Many homeowners wonder how to reduce condensation on windows in winter. Fogged glass, dripping sills, and black mould are common problems when the weather gets cold. Ignoring condensation can damage your windows and affect your health. Luckily, simple steps can solve the problem. This guide will show you how to reduce moisture and keep it dry.
Why does condensation form on windows?
Condensation happens when warm, moist air inside your home touches cold glass. Water droplets form because the air cools quickly and can’t hold all the moisture. Common sources include cooking, long hot showers, drying laundry indoors, houseplants, and aquariums.
In the winter, indoor air tends to be more humid compared to the cold, dry air outside. The Government of Canada confirms that lower humidity in winter reduces condensation. Lowering humidity also helps prevent mold growth.
Quick everyday fixes you can do right now
Try these easy fixes for immediate results:
- Wipe Sills and Frames Daily: Use a cloth or small squeegee after showers or when you see water buildup. This prevents mould and frame damage.
- Run Exhaust Fans: Use kitchen and bathroom fans for at least 10–20 minutes when cooking or showering. This pulls moist air outside.
- Open Windows: A quick 3–5 minute airing swaps humid indoor air with dry outdoor air. This is known as “shock ventilation” and works well in cold climates.
- Sunlight: Keep curtains open during the day so natural heat warms and dries the surface.
How to Control Humidity?
Too much moisture in the air leads directly to foggy windows. So, here are some tips for you to control the humidity:
Check Indoor Humidity
Get a hygrometer and place it in living areas, not right on the sill. In winter, keep relative humidity around 30–35%, according to the Government of Canada recommendations. When outdoor temperatures fall below –20°C, you need to lower the humidity closer to 25%.
Adjust Humidifiers
If you use a portable humidifier or a furnace-attached system, turn it down on cold nights. The colder it gets outside, the lower your indoor humidity should be. Also, avoid drying clothes inside and cover pots when boiling water.
Use Dehumidifiers and Ventilation
Portable dehumidifiers are useful in damp rooms like basements or bedrooms. For long-term control, heat recovery ventilators (HRVs) or energy recovery ventilators (ERVs) bring in fresh air. These systems reduce condensation risk and improve indoor air quality year-round.
Proven Ways to Improve Airflow & Ventilation
Good airflow keeps indoor air drier and reduces the chance of condensation. Take a look at these simple ways:
- Run bathroom and kitchen fans on a timer to keep moisture from staying in the air.
- Keep interior doors open after showers to let humid air escape.
- Leave trickle vents open if your windows have them, as they allow a steady flow of air.
- Use ceiling fans on low speed to circulate warm air and prevent cold spots.
- Upgrade to an HRV or ERV for ongoing condensation problems
Insulation, seals & window upgrades
Sometimes, condensation points to problems that need repair.
- Condensation between the panes means the seal is broken. The panel will likely need to be repaired or replaced.
- Replace old caulk and weatherstripping around frames to stop cold drafts.
- Upgrade technology for long-term prevention:
- Low-E coatings to reflect heat back inside.
- Argon-filled or triple-pane units for warmer glass.
- Warm-edge spacers to reduce heat loss at edges.
- High-performance frames for better insulation.
When to Call a Professional?
Sometimes DIY steps are not enough. Call a window specialist when:
- Condensation sits between panes.
- Mould keeps coming back even after cleaning.
- Excessive condensation damages frames or walls.
- Seals or glazing look cracked or broken.
Conclusion
Condensation on windows is common in winter, but it doesn’t have to harm your home. If water continues to build up or mold keeps returning, get professional help. Now that you know how to reduce condensation on windows in winter, you can protect your home and save energy.
