Published on July 28th, 2015 | by Henri


Moisture builds up after new windows installed

Q.  I live in a 40-year-old ranch and had new windows installed 3 years ago. Since they were put in a fair amount of condensation builds up within the house during the winter months. I run a dehumidifier to cut down on the amount of moisture build up on the windows but it still persists. The bottom of the windows have become dark with mold where the wood meets the glass.

Any suggestions on how to get more air circulation in the house to eliminate the excess moisture?

A.  Your old windows were quite leaky, allowing more air exchanges than the new ones. So moisture generated by your family and its habits (the number of people living in the house, the house size, length of showers, type of cooking, etc.),  water-loving plants, pets, firewood stored in the basement, clothes dried on racks, etc.) will accumulate and, when the dew point is reached on the window glass, condensation occurs.

You need to lower the inside relative humidity by changing some of the things that keep it too high. Ventilate the house often by opening windows on milder days, or run bathroom and kitchen fans for long period of time (be careful, though that the use of the fans depressurizing the house does not cause backdrafting of the heating appliance — this would draw carbon monoxide into the house.)

Or you can choose to have one or more room-size air-to-air heat exchangers, or a full-house one, installed.

Meanwhile, remove the mold on the bottom rail of the window sashes with a toothbrush dipped in a mixture of equal parts household bleach and water.

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