window condensation

Cold northern climate.
Although we havent yet turned on our heat (probably today), as the weather cools we're waking to find the interior of our windows are really wet with condensation. They're partly fixed pane and partly sliders. A fairly cheaply built 20 year old house. Placing pastic over the outside is ugly and hides the exterior. Would caulking the exterior where the glass meets the frame do it - although this looks pretty tight & I dont see openings. What about pulling the interior casing off and squirting expandable foam in there? What is the source? We cant afford to replace them so what can we do?
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Given the age and "fairly cheaply built", I'd not expect much in the way of r-value from the windows. Storms would help.
You can also find insulated, sealing curtains to close off the window from the inside.
What is the relative humidity inside? Temperatures?
Consider "chimney effect" to be important, too, but not so much so for your immediate problem. Meaning unwanted air leaks near min and max elevation of house, which could be transporting relatively warm humid air (low density) OUT the upstairs leaks. You won't sense cold air coming in there.
An infrared survey could really help find the facts.
HTH, J
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If this is in your bedroom - it is just your breath condensing. May want to look into a dehumidifier.
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frankg wrote:

First I suggest that they will likely dry out when you turn on the heat. Heating will start drying out the inside of your home, it may take a while.
Your calking will not help, although if it were leaking air it would make the room more comfortable and less expensive to heat.
Pulling off the casing and adding insulation will make the room more comfortable and reduce heating bills, but not reduce condensation.
You may want to start checking for sources of moisture inside the home. Do you have an un-vented or improperly vented dryer? Do you have vents in the bathrooms or at least open the windows after a shower? Any source of moisture inside the home will increase the problem.
It would be best to get a humidistat and see what the humidity is inside your home. 40-60 is nice, but you may need to drop to something like 30 to reduce the condensation without reducing your comfort in your home.
The problem is the inside of the glass is below the dew point of the air inside the home. You need to warm the glass or reduce the moisture inside the home. You can warm the glass with thermo pane glass or storm windows outside.
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Thanks for this info.
I will check the bathroom and dryer vents. Although i notice these wet window interiors early in the morning before anyone has shwered or switched on a dryer.
'>leaking air it would make the room more comfortable and less expensive to heat' Can you suggest an efficient way to check for leaking air without taking off all the window casings, or an expensive procedure like thermal/infra red photography? Holding my hand around the windows doesnt do it.
The fixed pane portions of the windows are double-glazed - is this what you refer to as 'thermo pane' ?

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frankg wrote:

It is the morning when you are most likely to see it since the windows will be the coldest.

Cigarette smoke on a windy day should do it.

If they are two panes sealed into a single unit. If the moisture is forming between the two panes (inside the window) then the seal is bad and the window will need to be replaced to correct the problem.

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Joseph Meehan wrote:

All good advice, but if the OP heats with natural gas, that's one of the major sources of moisture inside the home. Another major source are the home's occupants - bodies give off a lot of water vapor in respiration. Then there's cooking, showers, and houseplants. So, realistically, even if you locate and deal with other moisture sources in the home, you still have a considerable amount of moisture being generated on an ongoing basis.

Which may turn out to be either be unachievable or uncomfortable.

And even then, there'll be condensation issues when there's a substantial temperature differential between the outside and inside. Considering the R-value of even insulated glass is so far below that of surrounding walls, of course windows will get colder first, and moisture will condense on them first. It's one of the reasons why forced-air furnace ducts are typically located in outside walls near the windows, so the warm air helps warm the window.
Turning up the thermostat, since warmer air holds more moisture, helps too, but of course most of us won't want to spend that kind of money this winter. Applying the interior window film can help, too - when it's moderately cold, the additional R-value will reduce the condensation quite a bit, and in very cold weather it'll condense on the plastic film, instead of on the panes and wood frame.
Another option is having a heat recovery ventilator installed. It will exchange moist interior air for dryer exterior air while recapturing most of the warmth of the indoor air. They're a bit spendy to install but make homes considerably more comfortable in the winter months.
HellT
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Andersen says all this amounts to about 2 gallons per day of water.

Try numbers. That's not enough to cause condensation problems, except in extremely airtight houses.

That helps by warming the indoor glass surface.

Useless, in all but extremely airtight houses, IMO. An small exhaust fan with a humidistat can do the same job on a warm still day.
Nick
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Hell Toupee wrote:

Not when properly vented. If a gas furnace is a major source of moisture then he a much larger problem than wet windows. He also noted he had not started using heat yet.

Certainly can. However you would want to take a look at some of the more common sources.

Most people are OK at 30%, but it is there that most people start having problems. I agree that 30 is the low end of the comfort range and some people will be more comfortable higher. I try to keep mine at 35-40 depending on the outside temperature. My humidifier monitors the outside temp and adjust accordingly. It does a good job.

It does have an effect, but in reality it is really due to raising the temperature of the glass.

True.

This could help in some climates and some homes, but I suspect that the OP's home is not tight enough to benefit. Once the heating season kicks in I would guess his humidity is going to drop below 30% anyway. OP note: when it gets that cold the glass will be that much colder so it will still cause problems.

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