Condensation on the Inside of Windows Means the House Is Too Humid, Not the Window's Fault

Glass is the coldest surface in most rooms during winter, so it's the first place airborne moisture reaches its dew point and condenses. Single-pane glass condenses at higher indoor humidity than double or triple glazing because it stays colder, but any window will fog if indoor humidity is high enough relative to the outdoor temperature.

Persistent condensation, especially pooling on the sill, means indoor relative humidity is likely above the 30-50% comfort range for the season. Cooking, showering, and even houseplants add moisture; bathroom and kitchen exhaust fans, plus a dehumidifier in damp months, address the cause rather than the window.