Do I Need a Permit to Replace Windows in Colorado?
Quick Answer
Usually no — but yes if you change the size of the opening.
Colorado-specific rules
Colorado has no statewide building code — under home rule, cities and counties adopt and amend their own I-Code editions (confirm your jurisdiction's). The one statewide floor is energy: HB22-1362 (2022) requires any municipality or county that adopts or updates a building code between July 1, 2023 and July 1, 2026 to meet an energy performance floor of the 2021 IECC plus the state's electric-ready, EV-ready, and solar-ready provisions; from July 1, 2026 the floor shifts to the state's Model Low Energy and Carbon Code.
Sources: Colorado HB22-1362 (2022) — statewide energy code floor
When You Don't Need a Permit
Like-for-like window replacements — where the new window fits the exact same rough opening — typically do not require a building permit. This covers most standard window replacements where you are upgrading the glass, frame material, or energy efficiency without altering the wall structure.
When You Do Need a Permit
A permit is required when you change the size of a window opening (larger or smaller), add a new window where one didn't exist, convert a window to a door or vice versa, or install egress windows for basement bedrooms. These changes involve structural modifications (headers, jack studs) that must be inspected.
Energy Code Requirements
Replacement windows generally must meet the locally adopted energy code — most jurisdictions follow the IECC. Check the NFRC label on any window before purchasing and confirm your local edition's window U-factor requirement. This applies even when no permit is required — it's a code requirement.
Egress Windows
If you're adding a bedroom in a basement, most jurisdictions require an egress window with a minimum 5.7 sq ft net clear opening and a sill no higher than 44 inches above the floor (the IRC standard). Window wells deeper than 44 inches need a permanently attached ladder or steps. This always requires a permit.
Bottom Line
Swapping windows in the same opening? No permit needed. Changing the opening size or adding egress windows? Get a permit.