September 4, 2019 ENERGY STAR® Windows, Doors, and Skylights Version 7.0 Specification Discussion Guide Page 7 of 16the length of time a typical homeowner stays in a home—around 10 to 13 years.8 EPA will consider these approaches when evaluating cost-effectiveness. EPA requests stakeholder feedback for the following question:5.What sources should EPA consider when evaluating what is a reasonable payback period forbuilding materials like WDS?EPA is proposing three different methods for estimating the cost of ENERGY STAR WDS:

Component Bill of Materials: Using the Pathways Methodology, EPA is able to isolate specific components that have the greatest impact on product performance and determine what combinations of components have been certifiedfor different performance levels. EPA proposes to estimate incremental costs by comparing the totalcost of the components needed to achieve performance improvements. D+R International, under contract to EPA, plans to conduct interviews with component suppliers under a non-disclosure agreement to collect cost estimates for different component categories, including frame material, low-e glass type and configuration, spacer material and performance tier, and gas fill.

These categories align with the Windows Pathways Analysis Methodology. EPA plans to analyze component costs, assuming a standard 3-foot x 5-foot double-hung, residential grade window. Manufacturer Costs: In previous specification revision efforts, manufacturers have voluntarily provided incremental costs using a standardized spreadsheet template. EPA has developed an updated template to provide a standardized way to request manufacturer costs, which asks how manufacturers achieve a specific U-factor by using different components.

Manufacturers will be able to choose categories from a drop-down menu for each component and input a cost for each specific combination of components. The template also will ask manufacturers to indicate whether they produce 10 common pathways, and if so, how common those products are and what the cost to consumers would be. Manufacturers are invited to voluntarily provide this data under a non-disclosure agreement with D+R International.Retail Pricing and Mystery Shopping:EPA also will attempt to conduct research on pricing and confirm the availability of fenestration products through “mystery shopping” window dealers, installers, and big-box retail centers. This approach would provide a clear indication of the costs experienced by consumers; however, EPA recognizes that there are challenges to this research; namely, window prices vary between different sales channels and regions, and these price differences may not be solely due to the incremental costs related to energy performance. EPA proposes to mitigate this variability by focusing on low-cost and best-selling products and would use this approach to help confirm the accuracy of component bill of materials analysis and manufacturer cost estimates.8 Emrath, Paul. Latest Calculations Show Average Buyer Expected to Stay in Home 13 Years. National Association of Home Builders. http://nahbclassic.org/generic.aspx?genericContentID=194717

September 4, 2019 ENERGY STAR® Windows, Doors, and Skylights Version 7.0 Specification Discussion Guide Page 8 of 16EPA requests stakeholder feedback for the following questions: 6.What other methods for estimating the incremental costs of energy performance improvements for windows, doors, and skylights should EPA consider? 7.Which incremental cost estimation methods are the most accurate?8.Are there any additional component categories that EPA should consider researching?

Energy SavingsEPA and DOE have historically used the industry-standard RESFEN software from Lawrence Berkeley National Laboratories (LBNL) to calculate energy savings for individual households in different climates. To calculate national energy savings for the Version 6.0 specification, LBNL built a Microsoft® Excel-based model that compiled household-level energy savings calculations to develop regional and national energy savings projections using population weighting and regional window shipments data from Ducker International. However, EPA has received feedback from stakeholders that the current version of RESFEN does not use the best available energy model, known as EnergyPlus™. To address these concerns, EPA has worked closely with technical experts at LBNL and the

National Renewable Energy Laboratory (NREL) to refine the energy savings calculation methodologies. LBNL and NREL have each developed new building energy modeling tools that use EnergyPlus and considerupdated data from the U.S. Census, Residential Energy Consumption Survey, and total meteorological year data for a range of U.S. cities. The key differences between the two models are the baseline home characteristics for which energy consumption will be modeled. The LBNL model will calculate energy consumption for prototype homes developed by PNNL from geographically distributed U.S. cities.

NREL’s ResStock tool bases household characteristics on a sophisticated statistical sample that accounts for the diversity of the single-family housing stock and climates across the United States. If EPA decides to begin a specification revision process, it would run analyses using these new modeling tools to evaluate the local, regional, and national energy savings for a range of potential criteria and would publish the results from both models.

Additional Issues to ConsiderDuring its research and analysis, EPA plans to evaluate several issues related to the specification. EPA and/or stakeholders have raised some of these issues in the past, while others have more recently arisen from developments in the market and fenestration technology.Combining Southern and South-Central Climate ZonesEPA looks for opportunities to simplify specifications, when possible. One potential opportunity to simplify the WDS specification would be to combine the Southern (IECC zones 1 and 2) and South-Central (IECC Zone 3) climate zones. The DOE/PNNL field studies mentioned above suggest that buildersin Texas (IECC Zone 2) and Alabama (IECC Zone 3) install windows of similar performance, with a U-factor of 0.35 or lower.9 EPA pl ans to consider whether this indicates that consumers and partners would benefit from a simplified specification that combines these two zones, or whether there are 9 Cohan, David, et al. Beyond Compliance: The DOE Residential Energy Code Field Study. Published for the 2016 American Council for an Energy-Efficient Economy (ACEEE) Summer Study on Energy Efficiency in Buildings. https://aceee.org/files/proceedings/2016/data/papers/5_18.pdf

