# Condensation on Windows (PICS) - Advice Please



## Termite (Apr 13, 2008)

Pretty hard to stop with single pane glass, which it appears that you have.

It works just like a soda can on a humid day. The outdoor air would be the equivalent of the cold soda, your window is the can. When the warm humid air inside the house touches the cold glass, your air's moisture condenses on the inside. It is simple science and there's not much of anything that can be done about it.

This is a major reason that double pane windows with inert gases between them are now the industry standard.

I'd suggest keeping a good coat of paint on the interior side just to protect the wood from the water accumulation as best as possible.


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## creamaster (May 11, 2008)

I went through this as winter started this year and with brand new double pane low E Marvin windows. Even on these high standard windows we were getting condensation but because our indoor humidity was way too high. We had single pane with storm windows previously. There are a few things you can do to help this.

My home had humidity in the 60% region so by simply lowering our humidity the condensation on the windows jsut about went away. Some condensation is going to be normal if it gets really cold out. Ive researched normal indoor humidity levels and Marvin sent me info on it also and the a healthy range can be from 30 - 50 %. So you have some room to go down even further. Anything below 30% becomes unhealthy as certain viruses can proliferate. By lowering indoor humidity you then lower the dew point and may decrease your condensation.

You can also try using plastic shrink film that you can purchase in hardware stores that help to form an air barrier against the window kinda like a storm window works. this plastic will be mounted by double sided tape and a hair dryer can be used to shrink it tight.

To help achieve a lower humidity we also raised our indoor temperature from 66 to 68 deg F. Warmer air holds more moisture pur cubic foot than does colder air and this will help to lower your indoor humidity more. Plus it may raise the glass surface temperature therfore lowering the dew point.

But unfortunenatly for you like KCT stated double pane windows are the way to go these days. We made the switch and the difference is amazing. the house holds heat much better. With single pane glass there isnt much insulation there so the glass gets really cold and when the warm air touches it, blammo, condensation.


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## jogr (Jul 24, 2007)

Lower the indoor humidity and make sure there is nothing blocking air circulation around the windows (like curtains or blinds).


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## Ron6519 (Mar 28, 2007)

These look like older (Pella/Andersen) regular insulated glass. What sort of heat do you have? How close to the windows were the readings made? How cold outside is it there? I'm guessing low teens/ single digits.
Ron


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## cocobolo (Dec 16, 2008)

livinginthepark:
All the answers so far have the right idea.
It is hard to tell if you have single or double pane windows from your photos. But if you have only single pane, there is realistically nothing you can do. With properly installed double or triple pane windows, you should expect to eliminate - or at least seriously reduce - all that condensation.
It is simply a matter of the temperature on the outside of the glass compared to the inside of the glass.
If you have only single glazing, there will effectively be no difference in the glass temperature inside or out. Put your hand on the glass. Is it freezing cold? Do you get ice sometimes forming at the bottom of the window?
The best solution is to install a modern double or triple pane window.
I lived 5 years up in the Yukon Territory, and from experience I can tell you it is worth doing whatever you have to to improve the R rating of your windows. Your comfort level will go up, and your heating bill will go down.


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## livinginthepark (Nov 10, 2008)

Thanks for the responses. Here are some answers to some questions as well as some updated pictures. Since I posted a week ago it got relatively chilly (-5F) here in Minnesota and the frost on the inside of the windows got worse. Any additional suggestions would be great. Please review my answers to above listed questions:

Pane - These are double paned windows installed in 1990. Brand is Semco.
Temp - I raised the temp in the house a few degrees and it hasn't seemed to help much. I am now putting a fan on each window during the day to dry off and melt this condensation and rotating the fan between rooms. Quite annonying. 
Shrink - We put shrink on one window to see how it would work and there is about the same amount of frost forming on the inside as well. 
Heat Source - Gas furnace in basement
Temp/Humidity Reading - Taken about fifteen feet inside room and away from windows. 

Any additional reccoendations for this winter and/or work that I should look at completing this summer?


