Moisture on Windows

Condensation on windows is a special cold climate problem. Cold air can't hold as much water as warm air. When warm air gets cooled, water is the result. If you ignore water on the inside of your windows, they will start to mold and eventually rot.

In our old house with single pane glass and storm windows this wasn't a problem. The old house had enough natural ari exchange that water never pooled on our windows. With our new home there is some learning going on.

New homes are tight and air flow is regulated. Our house is very good about retaining heat, it also retains moisture from breathing, cooking, showers, plants etc. During this recent cold snap water and ice formed around the edges of our windows. Our windows are wood on the inside. Water and wood is not a good combination.

Here is what I have learned. In a modern home with double pane windows when the temperature gets to 15 degrees your humidity should be kept 35% or lower. When it hits twenty below you may need to keep the humidity lower than 20%.

If water forms around the edges of your windows the humidity in your house probably exceeds the numbers mentioned above. If you commonly have humidity on your windows you need to get it out. It is healthy to have some humidity in your house.

Someone in a slightly older home told me they turn down their humidfier when it gets cold and that works for them. Our house stays humid without a humidifier so we need to run our air exchanger more when it gets cold.

The meaning of the little dial on the air exchanger control became clear to me this weekend. It's a humidistadt that runs the air exchanger until the humidity is at the level set on the dial. I never have been good about reading directions.

I should ad a note to this information. If you have moisture between the panes of your double pane windows this is different. Your window has a broken seal and the glass needs to be replaced. Check with the window manufacturer, it may be under warranty for longer than you think.

J.T.