Problem with too much window condensation

I have double pane, insulating glass house windows that collect condensation during the winter heating months. The condensation is not between the panes, it is inside the home. The water builds up and runs down onto the wood frame causing rot. It occurs only on the bottom inch or two of the window. The home is in Northern Wisconsin where it is commonly 20 deg F outside and 70 deg F inside. The interior humidity is controlled and not excessive. Aside from setting the interior humidity to desert-like conditions, how can I remove the moisture and prevent further damage to the frame? Desiccant bags? Solar powered fans? Any ideas would be greatly appreciated.

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110100101108 years ago
is it supposed to be a vacuum window ? maybe it lost vacuum
Colder air cannot hold as much water vapour as warmer air. When the cold glass cools off the air which comes into contact with it the water vapour condenses onto the cold glass surface.

There are only two ways to solve this problem: 1) Warm up the glass surface or the air that comes into contact with it. 2) Lower the humidity of the air that comes into contact with the glass.

Here are some suggestions: Leave window coverings open so the air trapped behind them does not cool so much and the warmer air in the room can circulate across the window surface. Let the exhaust fans run when you shower, bathe or cook and leave them running for a while afterward. Turn the heat up a bit in the house or room with the condensation problems. If the house is way too humid at times leave a window open a crack for a few minutes to vent out the excess dampness. Leave the furnace fan running more to circulate air around the house.

Don't waste any money buying new windows that are supposedly more efficient. I live in Canada and repair windows everyday. This kind of condensation is common and occurs on even the most efficient and expensive windows on very cold days if the humidity level of the air in the house is anything above bone dry.

One thing you should do to protect your windows is to refinish the wood with a marine grade wood finish or at least something intended to be used outside in the weather. Once you have done that use a clear (not silicone) caulk and put a bead down along the glass/wood line all around the sash and also at the corners where you can see in the picture above that the water is getting into the joint between the sash rails. The mildew you can remove with a diluted bleach mixture after sanding off the old finish.

Hope this info helps. If you try all these suggestions and still have trouble with condensation measure the humidity level in the house. It should not be more than:
Outside Temperature Inside Humidity
20º to 40ºF Not over 40%
10º to 20ºF Not over 35%
0º to 10ºF Not over 30%
-10º to 0ºF Not over 25%
-20º to –10ºF Not over 20%
-20ºF or below Not over 15%

If you can't get rid of the condensation and can't live with it in the cold days of winter you can consider installing a Heat Recovery Ventilator. They are expensive but can improve indoor air quality and help control excess humidity without having to keep the fans running all the time and letting out the heat.
chiok9 years ago
Used to have terrible trouble with this in some of the places I lived at uni. Mould around window sills and huge patches hiding behind the wardrobe. The simple thing to do is open a window and let the cool air wick away the condensation. I find condensation to be greatest in the morning on my bedroom window when I wake up, so I open my window first thing and close it in the afternoon (since I'm not in the room anyway, not a problem). Got so bad on occasions, had to squeegie the insides. Other way is a dehumidifier to dry out the air in the room. Either electric or you can buy these disposable ones that have a layer of silica crystals (like you get in the DO NOT EAT packets). I've found these to be very effective and last 2 or 3 months. The ones that use calcium carbonate crystals have been ultimately rubbish. But these are unfortunately patch solutions to the problem of a leaky window which the other guys pointers should sort out.
Big Bwana9 years ago
Or during the cooler months you could use that shrinking plastic window covering film, and with the added airspace between the glass and the film you shouldn't get any condensation.... And what shape is the weatherstripping around the widow opening like ? You can get removable (( peelable )) caulking or a closed cell foam tape to replace / improve the seal around the window... To prevent further damage, clean off the damage with cleaner / sandpaper, dry it and refinish the window frame, and you'd be better using an outdoor or marine type finish even though it's on the inside of the window, they still get huge temperature variations and lots of sunlight / UV exposure which outdoor finishes are better for....
Kiteman9 years ago
If there's no leak (see Caitlinsdad and kelseymh's posts), then all you need is a bit more air circulation. Lower the indoors temperature a little as well - 70F is 21oC, more than comfortable.

Cooling the temperature slightly will cut down the amount of water that evaporates, and save you significant amounts of money. It's far cheaper to put on a pullover than to heat the whole house.

Also, think about twhere the water might be evaporating from - is it cooking steam? (Put a lid on your pans) Is it from the heating system? (Get it checked - fumes should be vented outside).
kelseymh9 years ago
As caitlinsdad implied, there is probably a leak there where the window closes, allowing the cold air in. Run weather strip along the inside of the frame at the bottom (where the crank is) and up the sides about half way. If you want to confirm that there's a leak first, use talcum powder (I've used Dr. Scholl's foot powder). Just spray a little bit an inch or two above the bottom of the frame. If there's a draft, you'll see the powder drift upward rather than just floating.
caitlinsdad9 years ago
Is it there is a tiny draft or leak where the window closes? You may have to put your ear up close to listen or else pump some smoke in from the outside. You may need to replace the weatherstripping along the sides of the windows where it presses inside or add some. They look like fairly good windows and since they pivot out you may just have a problem with the seal at the bottom. Good luck.
If it isn't the window itself, there may be a leak around the glass pane where it has been mounted to the frame and not caulked properly. You can recaulk around the window glass. The cool air will cause your condensation.
NachoMahma9 years ago
. A small fan should do the trick. Something the size of a CPU fan may be big enough.