How to Choose a Window Installer

There is no single answer to which window replacement company is right for a given home, and this article does not rank companies. What makes the choice manageable is a short, checkable process: get several written quotes that describe the same job, confirm the company's license where your state or city issues one, read the contract and both warranties before you sign, and walk away from the pressure tactics that consumer agencies list as warning signs.

The Federal Trade Commission's advice for any home improvement job follows the same lines: get recommendations from people you trust, get multiple written estimates, do not choose a bid on price alone, and ask why when the estimates are far apart ¹. The sections below turn that into steps for a window project, with the questions to ask and the official places to check the answers.

Start with what you want quoted

Installers can only quote like for like if you describe the job the same way to each of them. Before the first visit, write down:

• Which windows you want replaced, room by room, and whether any should change size or style.
• Whether you know the frames are sound or suspect rot or water damage, which decides between an insert and a full-frame installation (see full-frame vs. insert replacement).
• What matters most to you in the glass: keeping heat in, keeping summer sun out, or both (the energy-efficient windows guide explains the ratings).
• Your rough budget, informed by the ranges in the window replacement cost guide.

Then ask at least three companies to quote the same list. If one company suggests a different window or method, ask it to quote your original request as well, so you have one comparison that lines up.

What a written quote should list

A quote is easier to trust when it names the exact product. The FTC says a written estimate should describe the work, the materials, the completion date and the price ¹. For windows, that means each quote should show:

• Brand and series of every window, not only "vinyl double-hung".
• Glass package: number of panes, low-E coating and gas fill, plus the U-factor and Solar Heat Gain Coefficient from the NFRC label. NFRC's label reports the U-factor (lower keeps more heat in) and the SHGC on a scale from 0 to 1 ¹².
• Installation method: insert (new window inside the old frame) or full-frame (old window removed to the rough opening).
• What is included: removal and disposal of old windows, interior and exterior trim, exterior capping, caulking, and repair of any rot found once the old window is out.
• Permit: who pulls it, if your city requires one (see do you need a permit to replace windows).
• Dates: estimated start and completion.
• Payment schedule: deposit, any progress payments, and the final payment tied to completion.

Our line-item template for comparing window quotes puts these into a table you can fill in for each company.

How to check a license

Whether a window installer needs a state license depends on the state, and sometimes on the size of the job. Some states license contractors statewide, some register them, and some leave it to cities and counties. The safest habit is to look the company up on the official board's site yourself, by name and license number, before you sign. A few examples, each linked to the official source:

• California. The Contractors State License Board says that since January 1, 2025, an unlicensed person may take on a project only if the total for labor and materials is less than $1,000, no building permit is needed and no workers are hired ³. Look up a license on the CSLB license check.
• Florida. The Construction Industry Licensing Board's FAQ says window installation and replacement requires a general, building or residential contractor license, or a local license that covers window work, and that a glass and glazing specialty contractor holding the state's certification may also do it ⁴. Search on the DBPR construction industry page.
• Arizona. State law exempts small jobs from the Registrar of Contractors license only when the aggregate contract price, including labor and materials, is less than $1,000, the work is casual or minor, no local building permit is required and other conditions are met ⁵. Search the ROC contractor search.
• Oregon. The Construction Contractors Board requires a CCB license for anyone who works for compensation in construction involving improvements to real property, with narrow exceptions ⁶. Search the CCB license search.
• Virginia. The Board for Contractors requires a Class C license for a project of more than $1,000 and less than $30,000, a Class B license from $30,000 to under $150,000, and a Class A license at $150,000 or more ⁷. Use DPOR License Lookup.
• New York. The Attorney General's office says home improvement contractors need a license in New York City, the City of Buffalo and the counties of Suffolk, Nassau, Westchester, Putnam and Rockland, and links to local lookups for most of them ⁸.

If your state is not listed, search for your state's contractor licensing board or consumer protection office, and ask your city or county building department too. The FTC suggests confirming the license with your state or county government and asking the contractor for proof of insurance ¹. A question to put to every company: "What is your license or registration number, and which agency issued it?"

What the training and lead-safe credentials mean

You may see two credentials mentioned on installer websites. Knowing what each one is helps you ask about it; neither replaces your own check.

FGIA InstallationMasters. The Fenestration and Glazing Industry Alliance runs InstallationMasters, a training and certification program for installers of windows and exterior glass doors in homes and light commercial buildings, covering new construction and replacement ⁹. Classes cover installation practice from the first site inspection to final cleanup, and FGIA keeps a searchable directory of people who completed the program ⁹. If a company mentions it, ask which crew members on your job hold it and look them up in that directory.

EPA lead-safe firm certification. In homes built before 1978, EPA's Renovation, Repair and Painting rule requires firms paid to do work that disturbs painted surfaces to hold EPA certification and to use lead-safe practices ¹⁰. Replacing old windows may disturb painted trim and sashes. EPA provides a lead-safe firm locator where you can search for a firm by location ¹⁰. If your home was built before 1978, ask: "Is your firm certified under EPA's RRP rule, and who on the crew is the certified renovator?"

Product certifications are separate. Labels on the window itself, such as the NFRC energy label ¹² or WDMA's Hallmark program, which tests windows, doors and skylights against air, water and structural performance standards ¹¹, describe the product, not the person installing it.