September 4, 2019ENERGY STAR® Windows, Doors, and Skylights Version 7.0 Specification Discussion Guide Page 9 of 16significant technical or market differences that support keeping the Southern and South-Central climate zones separate. EPA requests stakeholder feedback for the following questions:9.Should EPA consider combining the ENERGY STAR Southern and South-Central climate zones?10.What impact would the potential merging of these climate zones have on consumers and partners? Establishing a Minimum Solar Heat Gain Coefficient (SHGC) for the Northern Climate ZoneEPA plans to analyze the potential impact of establishing a minimum SHGC in the Northern climate zone.

Previous analyses have suggested that significant energy savings may be possible with higher solar gain products in heating-dominant climates. In addition, some very low SHGC products also have very low visible transmittance (VT). These dark or tinted products reduce glare in southern, cooling-dominated climates, but are considered unacceptable to many consumers in the Northern climate zone.

Establishing a minimum SHGC for the Northern climate zone could improve the veracity of the ENERGY STAR label by disqualifying excessively dark (low VT) products and possibly improving energy performance through passive solar heat gain. EPA requests stakeholder feedback for the following questions: 11.Should EPA consider setting a minimum SHGC in the Northern climate zone?12.What impact would a minimum SHGC have on product availability, consumer expectations, and the veracity of the ENERGY STAR label in the window market? Evaluating IECC Zone 5 for the Northern or North-Central Climate Zone IECC Zone 5 is on the southern edge of the current Northern climate zone and has more cooling degree-days than zones 6 through 8, leading EPA to consider moving IECC Zone 5 to the ENERGY STAR North-Central climate zone.

The combination of zones that make up the ENERGY STAR North-Central climate zone is particularly important because it has the largest population concentration in the United States, resulting in a significant potential impact on national energy savings. The new energy models that EPA will use for its analysis have updated weather files that reflect the latest climate trends, which show that IECC Zone 5 may be more characteristic of the ENERGY STAR North-Central climate zone than theNorthern climate zone. In analyzing the energy savings and cost-effectiveness of different potential criteria, including minimum SHGC, EPA will consider whether IECC Zone 5 is best suited to the ENERGY STAR Northern or North-Central climate zone. EPA requests stakeholder feedback for the following questions:13.Should EPA consider moving IECC Zone 5 out of the ENERGY STAR Northern climate zone and into the North-Central climate zone?14.What impact would changing climate zone boundaries have on consumers and partners?15.What characteristics are most common among ENERGY STAR certified windows sold in IECC Zone 5?

September 4, 2019ENERGY STAR® Windows, Doors, and Skylights Version 7.0 Specification Discussion Guide Page 10 of 16 Applying the ENERGY STAR Windows Specification to Full-Lite Sliding Patio DoorsFull-lite sliding patio doors, classified by NFRC product code DDSG, are virtually all glass and share more components and features with windows than swinging doors. Therefore, EPA is considering applying the windows criteria to full-lite sliding patio doors to simplify the specification. Partners have requestedconsistent requirements for windows and patio doors to make it easier to specify similar glass packages. Currently, patio doors are considered (greater than) > 1/2-lite doors for the purposes of the ENERGY STAR specification.

Requiring that full-lite sliding patio doors have the same U-factor and SHGC as windows ensures that the products have a similar performance, ensures a more consistent glazing look to window and patio door products, and may reduce confusion for consumers when purchasing fenestration products for their home. EPA requests stakeholder feedback for the following questions:16.Should EPA consider including full-lite sliding patio doors in the ENERGY STAR Windows specification?17.What impact would this potential change have on consumers and partners?

Sunsetting the ENERGY STAR Door CriteriaEPA also will consider whether sunsetting the ENERGY STAR specification for swinging doors is appropriate. In previous criteria revisions, this category showed long payback periods for these products. EPA will study whether additional cost-effective energy savings are possible for swinging doors, and whether these products offer significant energy savings on a national level. However, EPA also understands the value of the ENERGY STAR brand in differentiating higher performing products for consumers and code officials, and is open to feedback and additional modeling to evaluate the issue.EPA requests stakeholder feedback for the following questions:18.

Should EPA consider sunsetting the ENERGY STAR specification for swinging doors if the analysis does not reveal significant cost-effective energy savings for consumers? 19.Should EPA sunset just part the criteria if additional cost-effective energy savings are only possible for some products, such as glass-only doors?Simplifying or Sunsetting the ENERGY STAR Skylight CriteriaEPA is considering options for further streamlining the ENERGY STAR WDS specification for skylights, including tubular daylighting devices.

