The builder will tell the customer that the window frosts, or get wet due to condensation forming on the inside, nothing to worry about. …Really?

First, we need to know what condensation is from and what causes it. Then we can reason on whether the answer is correct.

The insulation value on walls is about R-17 on average. A window is about R-2 for double glazed, R-3.5 for double glazed with Low-E, and R-4.5 if you also have Argon gas filled glazing.

That means that the window is has very minimal insulating value.

Now, think back to a warm, sunny summer day. Take a cold can of pop from the fridge and set it on the table. Within a few minutes, not only does the can have beads of moisture, but it probably also is sitting in a puddle of water.

Does this mean the can leaks? No. Why is this happening? Condensation.

If we use the pop tin and compare it to the window we can determine what is happening.

First, the tin represents the window. It is colder than the surrounding air.

Second, the cold pop is the same as the exterior cold temperature

Third, the air around the tin has moisture in it. As the moisture comes in contact with the cold container, the air cools and the air no longer is capable of holding that amount of moisture.

Since the moisture will only form on a solid object, the can becomes wet.

The window is the same. It is the coldest part of the exterior wall. The warm air contacts the glass, and the moisture in the air turns to liquid on the glass. The other term for this is the dew point, or when the air is saturated and cannot hold the moisture any longer.

Now, having said all that, shouldn’t windows built in 2005 eliminate this problem? The answer is no. Even with the maximum insulation value, (which will cost you big $$$$) a window will always be colder than the rest of the wall.

So, how can you get rid of condensation?  Here are a few simple rules.

1. Open the window coverings to let air access them.
2. Make sure the floor vent in front of the window is unobstructed by furniture.
3. Turn on the summer switch for the furnace. Moisture on the window will evaporate into the warm air being blown past the glass.
4. Lower the humidity in the house. Adjust your humidifier to a lower relative humidity.
5. Turn up the heat and keep it warm during nighttime as well. Warmer air can hold more moisture so it will be less likely to form on the windows.
6. If you are buying, install a window coating such as low-E or double low-E which not only blocks UV, but increases the insulation value of the window by reflecting heat wave back into the house.

So condensation is from combining a cold surface and moist air, and even the best windows will at time have condensation. If anyone tells you otherwise I would like to know as well.