Where I live, it's humid outside all fall, winter, and spring, and hovers around 45 deg F. Combined with indoor cooking, showering, etc., we always get a lot condensation on our windows. Rot & mildew love it here.

What can we do in the design & construction of a house to make it so this humidity, and the resulting condensation, don't cause rot & mildew around the windows or elsewhere?

(I know I can vent kitchen & in the bathroom, and I can install a dehumidifier. That's not this question.)


1 Answer 1


What you need to do is to keep the surfaces that moist air will touch warm so the condensation won't form in the first place.

So, for windows that means installing double glazing so that the interior pane is the same temperature as the room and the outside pane can be a lot colder.

For walls it's harder - but installing cavity wall insulation (assuming you have a cavity!) will help, as would installing insulated plasterboard (dry wall).

You won't get rid of 100% of the condensation, but you should be able to get rid of a lot - especially if you do make the improvements to the ventilation in the house.

You can improve the ventilation, but ideally you want to remove the moisture without removing the warmth so simply fitting a vent in an exterior wall to give the moist air somewhere to go isn't ideal. You can get heat exchangers that will take the warm, stale/moist air and transfer the heat to the incoming cold, fresh/dry air.

  • 2
    Are sure this will reduce condensation? Suppose you have two cold surfaces in the house, and you insulate one. Will the other now get 2x the condensation?
    – Jay Bazuzi
    Nov 15, 2010 at 13:56
  • 2
    @Jay - condensation is caused by warm moist air hitting a cold surface so yes, but it will mean that the air stays humid. You'll have to couple this with improved ventilation.
    – ChrisF
    Nov 15, 2010 at 13:57

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