Window Replacement in Denver, Colorado

In Denver, replacing windows with new ones of the same size, with no structural changes, usually needs no building permit. Denver's Community Planning and Development (CPD) says "permits are not required to replace doors, glass, or window frames," unless the property is a designated landmark or in a historic district, while new windows, egress windows and changed openings do need permits (CPD: residential remodel) ¹. The 2025 Denver Building Code sets out the same exemption for one- and two-family dwellings and townhouse units, with an extra exception for windows in hazardous locations ².

If the house is a designated landmark or in a historic district, the picture changes: the code then requires a building permit and approval from the preservation authority, Landmark Preservation reviews the windows, and vinyl windows are not allowed except in one district (2025 Denver Building Code; Window and Door Replacement Design Review) ²⁶. Denver also licenses contractors itself, and the occupational professions list of Colorado's state licensing division shows no general contractor or home-improvement license ³⁷.

Do you need a permit to replace windows in Denver?

The 2025 Denver Building Code lists, among work exempt from permits, "Replacement of windows and doors with no structural alterations and no change in size of opening in one- and two-family dwellings and townhouse units" (2025 Denver Building Code, Section 130.3) ². It names two exceptions ²:

• Preservation. When the structure is designated for preservation or is in a district designated for preservation, "a building permit and approval from the local preservation authority shall be required."
• Hazardous locations. When the replacement window or door is in a hazardous location, as defined in Section R324.4 of the Denver Residential Code. These are the spots where safety glass rules apply; the article on where tempered glass is required explains the usual cases.

CPD's remodel page adds the other side (CPD: residential remodel) ¹:

• "New window, egress window, and skylight installations require permits."
• Changing the size of an opening or creating a new one, inside or outside the home, needs a permit.
• Exterior work on a designated landmark or in a historic district needs a certificate of appropriateness from Landmark Preservation, and the city "highly recommended" getting it before applying for building and zoning permits.

The code also notes that an exemption from a permit does not authorize work that violates the code ². When a permit is needed, CPD takes applications through its online e-permits system, and the page says homeowners can apply for building permits without a contractor if they meet the criteria on the city's homeowner permits page ¹. Ask each installer whether your job is a same-size replacement, whether any unit sits in a hazardous location, and who will pull a permit if one is needed. The article on whether you need a permit to replace windows explains why the answer varies by city, and the article on egress window requirements covers bedroom and basement windows.

Who may do the work: Denver's contractor licensing

Denver issues its own contractor licenses through CPD. The city's licensing page says getting a supervisor certificate, or employing someone who holds one, "is the first step toward obtaining a contractor's license in Denver," and that Denver does not accept or reciprocate contractor licenses or certificates from other counties or states (CPD: contractor licensing) ³. Owner-occupants who do their own work may face a homeowner exam before some permits ³.

For windows, Denver has a specialty certificate. The Class D Custom Size Window Replacement certificate covers work "limited to town houses, one and two family dwelling unit buildings not requiring any structural alterations," and the city says "This certificate is only required if the work is being done in a landmark district" (Specialty Class D Certificates) ⁴. The same page says the license does not cover windows in commercial buildings ⁴.

Questions to ask, then check in Denver's contractor license search ⁵:

• Does the company hold a Denver contractor license, and which one?
• If your house is in a landmark district, does the crew work under a Class D Custom Size Window Replacement supervisor?
• If a permit is needed, who will pull it?

At the state level, the occupational professions list of Colorado's Division of Professions and Occupations includes electrical and plumbing licenses but no general contractor, home-improvement or window contractor program (Colorado DPO occupational professions) ⁷. In Denver, the city's license is the one to check. The guide on how to choose a window installer covers the rest of the vetting.

Landmark Preservation review

Denver's Landmark Preservation reviews window and door replacements on all individual landmarks and properties within a historic district, against the city's design guidelines (Window and Door Replacement Design Review) ⁶. What the review page says ⁶:

• Not allowed. "Vinyl windows and doors, except in the La Alma Lincoln Park Historic Cultural District," windows with only internal muntins between panes of glass, and windows with glued-on muntins.
• Keep historic windows. The city strongly encourages keeping historic character windows and character front facade doors; replacing common windows and doors may be an administrative review if it meets the guidelines.
• What to submit. Photos and drawings that show existing conditions and the proposed work, plus an existing-and-replacement window comparison worksheet for each window, with measurements in inches of all window features.
• How to apply. Through e-permits, by choosing "Landmark Certificate of Appropriateness."

