condensation

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Old 12-19-04, 01:30 AM
jayna
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condensation

I had some new windows installed a few months ago. Since the weather has gotten cold, I've been getting condensation (about 2 inches) across he upper and lower sashes. My window guy says the humidity level in my house is too high. However, my new bathroom windows do not seem to have the problem, and I have no ventilation in my bathroom. Another contractor told me it sounds like I don't have low-e, but I was supposed to get low-e and agron on all the windows. Everyone I've asked with newer windows does not have a condensation problem. So I'm not sure if I should pursue the problem with my window guy or just accept this problem as normal with new windows.

Thanks, Jayna
 
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Old 12-19-04, 08:27 AM
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IHI
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While I cant explain the bathroom window occurance which is very odd imo, condensation on the interior is a reflection of inside humidity which can come from many sources from kitchen, bathroom use, number of people in the home, washing machine, dishwasher, if there's a humidity controller on the furnace turn it down, kids/people draggin snow in from the outside, etc...
 
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Old 12-19-04, 08:31 AM
Sawdustguy
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I have a home that I just had built 3 months ago. I just had the humidifier installed 4 days ago. I have it set at 30% and I still get a few inches around some windows, "Horizontally" and not others. They also put what is called "Auto-Trac" on it which gauges the amount of humidity outside.

The quality of the windows they gave me wern't the greatest, because the builder has to make their millions.
 
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Old 12-19-04, 06:26 PM
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Humidity and condensation

Hi Jayna,

I have a couple of thoughts...

Which windows are showing the effects of excess humidity?
You mention that the bathroom is not doing so and yet you have no exhaust in there? Very odd. Like IHI said, I have no idea why that would be so.

Also like IHI said, virtually everything we do in a house produces moisture and in a modern "tight" house, that moisture really has no where to go.
In the "old days" houses leaked quite badly and in the winter the dryer outside aire constantly replaced the inner moist air and we did have less moisture problems than we do today. Of course it was also common for old single pane windows to have a thick layer of ice on the inside even when it was lower humidity in the house than we normally have today.

You mention that you have a humidifier installed and set at 30% RH. In a tight house, your RH can easily exceed that level in just normal day-to-day activities. IMO, there is almost never a need for a humidifier in a modern house. The actual issue is removing excess moisture from the air, not adding to it.

Most people really don't understand relative humidity and what it means, so I am going to add a bit about what it is and how it might be affecting your windows....hopefully, this won't be too tedious to read!

Relative humidity is the ratio of the amount of water vapor actually in the air compared to the maximum amount of water vapor the air can hold at that particular temperature (and pressure).
In other terms, it is the ratio of the air's water vapor content to its water vapor capacity at a particular temperature.

Relative humidity is given as a percent.
So, air with a 50% relative humidity actually contains one-half the amount of water vapor that it could hold at that temperature.
Air with 25% relative humidity contains one quarter of the amount of water vapor it could hold.
Air with 100% relative humidity is said to be saturated because it is filled to capacity with vapor.
Increasing or decreasing the amount of water vapor in the air will cause the relative humidity to go up or down as a consequence.

Dew point temperature is the temperature the air must be cooled to for saturation (or dew) to occur.
In a nutshell, the surface temperature of your windows is below the dew point or saturation capacity of the air in your home. When water vapor in the air comes into contact with a surface whose temperature is lower than the dew point, the water vapor will condense and moisture is the result.

The difference between air temperature and dew point can indicate whether the relative humidity is low or high, for example when the air temperature and dew point are far apart, the relative humidity is low; when they are close to the same value, the relative humidity is high. When the air temperature and dew point are equal, the relative humidity is 100%. ..makes sense?

And, with all that said, you can have a low Relative Humidity in your home and still have problems if the air temperature at the edges of your windows drop below the dew point of that particular RH. But, as the RH goes down, that does become less likely.

There is a standard measurement of the ability of a window's resistance to condensation. It is called CRF, which means Condensation Resistance Factor. Without going into formulas and all, windows are tested to condensation resistance with an internal air temperature of 70F and an external air temperature of 0F.
A number from 30 to 80 is then assigned to the window, with the higher the number the greater the ability to avoid condensation. Some manufacturers include this number on their NFRC labels and some do not.
A CFR rating of 35 is generally considered to be the minimum acceptable rating.

All this stuff isn’t really getting to the root of the problem, which is, how to control the moisture on the surface of your windows.
You can lower your indoor relative humidity by raising the indoor air temperature, but that really won't help much if the cool air at the edges of your windows drop the temperature below dew point. You really can raise your indoor air temperature enough to actually warm the window and raise the dew point, but it usually isn't practical or comfortable to do so.
A second option is to warm the surface of the glass to a temperature above the dew point…which is what people hope for with new windows in the first place.
ALL windows will “sweat” if the indoor air has enough moisture and the window glass is cool enough – which is subject to the outdoor temperature and the make up and quality of the window.

I am curious who is the window manufacturer, please?

Many windows today are built using IGU's (Insulating Glass Units, dual or triple pane) incorporating what are called Warm Edge Technology spacers. The spacer is the "thing" holding the glass apart in the IGU.

But, many IGU's are also built using aluminum spacer bars, which are not particularly good at stopping heat transfer along the edges of the window.
Even with LowE and argon fill, the edges of the window could be cold enough to make it very difficult to avoid dew around the edges, if the IGU's were built using other than a warm edge spacer system, and when it is cold enough outside.

On the bright side, this problem could be seasonal, meaning that as your home "settles" into winter it could go away on its own. It is not uncommon for windows to sweat a little in the change of the season from summer to winter and then this problem will correct itself as the air inside your home becomes drier as winter sets in.

But, it is also possible (unfortunately) that it could get worse as the air outside gets colder and subsequently your window surface temperature drops even lower below the dew point.

One other possibility is that when the affected windows were installed, the installers did a really lousy job of insulating around the units. This actually makes some sense when thinking about your bathroom windows not having problems. Please, which windows are affected? Which rooms...if all windows in a room are affected, or only some of them.
 
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Old 12-20-04, 08:42 AM
jayna
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Thanks for your detailed response. Most of what you said makes sense. My window guy basically said that the windows are so tight that the moisture cannot escape. What was perplexing me was that no one I know with new windows has this problem, and the bathroom window does not seem to have the problem. My dining room windows, on the opposite side of the house, get a little condensation, but not to the extent that the bedroom windows do. The bedroom windows (which are in the colder part of the house) get a lot of condensation overnight. I wipe them down in the morning and they usually stay dry all day. Yesterday was particularly cold, and the north and east windows developed condensation during the day, but the south windows stayed dry, so your explanation makes sense, in that the cold outside was causing the windows to be colder than the room itself. The south facing windows were actually warm due to the sunshine. My thought was that the low-e and argon would prevent the inside window surface from being so cold, so I was worried that they installed windows without the low-e and argon. The window brand was Kensington. What sold me on them was that they have insulation in the frames. Iím obviously no expert and was relying a lot on the salesman.

Jayna
 
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