Condensation on Windows

[Ivan Bauer]

Our house is 6 months old and we wake up every morning to condensation on the inside of the windows. We have noticed mildew growth where the water collects. I have read the previous questions and responses to the similar problems. We do not want to resort to using a dehumidifier if at all possible, and we are now trying some of the hints given in previous responses. The basement is not finished. We live in southern Ontario. Obviously, our house is airtight. Is this “problem” the responsiblity of the builder to fix? And if so, how?

[Bruce M]

Hi Ivan:
This is a topic I and others have spoken to in the past. You don’t mention what hints you have tried, but at the expense of repeating what has been posted before, let me offer a couple of points.

Yes, you are correct, the condensation probably indicates you have a ‘tight’ house. But the the excess moisture can be from any number of sources: long hot showers without running an exhaust fan; lots of kitchen cooking again without exhaust; an overly active central furnace humidifier you may not be aware of, in-house exercise equipment that when used vigorously, leads to lots of sweating and breathing or, as is our case, a ventless gas log set.

Without running a dedicated dehumidifier, the only means I have found (short of opening windows and doors) is to run the fan only in the central furnace, provided you have an A/C evaporator in the furnace plenum. The hundreds of aluminum fins of the evaporator that the house air circulates through are usually cooler than the house air and will condense out the excess moisture, dripping it to a collection pan and then hose drain it into a floor drain or to a pump to be pumped to a sink or other drainage spot. We will get a considerable moisture build up on windows if we don’t run our fan a couple of hours each evening.

It is possible you are getting moisture up through your basement. You can test this by taping a 2 foot square piece of plastic to the concrete floor and leaving it for 2 or 3 days and then taking it up. If the plastic has moisture condensed on the inside (surface facing the floor), you then have moisture rising up through the concrete.

I doubt the contractor/developer is responsible for excess moisture in the house, although it doesn’t hurt to ask. Many local building codes now require heat exchangers in new construction that pump inside air through the exchanger which extracts most of the heat, then pumps the air outside, bringing in new and cooler air to replace it.

Best wishes

Bruce M

[BrettP]

I have read past house moisture questions typically originating from the north. I am in a new two story home and each morning we awake to fogged windows upstairs. My fear is that moisture is also collecting in the CBS walls and not dissipating when the sun comes up. At present the night temperatures range from 75-80 and our indoor temp is lowered approximatedly five degrees to 71. Any information would be a big help. thank you in advance.

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