Questions to Ask Window Replacement Contractor
For homeowners collecting window bids who keep hearing lifetime warranty and never a spec. These 20 questions pin down insert versus full frame, glass numbers, flashing, trim repair and what the warranty really covers.
The questions
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How long have you been replacing windows in this area, and is window work your main business or one service among many?
Why ask it
Window replacement is its own trade with its own failure modes, and general remodelers often hand it to whichever crew is free that week. A company that installs windows every day knows how your local siding, stucco or brick details behave when a unit comes out.
Can you send me your license number and a current certificate of insurance, including workers' compensation, before we schedule the measure?
Why ask it
Producing paperwork without being chased is the cheapest signal of a real company you will ever get. Second story window work over a driveway is exactly the scenario where an uninsured crew becomes your liability.
Which brand and exact product line are you quoting, and are you a factory-authorized dealer for it?
Why ask it
Most manufacturers sell several tiers under one familiar name, so the brand alone tells you nothing about what is showing up on the truck. Get the series or model number in writing, because authorized dealers usually get better warranty support and faster parts than a supply house buyer.
Will someone measure every opening individually before the order goes in, and how long is the lead time from that measure to install day?
Why ask it
Custom windows are built to the exact opening, and a bid based on a window count plus a few sample sizes turns into shims, oversized trim and reorders. Ask for the lead time now, since a typical custom order runs six to twelve weeks and salespeople rarely volunteer that.
Is this an insert replacement into the existing frames or a full-frame tear-out down to the rough opening?
Why ask it
This is the biggest reason two bids on the same house differ by thousands, and it changes the result, not just the price. Inserts are faster and cheaper but leave the old frame and cost you an inch or more of visible glass in every opening, while full-frame is the only way to inspect and reflash what is behind the trim.
What frame material is in this quote, and why that one for my house and climate?
Why ask it
Vinyl, fiberglass, composite, aluminum-clad wood and wood all move differently with heat and hold paint or color differently over 20 years. A contractor who can explain why fiberglass over vinyl on a large sunny picture window is thinking about expansion, not just about markup.
Can you show me the NFRC label for the exact glass package you are proposing, and what U-factor and SHGC does it list?
Why ask it
The NFRC sticker carries tested numbers for that specific unit, while brochures quote a best case configuration you may not be buying. Lower U-factor means less heat loss, and SHGC controls how much solar heat gets in, so those two numbers are how you compare bids on performance instead of adjectives.
Are you putting the same glass on every side of the house, or varying the coating by orientation?
Why ask it
A west or south wall that bakes in the afternoon wants a lower SHGC, while a north wall or a cold-climate south wall may benefit from letting some solar gain in. An installer who has never thought about orientation is ordering off a single price sheet.
Double pane or triple, which gas fill, and what spacer sits at the edge of the glass?
Why ask it
Triple glazing adds weight and cost and is worth it mostly in cold climates or for noise, and argon fill is standard while krypton costs more for thinner gaps. The spacer matters more than most buyers realize, since a warm edge or non-metal spacer reduces condensation at the bottom of the glass and extends seal life.
When you pull a window out and find rotten sill, sheathing or framing, what happens next and at what rate?
Why ask it
Hidden rot around windows is the single most common change order on this kind of job, and you want the price fixed before a crew is standing in your open wall. Ask for a written hourly or per foot rate for repairs and a rule about who makes the call to proceed.
Which bedroom windows have to meet egress size, and where does code require tempered glass?
Why ask it
A replacement that shrinks a bedroom opening below egress minimums can fail inspection and cause a problem at resale, and inserts shrink openings by design. Glass within a set distance of a door, a tub, a shower or the floor generally has to be tempered, and quietly skipping it is a safety and code issue.
Are you pulling the permit, and does this house need historic district or HOA approval before the order goes in?
Why ask it
Many jurisdictions treat window replacement as permitted work, especially for egress and tempered glass compliance, and an unpermitted job surfaces during a future sale. Historic districts and HOAs often restrict frame color, grille pattern and material, and approvals have to happen before custom units are built.
Walk me through install day: how do you flash and seal each opening, and what fills the gap around the new frame?
Why ask it
Water gets in around windows, not through them, so the answer should mention a sill pan or sloped sill, flashing tape, and a proper order of laps that sheds water outward. Low-expansion foam rated for windows is the right gap filler, and hearing that they just stuff fiberglass and caulk the outside tells you what the next decade looks like.
How is the exterior finished around each window, and what happens to my old brickmould, capping or stucco?
Why ask it
The exterior detail is what you look at every day, and it varies from bent aluminum coil capping over old wood trim to new PVC trim to a stucco patch that has to be matched. Ask who does that work and whether the caulk joint is a quality exterior sealant rather than painter's latex.
Who repairs the inside afterward: drywall, plaster, stools, aprons and paint, and is that in this price?