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## Ron6519 (Mar 28, 2007)

Storm Windows or new windows. That's the worst case of condensation I've ever seen.
I'd try an experiment and put a piece of plexiglass over the exterior of the worst window. Clean off all the frost and dry the window and see if the issue comes back. In another room, put a dehumidifier and clean and dry the window and see if the issue disappears and at what humidity level. You might need a hygrometer if the unit doesn't have actual humidity settings.
Ron


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## cocobolo (Dec 16, 2008)

Ron's suggestion would be worth a try. I am of the opinion that the seals on your windows have failed.
This would not be unusual on windows that are nearly two decades old! If you are able to follow Ron's suggestion, I would also say to add some 6 mil poly on the inside, tape it on just for the winter. It might not look great, but your windows are at the end of their useful life. And this would aid in getting you through the worst part of the year. You can buy some quite nice clear film made for the purpose. After application, you fan it with a hair dryer to make it nice and tight. What you are trying to do here is to create extra sealed air cavities, which will bump up your insulating values.


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## Termite (Apr 13, 2008)

Cocobolo is right, your windows are shot. I'd take a hard look at replacement of at least the worst ones as soon as possible. New sashes may be an option if the window frame isn't water damaged.


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## cocobolo (Dec 16, 2008)

OOOOHH!! Ain't that the truth! I wonder how old the house is? You may be just as well off, when time and funds permit, to replace everything to do with the windows. When the new ones are installed, the spray in foam will seal up every little nook and cranny leaving no place for air infiltration. I would think at this point, as kc says, the sooner the better.


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## Probender (Dec 13, 2008)

Many times condensation is caused by moisture in the wall cavities.
Two reasons for this. 
You have moisture in your crawl space or basement walls or you don't have enough ventilation in your attic, or a combination of both.
We put vapor barriers (usually clear plastic sheeting) under slabs to prevent moisture from causing condensation on the floors.
If your basement floor wasn't poured on a moisture barrier or if there is no moisture barrier on your crawl space then moisture is coming up your walls and collecting on your windows.
Inadequate ventilation in your attic just compounds the problem because it blocks the moistures escape through your attic.


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## deanled (Dec 13, 2010)

I too have Semco widows. I am a builder and built my own house 3 years ago. I installed lo-E casement windows, aluminum clad, pine interior. I also get ice on below zero days and condensation is present whenever it is below freezing. What I did on some windows is to remove the screen, wrap plastic around it, and replace the screen. This acts as a storm window on the inside creating annother air space. I don't know if factory made storms are available, But I am going to build my own with wood frames and glass to see if that stops the moisture build-up. I tried running a dehummidifier and got the hummidity down to 38 %. and the condensation didn't go away. My window aren't argon filled but windows I installed in my parent's house last year are, and they aren't having any problems. We both have hydronic heat and burn wood in fireplaces for heat. I don't know if it's bad windows or if I would have the same problem with any window manufacturer. Good Luck.


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## Giles (Jan 25, 2010)

Something you might consider is how much moisture does your family induce by taking showers and cooking? Make sure all exhaust fans are working properly. It is unbelieavable how much moisture can be generated --even breathing:laughing: but you can't do anything about that:thumbsup:


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## oatlord (Dec 20, 2009)

I know everyone says lower the humidity, but doesn't higher humidity during the winter help to make the house feel warmer as well as reducing static electricity? Isn't the problem more related with cold air infiltrating on the inside glass pane? Far from an expert here, it just seems that's more the logical problem than trying to get a bone dry house, assuming your windows aren't in need of replacing.


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## oberon (Apr 29, 2006)

oatlord said:


> I know everyone says lower the humidity, but doesn't higher humidity during the winter help to make the house feel warmer as well as reducing static electricity? Isn't the problem more related with cold air infiltrating on the inside glass pane? Far from an expert here, it just seems that's more the logical problem than trying to get a bone dry house, assuming your windows aren't in need of replacing.


Do your windows have a LowE coating? The LowE has a greater effect on performance than does the argon fill. 

Keep in mind that there is a direct relationship between the indoor humidity level (moisture content) and glass temperature and condensation. 

I have posted this before, but here is my take on window condensation. 

In the interests of confusing the discussion a little, I am going to add my own two cents to the thread. 

Dew point is defined as saturation vapor density or 100% relative humidity.

Dew point is the transition temperature between evaporation and condensation. Despite popular usage it is not “the amount of moisture that the air can hold at a given temperature”. 

Warm air does not “hold” more moisture than cold air – that is a myth. However, it is not really a bad myth because it does help to explain the concept RH relatively easy to follow…. even if it isn't technically correct.

Condensation occurs on windows because the temperature of the glass is below the dew point temperature of the air resulting in moisture on the glass surface – it occurs on (or in some cases in) everything else for exactly the same reason.

