Part III: Condensation problem in houses during cold weather

Here is a typical question we get asked frequently at The Comfort Shoppe.

Why do we have water (condensation) running down our windows in cold weather(below freezing). Is there anything we can do about this?

-- Tom W., Hampton.

Tom: The humidity appearing on your window is due to the fact that your dew point or humidity in your home is too high. There is a direct relationship between humidity and the outside air temperature. As the outside air temperature drops, the maximum moisture the air can contain inside your home has to be lowered otherwise the air will "plate" out the excess moisture on the cold window surface. If the level of humidity is excessive and the window's cold enough, ice will form at the bottom. This condition over a period of time promotes mildew and can cause deterioration of the window frame. Here are suggested humidity levels.

The following can help to reduce humidity.

1. Too much moisture being generated. Make sure that you minimize the evaporation of moisture in the air. Cooking and steaming, hanging clothes in your basement, long hot showers all contribute to the above.
2. Run bathroom exhaust fans and/or install supplementary ones. This will increase the infiltration of drier air to come-into the home. Try cracking open a window where there are large sources of moisture being generated. The cold air when heated up to room temperature will be able to lower the humidity already in the house. Finally if severe problems are still in the house this is indicative of a "tight house" which can benefit from a heat recovery ventilation system. These systems are designed to recover waste heat from out going air and transfers it to dry incoming air. The results can be a comfortable home with high indoor air quality.