# Methods guides

> Methods and materials: independent, numbers-first guidance from Window Replacement Lab.

Canonical: https://windowreplacementlab.com/methods/

Last updated: 2026-11-08

## The two install types, and what each one does

Almost every window cost question comes back to one decision: does the existing frame stay, or does it come out? Everything else — frame material, glass package, style — is a choice made after that.

 |  | Option | What it is | Where it fits

 | Insert (retrofit) | A new unit set inside the existing frame and stops | Sound frame, original opening size, budget project

 | Full-frame | The whole frame is removed and the opening rebuilt | Rot, failed frame, changing the size, older houses

 | Vinyl frame | PVC extrusion, welded corners | Default for most budgets, no painting

 | Fiberglass frame | Glass-filled composite, often with wood interior | Better thermal edge, wider colour range, more cost

 | Wood or wood-clad | Solid timber, usually aluminium-clad outside | Historic homes, best interior finish, most maintenance

 | Double-pane Low-E + argon | Insulated glass unit with a low-emissivity coating | The efficiency sweet spot in most climates

## How the decision is made

The order matters: inspect the frame, then set the budget, then pick the material. Buyers who start with the material usually pay for the decision twice, because an insert over a rotted frame fails within a few years and the redo costs full-frame money.

An installer who quotes a method before looking at the frame and the flashing is guessing. The frame and the sill are the two places rot hides, and both are hidden until the trim comes off.

## What we check before recommending a method

- Is the existing frame sound, square and plumb? An insert needs all three.

- Is there rot at the sill, the jamb or the header? If yes, the method is full-frame.

- Does the glass package match the climate — solar gain versus heat loss?

- Does the warranty cover seal failure, and for how long?

- Will the new unit pass egress code if the opening is a bedroom?

The [cost hub](/cost/) carries the installed bands, the [comparison hub](/compare/) puts the closest options side by side, and the [calculator](/calculator/) prices both install types against your own window count.

### Which option lasts longest?

Exposure decides more than brand. A mid-range vinyl insert installed with correct flashing outlasts a premium unit installed without it, every time.

### Can I change method later?

An insert can become a full-frame job later, but not the reverse without extra trim work. Ask what the removal and disposal line would be before choosing the cheaper method now.

### Do I need a permit for an insert?

Often not, if the opening size and location are unchanged. Full-frame work and any size change usually do. Check with the local building department before signing.