Patrick

Dealing with a customer that has been a pain the entire job process looking over our shoulder the whole time we did the job. She complained about a slight condensation issue with her new windows and I just got this e-mail from her. I need to go out and inspect it but does anyone have any ideas here?
Customers E-mail:
"We continue to enjoy the added protection against the cold that we have from the windows that you installed for us.
However, on these cold mornings, we are still surprised by ice forming on the inside of the windows.
I have read the material on the manufacturers site about condensation. It says that if we are having condensation, the humidity level in our home is too high.
Actually, our home is very dry and we use a humidifier to add to the humidity. One of the windows you installed is on the rear of our home. On the same back wall of our home, in our 2nd story bathroom, there is another window that was installed when we updated our bathroom a little more than a year ago. That window has no condensation on it in the mornings.
We want to be sure that our windows do not have defects that should be corrected. Is there something that we could do to be sure about this?"

concretemasonry

Who picked out the windows? They could be lesser quality than the others installed earlier.

What is the relative humidity in the two different rooms? What is the temperature?

Assuming equal quality windows it sounds like different air circulation, room temperature or the effects of window coverings (curtains, drapes, etc.). Drapes and curtains will limit circulation and cause the window to be colder, causing condensation and possibly ice.

__________________
Dick

Patrick

the previously installed window was installed by another contractor in the bathroom and barely opens. The windows I installed were Harvey Signature windows which she specifically requested because they had the lowest air infiltration rate of any window that I carry. I install this brand all the time and have NEVER seen this issue before. When I came out to measure for windows in this room the inside of her old storm windows were soaked with condensation. I can fully understand condensation, but should the glass temperature be low enough to allow the condensation to freeze? granted the past two days have been around 10 degrees.

dougchips

Patrick, a little late now but windows with the warm edge spacer will have a higher center of glass interior temp. The metal that touches the outside glass draws the cold to the inside glass and will make the glass cold to touch. Glass that uses the foam/black goo (can't think of the term) will cause the interior pane to be warmer. With all of this said I would never promise a customer that they will not have condensation. Harvey has some very good literature that covers why you get condensation. You might want to call Harvey and have them have a tech nerd give her a call and explain it. I forget the number of gallons a day or week that the average household generates in moisture but the number shocks people (steam from showers, steam from cooking, people sweat..........). In the winter all this moisture wants to go outdoors it just can't find a way to open the windows.

BTW, I am not saying to brush her off on Harvey.

__________________
To get the best replacement windows, or sun rooms contact the replacement windows experts at FHI Vinyl Window Company.

ARCS

Usually what homeowners feel is low humidity is different than what is in the acceptable range of window manufacturers. Your window manufacturer will give you a chart that has their reccommended humidity level at specific temperature ranges. I would not trust any dials on humidifiers or decorative wall units. Get a Thermohygrometer
from Grainger to do these tests. These tools are accutate +/- 3%. The one I use is Grainger part number 4GU16.

Now, I get it all the time that a homeowner says it is way too uncomfortable to keep the home at 5% humidity when it is 30 below zero outside. That is where they have to pick between having the condensation on their windows or interior comfort. The windows are doing their job. Any water forming on the inside of the window is not leaking in from the outside. It is water from the inside trying to get out. They probabbly did not have that problem with their old windows because they leaked and the water could find its way out.

Now for ice forming, this may be looked at as a window failure, but when it is 30 below zero outside for 3 days straight, no double pane window is going to maintain a warm enough glass surface not to freeze standing water on it. The only solution is to get rid of the standing water and the only way to do that is to control the humidity.

I have been installing replacement windows in Northern Minnesota for 10 years, believe me I have seen every condensation issue that can come up. In our area we hold records for being the cold spot of the nation. We have a recorded temperature in our area without including wind chill at -64 degrees. We see weeks on end where it does not get above -20. I would say in climate like this it is just expected to get one out of 6 customers who change a whole house of windows to have a condensation with frost issue in January. And 1 out of 3 of those people will not believe anything you give them in writing or what you say about how to correct the condensation by regulating the humidity. As I speak right now looking at my window next to my desk it has condensation on it. It is not frozen because it is +23 today and the window will fight that temperature difference off without freezing, but believe me if it was 20 below this week it would be frozen. This just comes with the terrain of living in Northern MN. I just turn the humidity setting on my air exchanger down when it gets colder out and the problem goes right away.

ARCS

By the way, from what I have learned having a business that has installed somewhere around 20,000 replacement windows in Minnesota and trying about 10-15 different manufacturers, all that spacer talk is just sales rep BS. You can take any 2 vinyl windows, put them side by side and what you have are 2 vinyl windows. These companies take their finished product, submit them to testing and all come back with a same or similar U value. The U value rates the unit window as a whole, installed in an opening.

dougchips

http://www.edgetechig.com/ Not my day to educate, take a look at this site on your own.

__________________
To get the best replacement windows, or sun rooms contact the replacement windows experts at FHI Vinyl Window Company.

ARCS

Not to start an argument but you put me to a website of a MANUFACTURER .

I am sure they are going to say that their product is anything but the best. I am not saying that these products are bad, but every window has its own bells and whistles, but in the end they are rated as finished systems, and not by who has warmer glass, or better frames, or etc.

If you want to do better research start at www.nfrc.org or http://www.energystar.gov/index.cfm?....pr_ind_tested for unbiased opinions.

dougchips

I know where I sent you. Edgetech makes the product for window companies. You seem to have a working knowledge of condensation, look at their claims of how their product reduces it. I understand how the NFRC rating system works but it does not have any test data on condensation (to the best of my knowledge).

If you know of the gov web-site that has the thermal imagining study of foam filled frames, send me the link. Their study shows that the foam only helps on the top of the window and the rest is BS. I found the study once and can not find it again.

__________________
To get the best replacement windows, or sun rooms contact the replacement windows experts at FHI Vinyl Window Company.

Oberon

Windows can have an acceptable U-factor and can still have condensation issues in the right circumstances. There is an NFRC rating called "Condensation Resistance" or CR that rates a window's resistance to condensation, but it is a voluntary listing and not very many companies list it.

While U-factor is affected more by having a LowE coating than it is by the spacer used in the window, spacer material comparison is not manufacturer BS. A warm-edge spacer will help to prevent condensation and does relate directly to U-factor.

Different spacers will not affect the center-of-glass temperature of a window. In fact, after about 1-1/2" from the edge the different spacer used no longer affects the glass temperature. But, within that 1-1/2" there can be enough of a temperature difference at the edge between different spacer systems that can result in possible condensation issues.

Patrick, Harvey windows are LowE coated and argon filled? I believe that that is standard with them? And what spacer system do they use?

Finally, here is the really long version of window condensation that doesn't say much more than was said here previously - just a lot longer.

But, I think (hopefully) that it does point out a few facts about window condensation that not everyone might be familiar with - and please bear with me that this was written for homeowners and not contractors - so some of the ideas may be very familiar to folks who have worked with this stuff...

The reason why there is condensation or frost or ice on the interior of your interior window or storm window is 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, the explanation 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 – 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!

TimNJ

Look here too

http://www.coastalcontractor.net/cgi...ract.pl?id=142