why am i getting condinsation inside most of my windows, how can i stop it?

 

do you mean between the pain or the inside part of the window.

 

its inside the window, gets wett

 

Insulating glass units (IGU's) that get moisture between the panes of glass need to be replaced. If the moisture has not yet got to the point where it has permanently stained the glass with water spots, you could look into calling a company that "fixes" the IGU. I rarely recommend them. Your best bet is to replace the IGU by calling any glass shop in the yellow pages.

 

And if its on the inside pane of glass inside the house (I'm still not sure what you mean), you need to reduce the humidity in the house by using bath exhaust fans when showering, range hood when cooking, and maybe a de-humidifier.

 

in in the inside, meaning i can wipe it dry

 

Yes you need to lower RH in the home.

 

Also, increase the air movement or circulation on the window surface. Heavy drapes and blinds will increase the moisture and condensation.

No matter how good your windows are (panes, gasses, films, etc.) or what the seller claims, they are still a hole in the wall that will get cold and allow condensation.

You have to improve the air movement and increase the temperature of the glass to eliminate the moisture that can cause damge if allowed to migrate down into susceptable materials like wood, gypsum board and insulation.

dick

 

Okay, it is that time of year - here is the really long version!

You have interior condensation on your windows simply because 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, 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 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 – 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!

 

Excellent post. They should give out awards for most helpful poster and so on. Problem is then someone would have to coordinate it.

On to my question. I understand everything you said above, however I need to look up the exact calculation for dew point conversion. My question is this, I installed cellular blinds in my home because I was told they help insulate the windows. I made sure to keep the shade a few inches back from the window to allow for an air gap. This is going to drop my window temperature and thus create the potential for moisture. Is having some moisture on my windows OK, if I gain some savings on my energy bill? My windows are double pain low E, vinyl so cleaning them is easy and the moisture should hurt the frame.

-D in MN

 

I've lobbied to keep his post on the top, like a sticky... but alas, I'm simply a grunt.

In all likelihood, you will get more condensation on the glass due to the blinds blocking heat from warming the glass, and blocking airflow that helps condensation evaporate. You're probably also helping slow the rate at which heat leaves the home, but it's probably a situation of not being able to have your cake and eat it too.

The vinyl window itself will be fine, and can tolerate condensation. The problem may occur if that condensation weeps into the sash itself, where it may surround the edge of the IGU and freeze, possibly cracking the glass with a stress fracture. The other possibility is that the condensation may be so much (Oberon would probably LOVE to calculate how many grams of water would condense during a 12 hour period given a certain humidity level, dewpoint and glass temperature- ) that your glass could act like a dehumidifier and create so much condensation that it could ruin your trim if it runs down onto the wood/wall. Sounds extreme, but I've seen it happen.

 

By making sure you have fully vented range hoods (not the fake kind). By having bath fans that pull CFM's of around 100. By kicking grown kids out of the house. By not showering as much. By not cooking as much. And not washing and drying clothes as much. And make sure the dryer vent is also vented.
Or buy larger house that accomodate having more moisture in the house.

If you live up north where it gets cold, if you come in from the cold and someone's glasses fog up and stay that way for like 5 minutes, then you know you HAVE to cut back on moisture generation and solve venting problems.

I broke a thermopane (I have few work accidents, but this is one I had, costing me $150) when these people who lived in a tropical house, that fogged my glasses in said mannor, had huge ice mounds on the window sills + mildew, and they had towels in every window trying to wick it up to no avail (they were all water logged and the wood was black), and I used a hair dryer on the ice and the hot air richocheted off the ice and shattered the thermopane - a BIG one. I could not believe the heat did not absorb into the ice. I felt the glass, above the ice where I was aiming, after it broke and it felt like I could fry an egg on it. I couldn't believe it. Possibly, if it was a single pane of glass, the heat would have transfered to the outside, unlike the thermopane. Never again am I going to be doing that!

I told the lady of the house when she got home and she told me her moisture was coming from all the cooking she does for church. And then ontop of that, all the stuff going on with the 4 or 5? people living in the house like the stuff I mentioned above. I told her to run both bath fans in both bathrooms when she is cooking, as that might help. I should go over to the condo and remind her, as we are approaching winter here, quickly. We have already had 29 degrees.

[If you have fossil fuel burning heat in your home from whatever source, be aware that if you have excessive condensation on windows that it can be a sign of incomplete burned gasses getting into the blower system via a heat exchanger crack, or a venting problem. This should raise an alarm for you that there could be CO present in high levels!]

 

Thanks - but while my posts tend to be long and contain a lot of information (and occasionally ramble), I would personally nominate XSleeper and other folks like him who post really helpful information in concise and easy to understand replies.

I try to make my posts fun and even interesting, and hopefully people do get some benefit from them, but for true help there are many people who post here who offer great advice and are much more helpful to more people than I am - but I have fun!

 

Can someone please tell me how to stop window moisture on the inside windows. During the winter it freezes and large amouts of ice grow. How do i stop this?

 

I have tackled this problem many times myself - most of the time it requires a little investigation. You have air entering the window at some point - either through seal failure on the insulated glass or a poorly installed window. try taking a stick of lit incense and walking around the window and see if the smoke from the incense moves - if so you have located an air leak around the frame. You can also pop off the inside casing (trim) and check for the proper insulation between the window and the studs. Check for proper caulking inside and out on the window itself ( at the interior trim where it meets drywall and around the brickmould trim on the outside where it meets siding. If no luck with this - you probably have seal failure on the sash - if its a wood window - check with your local home center for a sash replacement system. If its an older aluminum window - get rid of it - they only have a lifespan of seven to 9 years tops. Good luck and keep us posted

 

You are getting condensation on the inside of the windows because cold air is being allowed from the outside to the inside because of lack of insulation, a leak around the storm windows(if applicable), a thermalpane window has lost it's integrity. Moisture
ALWAYS condenses on the WARM side of the glass. The inside is warmer than the outside, therefore moisture. Stop the cold air moving through the dead air space between the storm windows/thermalpane and the inside and the moisture will disappear. I have an old house with storm windows and I don't have that problem.

 

I have struggled for a long time with window/patio door condensation, all my windows and doors are new (approx 4 years old). I have hydronic heating and LP fire logs (btw, LP fire logs do not help your condensation problem, it makes it worse) It came to the point were the ice built up so much on my doors and windows that it caused two of my three french patio doors to loose their vapor seals; I live in New England. The water dripped down from the glass between the molding and bottom of the glass insert, when it froze it expanded and the seals broke. Now I had water outside the glass in the house and between the glass. My french doors are about three years old and were installed correctly, very well insulated. I installed a dehumidifier and kept close tabs on the humidity levels in the room. The problem got better with the dehumidifer but every time I opened the door it would start to accumulate rapidly. I tried an anti-fog product that is commonly used on automobile windows. Many say that it does not work that well for their cars and the reviews are terrible however it cured my problem. I do not use the dehumidifier anymore and about every three months I go over it again. No more window plastic, fans etc for me. This works long enough to get me through the cold months. As far as window coverings go, I still have mine in tact and still no condensation. If you have blinds that mount over your windows onto the window frame just make sure you remove the side spacers to allow the air to circulate. This seemed to work for me, hopefully it will help someone else. It really turned out to be the most cost effective (about $5.00) and the easiest solution. Just make sure that you read all labels and apply it correctly. I cleaned my windows with a good automotive glass cleaner first and presto problem gone. It may or may not work for you but it is worth a try.

 

Wow this post was 2 years old! Moisture on standard double pain windows is 99 % of the time is from bad IAQ. Increase ventilation and the issue will go away.