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Thread: Condensation and ice on bottoms of windows???

  1. #1

    Default Condensation and ice on bottoms of windows???

    Can anyone explain this phenominom usually around 0 or so ice forms at the bottoms of windows in the house. House is wood heat exclusively from inside draw, would outside draw help? Also house is a pretty tight build, is this the norm or what else can be done? In a recent addition a new series 10 pella low-e argon gets a bit or moisture on the bottom too but not as bad as others in the house.

  2. #2
    Member bushrat's Avatar
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    Pretty common for windows in back rooms or not close to heat source, the outside cold air penetrates through the window layers and descends to lowest part and when it meets the inside warmer air condenses and forms moisture and sometimes even ice. Doesn't usually happen here until -20 and lower, and it's -28 here now and we have just a tad of moisture low on the kitchen window. Your high quality triple-pane windows with argon or whatever will cut down on this, but they are spendy.

  3. #3
    Member Vince's Avatar
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    in the age of a tighter house the better; this is becoming more of an issue. In Fairbanks fresh air return vents are being fitted in to homes to reduce the condensations appearing in the house...

    two factors at work... 1 your vapor barrier is doing it's job
    2 no air leaks now... the vapor will not escape out side...

    apx. 80% is created while your cooking. the steam off the pot needs to go some where.

    the rest is bath room shower, drying boot, clothes , pets every thing that emits moisture including yourself.

    a fresh air return on your wood stove is a good idea in any circumstance.

    by drawing fresh air in you get a cleaner burn and reduce the negative pressure in the house making it easier for cold air to leak in.... at -20 and below the out side air is substantially heavier then the warm inside air.. and any leak will give you the same effect of some one holding an air hose to that spot and blowing in cold air. by reducing the negative pressure built up by the wood stove sucking air from inside the house thus REQUIRING replacement air you become more efficient in your heating.


    you can save a lot of moisture issues by installing vents or an HRV system.. this too will help circulate heat and cool( when necessary) as well remove unwanted moisture
    "If you are on a continuous search to be offended, you will always find what you are looking for; even when it isn't there."

    meet on face book here

  4. #4

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    While I also agree in having a dedicated air source for the stove, it will also make the condensation worse. Remember, the wood stove is using moist air to burn with out the dedicated air intake. That means it is drawing dry air into the home via the negative pressure.

    As soon as you add the air intake to the stove, you will draw less dry air from outside because of the reduction of neg. press., reducing the number of air exchanges to the interior of the cabin.

    If condensation is bad now, adding only an air intake for the stove will make it worse.

    A de-humidifier may be an option to consider. They work in a situation such as this. You are not the only person having these kind of problems. As homes are built tighter and tighter, the problems become worse.

    As to fresh air returns mentioned in the prior post, these are in reality "air to air heat exchangers". Cold incoming air is tempered by the interior air being exhausted from within, across the exchanger. In some designs you can bring up the incoming (outside air) temp by as much as 35* - 50*f. It again is realized that with the tightening of the envelope you need to supply a percentage of fresh air, along with removing moist air from the home. Heat exchangers do both.

    Adding a heat exchanger to an existing forced air system could run a few bucks. The cheap way out may be to install the fresh air intake for the stove for proper function, thereby not using heated air for combustion, and installing a de-humidifier. I'm pretty confident that will make a difference in both the effiency of the stove and also take care of the condensation trouble.

    By the way I work in this field of home energy usage. Knowing how a building functions is at the core of my job. Good luck with this problem. Do your best to fix it, mold is not a good thing. If you have a bad condesation problem on the glass, you may have moisture condensing in the wall where warm moist air meets the cold. Feel free to e-mail me with any particulars.


    Bob Dunn
    bdunn@dunnsenergy.com

  5. #5

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    One thing I did not mention. Check what the humidity level is in the area you are having trouble. It could be the older windows are a lot less efficient. Thus colder creating more ice. The interior hum. level should be about 20%. Anything approaching 30% in the winter will cause the trouble you are having. Keep it to 20% or less and don't drag your feet on the carpet. The little woman won't appreciate the static shocks.

  6. #6
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    Glass technology has come a long way, but in general, glass is still going to be the coldest surface in your house so that's where condensation will form first. In truth, there's frost probably forming around your exterior wall electric boxes but you can't see it. Bushrat is correct about the cold air in the dead airspace sinking to the bottom and causing the lower part of the inside pane to be the coldest part. It's a little more complicated than that but let's leave it at that. Triple pane gives you a second dead air space and newer windows use inert gas in the space. Both perform better because the inside pane surface temp is warmer than with typical double pane. Insulation factor is not the primary goal, raising the inside pane surface temp is. Why? Condensation. The warmer the pane, the higher the humidity can be in your house before condensation appears. Unless you want to do major surgery and change the glass the best way to deal with the issue is to reduce the humidity in the house. If that's not your desire? Get the air moving at the affected windows. In houses with central heat you'll always see heat vents under windows. Block a vent or close a blind? You get condensation. Most everyone has seen it happen. Keep air vents free and keep blinds partially open. Consider a fan.

  7. #7

    Default great ideas

    These are great ideas from all and i guess i'm intentially addding to the problem. lol i have two pots of water on the stove at all times for added humidity it "feels" pretty dry in here. Guess that was a mistake. First step i guess is to check in. hum. level. I guess i need to pick up a guage. I was avoiding the outside draw for the stove thinking that more convection heat circulation would be generated with inside, although I have no problems at all with that it works great with what i have done. A few of the windows although not that old less than 10 yrs. have "leaky" seals, but same condensation on the interior bottoms as the "good" sealed ones. Bushrat do you draw from outside with your stove? At -20 here there is heavy ice on the bottoms. But again that is evaporaporating a few gallons a day on the stove. So I know where to start.

  8. #8

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    Quote Originally Posted by dallsheep View Post
    lol i have two pots of water on the stove at all times for added humidity it "feels" pretty dry in here. Guess that was a mistake.
    "Can I have humidifier for $500 Alex?"

    Willing to bet it's nothing more than this. It makes for an easy solution though. Like you said, still check the humidity after you've removed the "humidifiers" on the stove. It could take a few days to equalize.

  9. #9
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    The humidity levels before you see condensation are absolutely a factor of the dewpoint. There is no mystery about it. I googled a link for you. The UofA Cooperative Extension Service used to have a great paper about this topic but it's been MIA for several years. This link looks pretty good at explaining what's happening.
    http://irc.nrc-cnrc.gc.ca/pubs/cbd/cbd004_e.html

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