Questions to Ask a Window Replacement Contractor
For homeowners collecting window bids who keep hearing lifetime warranty and never a spec, these are the questions to ask window installers before one of them opens your wall. The 57 questions run in the order the job goes: the company, the measure and scope, the windows and glass, the install method, install day, then price and warranty. Most of them are about the part no brochure covers: how the unit is fastened, flashed and sealed once the old one is out.
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The questions
Each question, and why to ask it
The company
Is the company that signs my contract the same one that installs, or is the job passed to another firm?
Why ask it
Some window sellers are sales organizations that hand the installation to a separate outfit, which is where warranty calls start bouncing between two phone numbers. The name on the contract, on the insurance certificate and on the truck should match, or someone should explain in writing why it does not.
Are the installers your own employees or subcontractors, and who answers for their work if something fails?
Why ask it
Subcontracting is ordinary in this trade and plenty of subcontracted crews do careful work, so the label matters less than the chain of responsibility. Get it in writing that the company on your contract comes back to fix a bad install itself, whoever was holding the drill.
Who will be the lead installer at my house, and can I talk to them before I sign?
Why ask it
The person who sells the job and the person who sets the windows are rarely the same, and promises made at the kitchen table only count if the lead has heard them. Five minutes on the phone also shows whether the lead knows your wall type or will be finding out on arrival.
Can you send me your license number and a current certificate of insurance, including workers' compensation, before we schedule the measure?
Why ask it
A company that sends its paperwork without being chased is showing you how it will behave after the deposit. Whether window work needs a license depends on your state or city, so check the number with the board that issued it, and have the certificate come from the insurer so you know the policy is live while a crew is on ladders at your second floor.
Can you show me photos of a job in a wall like mine, taken while the opening was still open?
Why ask it
Finished photos all look alike. A picture of the bare opening shows the sill pan, the flashing tape and how the frame meets brick, stucco or siding, which is the part of the work that disappears for good once the trim goes back.
How long have you been replacing windows around here, and is it your main business or one service among many?
Why ask it
Window replacement is its own trade with its own ways of going wrong, and a firm that fits windows between kitchens and decks gets far less practice than a crew that does nothing else. Years in your area also mean they have already met the local siding, stucco or brick details with a unit halfway out of the wall.
How many openings does one crew set in a day, and how many days are you allowing for my house?
Why ask it
Pace tells you how the company makes its money. A crew scheduled to finish a whole house of full-frame openings by dinner has no slack for a soft sill or a flashing detail that does not match the plan.
Can you tell me about a job that went wrong, how you put it right, and whether I could talk to that customer?
Why ask it
Every installer has had a unit arrive the wrong size or a leak show up after the first storm. How quickly someone came back, and who paid, tells you more than three references chosen because nothing happened.
Measure and scope
Will every opening be measured individually before the order goes in, and is that done by a salesperson or by an installer?
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. A final measure by someone who installs is the usual safeguard, since that person has to live with the numbers on install day.
When you measure, do you check each opening for square, level and plumb, and what do you do with one that is out?
Why ask it
Old houses settle, and a rectangular unit ordered for an opening that has become a parallelogram ends up shimmed crooked or hidden behind a wedge of caulk. Measuring the diagonals takes a minute per window, and hearing which of yours are out means the fix is being planned before the truck is loaded.
Are you planning to set inserts inside my existing frames, or to take every opening back to the rough framing?
Why ask it
This is often the biggest difference between two bids on the same house, and it decides what you end up with as well as what you pay. An insert goes in faster, keeps the old frame and leaves a little less glass in every opening, while a full-frame job costs more and is the only kind where anyone sees the sill and flashing behind the trim.
If you are recommending inserts, how did you confirm the old frames and sills are sound enough to keep?
Why ask it
An insert is only as good as the frame it is screwed into, and that frame stays in the wall with whatever flashing it was given decades ago. The check should have involved a probe or a moisture meter at the outside sill corners, not a glance from the living room.
Which of my windows would you install differently from the others, and why?
Why ask it
A bay, a window over a tub, a basement hopper and an upstairs unit above a porch roof each ask for something different at the sill and the trim. If every opening gets the same answer, the house was priced by count and nobody has looked hard at the awkward ones yet.
Will the new windows sit in the same position in the wall as the old ones, and what does that do to the sill and trim inside?
Why ask it
A new frame is rarely the same depth as the one it replaces, so the unit can land further in or out, which changes the interior stool, the exterior sill nose and where blinds can mount. Have them hold a tape at one window and show you where the new frame face will be.
Which bedroom windows have to meet egress size, and where does code require tempered glass?
Why ask it
Inserts make every opening a little smaller, and a bedroom window that ends up under the local escape size can become a problem at inspection or at resale. Rules for replacements vary and some places make exceptions, so have the installer say which code your town works to and mark on the order which openings need tempered glass, usually those near a door, a tub, a shower or the floor.
