Condensation
This is a very common problem and on this page we hope to inform you on how to deal with this problem. As with most things in life there is no simple answer. We have split this into three questions that we hope will help to inform.
What is Condensation, how does it form?
Condensation: the conversion of a substance (as water) from the vapor state to a denser liquid or solid state usually initiated by a reduction in temperature of the vapour.
What causes condensation on windows?
One or more of these factors causes condensation on your windows:
Cool Window Surfaces: If there is vapor in the air, whether it be on the inside of your home, or the outside, it will condense if the surface of your window is cool enough. Most often, condensation becomes and issue during winter, when there is a greater difference between inside and outside temperatures. During winter, we all heat our homes to remain comfortable inside. With thermally inefficient windows, there is no barrier for heat transfer. As a result, the glass becomes as cold as the outside temperature. These windows do not stop the heat produced by your furnace, warming the inside of your home and windows. Instead, they allow the heat to escape, creating cooler temperatures in the house and on the surfaces of your windows. With the glass surface getting colder and colder, eventually the air next to the windows will be cooled below the dew point, and condensation will form.
Well insulated windows will stop this heat transfer, increasing the
temperature of the air and the glass surface. When the temperature is raised,
the relative humidity is decreased. This means there is less chance of condensation.
The higher the surface of glass temperature, the better the condensation
resistance.
High Relative Humidity Levels: Relative humidity is a measure of the amount of water vapor the air is holding, compared to the amount that it will hold at a maximum, AT THAT TEMPERATURE. When air reaches a 100% relative humidity level, it is said to be saturated. It will hold no more vapor, and the vapor turns to liquid. Warm air can hold more vapor than cold air. This means that if the air temperature is increased, the relative humidity will go down. How does this affect the real world? The answer is simple: if your home air temperature is heated, the relative humidity goes down. This lowers the chance of condensation on interior surfaces, such as your windows. What it actually does is lower the dew point.
Lack of Air Movement: Evaporation is aided by increasing the amount of contact between water and air. Everyone has seen this phenomenon, but they probably haven’t related it to windows. Your exhaust fan in the bathroom is the key example of air movement aiding in evaporation. Taking a shower with and without the exhaust fan on, shows you immediately that air movement reduces condensation. Have you ever seen a puddle of water take two or three days to evaporate in the driveway. Have you ever seen what happens to that same puddle if the water is spread out by a broom or squeegee? When the water gets spread out over the ground, it evaporates much quicker. This is because more of the water gets exposed to air currents, and evaporation is quickened.
When vapor deposits (condenses) on a surface into liquid water, a lack of air current provides no energy for that water to revert back to the vapor phase. Increasing the contact between the collected water and surrounding air will help to clear up standing condensation. A curious thing sometimes happens when people replace old windows with new, energy efficient windows…they seem to condensate more often! This is because conditions inside the home have always been favorable for condensation, but the old windows allowed so much air leakage, that draft currents acted to evaporate any collected condensation. The condensation wasn’t noticeable, but the furnace never stopped running! Once the windows were replaced with a product that didn’t allow all the heated air to escape, the vapor content of that air had to go somewhere. This is actually a good situation. After sealing your home to heat loss, a better balance between temperature and inside humidity can be achieved. This will help in fuel costs, and in healthy living.
How can I stop condensation on my windows?
Condensation on your windows is a direct result of the interaction of temperature, air movement, and relative humidity. These three factors must be isolated and analyzed, to properly determine the cause, and the ultimate solution to condensating windows.
1. When replacing windows, make sure to invest in Low-E and inert gas fill
technology. This will keep glass surface temperatures higher.
2. Maintain indoor humidity levels in the range of 30-50%. Any humidity level
above 50% will likely produce condensation, even with low-e insulated products.
3. Maintain adequate air exchange in your home. To do this, you can:
Condensation is a dynamic factor, which can be controlled through proper
analysis of the determining factors. uPVC replacement windows are a great
step in eliminating cold window surfaces, which are favorable conditions
for condensation, but you must ultimately create an atmosphere that balances
healthy living conditions with the insulative properties of your home.