Hi All,
My wife and I just had our old windows of nearly 50 years replaced with Andersen Renewal windows. The windows have really made a deference in the comfort of our home but we are seeing condesation forming on the double hung windows in the bedrooms. On the bottom portion of the top window glass right above the seal where the two panels meet and on the bottom window glass between the pull handles there is roughly 1/2" - 3/4" of water droplets (not fog) and will not disapate. I wipe the glass in the morning and for the most part it will stay dry all day until the sun sets and then the moisture returns and water forms again. We live in northeast Ohio where the winters can be cold and the reason we chose these were because of the name, the way they were constructed and being custom made for our original replacement. I had the sales rep come out and see for himself and he told us that we have a moisture problem in the house. If this is so, then wouldn't the entire window have the water droplets form and why only in the bedrooms? I think Andersen forgot to do something with these windows like perhaps a seal or a window glass problem etc. I will admit that this is a small house and the shower is in the same area as the bedrooms but it is vented.
Could this really be a moisture problem or is it with our new windows?
Thanks - Denny
Condensation Issues
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windowmann2000
- Posts: 345
- Joined: Sun Feb 27, 2005 4:16 pm
What your describing sounds like a interior humidity problem. We've had a few calls this winter with the same problem. Typically at the meeting rail and the bottom of the bottom sash.
New windows will not let as much interior heated air escape and this warm moist air will form condensation normally at the areas you described. If you purchase a humidstat it will tell you what your relative humidity is inside your home and your window dealer should be able to provide you with a chart showing reccomended humidity levels.
If you have a ceiling fan in these areas running it will help and after that you need to determine where you'd like your humidity levels to be.
A little more humidity usually means more comfort, but also means a towel may be necessary now and then. It;s also possible after a few weeks it may go away as the stored up moisture from the summer and fall weakens.
New windows will not let as much interior heated air escape and this warm moist air will form condensation normally at the areas you described. If you purchase a humidstat it will tell you what your relative humidity is inside your home and your window dealer should be able to provide you with a chart showing reccomended humidity levels.
If you have a ceiling fan in these areas running it will help and after that you need to determine where you'd like your humidity levels to be.
A little more humidity usually means more comfort, but also means a towel may be necessary now and then. It;s also possible after a few weeks it may go away as the stored up moisture from the summer and fall weakens.
Thank you for the reply. This has been going on now for about two weeks but I'll keep an eye on this. I'm wondering if a de-humidifier would help? I do have a April-Air humidifier built onto the furnance, haven't used it yet and probably won't after reading your answer. I did get 2 casement windows and they don't seem to be getting anything near as much moisture as the bedrooms are. One of them was installed in the kitchen and after cooking the steam fogs the window but disappears quickly with no moisture.
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Windows on Washington
- Posts: 5343
- Joined: Fri Oct 27, 2006 11:23 am
- Location: DC Metropolitan Area-Maryland/Virginia/DC
Interior air humidity combined with a little cold air infiltration and edge of glass cold will probably cause the problem you are mentioning. The casements are inherently better sealing windows and there is little to no air coming in as compared to the double hungs. I would see if the problem lessens/disappears with time as the summer and fall humidity is exhausted. Humidity is also typically a little more concentrated around those areas where exposure is greater (ie shower/bathrooms and kitchens). If it is near the bathroom area that would make sense. Double check to make sure your exhaust fans are working properly and air out your home once or twice on a mild day to get some of that moist air moving.
Condensation On Renewal Windows
I'm going to throw a lot of statistics at you to address condensation on your windows. Keep in mind that these stats are based on a worst-case scenario of 0° outside and 70° inside, which sounds like it may apply to your climate but is not applicable to warmer, southern climates.
Now for some stats. If a window is clear double glazed insulating glass (doesn't matter if it's wood or vinyl), the center-of-glass roomside temperature would be about 44-45°F. (Incidentally, single pane windows with a storm window would be about the same) Adding a Low E coating to the glass bumps it up to about 52°F, and Low E insulating glass with Argon gas raises the glass temperature to 57-58°F. Not bad for 0° outside. Presumably your Renewal windows are Low E with argon gas.
