Skip to main content

Table of Maximum Fenestration U-Factor Requirements for New Homes as Listed in the 2009-2021 IECC and IRC

Description

The maximum U-Factor and Solar Heat Gain Coefficient (SHGC) requirements for fenestration (windows) and skylights in new homes, as listed in the 2009, 2012, 2015, 2018, and 2021 International Energy Code (IECC) and the 2009, 2012, 2015, 2018, and 2021 International Residential Code (IRC), can be found in this table.

Table 1. Maximum Fenestration U-Factor Requirements for New Homes as Listed in the 2009, 2012, 2015, 2018, and 2021 International Energy Conservation Code (IECC)a

Climate Zone

Fenestration U-Factorb,d

Skylightb U-Factor

Glazed Fenestration SHGCb,c

 

2009 IECC

2012
2015 
IECC

2018 IECC

2021 IECC

2009 IECC

2012
2015
2018
2021
IECC

2009 IECC

2012
2015
2018
IECC

2021 IECC

1

1.20

NR

NR

NR

0.75

0.75

0.30e

0.25

0.25

2

0.65d

0.40

0.40

0.40

0.75

0.65

0.30e

0.25

0.25

3

0.50d

0.35

0.32

0.30

0.65

0.55

0.30e

0.25

0.25

4 except Marine

0.35

0.35

0.32

0.30

0.60

0.55

NR

0.40

0.40

5 and Marine 4

0.35

0.32

0.30

0.30f

0.60

0.55

NR

NR

0.40

6

0.35

0.32

0.30

0.30f

0.60

0.55

NR

NR

NR

7 and 8

0.35

0.32

0.30

0.30f

0.60

0.55

NR

NR

NR

For SI: 1 foot = 304.8 mm. NR = not required.  Ci = continuous insulation.

  1. Table adapted from Table R402.1.1 in the 2009 and 2012 IECC, Table R402.1.2 in the 2015, 2018 IECC, and Table 402.1.3 in the 2021 IECC. (Table N1102.1 in 2009 IRC, Table 1102.1.1 in 2012 IRC, Table N1102.1.2 in 2015 and 2018 IRC, and Table N1102.1.3 in 2021 IRC).
    2012, 2015, 2018, and 2021 IECC: U-factors and SHGC are maximums.
  2. 2009-2021 IECC: The fenestration U-factor column excludes skylights; see the next column for skylights. The SHGC column applies to all glazed fenestration, i.e., both windows and skylights.

2018 and 2021 IECC: Exception: In Climate Zones 1 through 3, skylights shall be permitted to be excluded from glazed fenestration SHGC requirements provided that the SHGC for such skylights does not exceed 0.30.

  1. 2009-2021 IECC: There are no SHGC requirements in the Marine Zone.
  2. 2009 IECC Only: For impact rated fenestration complying with Section R301.2.1.2 of the International Residential Code or Section 1609.1.2 of the International Building Code, the maximum U-factor shall be 0.75 in Zone 2 and 0.65 in Zone 3.
  3. 2009 IRC Only: In the 2009 IRC, the maximum U-factor value is 0.35, not 0.3, in Climate Zones 1, 2, and 3.
  4. 2021 IECC Only: A maximum U-factor of 0.32 shall apply in Climate Zones 5 through 8 to vertical fenestration products in buildings located either:
  5. Above 4,000 feet in elevation, or
  6. In windborne debris regions where protection of openings is required by Section R301.2.1.2 of the International Residential Code.

More Info

Contributors to this Guide

The following authors and organizations contributed to the content in this Guide.

Pacific Northwest National Laboratory

Last Updated

Disclaimer

This content is a work created with funding provided by the United States Department of Energy under Contract no DE-AC05-076RL01830 for the operation of Pacific Northwest National Laboratory. The information and guidance provided by Pacific Northwest National Laboratory (PNNL) in the content are intended solely for educational purposes only and do not constitute formal training or certification. It is provided with the explicit understanding that neither the United States Government nor the United States Department of Energy, nor the Contractor, nor any or their employees, nor any jurisdiction or organization that has cooperated in the development of these materials, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness or any information, apparatus, product, software, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof, or Battelle Memorial Institute. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. Viewers assumes full responsibility for all actions that they may take from information provided in this content including ensuring the safety, code compliance, and proper functionality of any products they choose to install. Installation and use of such products should be performed in accordance with local regulations and manufacturer instructions.