The U.S. Environmental Protection Agency (EPA) released details for Draft 2 of Energy Star 7.0 today, including several updates for doors and windows. Officials tell [DWM] updates to the proposed criteria result partly from industry comment, but also from fresh data gleaned from a new version of Energy Plus, the modeling software used to make program calculations. EPA is maintaining the same prescriptive window criteria proposed in Draft 1 of Version 7.0, but revising the proposed equivalent energy performance levels based on updated modeling analysis. As a result, prescriptive pathways have been updated with new combinations of U-factor and solar heat gain coefficient (SHGC) ratings.

Officials say they received approximately 40 comments following the publication of Draft 1, including concerns over how supply chain issues might impact manufacturers’ abilities to produce new and updated products by the start of Version 7.0 requirements. Ultimately, EPA officials say they expect those problems to be eased in time for manufacturers to deploy on the proposed schedule. They’re also standing by an original assessment for the number of products currently available to meet the proposed criteria.

Requirements for Draft 1 were established using Version 8.9 of the Energy Plus software and while officials say they were aware of a newer version amid development, Version 9.5 arrived midway through the process. At the same time, researchers felt the changes presented in Version 9.5 would have little to no impact on performance requirements and calculations for energy savings, but numerous manufacturers begged to differ, prompting an upgrade. Initial analysis also relied on older population census data, which is used to weight results for energy costs by zone. New census data released in 2020 was used for Draft 2 calculations.

In the process, impacts to energy savings were calculated across 132 cities, comparing 288 products and more than 600,000 modeling runs, officials tell [DWM]. Cities were then grouped by climate zone to establish average energy savings per climate zone. New calculations primarily impacted solar heat gain coefficient (SHGC) ratings, prompting updates for Draft 2.

Modeling calculations for Energy Star requirements is performed by Lawrence Berkeley National Laboratories (LBNL), while the models used are developed by Pacific National Northwest Laboratory (PNNL).

As part of Version 7.0, proposed criteria retains base requirements, plus energy equivalent tradeoffs, which allow for higher U-factor ratings in the Northern climate zone in instances where SHGC ratings allow for greater use of solar energy (additional solar heat gain). New modeling supported changing prescriptive requirements, officials say, to what they suggest is a “similar, but easier to meet” set of criteria. While Draft 1 called for U-factors ranging from 0.23 to 0.26 and corresponding SHGC ratings that graduated by 0.05 over four prescriptive combinations, Draft 2 requirements call for just two SHGC ratings, including 0.35 and 0.40, over the same U-factor increments. (See the corresponding chart.) Those changes, officials suggest, are expected to make enforcement of program requirements easier. Additionally, EPA is backing off of its suggestion that sliding glass doors be grouped with the same requirements for windows. With Draft 2, officials opted to group sliding (glass) doors back with swing style patio doors “that are mostly glass.” Sliding, glass patio doors now fall under the same category and requirements as swing doors with greater than one half lite of glass. Requirements for those doors were previously proposed at u-factor of 0.28, while sliding glass doors were required to be 0.22. In draft two, both are required to be U-factor 0.25. That number, officials say, will be significantly easier for manufacturers of sliding doors to meet, though tougher for some swing style doors.

Following publication of Draft 2, officials say there will be another period of comments and responses, but the data used to develop the latest requirements will not be revisited or recalculated, they tell [DWM]. Following the comment period, a final draft with finalized specs is expected to be released in June 2022, after which updated program requirements expected to be deployed a year later.

If all goes as planned, manufacturers will need to be prepared for rollout in July 2023.

Draft 2 Version 7.0 Specification and Data Packages can be found HERE.

EPA encourages stakeholders to provide comments on this draft via email to windows@energystar.gov by March 28, 2022.

Proposed Requirements for Northern Climate Zone
Current version 6.0 prescriptive requirements: U-factor: 0.27; SHGC: Any
Proposed requirements in Draft 1 and Draft 2 of Version 7.0: U-factor: 0.22; SHGC: 0.17)

Requirements Under Equivalent Energy Performance