However, with insulating glass the edge-of-glass temperatures are much lower than center-of-glass. The type of spacer that separates the panes of glass greatly affects the edge temperature, and much could be said about the merits of different types of spacers. Naturally, condensation, and even ice, would normally occur at the edge first, since that's the cold "weak spot." Clear IG with an aluminum box spacer has an edge temp of only about 29°F. Low E glass with an aluminum spacer only raises it to about 32°. Then there are "warm edge" spacers, which are warmer and provide more condensation resistance. Stainless steel spacers (That's what Andersen mainly uses) are about 37° edge temp on a Low E/argon unit, and presumably (don't have exact stats on this) Superspacer and TPS (neither are used by Andersen) would be at the top at 39-40°. Again, warm edge spacers typically range from 35-40°, but still tend to max out usually in the upper 30°s. So Andersen didn't as you worded it "forget to do something with these windows like perhaps a seal or a window glass problem;" it's normal for windows to be colder on the edge than they are in the center.
Now for the fun part. If you cover a Low E/Argon gas unit with some type of roomside window treatment such as a shade, blind, etc., the center-of-glass temperature drops from about 57° to only 36°. That's an amazing 21° drop. I don't have any exact stats on what that does to the edge temperature, but I would imagine it must drop 5-15° as well. The reason it drops is because the air in the room is no longer freely circulating against the glass. Even a couch or desk in front of a window will significantly reduce the glass temperature if the furniture is partially blocking part of the window.
Enough stats. Condensation, and worse yet, ice, can NOT occur unless two conditions are present at the same time: high humidity and cold temperatures. The cold temperatures on your windows could be due in part to missing or defective weatherstrip, poorly-fitting windows, faulty installation, or just because of cold winter weather. If you have cold weather but low humidity, condensation can not occur. Both conditions have to be there. If you're experiencing condensation on your windows, you have too much humidity given the current outside temperature with the existing glass system that is in the home (assuming that the windows are properly installed and not defective in some way). There are TWO basic solutions: raise the glass temperature or lower the humidity. That's it in a nutshell - those two things. More about those in a bit. First, I'd buy a digital hygrometer from Home Depot, Radioshack, a hardware store, etc. to measure the amount of humidity in the house (about $10-$29). You need to know that. Then I'd contact Andersen or visit a window company's website for recommended humidity levels for various outdoor temperatures. Most window manufacturers including Andersen have brochures on condensation and recommended humidity levels. Your April-Air unit probably has a chart with suggested humidity levels shown right on the humidistat control. They usually will state that when it's 0 degrees outside your humidity level inside should be in the 20-25% range.
RAISE THE GLASS TEMPERATURE - One possibility is to raise the window shades up when it's really cold out. As mentioned before that can increase the glass temperature by an additional 21° or more, but unfortunately that leads to a lack of privacy. A compromise is to open them just slightly, maybe 4" to 8", so that warm air can circulate against the bottom of the glass (the most condensation-prone area) and partially warm the glass unit. For old existing windows, the best solution is often to replace them with modern, energy-efficient windows. But you've already done that and it's evidently still not enough given your humidity levels. For those who replace their windows, it's ideal to replace them with windows that have warm-edge spacers, Low E coatings, and gas fillings in the units to hopefully avoid condensation. If someone really wanted to get the absolute maximum condensation-resistent windows out there, there are windows that are triple glazed that have a better performance than what you currently have, but most modern "energy-efficient" windows are made with double glazing and that's usually all that is needed. An advantage of many triple glazing systems is that one can have higher humidity levels in the home before condensation issues would arise. Other ways to raise the glass temperature include taking out roomside casement screens during the winter, using free standing fans or ceiling fans to better circulate air against the glass, and adding another layer of glass or plastic (I hate to see that though - it shouldn't be necessary).
LOWER THE HUMIDITY - I haven't seen any previous posts on reducing humidity, but if they exist could someone please post a link to that topic? One of the best solutions for an airtight home is to have an air-to-air heat exchange ventilator installed to the furnace. It's required by code for new homes in some areas. It brings in the DRY fresh air from the outside and exhausts the stale HUMID air - giving you healthy air to breathe and lowering the humidity to the desired level. New homes are built so much more airtight than older homes, so they often need mechanical help to get air exchanges. Older homes exchanged air by being drafty. Dehumidifiers will help too, but are generally not as effective, since they usually can't get the humidity low enough. Great for basements though. Simply turning down your April Air humidifier probably won't do it - that simply means the humidifier won't turn on, but it won't remove humidity like DEhumidifiers are designed to do. Other ways include running exhaust fans when showering (and leave them on for a while), or simply stop bathing
In summary, condensation on windows can and will occur under the proper conditions. Even ice can form if the humidity is high enough, the temperature is low enough, and other factors are in place such as restricted airflow to the glass because of window shades. You need a humidity-measuring device to see if your humidity is too high. You need a humidity guide (from Andersen in your case) to suggest proper humidity levels. And ultimately somebody has to address raising the glass temperature or lowering the humidity.
