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jroach6346 11-11-2005 05:46 AM

The windows on our 13 year old house are metal double pane. Each time it gets cold we get condensation inside which caused rotting on some of the window sills. I have replaced the rotted window sills with marble. The problem is that there is nothing that stops the cold air from the outside to the inside. The window is metal against metal. Shouldn't there be something that seperates the metal frame around the glass from the metal fame it sets in? We get ice build up on the inside during the winter in cental Oklahoma where it does not get severly cold. Is there a fix for this problem without replacing the complete window and frame? I have thought of adding some inexpensive storm windows.

2pyrs 11-11-2005 09:50 PM

Make and model of windows?
Are windows cloudy?
How long has it been doing this?
Do the windows rock back and forth in there tracks?
Are you sure it is from windows and not other areas around windows? Some window manufactures have repair parts if windows have not been let go to the point they are worn out.
By the time you spend money on storm windows that by the way are not air tight you could have bought a few replacement windows.
Have you contacted the manufacture?
Most windows have a felt strip that runs down each side and across the bottom of the window.
Cheap fix’s: Stick on weather strips like those used on doors. Place around seems inside facing you not in window casing. Shrink wrap for windows, but keep in mind it still can sweat between the plastic and glass.


jroach6346 11-12-2005 08:35 PM

Thanks for the info 2PYRS. Not sure what type window they are, other than metal framed. I am sure they are just builders grade windows. Looks like very narrow space between panes, maybe 1/4 inch or so. We have heard many of our neighbors with the same complaint. Windows don't rock and they have been like that since we bought the house new almost 14 years ago. I have had the glass replaced due to the windows being cloudy. Still feels like cold air coming in. Our Master Bath got as low as 52 degrees last winter. I have a portable heater that we now run all the time when cold weather arrives. I do have weather stripping all the way around the window. I did notice that when I replaced the window sills with marble that there was no insulation around the bottom of the window. I bought insulation and stuffed it in before I put the marble sill in place. I am not sure that there is insulation around the side of the windows. I do need to look and see if there is felt, as I don't remember seeing any. I actually think they are just very cheap windows.

Thanks again,


2pyrs 11-14-2005 08:02 AM

Years ago when they started to make double pain windows all they did was place two pieces of glass together with a small air gap in aluminum frame. One of the problems was it would expand and contract so much that it would end up leaking or even warp the frames. New units today are vacuum sealed or have a gas in them.
The windows I installed are gas filled and can not be fixed here they would have to come out and sent back to the factory for repair. It sounds like that may be your problem. If you simply had a pane placed over the other glass it well cause condensation and most likely the seal has broke. Think of a plastic green house as the sun beats down on it and the air is cold outside warm inside it well cause condensation on the inside. I did mean to ask you where your heat is at in relation to the windows if your vents are under windows that can also cause problem. If you checked around the frames and there is insulation (not spray foam) inside. I would be looking for leaks around trim around the windows outside. You should have a drip strip above each window if your windows do not have built in edges that siding fits in. The amount of air you say you having in your bathroom has to be air leaking from around the window. I take a candle and move it slow around the window frame and seams ( best if it is a windy day)looking for it to flicker this tells me if there are air leaks.
May I suggest Econo heat panel they are great for the bath room and very safe, just plug it in and forget it, I run my whole house on them.
Sorry I wish I could be more help but in the end you may have to replace your windows. 2pyrs

jroach6346 11-15-2005 07:53 PM

Didn't think of lighting a candle to check for leakage around windows. Good idea. I beleive you are right in that there is no type of gas between our window panes. About half of all windows in the house have fogged over a little. I think will just have to replace all the panes or check into new windows altogether which gets real expensive. Thanks for your advice also on the Econo-Heat panels. I just checked their website. Thanks again.

Oberon 11-24-2005 07:24 AM

good morning all,

This is my first post in this forum...and it will be a long one.

By way of introduction, the following post was actually in reply to several emails that I received from folks at another site. Since condensation issues are the most common window complaint this time of year, I posted this thing on the website as well.

It is long, and while it doesn't directly address the specific question, it does address some basic window condensation concepts...

So, here goes! :D

The reason why there is condensation on the interior of your windows has a really simple explanation – the surface temperature of the window is below the dew point temperature of the air in your home - that’s it - a very simple explanation.

Unfortunately, the reason for the window surface temperature being below the dew point temperature is somewhat more complex, and it can be very difficult to correct, but I am going to offer a few thoughts and even throw in a few numbers that I hope might be of some help in your situation.

In the summer, when you pull something cold and refreshing out of the refrigerator, and the air is warm and humid, that cold and refreshing beverage container suddenly and quite magically becomes instantly wet – just as soon as it is exposed to the air. What has happened is that the temperature of the container fresh from the refrigerator is below the dew point temperature of the air – which has caused condensation on the outside of that container.

What happens to your windows in the fall and winter is that the surface of the glass is below the dew point temperature of the air in your home – which is causing condensation on the surface of that glass.

Dew point is defined as saturation vapor density...or put in simpler terms, when the air reaches 100% relative humidity and can hold no more moisture.

Relative humidity is, well, relative.

