You have condensation on your windows, and as you identify that is a problem. The obvious answer is to remove the moisture and you remove the source of condensation. However every action has unintended consequences. You sufficiently dry that interior air, you will remove the source of condensation. However you may make the house unlivable for you or your partner, and that is an unintended consequence. So exactly what problem got solved? Well at least you dont have condensation ;-). Now lets see if we can understand your situation, and only through understanding can we come up with a workable solution. You like 60% relative humidity in your house, and I would identify that this is plenty high. For reference, I run my dehumidifier to 40% R.H. in summer, and 45% R.H. in winter  I have a very tight house and run supplemental dehumidification year round. Like you, if it gets too dry I tend to have problems, and as I get older I actually prefer more humidity. Now my questions for you are what is the surface temperature of your windows, what window treatments are you using, and what is your target indoor air temperature? Let me illustrate why this information is needed. Assuming you keep your IAT at 70F, and at this temperature the saturation vapor pressure is somewhere around 25mb, so 60% R.H. would have a vapor pressure of around 15mb. At this vapor pressure, if the surface temperature of your windows is cooler than 55F and you donÂt have air moving across those windows, the air next to the windows will cool below the dew point and you get condensation. Now then, drop that R.H. to 45%, and you will get condensation on your windows at 45-50F. Drop it to 25%, get nosebleeds daily, use 3x more skin moisturizer, and be generally miserable, and you can get the surface temperature of that window all the way down to 30-35F before you get condensation. This is only one part of the equation - temperature. Your windows are 11 years old, so I think it is a fair assumption to say that the seals are probably broken so your argon fill is gone (assuming you had it int he first place, and if a spec house probably not). I woke up this morning, it was -5F outside. The place I am has thermally broken aluminum frame high performance gas-filled windows. Now I donÂt care what relative humidity you have inside in this environment you will see condensation if the air is not moving. As Susanka point out, when you put shades or curtains up, you restrict movement of air on the surface of that window, allowing that air to cool to the surface temperature of the glass (and if that surface temperature is below the dew point you get condensation). The easy answer is to remove humidity, but this may not actually buy you much if your glass temperatures are too low. However the less obvious answer is to increase airflow across surface of the window to prevent the air from cooling to the surface temperature of the window, thus eliminating condensation. I think the best answer is a combination. I would reduce the R.H., make sure your window treatments are not restricting airflow across the surface of your windows, and increase air circulation in your house (ceiling fans). And in a new house, I would recommend fiberglass windows  far superior to anything else currently available in the residential market.

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.

Izzie, About this time every year your question comes up - and not just on line. Anyway, here is the long version which is intended to (hopefully) start a discussion... You have interior condensation on your new windows simply because the surface temperature of the window is below the dew point temperature of the air in your homethatÂs itÂa very simple explanation. Unfortunately, as to why the surface temperature of your window (glass) is below the dew point temperature of the air in your home may be a bit more complex  so I am going to offer a few thoughts and maybe even throw in a few numbers that I hope might help 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. Put a bit more simply, 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 moisture...be 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 or it may completely solve your problem  depends on how you lower the relative humidity and what affect the "how" has on both the moisture level of your air and the temperature of your windows. All this because there are two ways to lower relative humidity  first, you can increase the air temperature in your home or second, you can decrease the moisture content of the air in your home. By increasing the air temperature in your home 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. So, while the RH is lower with higher air temperature, it may not effect condensation on window surfaces at all  unless the rise in air temperature also caused a corresponding rise in window glass temperature to a level above the dew point temperature. But, lowering the amount of water vapor or moisture in your air will lower the dew point temperature as well. And if it lowers the dew point temperature sufficiently to drop it below the temperature of your window glass  no more condensation issues. 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 hereÂs 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 windowsÂyet 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 donÂt have a condensation problemÂSWEETÂwell, 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. Oddly enough, a single pane with a good and tight frame and sash assembly may be more prone to condensation than will a less tight single pane window simply because air (and moisture) will leak out of the looser window while the tighter window may be more likely to trap the moisture inside the home. And, while a tight storm window can help the interior lite to avoid condensation (when compared with a single lite and no storm), the storm window itself may 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 much less likely that there will be condensation problem on those particular windows than there would be with a less energy efficient window - despite the relatively high relative humidity in the home. But, there is always a "but" Again, that 57 degree glass temperature is still a center-of-glass reading and the edge of glass temperature will be lower - actual temperature is dependent on both the spacer system used in the IG unit construction and on the material used to construct the sash. So even with a "57 degree" center-of-glass temperature it is still possible to get window condensation if there is enough moisture in the air. And consider that the interior glass temperatures are based on the fact that moving, warmer, indoor air is actually in contact with the glass at a given time. Curtains, shades, other obstructions can cause problems by blocking airflow across the glass  airflow that can have a huge effect on the condition of the window relating to condensation. Also, bay and bow windows can be more prone to condensation  again because of the possibility of decreased airflow over the glass. And finally, what can happen 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!