Are you pulling the permit, and does this house need historic district or HOA approval before the order goes in?
Why ask it
Permit rules for replacement windows are local: some building departments want one for any swap and others only when an opening changes size, so find out which applies at your address and who meets the inspector. Historic districts and HOAs often restrict frame color, grille pattern and material, and those approvals have to be in hand before custom units are built.
Windows and glass
Which brand and series is in this quote, and does the manufacturer list you as an authorized dealer or installer?
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 and look the dealer up on the maker's own site, since some manufacturers tie their full warranty support to an authorized installer.
How many jobs have you done with this exact product line, and what is tricky about installing it?
Why ask it
Every line has its quirks: a nailing fin that cracks in the cold, balances that need adjusting on site, a frame that bows when a screw is driven too hard. An installer who can name one has set enough of them to have opinions, and those opinions are part of what you are paying for.
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 the years. The answer worth hearing is tied to a particular opening, such as why fiberglass and not vinyl for a large picture window in full sun, where expansion matters most.
Can you show me the NFRC ratings for the exact glass package you are proposing, and what U-factor and SHGC do they list?
Why ask it
The NFRC label is the US rating sticker, and it gives a U-factor (heat loss, lower is better) and an SHGC (how much solar heat gets through) for that exact configuration, not for the best one in the catalog. Ask the crew to leave the stickers on the glass until you have checked them against the quote. Outside the US, ask for the national rating label instead.
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. One coating for the whole house is the simple default and a fair choice in some climates, so what you are listening for is a reason.
Is this quote for double or triple pane glass, which gas fill, and what kind of spacer sits at the edge of the glass?
Why ask it
Triple glazing adds weight and cost and tends to earn its place in cold climates; if street noise is your reason, ask whether laminated glass would do more than a third pane. Krypton costs more than argon and is used where the gaps are thin. The spacer gets less attention than it deserves, since a warm edge or non-metal one tends to reduce condensation along the bottom of the glass.
On the wide openings, such as a bay or a triple unit, are the windows joined at the factory or mulled together on site?
Why ask it
A wide opening is usually filled with several units fastened side by side, and that joint can be made on a factory bench or on your lawn. Where it is made affects how stiff and how well sealed it is, and the answer also tells you how many people it takes to carry the assembly in.
Is there any opening where you would change the style, say a slider to a casement, and what does that do to the install?
Why ask it
Changing style can rescue a window nobody can reach over the sink or one that never sealed, but it moves the hardware, the screen and the way the sash swings over a deck or path. Hear the consequences before the order is placed, while changing your mind is still free.
If I choose a dark exterior color, does the manufacturer set different warranty terms or heat limits for it?
Why ask it
Dark frames soak up more heat on a sunny wall than white ones, and some makers write separate terms for dark vinyl or painted finishes. Have the installer point to the line in the warranty document instead of telling you it will be fine.
Can I check the order sheet against my windows before it goes to the factory?
Why ask it
An order sheet lists each opening's size, color, grille pattern, glass and the side a casement is hinged on, and one wrong line builds a window you cannot use. Walk the house with the sheet in your hand, because custom units are rarely returnable and a mistake caught at this stage costs nothing.
Install method
Walk me through one opening: how do you flash and seal it, and what fills the gap around the new frame?
Why ask it
Leaks usually start at the joint between frame and wall, so the answer should mention a sill pan or sloped sill, flashing tape, and laps ordered so water runs outward. Low-expansion foam made for windows is a usual gap filler, and hearing that they stuff in loose fiberglass and caulk the outside tells you what the next decade looks like.
On an insert job, what do you do about the old sash weight pockets and the gaps around the old frame?
Why ask it
Old double-hung frames often hide empty weight cavities on both sides, which are uninsulated columns of cold air right next to a new window. Filling them and sealing the old frame to the wall is unglamorous work that an insert price may or may not include.
Where do the shims and screws go on this frame, and how do you check the sash still runs true once it is fastened?
Why ask it
A frame screwed tight without shims at the right points bows inward, and then the sash binds or the lock stops lining up. The check takes a minute: measure the diagonals, run the sash and look for an even gap between sash and frame before any foam goes in.
Which sealant do you use outside, and do you leave the weep holes and the bottom of the frame free to drain?
Why ask it
Windows are built to let a little water out at the bottom, and a crew that caulks the sill joint solid or plugs the weeps traps that water inside the frame. Write down the product name on the tube too, because it has to bond to your siding and to the frame material.
When you pull a window out and find rotten sill, sheathing or framing, what happens next and at what rate?
Why ask it
Rot around a window stays hidden until the unit is out, 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.
Do you carry lumber and sheathing on the truck to repair rot the same day, or does it mean a second visit?
