Condensation on windows and other cool surfaces in the home can be both annoying and possibly injurious to your home. Because the most often visible condensation is seen on windows, it is easy to blame condensation on the window. This is not true in most cases. Any cool surface will cause excess humidity to condense on it. If there is condensation on windows, you may be assured there is condensation on walls. This is more serious since that can penetrate the walls and cause internal problems.
The cause of condensation is air saturated with too much humidity or water. When this happens, air cannot hold the excess humidity. It gets rid of it by condensing it on the most convenient cool surface.
In other words, if condensation is to be reduced, the source and amount of humidity in the air need to be determined.
Warmer air holds more moisture than cool or cold air. This is illustrated on a humid, hot summer day when condensation appeared on a cold glass. This means that the amount of moisture in the air has reached its maximum and can’t hold anymore. Therefore, it gets rid of it by condensing it on the nearest cool or cold surface.
As the air cools, it can’t hold as much moisture and therefore, condensation will appear more quickly.
So what is the ideal amount of relative humidity in the air? Based on keeping an indoor temperature of 70º F, it will vary with the outdoor temperature. But as a guide, the following relationship should help.
If your relative humidity is above these levels, you probably will have condensation on any cool surface.
In some cases, this may be true. In older houses, the insulation and weather-stripping and other house tightening factors allowed the house to breathe and exchange drier air with inside more humid air.
Of course, windows also were not so air-tight and caused colder air to enter the house and can also cause the surface of the window to be colder.
Today, because we are all energy conscious, houses and windows are far more energy-efficient. This makes us all more comfortable, but may trap humid air inside the home.
The obvious answer is to reduce the humidity and decrease the number of cool surfaces in your home.
Your first step is to find what the humidity level in your home is. This will need to be monitored regularly as the temperature outside varies. Devices which measure humidity are called hygrometers. They can be purchased at most hardware and home center stores.
Windows, door and skylights have become an important part of the energy-saving plan. They do not allow cold air to enter around a window, thus cooling the surface. Spacers between glazing in double or triple-glazed windows are more energy-efficient and do not allow cold air to migrate through them causing the glazing to cool.
A special metallic coating has been developed (known as Low E or low emissivity) which reflects radiant heat and restricts its flow through glass. During cold weather, it will keep heat inside. In hot weather, it keeps heat outside.
Using energy-efficient windows will keep the interior glass surfaces warmer and thus reduce the interior cool surfaces on which moisture can condense.
In order to reduce condensation:
Remember, there is always a possibility that in very cold, unusual circumstances, you may still have some temporary condensation. But if the humidity level is proper and the home correctly vented, this will be short-lived.