To reduce condensation on the inside of your windows, start by controlling moisture and helping room air reach the glass. Wiping the window makes it easier to see, but the moisture can return if the conditions stay the same.

First, confirm that the water is on the surface facing the room. If the haze is trapped between sealed panes and cannot be wiped away, this indoor-humidity checklist will not repair the glass unit.

Start with a dry sill and a simple record

Dry the accessible glass, frame and sill with a suitable soft cloth. Avoid leaving water pooled against the finish. Then record the room, time of day and what was happening before the window became wet.

Try a short note such as: “Kitchen window, after cooking, blinds closed.” Repeat the check over several days. A pattern is more useful than judging the whole house from one foggy window on one cold morning.

Reduce moisture where it is produced

Use a kitchen exhaust fan that vents outdoors while cooking, and use the bathroom fan during and after showering. A recirculating cooker hood is not an exhaust path to the outdoors. Check how yours is configured rather than assuming every fan removes moisture from the home.

If you use a humidifier, review its setting when condensation becomes persistent. Also note indoor laundry drying or other changes that coincide with the problem. H recommends managing moisture sources and drying wet window frames and sills.

Let room air reach the window

Open tightly closed curtains or blinds and keep heating outlets unobstructed. Deep sills and nearby furniture can restrict air movement at the glass, as Natural Resources Canada explains.

You do not need to rearrange the entire room immediately. Start with the covering on the affected window and check whether the morning pattern changes. Keep track of the weather too, since a milder night can make an apparent improvement difficult to interpret.

Check humidity instead of guessing

A hygrometer measures relative humidity. Use it with a room-temperature reading and follow its placement instructions. Record the numbers alongside your window observations.

Health Canada gives 30–50% as general indoor humidity guidance. That range does not guarantee dry glass during an Ottawa cold snap. The outdoor temperature and the window’s performance affect when condensation appears, so recurring moisture deserves attention even if a reading seems ordinary.

If you have an HRV or ERV, check the operating manual and maintenance requirements. These are mechanical ventilation systems; guessing at unfamiliar controls is less useful than having persistent ventilation problems assessed by a qualified contractor. Health Canada’s ventila

Know when to ask for help

Arrange an assessment if water keeps collecting, materials are becoming stained or damaged, or the source remains unclear. Note whether water follows rain rather than indoor activities; it may require a different investigation.

Condensation alone does not prove every window needs replacing. If you are considering replacement, knowing where the moisture forms helps keep the discussion focused on the right problem.