Window problems

Fog between the panes is seal failure in the insulated glass unit. The window still works; it just lost its insulating gas fill and clarity. Ask whether the glass unit or the sash can be replaced before you agree to a whole new window.

Condensation on the inside surface of the glass in winter is usually a humidity problem in the house, not a defective window. Cold glass plus moist indoor air produces water. New windows can make it worse, not better, by tightening the house.

Drafts can come from the sash seal, the weatherstripping, or the gap between the frame and the rough opening hidden behind trim. That last one is common in older homes and is fixable without buying windows. Ask for a blower-door or infrared check if a company claims your windows are the source of high bills.

Soft, dark, or crumbling wood at the sill is the one to take seriously. That is water getting past the flashing, and the damage usually extends into the wall. This is where full-frame replacement earns its cost.

How to choose

Diagnose before you shop

Write down which windows fail, how, and in what weather. A company that gives the same diagnosis for every window in the house has not diagnosed anything.

Test drafts honestly

On a windy day, run a hand or a lit incense stick around the sash and then around the trim. Leaks at the trim are an air-sealing job, not a window job.

Fix humidity first

If glass is sweating on the room side, look at bath and kitchen venting and any humidifier before you spend on windows.

Probe suspected rot

Press the sill with a screwdriver tip. If it sinks, get the wall opened and inspected. Covering rot with a new window traps the problem.

Beware the single-cause pitch

"Your windows are why your bills are high" is a sales claim, not a measurement. Insulation and duct leakage are more often the bigger cost.