Design Temperature Limits for Residential New Construction

Welcome

Are you an HVAC designer, builder, or Rater working on a home or multifamily building that will be ENERGY STAR certified? If so, this page will explain one of the key requirements of the program – the outdoor design temperatures that must be used to calculate the heating and cooling loads.

Outdoor Design Temperature Limits

To meet the requirements of the program, the outdoor design temperatures used must not exceed specified limits. For homes and apartments following Track A, the maximum cooling season temperature and minimum heating season temperature can be found in Appendix A of ANSI/RESNET/ACCA/ICC 310. If pursing Track B, use the limits listed in the ENERGY STAR Certified Homes Design Temperature Limit Reference Guide (2019 Edition) (PDF, 4KB) that apply to the state/county or territory in which the home is to be built. For more information about Track A and Track B, visit HVAC Contractors. 

Example: A home will be certified in Travis County, TX. By consulting the reference guide, we find that the cooling season outdoor design temperature limit is 99 F and the heating season outdoor design temperature limit is 28 F.

This means that the designer must:

  • Use a cooling season design temperature that is less than or equal to 99 F.
  • Use a heating season design temperature that is equal to or greater than 28 F.
  • Not use the cooling sizing limit for a Condition B Climate because the HDD/CDD Ratio is 0.3, which is < 2.0.

If using Track B, two exceptions apply:

  1. Jurisdiction-Specified Temperatures: If a jurisdiction-specified design temperature is used that exceeds the limit defined in the ENERGY STAR Certified Homes Design Limit Temperature Reference Guide, designers must submit a Design Temperature Exception Request (PDF, 118KB).
  2. Temperature Exception Request: In rare cases, the designer may believe that an exception to the limits in the reference guide is warranted for a particular state/county or territory. If so, the designer must complete and submit a Design Temperature Exception Request (PDF, 118KB), including a justification for the exception, to energystarhomes@energystar.gov for review and approval prior to the home’s certification.

To obtain the most accurate load calculations, the EPA recommends that designers always use the ACCA Manual J, 8th edition, 1% cooling season design temperature and 99% heating season design temperature for the weather station that’s geographically closest to the home to be certified.

The state/county or territory and corresponding outdoor design temperatures selected by the designer will be documented in the HVAC Design Report, and the Rater will verify that the selected temperatures are within the required limits prior to certification. 

To learn more about the requirements for designers, visit Requirements & Resources for HVAC Designers.

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