2021 International Energy Conservation Code

Adoption
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Contact: Vladimir Kochkin
vkochkin@nahb.org
(202) 266-8574

The 2021 International Energy Conservation Code (IECC) Residential Code Adoption Kit is provided for HBAs and other stakeholders to help with evaluation of the new energy code provisions as local jurisdictions will be gearing up for the code adoption process.

The code adoption kit includes the following information:

  • List of significant changes to 2021 IECC residential provisions (below)
  • List of recommended amendments to 2021 IECC supported with substantiating information and cost-effectiveness data where applicable
  • Cost-effectiveness evaluation of the 2021 IECC code changes including analysis of energy savings and construction costs conducted by Home Innovation (a sample of information on simple paybacks is included in tables below)
  • A summary table with the status of state adoption of different editions of the IECC around the country

2021 IECC Simple Payback relative to 2018 Baseline Reference House, years

Configuration National Average CZ 2
Phoenix
CZ 3
Memphis
CZ 4
Baltimore
CZ 5
Chicago
CZ 6
Helena
CZ 7
Duluth
2021 IECC without additional efficiency package options 48 43 31 62 61 47 78
2021 IECC with HVAC option 38 47 39 39 32 19 24
2021 IECC with Water Heater option 32 20 20 54 54 42 79
2021 IECC with Ventilation option 67 90 49 75 68 50 63
2021 IECC with Duct option, slab house 38 38 36 46 39 23 26

Individual Insulation Requirement: Simple Payback relative to 2018 Baseline Reference House, years

Configuration CZ 2
Phoenix
CZ 3
Memphis
CZ 4
Baltimore
CZ 5
Chicago
CZ 6
Helena
CZ 7
Duluth
2021 IECC ceiling insulation 177 122 152 118 105 90
2021 IECC slab insulation, slab houses only   23 28 28    
2021 IECC wall continuous insulation     103 78    
2021 IECC window U-factor   11 7      

Significant Changes to 2021 IECC Residential Provisions

IECC Section Topic Description
R402.1.2
R402.1.3
Wall R-Value/U-Factor (Climate Zones 4 & 5) This change increased the prescriptive wall insulation levels for above-grade framed walls from R-20+5 to R-20 and R-13+10 to R-13+5.
R402.1.3 Slab Edge R-Value (Climate Zones 3, 4 & 5) This change increases the requirement for slab edge insulation in Climate Zones 3 (R-10 2 feet) and 4 & 5 (R-10 4 feet).
R402.1.2
R402.1.3
Attic R-Value/U-Factor (Climate Zones 2-8) This change increases the prescriptive attic insulation levels from R-49 to R-38 (CZ 2-3) and from R-60 to R-49 (CZ 4-8).
R403.3.2 Floor R-Value Increase for Ducts Located Inside Floor Cavity (Climate Zones 1 & 2) This change adds a requirement for R19 insulation at duct locations in floor cavities over unconditioned space.
R403.3.5 Testing Ducts Located Inside Conditioned Space This change requires testing of ducts located in conditioned space.
R403.6.3 (new) Testing Ventilation Systems This change adds a new requirement for flow rate testing on mechanical ventilation systems.
R404.1
R404.2
Interior Lighting Allowance and Design Option for Lighting Controls This change removes a 10% allowance for lighting sources and adds a new requirement for occupancy sensors and dimmers.
R404.1.1 (new) Exterior Lighting Requirements This change requires residential exterior lighting systems to comply with commercial lighting provisions.
R406.5 ERI Compliance Path – ERI Thresholds This change lowers the maximum energy rating index thresholds for all climate zones.
R401.2.5 ERI Compliance Path – 5% ERI reduction This change imposes an additional 5% reduction in the ERI values.
R406.3
R406.4
ERI Compliance Path – On-site renewable This amendment restores the design options for achieving target ERI.
R401.2.5 (new) Additional Efficiency Package Options This change introduces a new requirement for additional efficiency measures that are beyond the base requirements of the prescriptive and performance paths.
TABLE R402.4.1.1 Air Barrier Location at Rim Joist This change adds prescriptive guidance for installation air barrier at the rim joist.
R402.4.6 Air-Sealed Outlet Boxes in Exterior Walls This change adds a new requirement that all electrical and communication outlet boxes located in exterior walls must be air-sealed boxes.
R402.4.1.2 Air leakage rates This change allows the buildings that are designed using the performance path to have air leakage up to 5.0 air changes per hour in any climate zone provided the energy budget is met (i.e., trade-offs are allowed for building tightness). There is no change for buildings designed using the prescriptive path.

ICC codes can be viewed on ICC’s website free of charge or can be purchased as a subscription or pdf.

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