For the upright walls try mineral wool wall batts as they can be cut very slightly large and squeezed into gaps between battening to completely fill the gap. Press firmly against existing plasterboard or position proud if the board is being replaced. Fixed to the back of the battening you can have your choice of PIR or other rigid foil faced insulation. Tape the joins and between top, bottom and ends and the house structure, probably the wall studs. Make sure that the insulation reaches the timber supporting the connection between wall and sloping ceiling, preferably overlapping it. Fit foil faced plasterboard for the wall.
That completes the “easy” bit. The precise sequence will depend on which side of the wall you are working from.
Edit: I forgot to mention to tape around the window board and insulate.
Edit 2: it seems that only 3 consecutive posts are permitted, so my post(s) about the ceiling will have to wait until after someone else posts to this thread
Looking at the problem as described I would suggest that you have a wind washing issue and very low density fibrous insulation or none present. Would suggest a borescope to inspect. Replace with thicker, higher density insulation as outlined above covered with breather membrane and taped at the edges.
As @lloydham says, wind washing is a possibility, particularly if you have a fairly open structure to your insulation. My answers above are assuming that the wind is getting under the insulation too/instead. A breathable membrane as suggested above will reduce/prevent wind washing and also stop the insulation deteriorating due to ingress of dirt.
Thanks for the replies I might make a small hole to have a look to see what the cavity is like.
I was considering blocking off the space between the ground floor ceiling and the first floor to stop air leakage. Then using an air tight mebrane or blower proof on the plasterboard.
A half inch of wet applied plaster or foil faced plasterboard are normally considered airtight, assuming neither are damaged. The air leakage in/out of the habitable area is normally at the joins.
In the case being discussed the predominant air movement is over the external surfaces of the plasterboard. You are correct to treat the void. I also suggest topping up the cavity and sealing that.
Hello we have someone quoting for the job. We have a similar situation in our bathroom, But with an added complication of water vapour getting into the loft.
Should I Start a new thread?
Is the bathroom in question your only personal hygiene area? You need to consider alternatives while work is in progress, particularly if there will be strangers in the house.
Hi, you should (if you haven’t already) read the experience of Pottyone72 with a similar issue
Installing a vapour control layer on a (cold) loft floor
You are going to need to find the source of moisture.
According to @Steven_Draper’s original post the issue is vapour escaping the bathroom into the roof area. This is a common issue and should be addressed as part of the vapour barrier/insulation work.
Yes, @pottyone72’s experience could prove useful. The biggest difference in this case, I think, is access to parts of the area behind the plasterboard and therefore continuity of the installation. Without continuity the job could easily make matters worse in the medium to long term.
The bathroom ceiling plasterboard is foil lined, so I think all original plasterboard for the “in roof” parts are the same. We had the bathroom refurbished in 2021, before I knew of this great community.
A few small areas have new plasterboard, I don’t think this had foil on though. One area of new plasterboard is painted, the paint bubbles up after using the shower when it is cold.
A new extractor fan has been fitted into the ceiling above our new shower cubicle, it is the type that has a LED spotlight. The extractor air is fed through a flexi pipe to connect were the old in line extractor was near to the external wall. I have tried my best to keep this pipe under insulation, but it fills up with water, some of the water is leaking out.
We have had spot lights installed into the ceiling, I think this is another source of water vapour, the other is the extractor flexi pipe.
I will add pictures in further posts.
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Referring to @lloydham’s earlier post, you definitely need to read @pottyone72’s topic,
As an extra note you need the extract duct to rise vertically and then descend without interruption to the exit vent. That way moisture will either leave the building or fall back into the bathroom. You definitely don’t want water collecting in it. The whole structure needs to be insulated, of course.
Rigid ducting avoids the sagging between hoops so would be a good idea. Also, there is ready insulated ducting available, which would be helpful if you need to go above the loft insulation. Having said that do try to keep within the thermal envelope.
Any fire hood would do if taped down with airtightness tape, however you will also need to seal where the flex penetrates the hood. Certified Passivhaus hoods are also available.
In the “old days” sealing the spot lights caused an overheating problem but with LEDs that is no longer the case.
