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

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-Factor^b,d				Skylight^bU-Factor		Glazed Fenestration SHGC^b,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	0.30^e	0.25	0.25
2	0.65^d	0.40	0.40	0.40	0.75	0.65	0.30^e	0.25	0.25
3	0.50^d	0.35	0.32	0.30	0.65	0.55	0.30^e	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	0.30^f	0.60	0.55	NR	NR	0.40
6	0.35	0.32	0.30	0.30^f	0.60	0.55	NR	NR	NR
7 and 8	0.35	0.32	0.30	0.30^f	0.60	0.55	NR	NR	NR
For SI: 1 foot = 304.8 mm. NR = not required. Ci = continuous insulation. 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. 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. 2009-2021 IECC: There are no SHGC requirements in the Marine Zone. 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. 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. 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: Above 4,000 feet in elevation, or In windborne debris regions where protection of openings is required by Section R301.2.1.2 of the International Residential Code.

Last Updated

2021-09-15

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

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