E1b: Optimize building envelope thermal performance
A high-performing thermal envelope significantly reduces heating and cooling energy consumption and cost, ensures thermal comfort, and prevents condensation. In addition to a well-insulated building envelope, air sealing is of paramount importance. In an average building, up to 1/3 of heating and cooling loads are attributed to air leakage through the envelope.
- Use high levels of insulation to reduce heating and cooling energy loads
- In wood frame structures, use advanced framing to increase R-values
- Detail envelope to avoid thermal bridging
- Consider using rigid foam or insulated concrete forms (ICFs) for insulated foundation
- Size openings, select glazing types, and use shading devices (interior or exterior), overhangs, and vegetation to minimize unwanted heat loss/gain and to optimize daylighting
- Look for NFRC labeled windows with a U-value less than or equal to 0.3 (glazing with a low U-value minimizes energy use and may reduce need for perimeter heating)
- Install operable windows
- Use insulated core doors for all exterior doors
- Use best practices for window and door installation to ensure energy performance and durability
- Use best air and vapor barrier practices to prevent condensation inside exterior walls.
- Flash and seal all penetrations
- Reduce air infiltration by using expandable foam and caulk for framing, plumbing, and electrical penetrations
- Moderate interior temperature extremes by using thermal mass where appropriate
- Separate living spaces from areas that need less heating or cooling (e.g. entries, storage, mechanical, and utility spaces)
Publications and Links
City of New York Department of Design and Construction. High Performance Building Guidelines. New York, NY: April 1999
Efficient Windows Collaborative
See full list of recommended resources and links in our library.