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Fri, Feb. 28

Window condensation could mean your house is too humid

Q: Why is condensation forming on our windows?-Margaret and Jeff, Prescott

A: Window condensation is a real pain in the glass! YCCA receives a number of calls on what causes surface condensation on windows. Most people are quick to blame the manufacturer. The answer to this question does not relate to condensation caused by seal failure; this addresses glass and frames.

Condensation occurs on windows when warm, moisture-laden air comes in contact with a cold surface like a metal frame or glass and the dew point is reached.

Factors that contribute to the likelihood of window condensation include the climate or outdoor environmental conditions; the indoor relative humidity; whether window coverings/curtains are closed for a long time during cold weather; and the windows' Condensation Resistance Factor. The CRF is a number between 0-100. The higher the number, the greater the condensation resistance the window has.

Window condensation can be a sign of excessive indoor humidity. It is important that you control indoor humidity levels, which should not go above 40 to 45 percent. In cold weather, you need to lower the humidity levels to prevent condensation.

High humidity can be caused by humidifiers, plants, aquariums, lack of kitchen or bath exhaust fans, wet crawlspaces and basements, and poorly vented dryer exhausts. As soon as the moist, warm air comes in contact with the cold glass, it is cooled, and the moisture is released in the form of condensation.

There are causes of window condensation that can be temporary and need no action. Those include new construction or remodeling; the beginning of the heating season; and when we experience swift changes in temperature.

Wood, plaster, cement, and additional building materials that are used in new construction and remodeling usually create moisture. During the heating season, there may be a significant amount of temporary condensation, but after the first few weeks of heating, the condensation will dry out. Sharp drops in temperature can also cause temporary condensation problems.

If you didn't have as much condensation before replacing your old windows, it's probably because they were drafty. New, improved windows and insulation all create barriers to the air exchange of a home. When combined with the additional water vapor (moisture) from showers, cooking, or from clothes dryers not vented to the outside, the result is excess moisture and a high relative indoor humidity level.

Sometimes the amount of condensation that you might see on your window depends on the type of window. Recessed windows, like bay or bow windows, usually experience more condensation than other window styles. This is because air circulated around those window types is usually more restricted, and since they hang away from the insulated house wall, they could be a few degrees cooler in temperature. Drapes and window shades contribute to window condensation by restricting the flow of warm room air over the glass surface. Therefore, condensation is more apt to occur when drapes are closed and shades are pulled down. Today's heavily insulated drapes and tighter shades can contribute to the problem even more.

Vinyl windows help guard against the damaging efforts of condensation because of their higher insulating value. Also, double-glazed windows are far more resistant to condensation than single-pane windows. Single-pane windows allow for a higher percent of the indoor relative humidity.

Some window condensation is normal and should not really be a concern. When excessive condensation occurs, that can cause problems such as peeling or blistering paint around the window, which can lead to mold or mildew growth and wood rot.

Steps to take to avoid condensation are cracking open a window or door daily to air out your house; opening a window or running exhaust fans in the kitchen, bathroom and laundry room; opening drapes and blinds and allowing air to circulate against windows; and installing and using a dehumidifier.

If you find condensation between the two layers of glass in an insulated window, the airtight seal has probably been broken and the glass will need to be replaced.

Remember to tune in to YCCA's Hammer Time, played twice each weekend at 7 a.m. Saturdays and Sundays on KQNA 1130 am/99.9 FM, or on Listen to Sandy and Mike talk about the construction industry and meet your local community partners and contractors.

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