What is the difference between an insert and a full-frame installation?

An insert installation leaves the existing frame in the wall and fits the new unit inside it, so the sealing happens between two frames and very little behind the wall surface is disturbed. A full-frame installation takes the old frame out to the rough opening, which makes it the only version of the job in which the sill, the framing and the water detailing behind the trim can be seen, corrected and rebuilt.

How are replacement windows measured?

Against the opening they will sit in, which is why the order becomes final at the measurement rather than at the signature. An insert is sized to the frame that is staying; a full-frame unit is sized to the rough opening behind it. Ask which surface is being measured, ask whether the person measuring is the person who will install, and get it in writing who carries the cost if a unit arrives the wrong size.

Who pulls the permit, me or the contractor?

Whoever your local building department allows to apply, and whoever your contract says. Those are two separate questions and both need answering before work starts. The department sets its own filing rules, so its answer governs; the contract then decides who files and who pays the fee. Get it in writing, and ask to see the permit if one is issued.

How can I tell if windows were installed properly?

Most of the evidence disappears under trim, so the checks worth making are the ones you make while the opening is still open: the unit set plumb, level and square, supported on shims rather than forced, the perimeter gap insulated, and water detailing that drains outward. Once the trim is back on, what remains testable is behavior — every sash operating and locking, no air moving at the perimeter on a windy day, and no moisture where there should be none.

FOR THE PERSON HIRING, NOT INSTALLING

How Window Installation Is Done, and Where It Goes Wrong

Most installation guides are written for someone holding the caulk gun. This one is for the person paying for the work: what to watch, what to ask, and which questions only your building department can answer.

No obligation
We employ no installers
No permit rule asserted nationally

Watch the parts that get covered

The work that decides how a window performs is visible for a few hours and then hidden by trim for the life of the house.

The project in order →

A new window unit being set into a prepared opening, shims and insulation visible

You are buying an installed assembly, not a window

The unit is a component. What you live with is that unit plus the way it was fitted.

ENERGY STAR’s own installation guidance opens by pointing out that windows, doors and skylights can be drafty if they are poorly installed, however capable the product is. A certified unit fitted out of square into an opening that was never made good is not a certified assembly. Nothing in the ratings on the label describes the joint between the window and the wall, and that joint is entirely the installer’s work — work you never see again once the trim goes back on.

How the day runs at one opening

Four stages, repeated per window.

Protect and prepare
Floors, furniture and the ground outside are covered before anything comes out, and the order of the openings is agreed.
Take the old unit out
How much comes out is the method decision: sash and balances alone, or the frame as well.
Set, seal and insulate
The unit is shimmed true, fixed without being forced out of shape, sealed against water and air, and the perimeter gap insulated while it is reachable.
Make good and walk through
Trim, caulk, cleanup and haul-away, then every sash opened, closed and locked with you standing there.

Insert and full-frame are two different days of work

One phrase covers both jobs. What the crew does is not the same.

On the day	Insert installation	Full-frame installation
What is removed	Sash, balances and stops. The existing frame stays.	Sash and frame, usually with the interior and exterior trim.
What becomes visible	Very little. The wall behind the frame is not opened.	The rough opening, the sill, and whatever detailing was built in.
Where the sealing happens	At the joint between the new unit and the frame that stays.	At the rough opening, where flashing is detailed again from scratch.
The perimeter gap	Whatever is behind the existing frame stays as it is.	The gap between new frame and rough opening is insulated as part of the work.
Making good	Interior trim is often untouched; exterior work is usually capping and sealing.	Interior and exterior trim have to be refitted or replaced, then finished.
Exposure to weather	The wall is never open, so weather matters less.	The opening is open for part of the day, so scheduling follows the forecast.

Which method a quote assumes is settled opening by opening, not once for the whole house. Ask for it on the paperwork.

The second row matters most. Full-frame is the only version in which anybody sees the sill and the framing behind the trim, so where there is a history of water at that opening, the method is also a choice about whether the cause gets found. Which openings warrant which method is on window replacement, and whether the fault you are dealing with needs replacement at all is on repair or replace.

What a correct installation looks like before the trim goes back on

Six things to look at while they are visible.

Plumb, level and square

The unit is set true rather than fitted to whatever shape the opening has drifted into. Every check below assumes this one passed.

Shimmed, not forced

The frame is supported where the weight of the sash lands, not squeezed out of shape by fasteners driven too hard.

The perimeter gap is insulated

ENERGY STAR tells homeowners to make sure the space between the window frame and the rough opening is insulated during installation. It is also the last hour in which anyone can.

Water has a way back out

Flashing and sealing are detailed so water reaching the opening drains outward, not into the wall. Ask to see it before it is covered.