Why ask it
A crew that finds a soft sill at two in the afternoon either fixes it then or closes the opening with the problem still inside. Which one it will be at your house depends mostly on what is in the truck.
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. Find out who on the crew does it, and drive past a house they capped a few years ago if you can, because open corners and wavy bends show from the street.
Who repairs the inside afterward: drywall, plaster, stools, aprons and paint, and is that in this price?
Why ask it
Interior finish work is easy to leave out of a window quote, and full-frame installs almost always disturb the trim and the wall around it. Plaster cracks readily when old frames are pried out, 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 sashes and trim are a classic source of lead paint, and in the US a firm paid to disturb it in a house of that age has to follow federal lead-safe rules, while other countries set their own. A certified firm will describe plastic containment, HEPA vacuums and a cleanup check, and a contractor who shrugs at the question is cutting a corner you cannot see.
How do you handle the upstairs windows: from inside, from ladders or from staging?
Why ask it
Upper units can often be set from inside the room, which is safer and kinder to the flower beds, but the capping and caulk still need someone outside. Listen for whether the high openings get the same sealing as the ones at ground level or a quicker version.
Install day
Once the windows are ordered, when will I get an install date, and how much notice do I get if it moves?
Why ask it
The factory's build time is usually the longest part of the wait, and a date given at signing is an estimate until the units are on a truck. Ask whether they book you when the order is placed or only once the windows have arrived and been checked against the order sheet, which is the safer habit.
What time does the crew arrive, in what order will they work through the house, and will every opening be closed by evening?
Why ask it
The order matters if a baby naps in one room or you work in another. The firm rule to hear is that no window comes out unless its replacement goes in the same day.
What weather makes you reschedule, and what is the coldest you will install in?
Why ask it
Sealants, foams and flashing tapes each print a minimum application temperature on the package, and vinyl turns more brittle in the cold. An installer who names an actual cutoff has read the tube, and one who says they work in anything is telling you about their schedule.
What do I need to take down or disconnect before you arrive: blinds, curtains, alarm sensors, window air conditioners?
Why ask it
Crews generally expect clear access to each window and many will not rewire an alarm contact or rehang custom shades. A list in advance saves the first hour of the day, and it warns you if a narrower frame means your inside-mount blinds will not fit again.
How do you protect the floors and furniture in each room, and who moves what is in front of the windows?
Why ask it
Prying out an old frame drops plaster dust, paint chips and dried caulk onto whatever sits below it. Crews differ on whether they will shift a bed or a piano or expect a clear path to every window, and that is better learned on the phone than at eight in the morning.
Where will the crew set up to cut trim and bend metal capping, and how do you keep screws and glass out of the lawn and driveway?
Why ask it
Cutting trim and bending aluminum capping throws off metal slivers, screws and now and then broken glass, and the work table usually ends up on your driveway. A tarp under the bench and a magnet sweep at the end are small habits that say a lot about the rest of the job.
Will you show me the first opening after the old window is out, before the new one goes in?
Why ask it
That is the one moment you can see the sill and framing with your own eyes and watch the flashing go on. A crew that is comfortable being watched on the first window tends to do the rest the same way.
Who is my contact on site if something looks wrong, and can that person approve a change on the spot?
Why ask it
Decisions about rot, trim and a unit that arrived wrong get made at the opening, often within minutes. If the lead has to reach an office that has to reach a salesperson, the easy choice is to close the wall and move on.
If a unit shows up damaged or the wrong size, does the old window stay in until the replacement arrives?
Why ask it
A mis-sized window forced in with extra shims and a wide bead of caulk is the shortcut to rule out here. The answer to hold them to is that the old window stays put, the unit is reordered at their cost and the balance for that opening waits.
Before the crew leaves, will the lead go window to window with me and write down anything that needs fixing?
Why ask it
Open, close and lock every sash, look along each caulk line outside and try the screens while the person who can fix it is still holding a caulk gun. A written list with a return date is far easier to enforce than a remembered conversation in the driveway.
Is hauling away the old windows, storms and debris part of the job, and does it leave the same day?
Why ask it
Storm panels and old sashes are heavy, sharp and sometimes coated in lead paint, which makes a pile beside the garage more than an eyesore. Check that removal is a line on the quote and not a favor.
Price and warranty
Can you price each opening on its own line, with the install labor shown separately from the window?
Why ask it
A per opening price lets you add or drop a window without reopening the whole negotiation. Labor on its own line shows what each company charges to put a window in, the number a single total hides behind the price of the glass.
How much is due before the windows are ordered, and how much waits until they are in the wall?
Why ask it
A deposit to place the order is normal, since custom windows are hard to resell, but the rules on what a contractor may take up front differ by state and country. Check the rule where you live, and look for a schedule tied to things you can see: order placed, windows delivered, install complete.
