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How Energy Code Evolutions Will Impact Residential Fenestration

The National Glass Association’s Thirsty Thursday webinar on June 18, presented by Tom Culp, Birch Point Consulting and NGA technical codes consultant, dissected some of the upcoming energy code evolutions in 2020 on a national and regional level.

International Energy Conservation Code

The IECC is the primary energy code for residential building in the U.S., with the next update coming out in 2021. The fenestration industry likely will not be significantly affected by the changes, in large part “because we negotiated agreements on key items, so they were on the consent agenda and not subject to vote,” Culp explained.

Items up for vote before the 2021 adoption shouldn’t affect a standard Energy Star-rated window, but will reduce flexibility for non-standard products, said Culp, including confusing overlapping “backstops” on windows when using trade-off paths. Expect small changes in prescriptive U-factors, such as U-0.30 in zones 3-8 and allowances up to 0.32 in windborne debris regions or in areas with elevations higher than 4,000 feet, to allow for more flexibility in products.

Voting changes also introduced a new maximum solar heat gain coefficient in zone 5. There also is indirect positive pressure for fourth surface low-E and/or triple glazing in the next IECC.

California’s Title 24

Work on California’s Title 24 2022 edition is underway. Stakeholders are in a series of meetings now and working on case reports with the goal to enter the rulemaking phase next year.

Although no official proposals are on the table, Culp pointed to two residential fenestration points:

  • No new changes for windows will be enacted for single-family homes, in large part because the 2019 edition updated to a U-factor of 0.30 and solar heat gain coefficient of 0.23.
  • Multifamily might all fall under one standard, regardless of the size. Challenges revolve around how to account for windows in low-rise vs. high-rise, considering different construction, structural requirements and product types. Culp says to expect a draft case report for public review this fall.

He also said that some builders in California are putting in triple-glazed windows so they can lighten up on what Culp described as “dramatic changes” to wall insulation requirements.

Canada’s Energy Codes

Canada is also being what Culp described as “very aggressive about energy efficiency” and is finalizing the 2020 National Energy Code for Canada for Buildings. The country is committed to a net-zero energy ready model building code by 2030. Some provinces already use their own codes, such as the step codes in British Columbia and zero emissions building plan in Vancouver. Among other requirements, the code proposes reducing the U-factor in all zones, even beyond what ASHRAE 90.1 and the 2021 IECC requires. Culp says this “aggressive” proposals is achievable, but only for fixed fenestration; it’s problematic for operable windows.

Visit to read about four energy code updates that will affect the commercial construction industry.


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Laurie Cowin

Laurie Cowin is managing editor of Window + Door and its sister publication, Glass Magazine. Contact her at