Published Last updated 8 min read
How to Vet a Window Installer: 12 Questions That Weed Out the Bad Ones
The single biggest factor in a great window job is the installer, not the brand. Ask these 12 questions before signing any contract.
1. Is the contractor licensed?
Ask for the contractor's state license number and verify it yourself with the issuing body. License rules differ by state and city: for example, Texas has no state general-contractor license, while New York City requires a Home Improvement Contractor license.
2. What insurance do they carry?
Ask for a general liability insurance certificate and proof of workers' compensation coverage. Verify both by calling the insurer. Do not accept photocopies on their own.
3. Who actually installs the windows?
Confirm whether the crew is employed by the company or subcontracted. In-house crews carry lower risk of installation errors, and warranty claims are easier to resolve.
4. How experienced is the lead installer?
Ask how many years the lead installer has been with the company, and how many installs of your window type they have done.
5. Is the firm lead-safe certified?
If your home was built before 1978, EPA's lead renovation rule covers paid window replacement. The firm must be EPA-certified and use certified renovators and lead-safe work practices.
6. Who pulls the permit?
Permit rules vary widely. The City of Los Angeles treats window replacement as an Express Permit, while Dallas exempts same-size replacements that meet certain conditions. See our guides for Los Angeles and Dallas, and ask the installer to put in writing whether your job needs a permit.
7. Is the quote itemized?
Get a written quote that names the product line and model, the NFRC-labeled U-factor and SHGC for each window, the install method, and what is and isn't included.
8. What does the installation warranty cover?
Get the installation warranty in writing, separate from the manufacturer warranty. Ask what it covers for labor, water intrusion, air leaks and glass seal failure, and for how long.
9. What does the manufacturer warranty cover?
Ask for the actual warranty document for the exact product line. Check whether coverage transfers to the next owner, whether labor is included, and whether glass breakage is covered. Terms differ by maker. See our brand comparison.
10. Who measures, and what if something is wrong?
Ask who measures the openings and what happens if a window arrives the wrong size or damaged. Custom windows are usually hard to return.
11. What are the payment terms?
Ask for the payment schedule in writing, and be cautious about large deposits before any work begins. Confirm that payment is tied to progress and a final walk-through.
12. Can you talk to past customers?
Ask for three references from projects completed 3–5 years ago (not last month). Long-term references reveal how the installer stands behind work when problems appear later. Cross-check reviews on Google, BBB, and your state contractor licensing board.
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