The instructions were followed

ENERGY STAR states that certified windows are required to have installation instructions packaged with the product or readily available online, and that some manufacturers void the warranty when they are not followed.

Every unit operates and locks

Open, close and lock each sash while the crew is on site. A sash that binds today will not free itself.

The perimeter-insulation and manufacturer-instruction points are ENERGY STAR’s, read on 22 August 2026 from its residential windows, doors and skylights guidance. The remaining items are questions to ask, not requirements we can impose.

Permits are a local question

We will not answer it for your jurisdiction, and a site that answers it for every jurisdiction is guessing.

What we can and cannot tell you about permits

There is no national rule on whether a like-for-like window replacement needs a permit, and we have found no single source that answers the question across jurisdictions, so we publish no general answer.

The one municipal permit page in our source set that we have read in full is the City of Chicago Department of Buildings. It names an Express Permit Program and a Self-Certified Permit Application Program, and it describes permit-fee waivers for income-eligible homeowners aged sixty-five and over on residential buildings of one to three units. What it does not do is say whether a window replacement specifically requires a permit, which is precisely the shape of the problem.

So the answer has to come from your building department before the work is scheduled. Ask whether this work is permitted in your jurisdiction, and who is allowed to file for it. Where one is required it usually brings an inspection with it, which is a second pair of eyes on the work.

Chicago Department of Buildings permit programs read on 22 August 2026 from chicago.gov. We have not verified permit requirements for any other jurisdiction and do not state one.

Measurement

The unit is built for the hole, so the measuring visit is where the specification stops being editable. An insert is sized to the frame that stays; a full-frame unit to the rough opening behind it. Different surfaces, different numbers — which is why a quote with no method has no real price.

What an estimate should itemize →

What the labor is for

Upper floors, brick veneer, oversized units and altered openings change the work rather than the window — which is why one unit is priced differently in two houses on a street. Every figure here is quoted from a named publisher with the date it was read.

Full cost guide →

Warranty terms, and what we cannot check for you

Some warranty terms are really installation terms, which makes the crew a product question.

Conditions a warranty can put on the crew

Some manufacturers void a warranty when their installation instructions are not followed — ENERGY STAR says so.
Some warranties require an installer certified by the manufacturer, which makes the crew a product question.
Ask for that certification in writing, and check it with the manufacturer rather than the company holding it.
Ask which warranty you call first when the cause of a fault is not obvious.

What this site does not check

We verify no credentials, hold no roster and inspect no work, so nobody here is described as approved.
Licenses, insurance and registration stay yours to confirm, with the issuing body rather than the company.
We do not know which crew a company will send, or whether it holds any manufacturer certification.
We are not there on the day, and cannot tell you what was made good behind the trim.

How a request from this site reaches a company is set out on how it works.

Older houses: lead-safe work practices

Window work disturbs painted surfaces, which makes the age of the house an installation question.

ENERGY STAR’s homeowner guidance states that a house built before 1978 probably contains lead-based paint and should be inspected by a lead professional to know for certain. It also states that landlords and contractors must give the homeowner a brochure before beginning a window, door or skylight replacement. If your house is of that age, expect that brochure.

The rule behind it is the Environmental Protection Agency’s Renovation, Repair and Painting Rule, read 22 August 2026. Anyone paid to carry out work that disturbs paint in housing or a child-occupied facility built before 1978 must be certified in lead-safe work practices and must work for a firm certified as lead-safe. A homeowner doing the work in their own pre-1978 home is generally outside it; landlords and property managers are not. The EPA page states no square-footage threshold, so neither does this one. Ask to see the firm certification, and ask how the crew will contain the dust.

Read on 22 August 2026: the ENERGY STAR residential windows, doors and skylights guidance, and the Environmental Protection Agency’s own Renovation, Repair and Painting Rule page for the certification requirement and its limits.

Questions to ask a contractor

Six questions about the work, not the window.

Is this quote priced as an insert or as full-frame, opening by opening?
Who takes the final measurement, and is that person on the crew that installs?
Have you asked my building department whether this work is permitted here?
Who files for the permit, and who pays the fee?
How is the perimeter gap insulated, and how is water drained outward?
Does the crew hold the certification the product warranty requires?

Browse by state

All locations →

Code adoption and permit practice change with the address.

Common questions

It depends on the jurisdiction, and there is no national answer to give you. Permits are issued locally, model codes are adopted state by state and edition by edition, and the same work can require a permit in one city and not in the next one over. Ask your municipal building department before the work is scheduled, and ask each company what it has assumed.

Ask the installation questions first

Method, measurement, permits and warranty conditions, settled before the van arrives.