Is this amount of condensation right for new sash windows?

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NorthernLights811

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Just had my old single-pane timber sash windows replaced with new, double-glazed ones. I woke up to this amount of condensation, which is much better than the old crappy windows, but still, it can accumulate and build moisture etc.

Is this right at the end of the day for new windows? Should I expect some condensation at all?
Btw, I was sleeping in this room and it has a wooden plantation blind closed, but it's quite a big room, around 20m2 with tall ceilings.
 

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Unfortunately sash windows are not sealed units and you are getting the condensation at the cold bridge line where the two windows join . And as its a bedroom its amazing how much warm moist air we breathe out during 8 hours sleep.

You can improve the cold gap between the two windows by retrofitting an insulated plastic bar to the underside of the top window to close the gap when the two windows are together and vent the moist air of the bedroom to the the outside by adding trickle vents to the top of the fixed window.
 
martygturner said:
Unfortunately sash windows are not sealed units and you are getting the condensation at the cold bridge line where the two windows join . And as its a bedroom its amazing how much warm moist air we breathe out during 8 hours sleep.

You can improve the cold gap between the two windows by retrofitting an insulated plastic bar to the underside of the top window to close the gap when the two windows are together and vent the moist air of the bedroom to the the outside by adding trickle vents to the top of the fixed window.
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Good to know that this is normal behavior. And also unfortunate. I thought I was done with condensation for good with the new windows!
However, what you say makes sense, since this is the only room (plus its en suite bathroom) that gets condensation overnight.

Do you have an example pic and link to the material for this plastic bar that you mention?
 
A friend of mine used to repair victorian sliding sash windows. The process involved fitting new parting and staff beads with draught excluding brushes. The reduction in draughts occasionally resulted in condensation.
 
Draughts and condensation are linked, if you reduce the draughts (ie have a sealed windw where there wasn't one before), then the moisture in the air cannot escape, so will condense against the cold glass surface. You either have to reduce the mositure in the air or increase ventilation.
 
Cut down on the breathing.

Or try leaving the bedroom door slightly open.

You need to open the bedroom window every morning to air the room, or damp will accumulate.
 
It doesn't really matter what they mean, you need to increase ventilation to the room in some way or live with the condensation. A trickle vent can be a convenient solution, instead some people keep windows ajar over night on their night latch though you don't have that option with a sash. It may seem ilogical but uness you stop breathing there isn't any other way. There will always be a compromise between achieving the desired air tightness and adequate ventilation.
 
freddiemercurystwin said:
It doesn't really matter what they mean, you need to increase ventilation to the room in some way or live with the condensation. A trickle vent can be a convenient solution, instead some people keep windows ajar over night on their night latch though you don't have that option with a sash. It may seem ilogical but uness you stop breathing there isn't any other way. There will always be a compromise between achieving the desired air tightness and adequate ventilation.
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The weird part is that the condensation is only at the part where the sash windows meet. Also, I've been to places with aluminium windows or plastic sash windows and that doesn't happen. Hence my original question.
 
Condensation in houses is a fickle beast and can be very difficult to predict how and where it may occur.
 
at a guess the glass temperature is likely to be at least 10 degrees cooler than ambient room temperature

its concentrated near the meeting rail which is a bit of a thermal bridge


with shutters, the window reveal is still open to vapour from the room but the shutter is closing off the rooms heat to the reveal and so the air cools down in the space.....
 
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