Separate air, water and glass symptoms
Drafts, rain leakage and failed sealed-glass units are different problems.
Movement can be building-related
A suddenly sticking window or door may reflect hardware, seasonal movement or structural change.
Document weather patterns
Wind-driven rain and freeze-thaw can help distinguish intermittent failures.
Replacement should solve a defined problem
New units are most useful when the existing failure and installation scope are understood.
Safety boundary. General planning information only. Do not open, dismantle or work on hazardous electrical, gas, structural, fire-protection or contaminated-water systems unless you are appropriately qualified and authorized.