You have condensation on your windows because the glass temperature is below the dew point. Dew point temperature is the transition between evaporation and condensation. Dew point is defined as saturation vapor density, or actual humidity, or simply, 100% relative humidity. Go above the dew point temperature and you have evaporation, go below it and you have condensation. Dew point is "fixed" depending on the moisture in the air. "X" moisture level will always equal "Y" dew point. In other words, if the air in your home holds 5 grams moisture per cubic meter of air then the dew point will fall at 32 degrees F. Ten grams moisture per cubic meter and the dew point is at 52 degrees F. These numbers are totally independent of the temperature in your home, or the temperature outside, or any other temperature. Dew point is based on moisture level - period. Most folks will refer to relative humidity when dealing with window moisture issues simply because we use RH all the time while we rarely ever consider actual humidity. Relative humidity is the actual vapor density divided by saturation vapor density - or - the percentage of moisture in the air versus the maximum amount of moisture that the air can hold at a specified temperature. The really excellent calculator that Homesealed linked (I saved it in my favorites) allows you to adjust the the RH, temperature and dew point (again keep in mind that dew point is the temperature equivalent of the moisture in the air). If we set the dew point at 32 degrees and then "solve for" RH, we can adjust the temperature slide up and down see what the RH would be at several given temperatures. If we raise the dew point to 52 degrees, we have doubled the moisture level (as mentioned earlier) to 10 grams per cubic meter, and we can see the effect that change has on the RH at various temperatures. If we set temperature at 72 degrees and the move the RH to 50% - what is the dew point temp? So what does it all mean in your case? Basically, in order to stop condensation from forming on the surface of your windows you must: lower the dew point by removing moisture from the air, or warm up the window surface to a temperature above the dew point, or do some combination of both. So given a dew point of 32 degrees, if your glass temp is 32 degrees, then you are at 100% RH and dealing with condensation. Warm the surface to 40 degrees and you are at 75% RH with no condensation. Given a dew point of 52 degrees, if the glass is at or below 52 degrees then you have condensation. Since it is quite possible that the glass temperature of your windows could be right around this temperature, then lowering the level of moisture in the air is probably going to be your best solution. I think it's pretty much a given that the bath is putting a lot more moisture in the air than the exhaust fan is removing. A major gain of upgraded windows is that they tighter which helps to prevent air leakage to the outside. This is a good thing for keeping heat in, but it will also result in keeping moisture in as well. That excess moisture will raise the dew point in your home and can result in condensation that you never saw in the past. Since you mentioned that you had condensation issues in the past, you might want to see just how much moisture that you do have inside your home. You might consider that if you are seeing extensive moisture on your windows, there may also be condensation inside your walls that you aren't seeing. To help eliminate minor "misting" on your windows, use a fan to circulate warmer room air over the glass when bathing the kids, or at any time minor condensation becomes an issue. This should help to warm the glass to a level above the dew point. Also, as Homesealed asked, what was the outside temperature? As it gets colder outside the glass in your windows will also get colder which will increase the possibility of condensation. As it gets colder outside it's almost always a good idea to lower the moisture level inside.