REAL ESTATE ANSWERS: What causes window condensation, and what can you do about it?

What causes window condensation, and what can you do about it?

In the winter, the difference between outdoor and indoor temperatures often causes condensation to form on windows. This moisture can drip down to the window frame or sill, leading to surface deterioration and creating a favorable environment for mold to grow. Mold growth can also go unnoticed behind blinds and curtains, making it important to address condensation issues quickly.

When warm, moist air accumulates inside your home, condensation is more of an issue. Kitchens and bathrooms are often the biggest sources of moisture, which is why good ventilation in these areas is key. Plants and aquariums in the home can also increase the moisture in the air, as will an overzealous humidifier. (If you use a humidifier, you should check the settings. In most cases, you want the indoor humidity to be between 30 and 50 percent.) If you have leaks or water intrusion, these will exacerbate the problem, sometimes significantly.

To lessen or eliminate window condensation, you need to lower the moisture content in your home’s air.  One way to do this is to open windows or doors periodically to let moist air out. Use exhaust fans in the kitchen and bathroom, or open a window, to release excess moisture in the air from a hot shower or boiling a pot of water. Opening blinds and curtains regularly allows air circulation and helps dry any dampness on surfaces behind them. A dehumidifier can be a worthwhile investment if condensation remains a persistent issue. Addressing any leaks or water intrusion is also critical.

Double- or triple-pane windows are less prone to condensation, because the space between the panes serves as insulation between the cold outside and the warm interior of your home. Replacing single-pane windows is another way to address this issue, though it’s a substantial undertaking. If you have original, architecturally-attractive old windows, I personally am not a fan of swapping them for generic replacement windows, unless there is a serious need. Multi-pane replacements that preserve architectural style are available but are more expensive.

If you have existing multi-pane windows and those windows have condensation, it’s likely that the condensation is between the panes of glass. Over time, the seal between the panes of glass breaks down, allowing air and moisture to enter the space between them. Unfortunately, the only solution in this case is to replace the glass panels.