Stop Window Condensation: A Wet-Season Moisture Checklist

Why are my windows wet on the inside?

Condensation often forms in colder weather, when moist air inside the home comes into contact with cooler surfaces¹. Glass is one of the places it shows: large differences between inside and outside temperatures can cause water to condense on windows⁷.

So does a wet window mean your house is too cold? The cold glass is where the water collects, but the thing to fix is the moisture. NRCan lists heavy condensation on windows as one of the signs of too much moisture in a home². That's why this post works on the moisture and the airflow, not the thermostat.

Should you wipe condensation off windows?

Yes. Health Canada advises drying your window frames and sills daily, to keep water from dripping and causing mould to grow³. HealthLinkBC makes the same link: condensation on windows can lead to mould on frames or sills⁷.

Wipe the glass, then the frame and the sill. Run the cloth along the track too, so water doesn't sit there. Keeping a dry cloth by the windows that stream the most makes it a quick habit.

Wiping protects the frame and sill, but it doesn't lower the moisture in the air. If the windows are wet again the next morning, the moisture is still there. The next two sections deal with that.

How do I stop condensation on the inside of my windows?

There are two jobs: lower the moisture, and keep the air moving.

Lower the moisture

• Use the bathroom exhaust fan when you shower or bathe³.
• Run a dehumidifier if moisture is condensing on cold surfaces such as window panes³.
• Dry laundry in the dryer where you can: hanging wet laundry indoors can raise indoor humidity³.
• Unplug and put away humidifiers³.
• Aim for a relative humidity³ between 30% and 50%⁴. A humidity monitor (hygrometer) tells you where you are.

Keep the air moving

• Leave curtains and blinds open when you can. Heavy curtains or blinds can trap the cold and moisture and cause condensation on your windows³.
• Keep heating vents and baseboards clear of furniture, and leave interior doors open³. Air flowing across the glass helps keep it warmer, which is one reason heating vents and baseboard heaters sit beneath windows in many homes¹.
• Pull furniture back from cold windows. Deep sills, closed drapes and blinds, and nearby furniture can block air movement and let cool air pool near a window¹.

Keep the HRV on

If you have an HRV, make sure it's on¹. It increases ventilation and helps reduce humidity². Its filters are in the checklist below.

What can I put on my windows to prevent condensation?

What NRCan points to is the windows themselves: high-performance ENERGY STAR certified windows are more energy efficient and have less condensation than ordinary models¹. That's a replacement decision, not a quick fix. For the windows you have now, the answer is the same as above: less moisture in the air and more air moving across the glass.

The wet-season moisture checklist

These are the parts of your home that move moisture out. Check each one as the wet months start. Most of these are homeowner jobs. We don't remove or wash bathroom exhaust fan covers, change furnace filters, clean HRV filters or clean dryer vents.

Bathroom exhaust fan

• Use it when you shower or bathe³, and keep the fan running after a shower³; Health Canada and HealthLinkBC give specific guidance⁷.
• Make sure it vents to the outside, not into the attic³.
• Before you clean it, turn the fan off and follow the maintenance instructions for your model¹¹.
• Dust the fan blades periodically⁵ and vacuum the grille⁵.
• Check that the damper on the outside grille can open and close properly⁵. Do this from the ground only. If you can't see the vent from there, leave it for a qualified technician.

Range hood

Use the range hood every time you cook, preferably on the highest setting³; Pearly's deep and move-out cleans include range-hood filters, and our oven guide shows how to clean a range hood filter yourself.

Furnace filter

Health Canada says furnaces and their ductwork need regular maintenance, and that new air filters and periodic cleaning are essential to adequate furnace ventilation⁵. For how often to change your filter, follow your furnace's manual. Servicing the furnace and cleaning its ducts are jobs for a qualified technician.

HRV filter

CMHC says to clean or replace HRV filters every 2 months⁶, and Health Canada says they must be vacuumed or washed at least every second month⁵. Before any work on the unit, turn the HRV off and unplug it⁶. For the heat exchange core, check your owner's manual⁶. Health Canada also lists cleaning the core and the condensate drain and pan once a year⁵. If the ducts leading to and from the HRV need a more thorough cleaning, call an HRV service technician⁶.

Dryer lint trap and outside vent

Clean the lint tray every time you use the dryer³. Check that the dryer vents to the outside³. Inspect the outside exhaust vent routinely and clear any built-up lint³, and keep it clear of snow and foliage³. Check it from the ground only. Cleaning the duct between the dryer and the outside vent is a job for a qualified technician.

Window sills and tracks

While the windows are running wet, dry the frames and sills daily³, and wipe the tracks too. Our deep clean covers window sills and interior windows, including tracks and frames, so the season starts from clean. The drying between visits is still yours, though: a deep clean is a reset, not a substitute for wiping.

Victoria and the CRD: how wet the wet season gets

Here's what Environment and Climate Change Canada's 1991–2020 climate normals show⁸ for three Victoria weather stations⁹, as of October 2026¹⁰.

• At the Victoria airport station, average precipitation is 146.0 mm in November, 146.1 mm in December and 155.3 mm in January, against 19.5 mm in July⁸.
• The airport averages 18.9 days with at least 0.2 mm of precipitation in November, 19.4 in December and 19.8 in January, against 5.4 in July⁸.
• December and January are the coldest months there, with daily average temperatures of 4.4 °C and 4.6 °C⁸.
• At the Gonzales⁹ and University stations, precipitation peaks in November¹⁰; at the airport, it peaks in January⁸.

At all⁸ three stations⁹, November to January are the three wettest months¹⁰. That wet stretch overlaps the coldest months⁸, and condensation often forms in colder weather¹. These figures are for three Victoria stations, not the whole CRD.

Common mistakes that keep windows wet

1. Wiping the glass but leaving the frames and sills wet. Dry them daily³; condensation can lead to mould on frames or sills⁷.
2. Switching the bathroom exhaust fan off as soon as you're out of the shower. Keep it running after a shower; Health Canada³ and HealthLinkBC⁷ give specific guidance.
3. A bathroom exhaust fan that vents into the attic. It should vent to the outside³.
4. Closed curtains and blinds¹, or furniture against the heating vents³.
5. Drying laundry indoors, which can raise humidity³.
6. Running a humidifier while the windows stream. Unplug it and put it away³.
7. An HRV that's switched off¹, or filters left longer than CMHC's every-2-months guidance⁶.

When to call a qualified technician

Some jobs on this list need a qualified technician: servicing the bathroom exhaust fan, the furnace or the HRV, and cleaning the dryer duct or the furnace ducts. The same goes for any outside vent you can't check from the ground.

Mould. Mould will typically grow indoors where moisture is present³, and HealthLinkBC says high humidity or indoor air moisture causes mould growth⁷. That's why everything above is about prevention. If you already see mould, go to the official guidance: Health Canada's guide to moisture and mould and HealthLinkBC's mould file cover cleaning a small area³ and when to get help⁷. For health questions, call HealthLinkBC at 8-1-1, or 7-1-1 for deaf and hard of hearing callers⁷.

What Pearly's does. Our cleans include dusting vent covers and ceiling fans, on recurring visits and in the deep clean. The deep clean also covers window sills and interior windows, including tracks and frames.