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Hello,

With the arrival of winter and cold weather, some of you are experiencing higher levels of condensation on your windows. This phenomenon is the result of hot and humid air coming into contact with a cold surface. Before you worry about the quality or state of your windows, here are some explanations concerning this natural phenomenon and some tips to avoid the accumulation of water on the windows.

Air is a gas which, depending on its temperature, will contain a certain amount of water vapor. The warmer the air is, the more it can hold water without creating problems. For example, the glass windows do not fog up when it's 30 degrees Celsius during the summer and the relative humidity is 95%, yet when you take a bottle from the refrigerator, condensation forms on the outside of the cold container as it comes in contact with the humid air.

As such, the relative humidity can vary according to changes in temperature; it increases as the temperature decreases and decreases when the temperature rises. For example, if air heated to 23° C contains 35% relative humidity and the temperature is lowered down to 18° C overnight, the relative humidity increases up to 50% and surplus water vapor will settle on cold surfaces.

There are three variables to consider: the outside temperature, room temperature and relative humidity. Since we have no control over the outside temperature, we only need to take it into consideration. The colder the temperature outside, the colder the window surfaces, meaning there will be condensation on windows if the relative humidity is above the values shown in the following table (considering an average room temperature of 22° Celsius).

Considering that we need humidity for our comfort and the proper conservation of materials (e.g., wood flooring), it is important to maintain a 35% to 50% relative humidity level. Referring to the chart, we see that at -25° Celsius outside, there is a high probability that there will be condensation on the window glass if the recommended moisture content is at a minimum 35%. This natural phenomenon is by no means a serious problem, but during these colder periods we must pay attention to the condensation and not let water collect at the bottom of windows. It's a question of balance; you simply have to avoid excessive moisture that could damage the materials and cause mold.

Here are some simple tips to help you control the relative humidity level and window condensation:

• Obtain a hygrometer to precisely measure the humidity level

• Make sure your ventilation is working well, always leave the bathroom fan on during and after showering, always put on your range hood (stovetop fan) when cooking

• Avoid air-drying your clothes

• Avoid keeping too many plants in your condo

• Do not fully close your blinds or curtains so heat from your heating system warms the windows

• Leave interior doors open to ensure better air circulation between rooms

You are now ready to face winter condensation!

For more information on the topic, we recommend you consult the following articles:

• http://www.ecohome.net/

• http://www.apchq.com/quebec/fr/conseils-apchq.html_periodes-de-grand-froid-et-condensation-l-apchq-rappelle-quelques-trucs-pour-eviter-le-probleme22-01-201.html

• http://www.criticalcactus.com/reduce-home-humidity/

• http://www.envirovent.com/blog/14-ways-to-help-reduce-condensation-in-your-property/