Some window condensation is a temporary response to weather or indoor activity. Persistent water, damaged finishes or fogging inside a sealed glass unit deserve a closer look.

Before deciding whether condensation is normal, identify where the water is. “My windows are foggy” can describe several different situations, and the next step depends on which one you have.

Moisture on the room side

If droplets wipe away from the indoor surface, you are looking at room-side condensation. Note whether it follows showering, cooking or a cold night, and whether it clears or keeps returning.

An occasional light mist and water repeatedly running onto the sill are not the same observation. Dry the accessible wet surfaces and watch for a pattern. The aim is to understand the source before accepting repeated wetting as harmless.

Keep a photograph of the whole window as well as a close-up. It gives the person assessing the problem context that a picture of droplets alone cannot provide.

Dew on the outdoor surface

Exterior dew can appear when the outer glass is below the outdoor dew point. It may clear as the sun warms the glass. Pella’s condensation guide explains this weather-related pattern.

Outdoor dew by itself is not proof of a broken seal. It also does not prove a particular energy rating. Check the location carefully rather than treating every foggy view as an internal glass problem.

Do not climb outside or lean through an upper-floor opening just to test which side is wet. Leave an uncertain location for someone who can assess it safely.

Haze between sealed panes

Moisture trapped inside a sealed double- or triple-glazed unit is different from droplets on an exposed surface. It can indicate that the unit’s seal has failed. Natural Resources Canada distinguishes this from other condensation locations.

If you cannot confidently identify the location, describe what you can see and when it appears. A technician can determine whether the issue is in the sealed unit, on a surface or in a separate storm-window arrangement.

Signs that deserve attention

Arrange further investigation when you notice repeated soaking, peeling finishes, soft or swollen material, a musty smell or visible mould. Water appearing after rain also needs investigation rather than an automatic assumption of condensation.

Health Canada’s moisture and mould guidance emphasizes identifying and correcting the moisture source. Follow its cleanup guidance or seek professional help where the extent or cause is unclear. Painting over a damp area does not establish that the problem is resolved.

What information helps at an appointment?

Bring the window’s location, photos taken while the issue is visible, the time it usually appears and any relevant weather or indoor activities. Note whether the frame or wall gets wet, not only the glass.

If you are considering new windows, share those details with Northline. A useful replacement discussion should begin with what is happening at the opening, rather than assuming all condensation calls for the same solution.