaned from 2021 International Energy Conservation Code (IECC), Chapter 4 Residential Energy Efficiency, Table R402.1.2 Maximum Assembly U-Factors and Fenestration Requirements and Table R402.1.3 Insulation Minimum R-Values and Fenestration Requirements by Component.
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