Where window jobs go wrong
Window replacement failures fall into two categories: wrong product for the climate, and poor installation. The first shows up on your energy bill. The second shows up when you spot a water stain on your interior wall, and by then the damage has been happening for months.
The 10 pitfalls
Pocket install over a rotted rough opening
Pocket installs leave the existing frame in place.
No flashing at window rough openings
Proper flashing is a layered system: sill pan, side flashing, head flashing.
Wrong SHGC for the climate
A low-SHGC window in a cold climate blocks solar heat gain you could be using for free.
Skipping air sealing around the frame
The gap between the window frame and the rough opening is where air infiltrates.
Bait-and-switch on window model
The window quoted is not the window installed.
Not accounting for interior trim restoration
Full-frame window replacements often require interior casing repair or replacement.
Ignoring the installation warranty
The manufacturer lifetime warranty covers the glass seal and hardware.
No permit for structural changes
Enlarging a window opening or changing the window type requires a permit in most jurisdictions.
Paying in full before custom windows arrive
Custom windows are non-returnable.
No clarity on what happens if they find framing rot
You do not know what is behind the window until it is out.
The bottom line
Get the installation method in writing. Confirm flashing is included. Ask about air sealing. Get the exact model number in the contract. A window installed correctly will perform as specified and keep water out for decades. One installed poorly will not, regardless of what the spec sheet says.
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