Each winter, after the first really cold period, we receive a number of calls about moisture on windows. I am not a scientist but I understand the basic reason for this. A friend of ours (Darrell Paul) specializes in better building practices with regards to moisture and air tightness. I have pulled some information from his site that I find useful as a reference when explaining this phenomenon to our customers. So here we go…
In simple terms, when air cannot hold anymore humidity (vapour) it begins to turn to liquid, or sometimes referred to as “sweating” Condensation on windows is an indicator of high humidity in a home. There are many sources of humidity that can cause your windows to sweat..
If your windows are sweating (have condensation forming) then likely you have too much humidity in your house. Many people find that when they buy a new home or upgrade their old windows to new ones they get more condensation – That is true. Why?
Why new homes have more window condensation
Most new homes are built very energy-efficient. That means they have a sealed combustion furnace and are built very air tight. That also means minimal fresh air from outside coming in to dilute the humidity in the house. If the house is built energy-efficient and air tight you also won’t run the furnace as much which is how you get fresh air into the home. Unless you switch on the principal exhaust fan (located in the hallway near the thermostat) you won’t be able to reduce the humidity.