Key Proposals to Watch at ASHRAE 90.1

Increased stringency on the horizon; thermal bridge and trade-off proposals on hold

From the NGAThe glass and glazing industry came away with several positive takeaways following the recent ASHRAE 90.1 committee meeting held in October. During the meeting, the committee addressed three proposals that, if advanced into the 2019 version of ASHRAE 90.1, would have an impact on the glass and glazing industry, according to Tom Culp, technical consultant and co-vice-chair of the ASHRAE 90.1 committee and code consultant for the National Glass Association. They included a proposal to increase U-factor and solar heat gain coefficient requirements for glazing systems, a wide-reaching and controversial thermal bridging proposal and a potential proposal to limit envelope tradeoffs in measuring building performance.  

Below are three key takeaways from the meetings:

1. Stringency is on the rise

The 2019 version of ASHRAE 90.1 is expected to include more stringent U-factor and solar heat gain coefficient requirements for fenestration products in all commercial buildings as well as multifamily buildings four stories or higher. The changes are presented in Addendum AW, which calls for a comprehensive update to the fenestration criteria—U-factor and solar heat gain coefficient for windows, entrance doors and skylights. 

The proposal was carefully vetted across different industry interests and provides an increase in stringency while still being cost effective and practical, according to Culp. Additionally, the proposal moves to align the product categories in ASHRAE 90.1 to match those used in the International Energy Conservation Code without regard to material type. (Existing versions of ASHRAE 90.1 include separate U-factor requirements for non-metal versus metal glazing systems.)

 This proposal has been a work-in-progress for the past year. It went out for public comment this summer with only small corrections requested, and the committee made the corrections at the meeting. The new changes include correcting the proposed SHGC in zone 5 to better account for curtain wall systems, adjusting the residential skylight U-factor in zone 6 to account for unit skylights on curbs, and adjusting the U-factors for skylights in semi-heated spaces (e.g. warehouses). The overall proposal including these changes will continue to promote increased use of low-emissivity glass, thermally broken framing systems, warm edge spacers and argon gas fill. At the time of reporting, those minor changes were set to go up for public review in the fall. Assuming there are no more comments, the addendum will go up for final approval at the January meeting, according to Culp.

“Due to Tom Culp’s work representing NGA at the ASHRAE meeting last week, we’re very hopeful [Addendum AW] will pass in January and make it into the 2019 standard,” says Nicole Harris, NGA president and CEO. “Tom really stepped up for the entire industry and his efforts are appreciated.”  

2. Thermal bridging proposal is in question

The future of the controversial Thermal Bridging Proposal is in question after its first public review. The proposal addresses thermal bridges that bypass wall, roof and floor insulation. The portions of the wide-reaching proposal that potentially affect the industry involved rules on the intersection between window framing and the opaque wall, limitations on attachment area for sun shades, and questions of how thermal bridges could be traded off against wall and window performance. The proposal would also affect structural areas such as balconies, parapets and canopies.  

“It has been very controversial, and the proposal received nearly 250 negative comments. Many consider thermal bridging an important issue, but because it has the potential to negatively impact structural performance, feel that it is better addressed in design guides rather in a code,” says Culp. “Because of the unusually large number of comments, the subcommittee is trying to figure out whether to continue with it at all, and if so, how to fix it. This means it will not make the 2019 edition, if it continues at all.”

3. Trade-off limitations are on hold

A proposal to limit envelope trade-offs when evaluating energy performance was delayed. The proposal, of particular concern to the glass and glazing industry, looked to implement “envelope backstops” or limitations on trade-offs when using the performance path, according to Culp. If implemented, the proposal could limit product flexibility or, most concerning, could be used to limit window area in office and high-rise residential buildings, even if the project team showed equivalent or better energy performance. 

“Three different approaches have been suggested, and the subcommittee will spend more time to discuss and carefully analyze the potential impacts, meaning this would not make its way into the standard until 2022 at the earliest,” says Culp.