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Double Glazing - outside surface misting up

Discussion in 'Windows and Doors' started by ben67, 23 Sep 2006.

  1. ben67

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    I have just had my garage (which is integral to the house) converted to a room with the front double glazed. The windows have been in around one month

    I have noticed for the first time that the front of these windows (ie on the exterior) is misting up this evening. The mist can be wiped off. It was raining quite a lot today but the rain stopped around five hours ago.

    I cannot understand why these new windows are misting up, as the windows in the rest of the house do not mist up at all.

    Anybody any ideas, and whether there is a problem somewhere.
     
  2. oilman

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    The surface temperature is below the dewpoint.
     
  3. ben67

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    But the windows on the rest of the house do not mist up and they are only around 15 feet away and facing in the same direction! Why are only the new windows affected?
     
  4. nstreet

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    The sealed unit is probably made from 'K' glass or similar. This is very typical of this type of glass and nothing to worry about. Don't bother to wipe the mist off it will evaporate quite quickly.
     
  5. ben67

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    That's interesting about K glass. Never heard of it. I have since checked it out on google and have a better understanding of it. It does confirm that it can give rise to external condensation.

    Thanks
     
  6. biffvernon

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    Have you ever noticed your car windscreen has mist on the outside in the morning? Same process. Radiative cooling of glass to below ambient dew point. More common in an unheated room/garage/car on a damp morning after warm rain the night before - like yesterday.
     
  7. Richard C

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    I get this all the time on my new K gkass windows first thing in the morning; it quickly clears but the west facing windows take a bit longer.
     
  8. ben67

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    To Richard C

    My windows do happen to face the west. It took till around 11.30am today for the misting to disappear. It sound like this misting up is pretty normal with K windows.

    The misting up is not something I enjoy. I prefer my old double glazed windows which do not mist up. I doubt whether the benefit of K windows (ie improved efficiency) compensates for the inconvenience of the misting up.

    Thanks anyway for your comment
     
  9. Alisonjb

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    How strange - I came on here to post the same question and found my answer straight away !! We had new patio doors fitted in May and likewise these last mornings we have been misted up on the outside but not on our older windows. Least I know now there is no problem with them. Is annoying though as they didn't clear untill past lunchtime and couldn't see out of them very well. Just glad we didn't have ALL our windows replaced otherwise might never see daylight untill lunctime !!!! Must invest in one of those a window blades that cleaners use.
     
  10. McDebs

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    I have just noticed this problem on a double glazed unit that was installed in my house last year. It's ridiculous - you're meant to be able to see out of windows...
     
  11. sm1thson

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    I have an idea that may help!

    the effects of water forming on windows can be redused by altering the surface conditions of the window. in the same way you get antifog coatings in goggles etc (well actually theres 2 ways but the same as one of the ways). also note: a dirty window will show the effects of water/ mist / condensation on them more.

    if you rub a thin layer of soap over the window it will stop it misting for a while (rub it on then buff it off) -(it breaks down the surface tension of the window and stops droplets forming). -i once had a car that was prone to misting so shampooed all the internal windows and it was fine.

    -maybe theres a market for a product here -anti mist for k-glass windows. -hmmm.
     
  12. Delta number 2

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    Hi all, I work for a double glazing company and this is a problem which I am asked about frequently, and the solution is simple, the problem is caused by a lack of ventilation. When you have new double glazing installed the insulating qualities are much high than in older double glazed windows and doors, this is to conform with energy saving building regulation. K Glass has nothing to do with it, all new reasonable quality double glazed units will have K Glass. All K Glass does is reflect the suns heat back into the room stopping it escaping out the window, K Glass is made by sprayed a film over the side of the glass which faces the cavity of the sealed unit so there for could not be the cause of windows misting up.
    The misting up is cause by water vapour in the air condensing onto the glass in the evening when the temperature outside drops. This cause the glass to become the coldest part of the room and when the warm air in the room comes in contact with the now cold glass the air is cooled and can no longer hold the water vapour, so the water in the air condenses and the window mists up from the bottom.
    The problem is usually most apparent in the morning especially in bedrooms, as during the night a single adult can breath out as much as a pint of water over the course of 8 hours. That means in the average double bedroom there are at least 2 pints of water in the air, and a percentage of that is going to have condensed on the window.
    So by leaving the sun to evaporate the water from the misted window all you are doing is returning the water to the air and the whole process will happen all over again the following night. To solve the problem we recommend sleeping with a window slightly open to minimise the build up of moisture in the air, as well as opening the windows wide for a short time at some point during the day to air the room and remove most of the moist air.
     
  13. JohnD

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    so not the breathing inside the room this time.
     
  14. Delta number 2

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    No not breathing this time, however misting up externally can be caused by the same sort of thing, heavy, wet air. After the rain stops it starts to evaporate back into the air and as the evening comes the air cools and can no longer hold the water and as the glass is cooling faster then the rest of the environment (bricks and concrete hold their heat for a good while in the evening) the glass is where the water condenses. The same thing happens to cars and vans on cool evenings the water condenses on them.
    However it is a good sign to have a small amount of condensation on the outside every so often as it means your sealed units is working well as less heat is escaping out through the window, so your house stays warmer
     
  15. Raybeas

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    Commiseration with those suffering the same problem.
    We've just had two sets of patio doors fitted and have condensation over the whole door with just a slight gap around the outside.
    Yesterday it took until 2pm for the exterior condensation to clear!
    Agreed the new K glass units may provide better insulant but the idea of windows is to be able to see out.
    Surely this should be mentioned at the point of sale with an option to go for the less well insulated but transparent older units.
    Is there something that can be wiped over the glass?
     

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