The 2027 edition of the International Energy Conservation Code (IECC) is now final. It's the model energy code that most US states base their building energy rules on. No appeals were filed against the residential or the commercial part, the Energy Efficient Codes Coalition reported, and the International Code Council expects to publish the code around December 1, 2026.
What changes for windows
The home (residential) part tightens the limits for new windows. The Window & Door Manufacturers Association, which helped write the window proposal with glass industry groups, gave these changes:
- U-factor (how much heat escapes; lower is better): 0.45 in climate zones 0-1 (was 0.50), 0.35 in zone 2 (was 0.40) and 0.27 in zones 5-6 (was 0.28).
- Solar heat gain coefficient (SHGC) (how much of the sun's heat gets in; lower is better): 0.23 in zones 0-3 (was 0.25). Those are the hot southern zones.
The commercial part also updates its U-factor and insulation tables in several climate zones. We haven't seen its final window numbers, so we don't list them here.
What it means for window film
- Nothing changes today. A model code only applies once a state or city adopts it. The first states are expected to adopt it around 2028, and many still use older editions.
- It's about new windows, not film on the glass you have. The IECC sets limits for new and replacement windows. It doesn't require film on existing windows, and adding film isn't a way for a new window to meet the limits.
- The SHGC number is a handy yardstick. An SHGC of 0.23 means about 23% of the sun's heat gets through the window. If you have older windows in a hot climate, a solar control film can lower their SHGC without replacing them. Compare films by their NFRC-rated SHGC on glass like yours, not by how dark they look.
Learn more in our guides on how window film works and the benefits of home window film.
What isn't confirmed yet
The printed code isn't out yet, so small editorial changes are still possible before December. Each state decides whether and when to adopt it, and states often amend the window limits when they do.
