Why Does Condensation Appear on the Inside of Windows?

Interior window condensation: a common phenomenon 

Interior condensation occurs when warm, humid air inside your home comes into contact with a cold surface, such as window glass. Several factors can contribute to this situation, and identifying them is key to addressing the issue effectively.

Why does condensation form inside the home? 

• Indoor sources of moisture: Everyday household activities such as cooking, showering, washing dishes and laundry increase indoor humidity. The presence of numerous plants or an uncovered aquarium can also contribute.
• Damp basement: Moisture from a humid basement can rise and affect the entire home, increasing condensation on windows.
• Cold temperatures: In winter, windows are often much colder than indoor air, creating ideal conditions for condensation to form.
• Poor ventilation: Insufficient air circulation prevents moisture from escaping properly, raising indoor humidity levels.

How can you reduce interior condensation? 

If you notice condensation on the inside of your windows, several strategies can help reduce it:

• Eliminate or reduce indoor moisture sources: Limit the number of plants, cover aquariums, ensure your basement is well ventilated and repair any leaks.
• Use a dehumidifier: A dehumidifier can be especially effective in basements, particularly during humid seasons such as fall, spring and summer.
• Monitor humidity levels: Use a hygrometer to keep your home’s relative humidity at an appropriate level. In winter, it should not exceed 45%, but it should also not be allowed to drop too low.
• Keep curtains and blinds open: This allows warm air to circulate against the window surface, helping reduce condensation.
• Ensure proper ventilation: Use exhaust fans in kitchens and bathrooms, and regularly open windows to refresh indoor air. Persistent condensation may also indicate that your air exchanger or ventilation system requires inspection and maintenance.

Interior window condensation is a sign that indoor humidity levels are too high. By taking steps to control moisture, you can reduce or eliminate window fogging and create a healthier, more comfortable indoor environment. If condensation persists despite your efforts, consulting one of our professionals for a more thorough evaluation may be beneficial.

If you sometimes notice condensation on the exterior side of your windows, click here.

If you observe condensation between the panes of glass, this may indicate a problem with the insulated glass seal. It is often a sign that the seal has been compromised, allowing moisture to enter between the layers of glass. If condensation is present between the panes and persists over time, we recommend contacting our SAV+ after-sales service team (SAV+ contact  details here). We will be happy to assess the situation and send a technician if needed.