Can the contract describe the install itself, meaning method, flashing, gap fill, exterior finish and interior finish, and not only the windows?
Why ask it
Window contracts tend to describe the product in detail and the labor in one line. The method is where bids differ and where shortcuts hide, so a sentence each on insert or full-frame, sill pan, foam and trim gives you something to point to later.
Besides rot, what would make you raise the price once the old windows are out?
Why ask it
Stucco that crumbles, frames buried under two layers of siding and openings badly out of square are the usual candidates. Each should carry either a stated price or a written promise that it is already covered.
How much of the final payment can I hold until the punch list is done and any inspection has passed?
Why ask it
Money still owed is the reason a crew comes back for a sticky sash or a missed caulk joint. Agree the amount and the trigger before the job starts, because proposing a holdback on the last afternoon is an argument.
How long is your own labor warranty, apart from the manufacturer's cover on glass, frame and hardware, and does either pass to a buyer if I sell?
Why ask it
A window job comes with two sets of promises: the manufacturer's on the glass seal, frame and hardware, and the installer's on the work. They usually run for different lengths, and the labor term is the one people forget to get in writing, along with whether either survives a sale of the house.
If a window leaks at the wall and not through the glass, is that covered by your labor warranty, and does it include the damage inside?
Why ask it
Manufacturers cover the unit, while a leak at the flashing or the caulk joint is the installer's own work and often the shortest promise in the folder. Stained drywall and swollen flooring are a further step, so ask whether the labor warranty repairs what the leak ruined or only the joint.
When a glass seal fails years from now, do you come out and swap the sash, or do I deal with the manufacturer myself?
Why ask it
A fogged pane is a familiar warranty claim on a window, and the paperwork often covers the glass while leaving you the service call. Ask what that visit would cost today and how long a replacement sash takes to arrive, so the answer is a number and not a reassurance.
Do you have a service department, or do the install crews handle callbacks between jobs?
Why ask it
A company with someone whose whole job is service can usually send a person within days. Where callbacks wait for a gap in the install calendar, a sash that will not lock in the busy season can sit for a long time, so ask what the normal wait is.
What would void the manufacturer's warranty on these windows, and which of those conditions are yours to meet?
Why ask it
Makers can refuse a claim when a unit was not installed to their instructions, was sealed with the wrong product or later had film applied to the glass. Have the installer sort the list for this line into what they must get right on install day and what becomes yours to keep up afterward.
Getting Window Bids You Can Actually Compare
Practical guidance for the conversation itself
Which Questions to Ask at Which Stage
By Phone, Before Anyone Visits
Everything under The company can be asked by phone or email, because none of it depends on your house. Settle them before you give up an evening to a measure: who signs the contract, who sets the windows, whether the license and insurance check out, and whether they have open-wall photos of a house built like yours.
At the Measure
Walk the house with whoever holds the tape and work through Measure and scope at the openings themselves, then Windows and glass with a sample or the label in hand. Have them say insert or full-frame out loud at each window, and write it on your sketch next to the opening number.
With the Written Quote in Front of You
Install method and Price and warranty belong to the moment a quote is on paper. Put the same questions to each company and note the answers in columns, since flashing, gap fill, trim and the labor warranty are where a low bid and a careful bid usually part ways.
The Week of the Job
Save Install day for the scheduling call and for the lead installer on the first morning. Ask how the rooms will be protected, see the first bare opening, agree who can approve a change, and do the window by window check before the last payment leaves your hand.
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 every company you call. Without it, the cheapest bid is often the one that quietly quoted 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 one issued in spring says nothing about a policy that was cancelled over the summer.
Specs and Numbers to Have in Your Head
Window Specification Cheat Sheet
- U-factor measures heat loss and lower is better, and in the US Energy Star sets a maximum for each climate zone, so look up the current figure for yours
- SHGC measures solar heat gain, so aim low in hot climates and on west facing walls, higher on south walls in cold climates
- Any quote for a US-rated window can come with the NFRC numbers for the exact unit being sold, and the sticker on the delivered glass should match them
- 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 tend to reduce condensation along the bottom edge of the glass
- Triple pane pays off mainly in very cold climates and adds weight to large operating sashes, and for street noise laminated glass is worth pricing beside it
- Bedroom egress windows generally need a minimum clear opening, so ask how your local code treats an insert that makes one smaller
- 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
- In the US, paid work on a pre-1978 home calls for an EPA Lead-Safe certified firm, and other countries set their own rules
Red Flags in a Window Quote
- A single lump sum with no per opening breakdown and no window sizes listed
- A brand name with no series beside it, and no U-factor or SHGC written down for the glass
- The words insert or full-frame never appear, so the method is left ambiguous
- A lifetime warranty promised out loud, with nothing in writing that gives the installer's labor its own term
- 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