What's the Difference Between Insert Replacement and Full-Frame Replacement?

This is one of the most important questions to ask when getting bids, because the two approaches have very different costs and outcomes.

Insert (pocket) replacement: The new window is installed inside the existing frame, which stays in place. This is faster, less disruptive, and less expensive — but it only works when the existing frame is structurally sound and square. The trade-off is a slightly smaller glass area, since the new frame sits inside the old one.

Full-frame replacement: The old window — frame, sill, casing, and all — is removed down to the rough opening. This is the right approach when the existing frame is rotted, significantly out of square, or when you're changing the window size. It costs more and involves more finish work, but it's a true fresh start and allows for better insulation and air sealing at the rough opening.

When in doubt, go full-frame. Saving money on an insert replacement into a compromised frame is a short-term decision that tends to come back around.