Relative humidity is a comparison of the actual vapor density versus the saturation vapor density at a particular temperature. Basically, dew point is 100% relative humidity or the point where the air - at that temperature - is no longer able to hold any more moisture. If the air has reached vapor saturation (100% relative humidity), then the air will release it on the outside of that cold beverage container in the summer time, or be it on the interior glass surface of your windows in the winter time, it makes no difference. If the surface temperature happens to be below freezing, then that moisture becomes frost or even ice.

In order to stop condensation from forming on the surface of a window, you either have to lower the dew point temperature of the air in your home to a level below the dew point temperature of the window surface, or you have to warm up the window surface to a temperature above the dew point temperature of your home, or a combination of both.

Lowering the relative humidity of the air in your home MAY have absolutely no effect on controlling window condensation…and I bet that that statement is a bit of a surprise to some folks…it is true however.

There are two ways to lower relative humidity – increase air temperature or decrease moisture content. If you increase the air temperature you will lower the relative humidity but you will not change the dew point - which is based on the amount of water vapor in the air and is not based on the temperature of the air.

The amount of moisture in the air is measured in grams per cubic meter, which is kind of nice for our metric folks but not so nice for our non-metric folks; but the metric version is much easier on the calculator than the English version. However, in the interest of making this stuff easier to understand for all of us non-metric types, I am going to use Fahrenheit rather than Celsius temperatures in the calculations.

Okay – consider your home at 65 degrees F and with a relative humidity reading of 40%. There are 6.25 grams of water in a cubic meter of air in your home in that particular scenario - which then equates to a dew point temperature of 38 degrees F. So at 38 degrees the air will be at 100% relative humidity or at saturation vapor density.

Now, if your neighbor keeps her house at 75 degrees, but she also has 6.25 grams of water per cubic meter in her air, then the relative humidity in her home is 29% - versus your 40%. But, and here’s the kicker, the dew point temperature in her home is still 38 degrees.

While the relative humidity in her home is much lower than is the relative humidity in yours; if the surface temperature of the windows in her home is 35 degrees she will have condensation on those windows…yet if the surface temperature of your windows is 40 degrees – only five degrees warmer – you will not have condensation on your windows.

So, while her handy humidity gauge reads (correctly) only 29% RH – she has a condensation problem.
While your handy humidity gauge reads (correctly) 40% RH – you don’t have a condensation problem…SWEET…well, for you anyway, not her.

If your home hygrometer measures the relative humidity in your home at 60% while the temperature of your home is 70 degrees, you will have a dew point temperature of about 51 degrees – meaning that if the temperature of the window surface is below 51 degrees then you will have condensation - so now we talk a little more specifically about windows.

The interior surface temperature of a single lite of glass, when the temperature outside is 0 degrees F and the inside air temperature is 70 degrees, will be about 16 degrees.

Add a storm window on the outside and the surface temperature of the inside lite jumps up to about 43 degrees – a huge improvement.

But these are center-of-glass readings and not the temperature readings at the edge of the window where condensation usually forms. A typical clear glass dual pane window is going to have center-of-glass temperature reading pretty much the same as a single pane with a storm – something that is often claimed (correctly) by folks who advocate refurbishing windows rather than replacing (something that I am not going into here – I am NOT advocating either replacement or restoration in this post. It is long enough and detailed enough already without opening that particular can-of-worms!)…

However, if that dual pane has a LowE coating and an argon gas infill then the center-of-glass temperature will be about 57 degrees – a 14 degree improvement over a clear glass dual pane or a single pane with storm window – but again, and more importantly, there will be a comparable edge of glass improvement as well, particularly if the IGU (Insulating Glass Unit) was manufactured using a warm edge spacer system. Also, the dual pane is going to have desiccant between the glass layers. Desiccant absorbs moisture keeping the inside of the dual pane system very dry.

The advantage? If it gets cold enough outside, the temperature in the airspace between the lites can get very low. By keeping that space dry, it helps to keep the dew point temperature very low as well; something not always possible when using a single pane and storm window.

Although a single pane with a good and tight storm window can help the interior lite to avoid condensation (when compared with a single lite and no storm), the storm window itself will frost up when the temperature is low enough – at a temperature usually well above the temperature that will cause the dual pane to ice up. It is unavoidable given the right circumstances

So what does a window temperature of 57 degrees mean? Well, as I mentioned earlier a home kept at 70 degrees with a 60% relative humidity has a dew point temperature of 51 degrees so it is unlikely that there will be condensation problem on those particular windows despite the relatively high relative humidity in the home.

But what happens to the dew point if you keep your home at 70 degrees and you have a 65% relative humidity? Well, for one thing the dew point has jumped up to 57 degrees which we have already noted is the same as the window temperature. For another thing, anyone with 65% relative humidity in a home at 70 degrees has way too much moisture in their air and they are in serious need of some sort of ventilation system – or at least several good exhaust fans!

Somewhere back in this post I mentioned that lowering the relative humidity in your home may not help control condensation…that is still true…IF the relative humidity is lowered because of an increase in temperature. But, lowering the relative humidity by removing water is a different story because in that case you will also be lowering the dew point as you lower the relative humidity and that WILL help to control condensation on your windows.

Okay, there is much more to cover in this area, but I am going to stop now because this thing is long, even for me, and I am hoping that some folks have made it this far and have questions or comments - because that is the fun part of a post like this one!

Have a great day all!

jroach6346 11-29-2005 12:55 PM

Window Condensation
WOW! That was a lot to comprehend. Thanks Oberon, I think I will move to a warmer climate and call the problem fixed.

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