Why is there condensation on my windows?

Moisture and condensation on your windows can seem like a worrying problem, but there is good news and bad news that will help you understand what’s going on a little better, as well as some of the ways that you can deal with the issue.

During the summer months, it’s fairly rare for most homes to experience condensation on their windows. The reason is simply that you probably have more airflow coming in and out of your home in the summer, and that keeps moisture from being trapped inside. Air conditioners reduce moisture, having windows or doors open will vent the moist air, and the temperature also keeps damp air from clinging to the window.

However, in the winter, many homes end up trapping moisture inside, and it’s most common in newer homes which are built these days with better insulation and moisture-trapping materials. Older homes, which can be more expensive to heat, tend to vent air and moisture through any number of areas.

So, why does moisture appear on windows in the winter? When the air in your home becomes saturated with water, which can come from a number of sources that we’ll look at next, it turns back into water when it touches cold surfaces like your window panes. For most homes, the moisture level will rise and fall naturally, and it should disappear within a few days. For most home owners, the condensation on their windows will also only cover a small portion of the window pane–likely in the corners, or in the centre of each pane.

For some other home owners though, the problem can become much worse. Window condensation can cover the entire window, or it might even start leaking down the window and over window sills, walls, or it might turn into mould, mildew, or fungus if it has enough time to sit and grow.

So, what can you do if humidity becomes an issue in your home? Here are a few things to keep in mind when trying to solve the problem:

1. Check your furnace or household heating system. Many furnaces and some heating systems include a built-in humidifier to keep your home from getting too dry. Ensure that the setting is appropriate for your home and either reduce the level, or turn it off entirely. If you have a separate humidifier, check the settings and how often you run it to be sure it’s running properly and that you are not running it excessively or needlessly.
2. Check your vents. Blockage to your vents can cause buildup of moisture, especially from your clothes dryer, from your bathroom, and from the kitchen. Make it a seasonal point of interest to check your vents for anything that might block the air flow, especially on the outside of your home, or even just in the buildup of dust and particles at the vent opening. If these are clear, you should also assess whether there is enough ventilation from your bathrooms and showers. Insufficient ventilation can cause moisture to build up quite quickly.
3. Take a few moments to vent your home. If the previous points don’t help, simply trying cracking open a window for a few minutes to vent moisture from your house. This is not a solution to the problem, but it can help tremendously until you solve the moisture issue.
4. Check the vents from your attic. If the vents from your attic are not working properly, moisture can build up in the home, and you could experience other issues as well. This may require you to get a professional into your home to take a good look and asses your vents and your attic.
5. Take a look at how many house plants you have. If you have a lot of plants in your home, that can also lead to excessive moisture. Over-watering them can also lead to issues, and having them close to the windows can lead moisture to build-up on your windows.

If none of these ideas help your problem, consider having an expert look at your home to find a solution. Keep in mind that the sooner you solve the issue, the less likely the moisture will lead to bigger problems, like rot and mould.