Replacing windows: cost, permits and energy efficiency
For Silicon Valley homes · Updated October 2026 · Sources below
Windows account for 25% to 30% of the energy a home uses for heating and cooling, so drafty single-pane windows are a common upgrade. In San José, a retrofit window set into the existing frame usually needs no permit; changing the frame, flashing or stucco does. New windows must also meet California's energy code.
The short version
- Windows drive 25%-30% of home heating and cooling energy use
- San José: simple retrofit windows usually need no permit
- Changing the frame, flashing or exterior finish needs a permit
- Lower U-factor = better insulation; lower SHGC = less heat from the sun
- Homes built before 1978: window replacement always falls under EPA lead-safe rules
Need a window installer?
Tell us about the job in 2 minutes - free. We send it to one local pro at a time, never a crowd.
What it costs
- Replace a window (per window)$300 - $2,100 (average $850)
- Replace 10-15 windows$4,000 - $10,500
National figures - Bay Area installs usually cost more. Frame material, size, retrofit vs. full-frame install and stucco work change the price.
Typical ranges from published cost guides - mostly national figures. Bay Area prices usually run higher. Your actual price depends on your home and the job, and a pro gives you the real number. Source: HomeAdvisor cost guide (national) (Jun 2026). Have a quote? Check it with the Quote Explainer
Signs it's time to replace
- Fog or moisture between the panes of a double-pane window
- Drafts you can feel even with the window closed and locked
- Frames that are rotted, warped or hard to open
- Single-pane glass and rooms that are hard to keep comfortable
- Condensation that keeps damaging sills and walls
Repair, upgrade or replace?
- If the frames are in good shape, caulking, weatherstripping, storm windows or better coverings are often the cheapest way to cut drafts.
- Retrofit (insert) windows go into the existing frame - less cost and, in San José, usually no permit.
- Full-frame replacement removes the old frame and often some stucco - needed for rot or leaks, and it needs a permit.
- Compare the NFRC labels: look for a low U-factor, and a low SHGC for west- and south-facing windows that get hot afternoon sun.
In Silicon Valley
- San José: a retrofit window doesn't need a building permit. You do need one if the frame is altered (for example to lower a sill for egress), the flashing or nailing fin is changed, or stucco or other wall finish is removed - and for any window on a property on the City's Historic Resources Inventory.
- California's Energy Code (Title 24, Part 6) sets maximum U-factor and SHGC values for replacement windows. Your installer documents compliance with NFRC-rated values or the code's default values.
Questions homeowners ask
Do I need a permit to replace windows in San Jose?
Not for a simple retrofit window that goes into the existing frame. You do need a permit if the frame or flashing is changed, stucco or siding is removed, the opening is enlarged, or the home is on San José's Historic Resources Inventory. Other cities have their own rules, so check before you order.
How much does it cost to replace windows?
National cost guides put a replacement window at about $300 to $2,100 each (average about $850), and 10 to 15 windows at about $4,000 to $10,500. Bay Area prices usually run higher, and full-frame installs with stucco work cost more than retrofits.
Are new windows worth it for energy savings?
Windows are responsible for about 25% to 30% of home heating and cooling energy use, so replacing single-pane or leaky windows can make a real difference in comfort and bills. If your windows are in good shape, the Department of Energy suggests sealing leaks and adding storm windows first, since that often costs less.
What do U-factor and SHGC mean?
U-factor measures how well a window keeps heat from escaping - lower is better. SHGC (solar heat gain coefficient) measures how much of the sun's heat comes through - lower means a cooler room. Both are on the NFRC label.
My house was built before 1978. Does that matter for new windows?
Yes. Old paint may contain lead, and EPA rules say window replacement in pre-1978 homes is always covered by lead-safe work requirements, no matter how small. Ask the installer how they contain dust and clean up.
Retrofit or full-frame windows - which do I need?
Retrofit windows fit inside the existing frame, cost less and usually skip the permit in San José. Full-frame replacement is the better choice when frames are rotted or leaking, but it means removing trim or stucco and pulling a permit.
Do you need a permit?
Depends on the city and the work - check before you order.
General guidance based on California's building code - your city can have stricter rules, and zoning, historic and HOA rules can apply too. Check with your city's building department before you start.
Check the rule for your cityQuestions to ask the pro
- Retrofit or full-frame for my windows - and why?
- What are the U-factor and SHGC of the windows you're quoting?
- Does my city need a permit for this job, and is it in the price?
- How do you flash and seal the new windows against leaks?
- If my home is pre-1978, how do you handle lead-safe work?
- What warranty covers the windows and the installation?
Before you sign, check the contractor's license at cslb.ca.gov. How to hire a contractor in California
Need a window installer?
Tell us about the job in 2 minutes - free. We send it to one local pro at a time, never a crowd.
Related answers
Sources
- U.S. Department of Energy - Energy-efficient windows
- U.S. DOE / ENERGY STAR - Consumer guide to energy-efficient windows (PDF)
- City of San José - Window Replacements
- California Energy Commission - 2025 residential alterations compliance form (CF1R-ALT-05)
- U.S. EPA - Renovation, Repair and Painting Program (lead-safe work in pre-1978 homes)
General information for Silicon Valley homeowners, not professional advice for your home. Rules and programs change - check the source, and have a licensed pro look at your situation.