CONDENSATION ON WINDOWS

[winchman]

My home is going on three years old and I've been having a problem with condensation on the bottom edge of my windows(the glass). Would like to eliminate it cause its causing mold on the wood part of the window frame. Any suggestions?? I'm considering on purchasing a humidity monitor of some kind? My home is heated with baseboard hot water and also have a woodburner going in the basement. No ductwork. Just open the stairdoor and let the heat come up. All suggestions appreciated.

Thanks,
winchman

 

[beenthere]

The condensation is hard to beat, as the window glass is not a good insulator, and the difference between its temp and the room temp is going to squeeze out moisture from the air in the room. Just moisture from use of water in the house and moisture from people will be sufficient to condense on the glass.
What you can do about the mold is mix a solution of laundry bleach and water and spray the area where the mold is growing. I place some borax (twenty mule team variety) along the lower edge to combat any mold and to keep the wood from decaying. Borate in the wood is a preservative, as I understand. The condensation will help carry the borate into the wood.

 

[BHarrison]

Just a shot in the dark, but would a dehydrator in the HVAC system work for you? Not sure about your climate, but if you take moisture out of the air, then there's less to accumulate on the windows.

 

[heehaw]

my home is 16 years old, this is the fist year we have had condensation on the inside of any of the windows. We have triple pane, aluminium frame windows, this type has the "storm" window on the inside. The reason for the condensation appears to be the outside windows leaking, and letting cold air in on the "storm" window. with one side being considerably colder than the other, causes the condensation. with the type of heat you have, i would not expect moisture to be a problem, unless it's to little moisture. if you have double pane,aluminium frame windows, that do not have a thermal break built into the frame, you can get a lot of condensation. external storm windows will help with this; wood or pvc frame also helps with this problem. "if i ever build again", i will install anderson windows, a guy i work with bought a 20+ year old house, he had a problem with a couple of the windows, anderson replaced all of his windows that had any kind of problem, no charge. what type of windows do you have?
heehaw

 

[DVerbarg]

Winchman,

Don't know if this will help you or not but it helped a friend of mine who built his own house. This friend's house was built very tight, too tight. He installed vapor barrier on all the inside walls and ceiling. He had the same problem you are having with condensation. After a couple years of struggling with this he removed the vapor barrier from the entire ceiling. He worked from the attic space and removed the insulation from the ceiling in sections and then used a knife to cut the vapor barrier then replaced the insulation. After a few days there was a remarkable change in the condensation problem and has been fine for the past 3 years.

The house needs some way to release the water vapor. Old houses with the drafty doors, windows and walls provided more then enough exchange but today's tighter homes need help in these areas.

 

[Anonymous Poster]

Winchman, condensation buildup is common in houses built very tight. I experienced this problem and solved it in my previous house. My house with the problem had a poly vapor barrier on all exterior walls and ceiling.

There are two ways to solve the problem, the first is to reduce the amount of moisture introduced into the air in the house. The second is to remove the moisture from the air. The cold outside air when warmed up in the house will become very dry, so you must have a tight house with a low infiltration rate or generate a large amount of moisture to have this problem.

Do not perforate your vapor barrior! Cutting the vapor barrior as was suggested will allow the moisture and heat to rise into the attic insulation. The moisture will condense inside the insulation making it wet. This wet insulation will not insulate very well and will lead to rotting any wood in contact with it.

The easiest thing to do is reduce the moisture added to the air. Make sure you have bathroom vent fans and always use them during and after showers. A kitchen vent fan should be used if you do a lot of cooking. If you bring in wet or snow covered fire wood, that will introduce a lot of moisture to the house too. Consider covering your wood. If you use a humidifier, turn it off. Reducing the added moisture may solve your problem.

Eliminating the existing moisture can be accomplished with a dehumidifier. While they work well in the summer, they often will ice up in the slightly lower indoor temperatures of winter, but if the house is warm enough it will work. Venting the house by opening a window will also remove moisture at the expense of heat. If your wood heat source is free this may be an option.

I installed an air to air heat exchanger to solve my moisture problem. The heat exchanger works by exhausting moist indoor air to the outside and bringing dry outside air inside. The heat exchanger transfers the heat from the indoor air to warm the outside air. I was getting more than 90% efficiency in this heat transfer process. There are many commercially available heat exchangers on the market although they tend to be somewhat expensive. I built my own, but that is more in depth than needed for your question.

Hope this helps,

Andy

 

[DVerbarg]

Andy,

<font color=blue>Cutting the vapor barrior as was suggested will allow the moisture and heat to rise into the attic insulation. The moisture will condense inside the insulation making it wet. This wet insulation will not insulate very well and will lead to rotting any wood in contact with it.</font color=blue>

This was my belief also until my friend talked to a couple contractors and followed their recommendation. Yes, for awhile the wood was a little wet in his attic space but dried out within a couple weeks. He has checked the attic since looking for signs of moisture and has not found signs of abnormal moisture.

When my new house was built the insulation contractor would not use the stabilized cellulose if an internal vapor barrier was being used. Had a couple long talks with him about it and after looking at past jobs he has done, considering his reputation for re-doing others work which had moisture problems on windows and inside walls, and his credentials as a speaker to different trade conferences we went with his quote -- no internal vapor barrier. So far he has been right, moisture that gets into a wall can get out, letting the wall dry (we had a roof leak due to a piece of missed flashing /w3tcompact/icons/frown.gif).

It seems that the type of insulation, quality of the application (plugging of cracks and crevices) and type of exterior sheeting used make a big difference in determining whether a vapor barrier is a benefit or liability.

 

[Joe_W]

One thing which will work, is to install clear plastic sheeting on the inside of the windows. It is held in place by double sided tape, then you heat the plastic with a hair dryer to shrink the plastic and make it a tight fit. Then you trim away the excess plastic around the window. This will form a 1-2" gap between the plastic and your window, which will eliminate the thermal difference. When properly installed, you can't even tell it's there. Only downside is you will want to take it off in the spring so you can open the windows. It's not very expensive, as we can do all our windows for less than $15. The only brand that I have found to work well is 3M.
Joe W.

 

[Lane]

Andy,

I'd be very interested in the details of construction of your heat exchanger and it's capacity / performance.

 

[beenthere]

Very well said, Andy, and you obviously know what is happening with moisture in a house.