Sounds like your windows are not Argon or Krypton filled. I had a customer with the same problem. Their windows were only 3 yrs old and they had a problem with them since they built the house. The contractor put in double pane windows but they were not Argon filled or Low E. Once I put in the new windows with Low E and Argon they had no condensation on there windows. Sometimes its the house, sometimes its the windows.

Please , I have same problem! More answers from anyone knowing how this happens!

Hi Tia, I believe I can help.

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. You didn't mention if your windows are Low E; hopefully they have and that they have the argon gas as well.

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 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 are about 37° edge temp on a Low E/argon unit, and Superspacer and TPS spacers would be at the top at about 39°. Again, warm edge spacers typically range from 35-39°, but still tend to max out usually in the upper 30°s. So 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 (or door) will significantly reduce the glass temperature if the furniture is partially blocking part of the window. You mentioned the condensation you're experiencing tends to lessen or dry up by noon. That's classic. Cold/condensation caused (in part) by the shades being down at night, condensation showing when you finally open the shades in the morning, but drying up or reduced by mid-day because the windows now have circulation against them.

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 in the house, 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 the manufacturer if possible or visit a window company's website for recommended humidity levels for various outdoor temperatures. Most window manufacturers have brochures on condensation and recommended humidity levels. They usually will state that when it's 0 degrees outside your humidity level inside should be in the 20-25% range. I'm guessing your humidity level is higher than that. New homes are more airtight, and because they are not as drafty as older homes, the humidity is somewhat trapped in the home instead of exchanging with the dry air outside. Also, new homes have more humidity because they are new - the floors, walls, lumber, etc. have a higher moisture content and will take several years to dry out if it has a way of escaping.

RAISE THE GLASS TEMPERATURE - One possibility is to raise any 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 have newer windows 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-resistant 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. Some even have between-glass shades to avoid temperature drops when closed for privacy. 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 - 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 to suggest proper humidity levels. And ultimately somebody has to address raising the glass temperature or lowering the humidity.

Tru_blue,

You're awesome. Thank you so much.

I saw the contractor install the windows. They insulated them all around. I believe the inspector didn't see anything wrong with the windows. I guess the house may be tight for a while.

Since you are so knowledgeable about this, can you recommend an air to air heat exchanger? I guess in the long run it make be cost/health efficient to do so.

The irony is that when we moved in the humidifier was running. This year it never kicked on. I'll check the humidity. I'm concerned that if the humidity is too high all the time, things may start smelling musty in the future. You never can get that smell out. The house is approx 2500 sqft with most of the sqft (2000) on the first floor. I don't know if that makes a difference what type of air exchanger I'll need.
Thanks ;)

The air to air heat exchanger question would be best answered by a heating and air conditioning guy (or gal).

Another thing comes to mind, also. When I was hunting for a contractor to build my custom home, I ran into one guy who was a big fan if wrapping the house in VISQUINE. He said all the moisture in the home would then go out thru the attic. Well, I had been studying on house wraps long before I met him, and I ran like h*ll away from him. So if the house is wrapped in this stuff the house can't breathe and will have a lot of condensation.

Also, super-insulated houses and houses built with extremely tight construction will present this problem and then an air-to-air heat exchanger is absolutely necessary. Sometimes, it pays to have little air leaks around doors to provide some fresh air exchange!!!! I remember doing research on these exchangers when I was preparing to build, but ended up not needing one. I'd do an internet search to start looking at them and, like the above poster said, you might call some HVAC companies and start discussing this issue with them. I'm suspicious that your problem goes beyond any window issues. It's too bad heating costs are so high. You could crack a couple windows in the house to see if the moisture goes away. If it does, then you would KNOW for sure that you don't have enough air exchange.

I would get humidity measuring devices and put them all over the house to see what the relative humidity is. Put a few right by the windows and one far away from the windows to see if the humidity is constant or fluctuates with room position.
If this is a developement, check with your neighbors to see if they have the same issues.
Ron