Window Replacement in Seattle, Washington

In Seattle, whether a window job needs a permit comes down to two lines the Seattle Department of Construction and Inspections (SDCI) draws. Its permit page says that, unless you are in an environmentally critical area, you don't need a permit for minor repairs or alterations that cost $6,000 or less in any 6-month period, but that you do need one for "changes to the building envelope" and for work that reduces egress, light, ventilation or fire resistance, "no matter how small the project" (SDCI: Do you need a permit?) ¹. The page does not say whether a same-size window swap counts as a change to the envelope, so ask SDCI about your job before work starts.

Two other rules shape the job. The 2021 Seattle Energy Code requires almost all window glazing to carry an NFRC label or label certificate (SDCI Tip 403) ³. And if the house is a city landmark, changes to its designated features need a Certificate of Approval first, as do changes to the external appearance of any building in one of Seattle's eight historic districts (Certificate of Approval) ⁴⁵.

Do you need a permit to replace windows in Seattle?

SDCI's page does not mention windows by name. What it says (SDCI: Do you need a permit?) ¹:

• The $6,000 line. Minor repairs or alterations costing $6,000 or less in any 6-month period usually don't need a permit, and the limit "is based on fair market value of labor and parts, even if you do the work yourself" ¹.
• Always a permit. Work on load-bearing supports, changes to the building envelope, and work that reduces egress, light, ventilation or fire resistance need a permit regardless of cost ¹.
• Critical areas. The usual exemptions do not apply in an environmentally critical area ¹.
• Code still applies. Even when no permit is needed, the work must meet all code requirements and development standards ¹.

Whether replacing a window with one of the same size counts as a change to the building envelope is the question to put to SDCI before work starts. Changing a bedroom window in a way that reduces its escape opening falls on the permit side of the page's own wording, and resizing an opening is the kind of envelope change to raise with SDCI ¹. The article on egress window requirements explains why bedroom windows get extra attention.

For small jobs, SDCI offers a Subject-to-Field-Inspection (STFI) construction permit, "a construction permit for small projects that meet certain criteria," issued through the Seattle Services Portal, with fees based on the value of the project (STFI permit/construction-permit---subject-to-field-inspection>)) ². On sites with steep slopes or other listed critical areas, that page requires a topographic survey or geotechnical report for exterior work "other than window, siding, or roofing replacement" ². Ask each installer who quotes the job whether they will pull the permit and whether its cost is in the price. The article on whether you need a permit to replace windows explains why the answer differs from city to city.

The Seattle Energy Code and window labels

SDCI's Tip 403, updated April 7, 2025, sets out how the 2021 Seattle Energy Code treats windows (SDCI Tip 403) ³:

• NFRC ratings. Under the code, the U-factor of a window, door or skylight is determined under NFRC 100 by an accredited outside laboratory, and the manufacturer labels the product; the solar heat gain coefficient (SHGC) also goes through NFRC ³.
• No SHGC rule for houses. The residential portion of the code, which covers single-family and two-unit dwellings plus townhouses, has no solar heat gain coefficient requirement ³.
• Exceptions. Windows with no NFRC rating, such as salvaged or owner-built units, may use the code's default U-factor tables, and windows made by a Washington State small business (fewer than 50 employees) may use separate small-business tables ³.
• Where to look. For houses, the window sections are R303.1.3 and R402.3 ³.

In practice: ask for the NFRC-rated U-factor of each unit in writing, keep the labels on until inspection, and ask whether the quoted window meets the energy code for your job. The U-factor explainer covers what the number means.

Landmarks and historic districts

Seattle's Department of Neighborhoods runs the city's historic preservation program. Its page says the city has "eight historic districts" and more than 400 landmarks, and links a landmarks map and list for checking an address (Seattle historic preservation) ⁴. The districts include Ballard Avenue, Columbia City, Harvard-Belmont, Pioneer Square, Pike Place Market and the International Special Review District ⁴.

A Certificate of Approval is "a written authorization, much like a permit, that must be issued before any changes can be made" to a landmark's designated features, and it is needed for changes to the exterior of buildings in the historic districts (Certificate of Approval) ⁵. How it works, from that page ⁵:

• Apply through the Seattle Services Portal, using the city's checklist of materials.
• Staff respond within 28 days of receipt; corrections are reviewed within 14 days.
• Decisions must be issued within 45 days of the application being found complete, by the board or commission or the director.

The page does not list windows by name, so if your house is a landmark or in a district, ask preservation staff whether your window job needs a certificate before you order windows. A homeowners association may also have its own rules; check them. The article on historic home window replacement covers the repair-or-replace question.

Who may do the work

Washington State's Department of Labor & Industries says: "Washington State requires all construction contractors to register with L&I" (L&I: register as a contractor) ⁶. The Washington page covers the exemptions and the difference between general and specialty registration. Is the installer registered, and does the registration cover window work? You can check by name, license number or UBI number in L&I's verify tool ⁷. The guide on how to choose a window installer covers the rest of the vetting.

Seattle's climate and the glass

ENERGY STAR places King 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 an 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; all qualifying windows also meet an air leakage limit of 0.3 cubic feet per minute per square foot (ENERGY STAR criteria) ⁸.

NOAA's 1991-2020 normals for Seattle-Tacoma International Airport show a winter (December to February) average high of 48.4°F and low of 37.5°F, and a summer (June to August) average high of 75.4°F (NOAA climate normals) ¹⁰. Heating degree days (4,376) far outnumber cooling degree days (265), and the station records about 93 days a year with at least a tenth of an inch of precipitation, out of 39.34 inches a year ¹⁰. Long, cool, damp winters put U-factor first, and they are when window condensation shows up; careful flashing matters as much as the glass. The energy-efficient windows explainer goes deeper.

What window replacement costs

This article does not quote a Seattle 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 Seattle

Get two or three written quotes that name the brand and series, the NFRC-rated U-factor of each unit, full-frame or insert installation, and who handles any SDCI permit or Certificate of Approval. 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 Seattle.

About these figures

• ¹ Official record: SDCI Do You Need a Permit? page ($6,000 in any 6-month period, fair market value rule, permit for building envelope changes and reduced egress, light, ventilation or fire resistance, critical areas), checked October 27, 2026.
• ² Official record: SDCI Subject-to-Field-Inspection permit page (scope, Seattle Services Portal, fees based on value, window replacement excluded from the critical-area survey and report triggers), checked October 27, 2026.
• ³ Official record: SDCI Tip 403, NFRC labeling under the 2021 Seattle Energy Code, updated April 7, 2025 (NFRC 100 rule, no residential SHGC requirement, default and small-business tables for firms under 50 employees, sections R303.1.3 and R402.3), checked October 27, 2026.
• ⁴ Official record: Seattle Department of Neighborhoods historic preservation page (eight historic districts, more than 400 landmarks, map and list), checked October 27, 2026.
• ⁵ Official record: Seattle Certificate of Approval page (scope, Seattle Services Portal, 28-day and 14-day staff review, 45-day decision), checked October 27, 2026.
• ⁶ Official record: L&I register as a contractor page (all construction contractors must register), checked October 27, 2026.
• ⁷ Official record: L&I verify tool (search by name, license number, workers' comp account or UBI), 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 (King County, Northern), checked October 27, 2026.
• ¹⁰ Official record: NOAA 1991-2020 normals for Seattle-Tacoma International Airport (winter high 48.4°F and low 37.5°F, summer high 75.4°F, 4,376 heating and 265 cooling degree days, about 93 days with 0.10 inch or more of precipitation, 39.34 inches a year), 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.