Condensation Question

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jonandabby
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Joined: Mon Jun 27, 2005 8:04 am

Condensation Question

#1 Post by jonandabby » Mon Jun 27, 2005 8:05 am

Last summer I replace all the windows in my house with Certainteed Bryn Mawr II windows. This morning I woke up (in the VERY sticky Northeast US) and found that some of them had condensation on the outside window. There was no moisture in the inside. Given that some did not have condensation and some did, I thought there might be a problem. Any thoughts?

researcher
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#2 Post by researcher » Mon Jun 27, 2005 3:56 pm

This morning I woke up (in the VERY sticky Northeast US) and found the same thing. Only some windows had it because of how they were exposed to the atmosphere. The one's that were more sheltered did not have it. If anybody here can explain how this happens, I would appreciate it. The temperature in the house was 74 and the temperature outside was 74 or 75. So how can condensation form on glass that is almost the same temperature? Can dew point go to nearly 100%?

Window4U (IL)
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Location: Sales and Installation in Chicagoland and Central Illinois

#3 Post by Window4U (IL) » Mon Jun 27, 2005 4:37 pm

Dew points in the low 80's all the way up to 90 are possible with the right conditions. (Dew points are a Fahrenheit degree measurement, not a percentage like in humidity).
Unusually high humidity and heat, aided by evaporation from soil, and water (from lakes, the ocean, standing water) and a stable layer of air aloft can prevent moist air in the lowest few thousand feet from mixing with drier air above, causing high dew points.
In other words, there is nothing wrong with your windows. Rather, you have witnessed a semi-rare meteorological phenomenon.
Last edited by Window4U (IL) on Mon Jun 27, 2005 5:04 pm, edited 1 time in total.

researcher
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#4 Post by researcher » Mon Jun 27, 2005 4:45 pm

Window4U, Thank you for your reply.

jonandabby
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#5 Post by jonandabby » Tue Jun 28, 2005 7:09 am

My only follow-up question is why one window would have it, and another right next to it (same room, 6 inches away, that sort of thing) would not have it. Very odd.

Window4U (IL)
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Location: Sales and Installation in Chicagoland and Central Illinois

#6 Post by Window4U (IL) » Tue Jun 28, 2005 7:45 am

It is odd but dew is a natural exterior phenonomen and can be affected by such things as even slight air flow differences or a host of other factors.
I'm sitting here at 7:30a.m. in Illinois right now looking out my front windows which are made up of 9 awning windows stacked 3 across and 3 high. I have exterior condensation on the lower left one, and a little bit on the one next to it. The windows have the exact same glass, but those two have a big potted plant in front of them that was watered last night. That might have been the difference.
All I can say is to not let it worry you. It's just mother nature.

researcher
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#7 Post by researcher » Tue Jun 28, 2005 8:02 am

Hi jonandabby,

I would say maybe that the flow of air from your AC is hitting one window more than the other and making the glass cooler. If that is not the case, I have no idea why. Even if one window did not have Argon in to, to me should not make a difference if the inside air and the outside air are about the same temperature. Maybe Window4u or someone else could answer that. I would surely like to know.

Window4U (IL)
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Joined: Thu Oct 07, 2004 8:46 am
Location: Sales and Installation in Chicagoland and Central Illinois

#8 Post by Window4U (IL) » Tue Jun 28, 2005 8:41 am

Good thinking Researcher. I was only lookng at exterior causes.
I just noticed that the interior air vent for my AC is directly below the windows I have exterior condensation on. This would lower the glass temperature even on the outside which would make them condensation prone because of a high exterior dew point.
Good post.

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#9 Post by researcher » Tue Jun 28, 2005 10:31 am

I would like to say that in my case I had a window in a half-bath that has no AC outlet in it and condensation fomed on the outside and the air temperature in that room, I would was 74 or 75 and the air temperature outside was 74. This is why I wanted to understand dew-point better; in other words, what is happing if dew-point is at 100, is it aken to actualy spraying windows with water? I also know that the humidity on the inside was low, around 25% but do not know if that is conducive. I don't think it is, but who knows. So I still don't know for sure how condensation could form under these condections. A meterealagest surely would know.

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#10 Post by researcher » Wed Jun 29, 2005 9:36 am

I found this to be very helpful in understanding dew-point.

"Dew points indicate the amount moisture in the air. The higher the dew points, the higher the moisture content of the air at a given temperature. Dew point temperature is defined as the temperature to which the air would have to cool (at constant pressure and constant water vapor content) in order to reach saturation. A state of saturation exists when the air is holding the maximum amount of water vapor possible at the existing temperature and pressure.

When the dew point temperature and air temperature are equal, the air is said to be saturated. Dew point temperature is NEVER GREATER than the air temperature. Therefore, if the air cools, moisture must be removed from the air and this is accomplished through condensation. This process results in the formation of tiny water droplets that can lead to the development of fog, frost, clouds, or even precipitation."

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