Ceiling condensation in bedroom

[sharpey143]

I have a strip of condensation in one bedroom which seems impossible to sort out..?? I have even had a surveyor look at it (who did the report on our property prior to purchase, and he is stumped..) The patch forms only when the temperature is round freezing, forms very small droplets, but no staining on the ceiling at all. When the room reaches a decent temperature, it goes away. The property is a bungalow, the loft is adequately insulated, and the walls have cavity insulation. The property is at least 50 years old, the windows are double glazed, but at least 20 years old..?? There are no trickle vents in the window frames, (they are VERY solid tilt/open type windows) The surveyor suggested it may be the fact that it was forming above the headboard..?? Possibly caused by breathing in the night..so we have recently moved the bed onto another wall. (One frost since and it formed again)
I will try to show a picture of the offending patch..not the best picture, but you can just make out the patch on the ceiling above the picture frame..??sorry
Any ideas please..??

 

[^woody^]

That area must be a cold section of ceiling - either no or less insulation than the rest of the ceiling, or cold air coming in from the eaves if there are eaves in this location.

Either way, you need to address this cold surface, and treat the mould before redecorating

 

[ratman123]

As woody says, likely cold bridging, I assume that purple wall is external.

Haul yourself into the loft, and see if there is insulation missing there, or if it coincides with a joist/rafter (the stud "could" act as a cold bridge, but more likely there is a gap between the joist and the insulation).

What you may find is that it is on the corner of the building, and that the insulation does not fully cover that area (as you have to leave room for ventilation), bear in mind cold air can flow through mineral wool insulation, so corners are colder.

You could try getting a slab of rigid foam insulation, and cutting small strips, and fitting these tight between the rafters over the plasterboard (do not block the ventilation path). You can then butt the mineral wool insulation to this strip of foam. the idea being that it will stop air blowing through the mineral wool, and is a better insulator itself, so reduces cold bridging at the corner (yea, this is as fiddley as it sounds).

Poorly drawn image below / blue = rigid foam / brown = mineral wool

Either that or add some insulation backed plasterboard over your existing ceiling.

Untitled

• ratman123
• 9 Nov 2011
• 1

 

[sharpey143]

Thanks for this guys, the area where the condensation is is very well covered with insulation, in fact we had a bit extra put on top as we thought too that it may just be a cold spot..?? Actually as I am sitting writing this 3 of Carillion's finest are in the loft laying more insulation to top up what was in, so may get some benefit from that.
Ratman; thanks for your drawings etc, interesting theory..??!! If no change will try to sort it that way...
Again, much appreciated.

 

[joe-90]

Hey Ratman. Love the image - how did you do it?

 

[ratman123]

Download google sketchup (really easy to use, that image took less than a minute).

Then just screen print and crop.

 

[Nige F]

freezing, forms very small droplets, but no staining on the ceiling at all.l]

Has the ceiling been painted with vinyl silk emusion in the past

 

[sharpey143]

Re the paint, its a possibility, I havent painted it as yet. As the weather continues to be mild (long may it last...) I haven't seen any more condensation (yet) Be interesting to see if the newly installed insulation makes a difference.The chap from Carillion said he made sure it was fitted snugly in that particular area.