The page says most projects are reviewed with Chapter 2, Guidelines for Preserving Historic Buildings, and that projects in the Lower Downtown Historic District are also reviewed with that district's own guidelines ⁶. If your house is in a district, ask any installer whether the windows they quote meet these rules before you sign. A homeowners association may have its own rules too; check them. The article on historic home window replacement covers repair versus replacement.

Denver's climate and the glass

ENERGY STAR places Denver County in its Northern climate zone (ENERGY STAR climate zone finder) ⁹. Under the Version 7.0 criteria, a Northern-zone window qualifies with a U-factor of 0.22 or less and a solar heat gain coefficient (SHGC) of 0.17 or more, or with U-factors of 0.23 to 0.24 paired with an SHGC of 0.35 or more, or 0.25 to 0.26 with 0.40 or more; every qualifying window also meets an air leakage limit of 0.3 cubic feet per minute per square foot (ENERGY STAR criteria) ⁸.

NOAA's 1991-2020 normals for Denver International Airport show a winter (December to February) average low of 18.9°F and about 156 days a year with a low of 32°F or colder, against a summer (June to August) average high of 86.9°F and about 46 days at 90°F or more (NOAA climate normals) ¹⁰. Heating degree days (5,862) outnumber cooling degree days (about 850) roughly seven to one, and the air is dry, with 14.48 inches of precipitation a year ¹⁰. Heat loss comes first, so U-factor leads; the Northern zone's minimum SHGC lets winter sun help, while west-facing glass may still warrant attention in summer. The U-factor explainer and the article on low-E glass cover the ratings.

What window replacement costs

This article does not quote a Denver price, because the cost surveys it relies on report national figures. As a national reference, Fixr reports an average of about $800 per window, typically $450 to $1,200 (updated January 21, 2026) ¹¹. The window replacement cost guide compares several national surveys. Your written quotes are the local number that matters.

Getting quotes in Denver

Get two or three written quotes that name the brand and series, the NFRC-rated U-factor and SHGC, full-frame or insert installation, the Denver contractor license number, and who handles any permit or landmark review. The article on how to compare window quotes shows how to line them up. When you are ready, you can compare quotes from window installers in Denver.

About these figures

• ¹ Official record: Denver CPD residential remodel page (no permit to replace doors, glass or window frames except landmarks and historic districts; permits for new windows, egress windows, skylights and changed openings; certificate of appropriateness; e-permits; homeowner applications), checked October 27, 2026.
• ² Official record: 2025 Denver Building Code, Section 130.3 item 24 (same-size window replacement exempt in one- and two-family dwellings and townhouse units, with preservation and hazardous-location exceptions), checked October 27, 2026.
• ³ Official record: Denver contractor licensing page (supervisor certificate first, no reciprocity, homeowner exams), checked October 27, 2026.
• ⁴ Official record: Denver Specialty Class D certificates page (Custom Size Window Replacement scope, required only in a landmark district, not for commercial buildings), checked October 27, 2026.
• ⁵ Official record: Denver contractor license search, checked October 27, 2026.
• ⁶ Official record: Denver Landmark Preservation window and door replacement design review page (scope, vinyl not allowed except La Alma Lincoln Park, muntin rules, worksheets, e-permits, guidelines), checked October 27, 2026.
• ⁷ Official record: Colorado DPO occupational professions list (electrical and plumbing licenses, no general contractor or home-improvement program), checked October 27, 2026.
• ⁸ Official record: ENERGY STAR Version 7.0 window criteria for the Northern zone (U-factor 0.22 and SHGC 0.17, equivalent options at 0.23 to 0.26) and air leakage 0.3, checked October 27, 2026.
• ⁹ Official record: ENERGY STAR county climate zone list (Denver County, Northern), checked October 27, 2026.
• ¹⁰ Official record: NOAA 1991-2020 normals for Denver International Airport (winter low 18.9°F, about 156 days at 32°F or below, summer high 86.9°F, about 46 days at 90°F or more, 5,862 heating and about 850 cooling degree days, 14.48 inches of precipitation), checked October 27, 2026.
• ¹¹ Reported: Fixr national window replacement cost (about $800 per window, typically $450 to $1,200; updated January 21, 2026), checked October 27, 2026.