Why ask it
Interior finish work is the most commonly excluded line in a window quote, and full-frame installs almost always disturb the trim and the wall around it. Plaster homes are especially prone to cracking, so establish whether they leave a paint-ready surface or a hole for your own painter.
My house was built before 1978. Are you an EPA Lead-Safe certified firm, and how will you contain the dust?
Why ask it
Old window sashes and trim are a classic lead paint source, and disturbing them is federally regulated work for pre-1978 homes. A certified firm will describe plastic containment, HEPA vacuums and a cleanup verification step, and a contractor who shrugs at the question is cutting corners you cannot see.
Are the installers your own employees or subcontractors, and is the lead installer manufacturer or AAMA certified?
Why ask it
Installation quality drives more window failures than the window itself, and a subcontracted crew paid per opening is incentivized to move fast. Ask who the crew lead on your house will be and how long they have installed this specific product line.
Split the warranty for me: glass seal failure, frame, hardware and screens, and your own labor. How long is each, and is any of it transferable if I sell?
Why ask it
Lifetime is a marketing word, and in practice glass, vinyl, hardware and labor are almost always covered for different periods by different parties. Labor is the expensive part of a warranty claim, so find out how many years the installer covers it and whether coverage survives a sale of the house.
If a pane fogs up in year eight, who do I call, who pays for the labor, and how long does a replacement sash take?
Why ask it
This is the real test of a warranty, because a failed seal is common and the paperwork often covers the glass while leaving you the service call. The answer also reveals whether the company still exists in service mode or only in sales mode after the check clears.
What is the itemized price per opening, what is the payment schedule, and is any part of this discount contingent on signing today?
Why ask it
Per opening pricing lets you drop or add windows without renegotiating the whole job, and it exposes bids that are padded on the easy openings. A modest deposit with the balance at completion is normal, and a price that only exists while the salesperson is in your kitchen is a pressure tactic, not a deal.
Getting Window Bids You Can Actually Compare
Practical guidance for the conversation itself
How to Run the Bidding Process
Write One Spec and Have Everyone Bid It
Decide the method and the spec before you call anyone, for example full-frame tear-out, fiberglass frames, double pane with a low-E coating and argon, warm edge spacer, and interior trim left paint-ready. Hand that same sheet to all three companies. Without it, the cheapest bid usually wins by quietly quoting inserts and a lower glass package.
Number Your Openings and Price Them Individually
Walk the house, label every window on a sketch, and ask for a price next to each number. This makes it obvious when one bid excluded the two hard second story units or the picture window, and it lets you phase the job by room if the total comes in high.
Ask What They Would Not Replace
Some windows are worth repairing rather than replacing, especially solid old wood sashes that just need reglazing, new weatherstripping and a storm window. A contractor willing to talk you out of two openings is worth more than one who wants all fourteen.
Verify Insurance With the Agent, Not the Contractor
Get the insurance agency name and number and call to confirm the policy is active and includes workers' compensation. A certificate PDF is easy to edit, and an expired policy looks identical to a current one on paper.
Specs and Numbers to Have in Your Head
Window Specification Cheat Sheet
- U-factor measures heat loss and lower is better, with roughly 0.30 or below typical for Energy Star in cold zones
- SHGC measures solar heat gain, so aim low in hot climates and on west facing walls, higher on south walls in cold climates
- Every real quote can produce an NFRC label with those numbers for the exact unit being sold
- Insert or pocket replacement keeps the old frame and costs you visible glass, full-frame goes to the rough opening and lets the sill be reflashed
- Argon is the standard gas fill, krypton performs better in narrow gaps and costs noticeably more
- Warm edge or non-metal spacers cut condensation at the bottom of the glass and outlast aluminum spacers
- Triple pane pays off mainly in very cold climates and for street noise, and it adds weight to large operating sashes
- Bedroom egress windows generally need a minimum clear opening, so confirm inserts do not drop yours below it
- Glass near doors, tubs, showers and floors typically has to be tempered
- Low-expansion window foam belongs in the gap around the frame, not standard expanding foam that can bow the jamb
- Pre-1978 homes require an EPA Lead-Safe certified firm for this work
Red Flags in a Window Quote
- A single lump sum with no per opening breakdown and no window sizes listed
- No brand, no product line and no NFRC numbers anywhere on the paperwork
- The words insert or full-frame never appear, so the method is left ambiguous
- Lifetime warranty claimed verbally with no document naming glass, frame, hardware and labor separately
- No line addressing rotten sills or framing and no rate if they find it
- Interior trim and paint quietly excluded on a full-frame tear-out
- A sales visit that runs three hours and ends with a price that expires tonight
- Large deposit demanded before the measure has even happened
- No mention of lead-safe practices on a house built before 1978
- Vague answers about who the installing crew is or whether they are subcontracted