ASHRAE 90.1-2019: Increased stringency, VIGs and requirements for renewables

The Glass Advocate | Education, Advocacy and Technical Content from the NGA
Tom Culp
March 20, 2019

NGA logoThere was a frenzied rush at the ASHRAE meeting in January to finalize proposals for the 2019 edition of ASHRAE 90.1. For the glass and glazing industry, final proposals include items that industry code advocates have been diligently working on for multiple years, as well as some last-minute items of interest.

Items to track

1. More stringent performance requirements

First and foremost, the comprehensive update to the prescriptive fenestration requirements has completed the review process and was approved for final publication, including the next step for U-factor and solar heat gain coefficient requirements for windows, doors and skylights in commercial buildings as well as mid-rise and high-rise residential buildings. The NGA advocacy team worked over the last two years with both allies and adversaries, including other industry associations and public sector advocates, to successfully negotiate a joint proposal that achieved near unanimous support. 

The proposal provides increased energy savings that will continue to push improved framing with more advanced thermal breaks, warm-edge spacers, argon gas fill and 4th surface low-emissivity coatings, while still being cost-effective and practical. Additionally, the proposal has no reductions in window area. 

In many cases, the new requirements very roughly represent a “zone shift” between 2016 and 2019. What was required in Zone 7 will move to Zone 6; Zone 6 to Zone 5; etc. This will give the industry more confidence about the practicality of the requirements. If you currently already have the product for one zone, it will not be a difficult push to provide that product in the next zone. 

Find details about the new requirements at 

2. VIGs in refrigeration

One of the new last-minute proposals approved by the committee in hopes of making ASHRAE 90.1-2019 would remove a barrier to the use of vacuum insulating glazing, or VIG, in reach-in doors for walk-in coolers and freezers commonly seen along the perimeter of grocery stores and convenience stores. There is strange wording in a federal regulation and the energy codes that could be misinterpreted as not including VIG despite far exceeding performance requirements. 

NGA worked with the Air-Conditioning, Heating, & Refrigeration Institute to pass a proposal to clarify in 90.1 that the use of VIG is allowed in these applications, and we are also working with the U.S. Department of Energy and AHRI on an interpretation to address the same issue in the federal regulation. Similar proposals have also been submitted to clarify the IECC.

3. Onsite renewables

The most significant last-minute proposal is for a new prescriptive requirement to provide a minimum amount of onsite renewable energy on all new buildings or building sites. This would require a renewable energy system capacity of 0.25 W/ft2 multiplied by the sum of the conditioned floor area of up to the largest three floors. 

Although the proposal is written around solar photovoltaics and would strongly push both rooftop photovoltaics and building integrated photovoltaics, other types of onsite renewable systems can also be used, or the building can make up for it in performance path. 

This would be an important milestone as the first prescriptive requirement for renewable energy in a national base energy code (not just a voluntary green code). However, even though the proposal was approved by the committee, it still must go through the public review process, and it is uncertain whether the proposal will be completed in time to make it into the 2019 edition of ASHRAE 90.1 or later. 

Not included

Also of note are the proposals that will not make it into the 2019 edition of ASHRAE 90.1, including proposals to address thermal bridging and to add new envelope “back stops” or trade-off limits. These controversial and complex proposals will continue to be discussed in the next cycle. Read more about the proposals

Tom Culp is technical code consultant for the NGA and owner of Birch Point Consulting LLC. He can be reached at