# Condensation on windows after attic insulated



## Charley (30 Oct 2012)

Hi, we are having an issue with condensation on the upstairs windows in the mornings.

The problem only began last winter after the attic was insulated.  I don't recall any issues with window condensation before that.  The windows are in about 15 years and are double glazed.

Has anyone else solved this problem & did you have to remove some of the attic insulation?


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## bstop (30 Oct 2012)

Warm air carries more water vapour than colder air. The vapour  will  condense out of the air when it contacts a cold surface. When you  insulate the attic you will have warmer air in the house than you had  prior to upgrading your insulation. The result now is that your warmer air can now carry extra water  vapour and there are less cold areas  for the vapour to  condense on so more vapour will condense on your windows. You will have to provide more ventilation to reduce the window condensation.


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## Superman (4 Nov 2012)

Upgrade your windows' u-value [so that they are no longer as cold relatively] or consider putting in demand control ventilation:
[broken link removed]

[no connection to firm]


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## hazelgreen (6 Nov 2012)

You might think of getting a dehumidfier to run in winter months or check ventilation in various rooms.  Keeping a window somewhere open all the time or ensuring air bricks are working will make a difference.


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