Frost forming on my Softlite Imperial LS windows

A place to ask all your replacement window questions
Post Reply
Message
Author
JimK
Posts: 7
Joined: Sun Feb 10, 2013 1:48 pm

Frost forming on my Softlite Imperial LS windows

#1 Post by JimK » Mon Jan 06, 2014 9:35 pm

We had our windows replaced in March of 2013. I have noticed condensation a couple time on the inside of the windows, but tonight happens to be very cold. It's somewhere between -5 to -10 degrees. My concern is that frost is forming on the inside of the windows near the bottom of both top and bottom sections of the double hung window. I had 25 windows replaced and it seems that just about all of them have frost forming. I assume this should not be happening. Do I need to contact the window installer to come re-install the windows with more insulation in the frame, or is the window faulty?

Thanks,
Jim, Cleveland, OH

tru_blue
Posts: 217
Joined: Fri Jan 13, 2006 2:02 am

Re: Frost forming on my Softlite Imperial LS windows

#2 Post by tru_blue » Tue Jan 07, 2014 4:04 am

Hi Jim

Is the frost on the edge of the glass or between the sash and the frame? It is likely that the window is not faulty, and that the installation is ok as well, although I can't rule that out. It would be helpful to know if your windows are double glazed or triple glazed, and what brand they are. Condensation and frost can indeed occur on energy-efficient windows under certain conditions, even if they're installed correctly and are less than a year old.

I'm going to throw a lot of statistics at you to address the condensation on your windows. Keep in mind that these stats are based on a worst-case scenario of 0° outside and 70° inside, which certainly applies to your current 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 are and that they have the argon gas or equivalent 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." And the bottom edge is typically colder than the sides and top (warm air rises). 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 38° to 42°. Again, most 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 typical 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. Condensation often tends to lessen or dry up by mid-day because cold/condensation caused (in part) by the shades being down at night are now opened and the windows now have circulation against them.

Enough stats. Condensation, frost, 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 cannot 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 of your windows if possible or visit their 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. (Again, this is a worst-case scenario) I'm guessing your humidity level is significantly higher than that.

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 the shades 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. In homes with older existing windows, the best solution is often to replace them with modern, energy-efficient windows. But you already have newer windows with the same issue 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 evidently 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 - The bottom line here is proper ventilation and insulation. 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 (or inspecting the windows for other issues, however unlikely).

I hope this helps!

User avatar
Windows on Washington
Posts: 4195
Joined: Fri Oct 27, 2006 11:23 am
Location: DC Metropolitan Area-Maryland/Virginia/DC

Re: Frost forming on my Softlite Imperial LS windows

#3 Post by Windows on Washington » Tue Jan 07, 2014 7:15 am

Well said sir.

Here is one that I have copied from you long before.

From tru_blu:

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 are 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. Condensation often tends to lessen or dry up by mid-day because cold/condensation caused (in part) by the shades being down at night are now opened and 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 cannot 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 of your new vinyl windows if possible or visit their 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. (Again, this is a worst-case scenario) I'm guessing your humidity level is significantly higher than that.

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 your older existing windows, the best solution is often to replace them with modern, energy-efficient windows. But you've already have newer windows with the same issue 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 - The bottom line here is proper ventilation and insulation. 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

JimK
Posts: 7
Joined: Sun Feb 10, 2013 1:48 pm

Re: Frost forming on my Softlite Imperial LS windows

#4 Post by JimK » Thu Jan 09, 2014 8:00 pm

Thank you very much. I turned off the humidifier on the furnace and the frost is gone. I so think the windows are great, I'm now just concerned that the company that did the replacements didn't insulate around the window as well as they should have. I guess il have to wait until the weather warms up, maybe take the outside flashing off and re-insulate around the replacement windows.

Thank you for the answers!

User avatar
Windows on Washington
Posts: 4195
Joined: Fri Oct 27, 2006 11:23 am
Location: DC Metropolitan Area-Maryland/Virginia/DC

Re: Frost forming on my Softlite Imperial LS windows

#5 Post by Windows on Washington » Fri Jan 10, 2014 7:35 am

If you don't have much air coming around the windows, it is unlikely that they were not sealed properly.

Ice formation on windows is a normal phenomenon in the right (-5 degrees is supremely cold and generates that condition) conditions.

The added humidity will close the loop and = ice.

Randy
Posts: 1035
Joined: Fri Oct 08, 2004 7:26 am
Location: Houston, TX

Re: Frost forming on my Softlite Imperial LS windows

#6 Post by Randy » Sat Jan 11, 2014 7:21 am

While we don't know the details of the installation, this is one of the primary reasons why sealing the perimeter of the window with minimal expanding foam is so important. Creating as tight of an air barrier around the window as possible will help reduce the possibility of having this occur.

uncle eddie
Posts: 94
Joined: Tue Sep 18, 2012 7:52 pm

Re: Frost forming on my Softlite Imperial LS windows

#7 Post by uncle eddie » Tue Jan 14, 2014 1:07 am

That is coooolllddd! I've seen windows iced from top to bottom in weather like that. I agree with the other guys.

Post Reply