Questions to ask every company

Put the same questions to each company and write down the answers:

1. What is your license or registration number, and which agency issued it?
2. Can you show proof of liability insurance, and do you carry workers' compensation for the crew?
3. Will your own employees install the windows, or a subcontractor? Who supervises the job?
4. Which brand and series are you quoting, and why that one for my home?
5. Is this an insert or full-frame installation, and what happens if you find rot when the old window comes out?
6. Who pulls the permit, if one is needed, and who schedules the inspection?
7. If my home was built before 1978, is your firm certified under EPA's RRP rule?
8. What does the manufacturer's warranty cover, and what does your installation (labor) warranty cover, for how long, and is either transferable if I sell?
9. What is the deposit, when are the other payments due, and what triggers the final payment?
10. How long from signing to installation, and how many days on site?
11. Can I see a recent job of similar size, or speak with a past customer?

Warranties: product vs. labor

Two different promises usually come with new windows. The manufacturer's warranty covers defects in the window itself, such as a failed glass seal or broken hardware, and it often excludes or limits labor. The installer's warranty covers the work: leaks, drafts or operation problems caused by how the window was set, flashed and sealed. Ask for both in writing and keep them with the contract. Manufacturer terms vary by brand, by series and by who owns the home; window warranties explained sets out how six manufacturers word theirs.

Contracts and payments

The FTC says the contract should include the contractor's name, address, phone number and license number, estimated start and completion dates, and any promises made in conversation about scope and costs, with every blank filled in ¹. It also advises against paying the full amount up front and against making the final payment until the work is done and you are satisfied ¹.

Some state agencies give a figure for the deposit. California's CSLB cautions that a down payment should not exceed 10 percent of the contract price, and that later payments should not exceed the value of work completed or materials delivered ³. Virginia's Board for Contractors recommends a down payment of about 10% of the contract, or about 30% when the job requires custom-made items ⁷. Replacement windows are usually made to order, so a larger deposit on a window job may reflect that; ask what the deposit pays for.

If you sign a contract at home, the FTC's Cooling-Off Rule may give you until midnight of the third business day after the sale to cancel; it does not cover sales under $25 made at your home, and it has other exceptions, including sales finalized at the seller's permanent place of business ². The FTC also says the contract should include a written statement of this cancellation right ¹.

Red flags

The FTC lists tactics that point to a scam: a contractor who knocks on your door because they are "in the area", claims to have leftover materials from another job, pressures you for an immediate decision, asks you to pay everything up front or accepts only cash, asks you to get the building permits yourself, or suggests you borrow money from a lender they know ¹. New York's Attorney General adds that a legitimate contractor will not pressure you to sign and pay a deposit on the spot, and warns against signing any document with blanks ⁸.

For window jobs specifically, also be wary of:

• A price that is only good "today", or a large discount that disappears if you want time to compare.
• A quote that names no brand, series or glass package, so it cannot be compared.
• No street address, or a name you cannot match to a record on the state or local lookup.
• Reluctance to put the installation warranty, the start date or the payment schedule in writing.
• An answer of "you won't need a permit" without checking with your building department.

Comparing the quotes you get

Lay the quotes side by side only after each one describes the same windows, glass, method and scope. When one is far lower, the FTC suggests asking for an explanation ¹; often a lower number leaves out trim, disposal, rot repair or the permit. Our quote comparison template shows where those gaps tend to hide.

FindAWindowPro is a lead-generation service, not an installer, and it is paid by window companies when a reader requests quotes. If you want more quotes to compare, you can compare quotes from window installers, then check each company the same way.

About these figures

• ¹ Official record: FTC signs of a home improvement scam, advice to check licenses and insurance, get multiple written estimates, what a contract should include, and not to pay in full up front, checked October 22, 2026.
• ² Official record: FTC Cooling-Off Rule, cancellation until midnight of the third business day and the $25 floor for sales made at home, checked October 22, 2026.
• ³ Official record: CSLB release on the $1,000 license threshold effective January 1, 2025, the permit and worker conditions, and the 10 percent down payment caution, checked October 22, 2026.
• ⁴ Official record: Florida CILB FAQ on the licenses that cover window installation and replacement, checked October 22, 2026.
• ⁵ Official record: Arizona statute exemption below $1,000 for casual or minor work with no local building permit, checked October 22, 2026.
• ⁶ Official record: Oregon CCB statement on who must be licensed, checked October 22, 2026.
• ⁷ Official record: Virginia Board for Contractors license classes by project value ($1,000, $30,000 and $150,000) and the 10% and 30% down payment recommendations, checked October 22, 2026.
• ⁸ Official record: New York Attorney General list of localities that license home improvement contractors and its red flags, checked October 22, 2026.
• ⁹ Reported: FGIA description of the InstallationMasters program and directory, checked October 22, 2026.
• ¹⁰ Official record: EPA RRP rule scope for pre-1978 homes and the lead-safe firm locator, checked October 22, 2026.
• ¹¹ Reported: WDMA description of the Hallmark product certification program, checked October 22, 2026.
• ¹² Official record: NFRC description of the U-factor and SHGC on the energy performance label, checked October 22, 2026.