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Wet windows in Ohio winter

shorne | Posted in General Questions on

We have a 2500 sq ft ranch home that is about 7 years old, in Northeast Ohio, zone 6a, when the temp drops below freezing outside our Anderson A line, double hung windows, get very wet and will even develop ice where the sashes meet.  Our indoor temp is 68 degrees and the RH varies from 39-42%.  We are being told that our indoor humidity is too high, but everything we see online says otherwise.  We are wondering if this is an issue with the windows or if the house is in need of ventilation.

We are looking at ERV/HRV/whole house dehumidifier as options to correct our problem, any advice would be much appreciated

Thank you

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Replies

  1. Expert Member
    BILL WICHERS | | #1

    You'll get water condensing out on window glass (and even frames) whenever the window drops below the dew point temperature for the inside air. You can "fix" this by either getting better insulated windows ($$), or by lowering the indoor humidity.

    Ideal humidity levels for people are around 40% or so, but for the building, ideal levels are lower. My Ecobee thermostat has a setting that allows it to adjust the humidity setpoint a little when it gets really cold out, so I don't usually have much trouble, although I do ocassionally see some condensation. I'd try lowering your humidity to around 34-35% and see if that improves things.

    Bill

  2. Expert Member
    Michael Maines | | #2

    With those conditions, condensation will occur on surfaces about 45° or lower. If you follow Bill's advice and lower the indoor RH to 35% or so, that drops the dewpoint--when condensation will occur--to about 40°F.

    Triple-glazed windows largely avoid this issue because the inner surface is much closer to room temperature than double-glazed windows.

    Double-hungs are also notorious for leaking air between any moving parts, though some brands are worse than others. If cold air is leaking in, it will be hard to eliminate condensation.

    Installing shrink-wrap plastic on the interior would solve both problems. It's expensive; you can extend its lifespan by installing it over a removeable frame. It's not resistant to cat claws, I've found. You could also try the removable clay caulking sold for sealing window air leaks.

    1. Expert Member
      BILL WICHERS | | #4

      A quick "fix" for leaky windows for testing purposes is to tape the gaps with painter's tape. I've done this sometimes as a test, and other times as a quick'n'dirty "fix" ("fix" is a strong word here :-) for stuff I can't properly deal with until warmer weather.

      Bill

      1. Expert Member
        Michael Maines | | #6

        Good idea. Blue tape has been holding a couple of my triple-track storm windows together for ten years now ;-)

  3. shorne | | #3

    Thank you. Do you have an opinion on what option would be best, whole house dehumidifier, HRV, or ERV, system?

    1. Expert Member
      BILL WICHERS | | #5

      An HRV would be the "proper" way to do it in a tight house, and would be most efficient. If you need something fast though, just crack a window or three open -- the outside air in the winter is going to be much drier than your indoor air, so air exchange from an open window will bring down indoor humiditity levels. The down side is you are loosing heat to the outdoors this way. An HRV is better because it has a heat exchanger in it to help recover some of that heat that would otherwise be lost.

      Bill

  4. walta100 | | #7

    I don’t think a dehumidifier is a good answer to high winter humidity in a cold climate.

    To my ear 42% at 68° sound very reasonable.

    How wet are your windows?

    Seems to me a little water that stays on the glass when the outdoor temp is in the single digits with dual pain windows sounds normal. When it gets below zero, I expect to mop up the water on the windows twice a day. I would not be surprised to find frost on the inside of the window at -25 or so.

    I would be uncomfortable if the humidity got below 40% or so. Before you invest in equipment to lower the humidity crack open a window this will being in more cold dry air and lower the humidity and find out what you can tolerate. Then get an HRV.

    If you decide to lower the humidity, see if you can eliminate the moisture sources before buying equipment. Do you run the vent hood when cooking? Do you run the vent fan when showering? Can you get rid of some house plants? Hot tub, aquarim?

    Walta

  5. shorne | | #8

    I've attached a couple of pictures. Outside temps were single digits, so there is a lot of ice. Anderson doesn't make a storm window for their A line, which is supposed to be their best window. We may need to have some made.

    1. krackadile | | #11

      This may be a stupid question, but are your windows completely closed with the sash locks closed?

      1. Expert Member
        Michael Maines | | #12

        That's actually a very good question. As part of being a designer I go into a lot of homes, and it's very rare to see windows properly latched. I can't even get my mom to latch her windows.

      2. shorne | | #13

        LOL, not a stupid question at all, but yes all are locked. I've even unlocked them and tilted them and relocked them.

  6. | | #

    Every window in the house gets this way

  7. Expert Member
    Akos | | #9

    Sometimes if the windows are not installed properly and are not fully foamed in, you can get a lot of air leaks between the window and the rough opening. The air leaks would tend to cool the window frames down and you can get a lot of condensation there. Not sure if this is the case for you but something to watch for.

  8. oberon476 | | #10

    Do you know if your windows have a surface 4 coating? Andersen calls it Heatlock, but it might also be referred to as i89. While the coating does improve U factor performance, it can also make the glass more susceptible to surface condensation, especially along the edges.

    As Michael Maines pointed out previously, a temperature of 68° with 40% Rh results in a dew point of 45°, meaning that anything that has a temperature below 45° (your windows) will have condensation build up. That you are seeing ice along the edge means that the window glass is below 32° wherever ice is forming.

    That you are seeing a great deal of water as well as ice on the glass along with apparent condensation on the sash suggests that you might be covering your windows with shades, curtains, blinds, whatever. If that is the case then by covering the windows the glass temperature is significantly lowered making condensation almost inevitable. If you can avoid covering your windows the glass has a better chance of being warmer and condensation becomes less likely. If you do usually cover your windows then try not doing so for a few days and nights just to see if that might help to alleviate or even best case eliminate the condensation.

    Simplest explanation is that you either need to raise the temperature of your windows to a level above the dew point or else lower the dew point to a level below the temperature of your windows. Although there are a number of ways that you can warm up your windows, the only way to lower the dew point is to remove moisture from the air in your home .

    Windows are assigned a rating for their ability to resist condensation. The higher the condensation resistance rating, the less likely that you will have wet windows. Assuming that you have Andersen A series double hung windows, condensation ratings per NFRC range between 38 and 67. Dual pane IGU with surface 4 coating results in the 38 while triple pane without surface 4 coating equals 67. Basically, a rating of 38 means that you will be unlikely to avoid condensation anytime the outside temp drops below freezing, using your current indoor temp/humidity settings, while a 67 means that you much less likely to see window condensation under even relatively severe conditions at your current settings.

    I am enclosing a chart that compares inside temperature and humidity levels against outdoor temperatures in order to give you some idea of where you might need to be in order to avoid wet windows.

    To clarify the chart, the numbers below the outside temperatures listed (red -40, -30, etc.), are the condensation resistance rating values. These ratings do not represent a temperature, rather they are simply a rating based on the higher the number the less likely you are to see condensation.

    1. shorne | | #14

      I'm not sure about the surface 4 coating, but I will see if I can find out. I really appreciate your chart. In desperation, we took one of the screens and covered it with plastic then installed it on one window to see if it made a difference. The window is much drier this morning, still very small amount of condensation and the room is one degree warmer. Anderson does not seem to make a storm for their A line windows. :(

      1. oberon476 | | #15

        Something else you might want to look at is how did they insulate around the windows when they were installed?
        Currently very few suppliers for storm windows anymore, so no surprise that the A series doesn't have that option.

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