Windows
Replacement vs. New Construction Windows: What Is the Difference?
Not every window replacement is the same job. You can drop a new window into the old frame, replace the whole unit down to the opening, install a new construction window with a nailing fin, or swap just the sashes. The right choice depends on the condition of the frame and what else is happening on the outside of the house.
Key points
- An insert replacement window fits inside the existing frame; it is quicker but keeps the old frame and sill.
- A full-frame replacement removes everything down to the rough opening, so rot can be fixed and the opening flashed properly.
- New construction windows have a nailing fin and are installed from the outside, usually when siding or trim is coming off anyway.
- Sash replacement keeps the frame and swaps only the moving parts, which works when the frame is still sound.
Insert (pocket) replacement
An insert window is sized to fit inside the existing frame. The interior and exterior trim stay, so the job is quicker and less disruptive. The tradeoffs: a little less glass, and the old frame and sill stay in place, so they have to be in good shape.
Full-frame replacement
Everything comes out down to the rough opening. That lets the installer fix rotted sills and framing, insulate around the window, and flash the opening properly before the new window and trim go in. It costs more than an insert and is the better choice when the frame is damaged or water has been getting in.
New construction windows
New construction windows have a nailing fin around the outside and are installed from the exterior, tied into the house wrap and flashing. They make the most sense when the siding or trim around the window is coming off anyway, for example during a siding replacement.
Replacing only the sash
Sash replacement kits swap the moving parts of a double-hung and keep the frame. It is a good option for a sound frame with worn sashes, and on historic homes where the original frames and trim are worth keeping.
Frequently asked questions
Which type of replacement do I need?
If the frames and sills are solid and dry, an insert can work. If there is rot or water damage, a full-frame replacement is the right fix.
Can basement and cellar windows be replaced too?
Yes. Cellar windows are often the most worn windows in the house and are replaced the same way, sized to the foundation opening.
Do new construction windows mean new siding?
Not always, but the siding and trim around each window have to come off, so they are most common during siding work.
Planning to replace your windows?
Cedar House Carpentry handles window replacement across Cape Cod and the South Shore with our own in-house crew, fully licensed and insured.
See our Window Replacement work · Find your town · (774) 470-7150