09/24/2026
Single-hung windows. Do they leak air?
Yes. They do.
That’s part of the nature of the mechanism. An operable window has moving parts, seals, and tolerances. It isn’t a monolithic wall.
Is that okay?
Also yes.
The amount and location of that air infiltration is minimal and, when properly installed, well within our tolerance for how an operable window should perform.
The point isn’t to pretend there’s zero air leakage. The point is to understand where it happens, how much happens, and whether it matters.
If you’re aware of it, you can decide your level of tolerance.
Trust but verify.