EPA is seeking stakeholder feedback on two possible options:Simplification Analysis of skylights is difficult because there is a wide range of performance among a relatively small number of available ENERGY STAR certified products, and energy modeling involves additional technical complexities. For these reasons, it is difficult to know whether a proposed specification is consistent with the ENERGY STAR Guiding Principles. One option for streamlining the specification may be to rely primarily on the analysis of windows and then propose criteria for skylights based on an appropriate adjustment factor so that the criteria for windows and skylights promote similar energy-efficient features. EPA has performed a preliminary analysis to evaluate a new criteria development approach that compares the U-factor and the SHGC of windows with identical technical pathways at 90° and 20°angles. The preliminary results of EPA’s modeling are shown in Appendix B.

September 4, 2019ENERGY STAR® Windows, Doors, and Skylights Version 7.0 Specification Discussion Guide Page 11 of 16 On average, the U-factor for skylights was 0.037 (9 percent) higher than a window with identical technical pathways, with the largest difference found to be 0.076 (18 percent). EPA recognizes that the mounting method for skylights (i.e., curb-mounted vs. deck-mounted) has an impact on energy performance that should be considered, as well as other technical and market issues.EPA requests stakeholder feedback for the following questions:20.Should EPA consider including skylights in the ENERGY STAR Windows specification? 21.

What significant technical and market differences between windows and skylights should EPA consider in its analysis?Sunsetting EPA also will consider whether sunsetting the ENERGY STAR specification for skylights is appropriate. In previous criteria revisions, this category showed long payback periods for these products. EPA will study whether additional cost-effective energy savings are possible for skylights and whether these products offer significant energy savings on a national level. However, EPA also understands the value of the ENERGY STAR brand in differentiating higher performing products for consumers and code officials, and is open to feedback and additional modeling to evaluate the issue.

EPA requests stakeholder feedback for the following questions:22.Should EPA consider sunsetting the ENERGY STAR specification for skylights if the analysis does not reveal significant cost-effective energy savings for consumers? Dynamic Glazing and ShadingProducts with dynamic glazing and integrated shading systems are currently available for sale. EPA seeks to understand how common these products are, and whether the current approach for certifying these products is appropriate. Currently, NFRC certification for dynamic products provides performance ratings for products in the fully open and fully closed states; however, EPA understands that the schedule by which the product shifts between open and closed states may affect the overall energy performance of the dynamic product. EPA will consider clarifying criteria and/or including allowances for such dynamic products in a potential revised specification, provided that the energy performance can be measured and verified through physical testing of the product and the schedule properly modelled. EPA requests stakeholder feedback for the following questions:23.

What is the market penetration of products with dynamic glazing or integrated shading systems for residential applications? Do stakeholders expect the market for such products to expand in the next few years?24.How should the process for certifying and listing dynamic and/or integrated products be revised to better evaluate the performance and availability of such products? High Altitude and Impact ResistanceEPA is aware that proposals to provide allowances for impact-rated and high-altitude products were preliminarily accepted for the 2021 IECC. EPA has evaluated this issue in past specification revisions and has concluded that such allowances are not appropriate for the ENERGY STAR specification because they

September 4, 2019ENERGY STAR® Windows, Doors, and Skylights Version 7.0 Specification Discussion Guide Page 12 of 16 would introduce significant complexity to labeling requirements, would save less energy over market baselines compared to other ENERGY STAR certified products, and there are products in the market that could meet even an improved ENERGY STAR specification in these locations. EPA requests stakeholder feedback for the following questions:25.What share of residential WDS are sold in places where high-altitude and/or impact-resistant products are necessary?26.Should EPA reconsider allowances for high altitude and/or impact resistance in a potential revised specification, and why or why not? Extended Implementation Schedule Typically, new criteria become effective 9 to 12 months after publication of a final specification document. However, EPA is open to extending the implementation schedule to help ensure that there will be products available for sale that meet a potential revised specification. EPA is interested inlearning whether manufacturers would value an extension to give them more time to invest in process and capital improvements, if they so choose. EPA requests stakeholder feedback for the following questions:27.

Should EPA consider extending the effective date beyond the typical 9 to 12 months after release of a final specification?28.How would an extended implementation schedule make it easier to meet a potential revised specification?Next Steps The process for considering a potential Version 7.0 specification revision for ENERGY STAR Windows, Doors, and Skylights will be iterative and offer multiple opportunities for stakeholder comment. The next step in this process is for stakeholders to provide comment on the issues and methodologies introduced above. Please submit all comments on this Discussion Guide to windows@energystar.govby October 4, 2019. All comments received will be posted on the ENERGY STAR specification development webpage. In addition, interested manufacturers of finished window products or fenestration components are invited to provide voluntary cost estimates to D+R International, which will be held confidential. EPA also will publish written responses to the submitted comments. If EPA determines that it is appropriate to propose a revised specification, it will publish a Draft 1 specification, along with a Criteria Analysis Report (CAR) that lays out the results of its analyses. EPA would then invite comment on Draft 1 and the CAR, and publish a Final Draft Specification that addresses stakeholder comments. Stakeholders would have a final opportunity to offer comment, following which EPA would publish a Final Version 7.0 Specification.

 

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