Condensation may occur on the interior or exterior surfaces of the window or between the lites of a dual pane window if you have seal failure. Seal failure only affects condensation between the lites of an IG unit. If you have condensation that you can touch, it has nothing to do with seal failure. 

In order to stop condensation from forming on the surface of a window you have to: 

(a) lower the dew point temperature of the air to a level below the temperature of the window surface, or 

(b) you have to warm up the window surface to a temperature above the dew point temperature of the air, or 

(c) a combination of both. 

Because there are two ways to lower relative humidity – either increase the air temperature or decrease the moisture content of the air – simply lowering the relative humidity of the air may have absolutely no effect on controlling interior surface condensation, or it may completely solve the problem.

How the relative humidity is lowered, and the affect that the "how" has on both the moisture level of the air and the resulting temperature of the glass, will determine whether or not a condensation problem can be controlled or eliminated. 

Because there are two ways to lower relative humidity – either increase the air temperature or decrease the moisture content of the air – simply lowering the relative humidity of the air may have absolutely no effect on controlling interior surface condensation, or it may completely solve the problem.

Increasing air temperature will lower relative humidity but it will not affect the dew point temperature – which is based on the amount of water vapor in the air and is not based on the temperature of the air. 

So while the RH is lower with higher air temperature, it may not effect condensation on window surfaces – unless the rise in air temperature also results in a corresponding rise in glass temperature to a level above the dew point. 

Lowering the amount of water vapor or moisture in the air will lower the dew point temperature and if the dew point temperature drops sufficiently – to below the surface temperature of the glass – then it will affect condensation formation on the surface of the glass. 

The amount of moisture in the air is most easily measured in grams per cubic meter (versus fluid ounces per cubic foot), which is kind of nice for metric folks but not so nice for 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 for a couple of quick example calculations.

So consider a home at 65°F with a relative humidity reading of 40%. 

- In this scenario there are 6.25 grams of water in a cubic meter of air in the home which equates to a dew point temperature of 38°F. 

- 38°F is 100% relative humidity or saturation vapor density or the temperature where condensation occurs. 

- Consider a second home at 75°F but also with 6.25 g/m³ of water in the air. This second home has a relative humidity of 29% - versus 40% in the first home - but, and here’s the kicker, the dew point temperature hasn’t hanged. In the second home it is still 38°F. 

So, while the relative humidity in the second home is much lower than is the relative humidity in the first; if the surface temperature of the glass in either home is 35° or lower those windows are likely to have surface condensation regardless of the substantially lower RH reading in the second home. But if the glass surface temperature of the windows is 40° – only five degrees warmer – it becomes much less likely to find condensation on the windows. 

A very quick rule of thumb on window performance: 

Single Pane – R1 or U1
Single Pane and storm window – R2 or U.5

Dual Pane, clear glass – R2 or U.5
Dual Pane, LowE coated – R3 or U.33
Dual Pane, LowE coated, Argon fill – R-3.5 or U.29

Triple Pane or dual pane with storm, all clear glass – R3 or U.33
Triple Pane, one lite LowE coated – R4 or U.25
Triple Pane, two lites LowE coated – R5 or U.20
Triple Pane, two lites LowE coated, argon fill – R6 or U.17
Triple Pane, two lites LowE coated, krypton fill – R7 or U.14 
Keeping in mind that these are glass-only numbers that will vary depending on factors such as airspace width, type of LowE coating used, and other specific construction details. 

Whole window performance will vary even more depending on style (casement versus double hung for example), sash and frame material (wood versus vinyl versus fiberglass versus aluminum), etc etc etc


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## Thurman (Feb 9, 2009)

From the photos posted I would say these are double-panes windows. Photo's #3 and #4 clearly show the divider between the two panes of glass. From what I see the moisture is migrating between the actual wooden window frame and the double-glass panel. When weather permits I would check the integrity of the exterior window glazing for sure. This moisture will certainly lead to the degradation of the wood of these windows and fast. My first thought for a quick, easy, "cost-effective" fix would be to install either a storm window or to make some type of storm window (as previously mentioned) using a wooden frame and some 4 or 6 mil clear plastic. Stopping the cold air from actually getting to the window frame is the goal here. IF a temporary storm window works--then it would be worth the cost to have storm windows made to fit properly. Believe it or not, I had this type problem (but not this bad) way down here in S. GA. After installing storm windows I have no humidity forming on my single pane windows. Good Luck


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