Window Energy Code Requirements
When a window permit is required, the new windows must meet energy code minimums for your climate zone. This section covers everything about U-factor requirements, SHGC rules, and how to verify compliance.
U-Factor Requirements by Climate Zone
The primary thermal standard. Find your zone, get your requirement, and understand what windows meet it.
→SHGC Requirements
Solar heat gain rules for hot climates. Required in Zones 1–3; not regulated in 4–8.
→ENERGY STAR Requirements
Version 7.0 requirements by region and how ENERGY STAR relates to code minimums and federal tax credits.
→IECC 2021 Changes
What tightened in the 2021 code edition and how it affects what you must buy in adopting states.
→Low-E Glass Explained
How low-emissivity coatings work, the difference between hard and soft coat, and historic district considerations.
→Reading the NFRC Label
What every metric on the window label means and what the inspector looks at during final inspection.
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