Condensation, or moisture on surfaces, generally occurs inside the home when it is extremely cold outside and the humidity level inside the home is at a higher level than recommended.
Condensation will show in the form of moisture, and will be seen on cooler surfaces, such as glass, hinges and hardware. The surfaces are more susceptible because they are closer to the outside versus an inside wall or table.
Condensation can be visible across interior window surfaces, which is odd because windows made of glass and vinyl are not capable of making surface water. Why is this happening?
Condensation occurs when the temperature of the surface is colder than the Dew point temperature.
So the air temperature inside the home, mixed with the humidity or moisture level inside the home, will establish the Dew Pointe temperature, which is always lower than the inside air temperature.
If the surface inside the home is colder than the defined Dew Point temperature, then condensation will occur on the surface. For example you have a glass, fill it with ice, add water and set it aside. After a while there will be moisture on the outside of the glass. That might make you wonder “Is the glass leaking?” The simple answer is no. Because the glass is cold, the air surrounding the glass is getting colder. Once the air temperature drops below the established Dew Point temperature, the air can’t hold any more water, so the water will leave the air and propagate on the colder surface.
This concept will be the same with windows as it was with the glass example. You start by obtaining the outside temperature, because the outside cold temperature will affect the inside glass and vinyl temperatures. The colder it is outside the colder the inside surface will be.
Glass for windows is typically dual pane with argon gas so you can expect the window surface to have a 30-degree temperature difference from the outside to inside temperature. So if the inside glass surface temperature is below the established Dew Point temperature, then water will leave the air and lay on the glass surface.
To prevent this from happening the inside humidity level must be reduced enough to lower the Dew Point temperature, so it is below the temperature of the surface it is compensating on.
There are multiple things in the home creating moisture like showers, cooking, laundry or when a large group of people gather. Elevated moisture levels can also lead to mold and rot in unseen areas of the home.
Reducing the humidity percentage inside the home when it is cold outside usually solves the problem. When the outside air temperatures are below 30 degrees and lower maintaining the same inside level of humidity condensation will be an issue.
If water is collected on the inside glass, hinges etc., identify and reduce the cause of the excess moisture in the air. For example, a fogged mirror in a bathroom after someone showers; the air is in an enclosed space and is saturated with moisture from the shower and then lays on adjacent surfaces that are cooler. Once the door is opened, the excess moisture will mix with the dry air outside the room and the condensation will go away.
Exterior Condensation will happen when the Dew Point temperature is higher than the surfaces that have condensation. At night, as outside temperatures drop, so do surface temperatures on items such as exterior window glass, siding, grass and cars.
In the morning as the temperature starts to rise and humidity levels increase, the Dew Point temperature rises faster than the surfaces, which is still cool from the night before. When this happens condensation will form on these cooler surfaces. As the temperature warms the moisture on these surfaces goes away. Your window is working as designed and acting like an exterior wall, keeping the moisture outside and warm air inside.
This stopped working on your older windows and that is why you did not see this. Newer more energy – efficient windows will not allow as much warmth from the inside to reach the outside glass pane, therefore the outside pane remains cooler than the dew point, allowing condensation to form.
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