Now for some stats. If a window is clear double glazed insulating glass (doesn't matter if it's wood or vinyl), the center-of-glass roomside temperature would be about 44-45°F. (Incidentally, single pane windows with a storm window would be about the same) Adding a Low E coating to the glass bumps it up to about 52°F, and Low E insulating glass with Argon gas raises the glass temperature to 57-58°F. Not bad for 0° outside. Presumably your Renewal windows are Low E with argon gas.
However, with insulating glass the edge-of-glass temperatures are much lower than center-of-glass. The type of spacer that separates the panes of glass greatly affects the edge temperature, and much could be said about the merits of different types of spacers. Naturally, condensation, and even ice, would normally occur at the edge first, since that's the cold "weak spot." Clear IG with an aluminum box spacer has an edge temp of only about 29°F. Low E glass with an aluminum spacer only raises it to about 32°. Then there are "warm edge" spacers, which are warmer and provide more condensation resistance. Stainless steel spacers (That's what Andersen mainly uses) are about 37° edge temp on a Low E/argon unit, and presumably (don't have exact stats on this) Superspacer and TPS (neither are used by Andersen) would be at the top at 39-40°. Again, warm edge spacers typically range from 35-40°, but still tend to max out usually in the upper 30°s. So Andersen didn't as you worded it "forget to do something with these windows like perhaps a seal or a window glass problem;" it's normal for windows to be colder on the edge than they are in the center.
Now for the fun part. If you cover a Low E/Argon gas unit with some type of roomside window treatment such as a shade, blind, etc., the center-of-glass temperature drops from about 57° to only 36°. That's an amazing 21° drop. I don't have any exact stats on what that does to the edge temperature, but I would imagine it must drop 5-15° as well. The reason it drops is because the air in the room is no longer freely circulating against the glass. Even a couch or desk in front of a window will significantly reduce the glass temperature if the furniture is partially blocking part of the window.
Enough stats. Condensation, and worse yet, ice, can NOT occur unless two conditions are present at the same time: high humidity and cold temperatures. The cold temperatures on your windows could be due in part to missing or defective weatherstrip, poorly-fitting windows, faulty installation, or just because of cold winter weather. If you have cold weather but low humidity, condensation can not occur. Both conditions have to be there. If you're experiencing condensation on your windows, you have too much humidity given the current outside temperature with the existing glass system that is in the home (assuming that the windows are properly installed and not defective in some way). There are TWO basic solutions: raise the glass temperature or lower the humidity. That's it in a nutshell - those two things. More about those in a bit. First, I'd buy a digital hygrometer from Home Depot, Radioshack, a hardware store, etc. to measure the amount of humidity in the house (about $10-$29). You need to know that. Then I'd contact Andersen or visit a window company's website for recommended humidity levels for various outdoor temperatures. Most window manufacturers including Andersen have brochures on condensation and recommended humidity levels. Your April-Air unit probably has a chart with suggested humidity levels shown right on the humidistat control. They usually will state that when it's 0 degrees outside your humidity level inside should be in the 20-25% range.
RAISE THE GLASS TEMPERATURE - One possibility is to raise the window shades up when it's really cold out. As mentioned before that can increase the glass temperature by an additional 21° or more, but unfortunately that leads to a lack of privacy. A compromise is to open them just slightly, maybe 4" to 8", so that warm air can circulate against the bottom of the glass (the most condensation-prone area) and partially warm the glass unit. For old existing windows, the best solution is often to replace them with modern, energy-efficient windows. But you've already done that and it's evidently still not enough given your humidity levels. For those who replace their windows, it's ideal to replace them with windows that have warm-edge spacers, Low E coatings, and gas fillings in the units to hopefully avoid condensation. If someone really wanted to get the absolute maximum condensation-resistent windows out there, there are windows that are triple glazed that have a better performance than what you currently have, but most modern "energy-efficient" windows are made with double glazing and that's usually all that is needed. An advantage of many triple glazing systems is that one can have higher humidity levels in the home before condensation issues would arise. Other ways to raise the glass temperature include taking out roomside casement screens during the winter, using free standing fans or ceiling fans to better circulate air against the glass, and adding another layer of glass or plastic (I hate to see that though - it shouldn't be necessary).
