Two ways to replace a window
There are two main ways to install a replacement window. An insert, sometimes called a pocket replacement, fits a new window inside the existing frame. A full-frame replacement removes the old window, frame and all, down to the rough opening in the wall, and installs a complete new window. Both are legitimate. Which is right depends on the condition of the existing frame and what you want from the project.
Insert replacement
The old sashes, stops and hardware are removed, and a new window unit is fitted into the existing frame, then sealed and trimmed.
- Less disruption. Interior trim and exterior siding or stucco usually stay in place.
- Usually faster and less expensive than full-frame.
- Slightly less glass. Because the new window sits inside the old frame, the glass area shrinks a little.
- Requires a sound frame. The existing frame has to be solid, square and dry. An insert installed into a rotted frame hides the problem rather than fixing it.
Full-frame replacement
The whole window comes out, down to the framing of the wall. The opening is inspected and repaired, flashing and water barriers are installed, and a new window is set, insulated and trimmed.
- The opening gets inspected. Hidden rot, water damage and insect damage can be found and fixed.
- New flashing. The connection between the window and the wall's weather barrier is rebuilt, which matters if the old windows leaked.
- More glass area than an insert, and a chance to change the window size or style.
- More work. Interior trim and exterior finishes have to be removed and replaced or patched, which adds cost and time.
Signs a frame isn't sound
- soft or crumbling wood on sills or jambs;
- water stains on the wall below the window;
- peeling paint or swelling around the frame;
- a frame that's visibly out of square, so sashes stick or gaps show;
- past leaks.
If any of these show up, ask the contractor to probe the frame and sill and explain what they found.
Stucco and siding
On stucco houses, full-frame replacement means cutting back and repairing stucco around each opening, which is skilled work. Some replacement windows are designed to install over the old frame with a flange that covers the gap, avoiding stucco removal. On sided houses, siding around the window can usually be removed and reinstalled. Ask the contractor exactly how the exterior will be finished and who does the patching.
Water management
Most window leaks happen around the window, not through it. In a full-frame job, the contractor should integrate the window with the wall's weather barrier: flashing tape or pans at the sill, sides and head, overlapped so water runs out and down, not in. With an insert, the existing frame's water management is kept, so its condition matters.
Insulating the gap
With either method, the gap between the new window and the frame or opening should be insulated, usually with low-expansion foam or backer rod and sealant, then sealed on the interior to stop air leaks.
Which is right for your house
Insert replacement often suits houses with sound, square frames and no history of leaks. Full-frame often suits houses with rot, leaks, aluminum frames being replaced with a different material, or homeowners who want larger glass or a different style. Many projects use both, depending on the window.
Questions to ask
- Which method are you proposing for each window, and why?
- Did you probe the frames and sills? What did you find?
- How will you flash and seal each window?
- How will you handle stucco or siding, and interior trim?
- What happens if you find rot during removal, and how is it priced?