LOWER THE HUMIDITY - I haven't seen any previous posts on reducing humidity, but if they exist could someone please post a link to that topic? One of the best solutions for an airtight home is to have an air-to-air heat exchange ventilator installed to the furnace. It's required by code for new homes in some areas. It brings in the DRY fresh air from the outside and exhausts the stale HUMID air - giving you healthy air to breathe and lowering the humidity to the desired level. New homes are built so much more airtight than older homes, so they often need mechanical help to get air exchanges. Older homes exchanged air by being drafty. Dehumidifiers will help too, but are generally not as effective, since they usually can't get the humidity low enough. Great for basements though. Simply turning down your April Air humidifier probably won't do it - that simply means the humidifier won't turn on, but it won't remove humidity like DEhumidifiers are designed to do. Other ways include running exhaust fans when showering (and leave them on for a while), or simply stop bathing
In summary, condensation on windows can and will occur under the proper conditions. Even ice can form if the humidity is high enough, the temperature is low enough, and other factors are in place such as restricted airflow to the glass because of window shades. You need a humidity-measuring device to see if your humidity is too high. You need a humidity guide (from Andersen in your case) to suggest proper humidity levels. And ultimately somebody has to address raising the glass temperature or lowering the humidity.
wow--thanks for the info.
i have steam heat and fish tanks, so th RH in my home is always high. i just installed new windows and in some parts of the house i get it, and it is where the fish tank is or near where the steam vent is. great stuff. i didn't go for the top of the line windows, so i know they aren't the best, but better than the 100 year old ones we had. i did the install myself so i'm sure they aren't perfect. thanks again for taking all that time to answer--very informative!!!!
i have steam heat and fish tanks, so th RH in my home is always high. i just installed new windows and in some parts of the house i get it, and it is where the fish tank is or near where the steam vent is. great stuff. i didn't go for the top of the line windows, so i know they aren't the best, but better than the 100 year old ones we had. i did the install myself so i'm sure they aren't perfect. thanks again for taking all that time to answer--very informative!!!!
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window dan
- Posts: 12
- Joined: Mon Aug 28, 2006 9:52 pm
1) Did you insulate around the gaps of the replacements?
2) Did you caulk the windows to the stops?
3) When you look down at the interlocks (where the top a bottom sash meet together) do you see daylight in the corners where they meet together? If you do you did not shim properly.
4) Did you lay a bed of insulation at the bottom of the old windows and set the replacements on top of it?
5) Did you insulate the weight pockets?
Just some things to think about to cure the problems you describe to us.
Good luck
Dan
2) Did you caulk the windows to the stops?
3) When you look down at the interlocks (where the top a bottom sash meet together) do you see daylight in the corners where they meet together? If you do you did not shim properly.
4) Did you lay a bed of insulation at the bottom of the old windows and set the replacements on top of it?
5) Did you insulate the weight pockets?
Just some things to think about to cure the problems you describe to us.
Good luck
Dan
There is one thing that a lot of people , even the experts, miss on condensation on windows. The area on a double hung window at the meeting rail and also at the bottom lift rail act as shelves for cooler air to settle. This cooler area doesn't get the air flow and is a natural cool spot which can cause condensation to form. If the meeting rail weatherstripping was loose there would be air flow and condensation would have a harder time appearing.
My 2 cents!
My 2 cents!
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Stephen Thwaites
- Posts: 23
- Joined: Wed Feb 08, 2006 10:35 am
- Location: Ottawa, Ontario, Canada
On Double Hung meeting rail condensation:
It is certainly true that the 'shelf effect' results in lower air velocity where glass meets sash, encouraging condensation to form. We see this 'shelf effect' when recessed triple glazed windows get condensation before double glazed doors.
But, it is also true that condensation forms at the meeting rail because the bottom rail of the upper sash (upper meeting rail) is cold not just on its outside face but also on its bottom edge; kind of like a skylight.
By my way of thinking, it is normal for double hungs to show condensation on the bottom of the upper sash before elsewhere; this certainly seems to be the case on mine.
It is certainly true that the 'shelf effect' results in lower air velocity where glass meets sash, encouraging condensation to form. We see this 'shelf effect' when recessed triple glazed windows get condensation before double glazed doors.
But, it is also true that condensation forms at the meeting rail because the bottom rail of the upper sash (upper meeting rail) is cold not just on its outside face but also on its bottom edge; kind of like a skylight.
By my way of thinking, it is normal for double hungs to show condensation on the bottom of the upper sash before elsewhere; this certainly seems to be the case on mine.
Re:
Humid in the house can cause molds and mildews. It is good that you have noticed it earlier. I guess you need to install devices to get rid of those humid. Maybe the new windows are the problem, so have it check at once. Ceiling Fans