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We're in the process of renovating (refreshing) a 1930's semi and being a solid brick construction, the exterior walls are sucking the heat from the house. The bedroom with the most exterior walls also had the joy of woodchip wallpaper with gloss paint over, resulting in corners of mould.
The woodchip has gone, but the mould has crept into the plaster.
So, should the plaster be hacked off to get rid of the mould?
Is thermal plasterboard the best way to retain the heat?
We're only likely to thermal board one wall as it'll be too costly to work around the window sensibly, so is something like Wallrock Thermal Liner the answer? It certainly sells itself, but we don't want paper seams.
I'm lost in a downward spiral of plasterers quotes and conflicting trade advice, so thought I'd give that joy to Singletrack.
You'll need a thermal break if you want a meaningful difference. Not sure what a 3mm thick thermal paper product will do.
What's wrong with the window walls? You could trim them out to hide the drywall edges as opposed to finishing the returns.
We've got a similar sounding 30s house. The master bedroom has two outside walls, one with a window, one without. I've put 50mm insulated plasterboard on the solid wall. It's made a pretty big difference. The wall was like an ice block and now it's warm to the touch. We don't have the heating on at night or in the morning and it used to be pretty chilly in the morning, now it's quite tolerable even in mid winter.
I struggled to find much information about vapour barriers and air gaps so I just went for it. 3 sheets of insulated plasterboard, tightly fitted together screwed to the brick. Taped and filled the joints. Wallpaper over the lot. Visually you'd never know anything has been done.
I also insulated the the loft above. That was about 5 years ago. No issues with damp and as mentioned the room is much improved. I don't thing the window wall will make much difference
Are you trying to get rid of the mould and damp or are you trying to retain the heat? With an old solid wall property ( I know, I own 3) you have to adapt to the reality. I've had a couple replasterered over a membrane and passive dehumidifier vents installed. Very successful at getting rid of the damp and mould. Not toasty warm though.
@bigjohn, both. I want the mould gone and I'm hopeful that it's a result of rubbish paper/paint along with a leaking roof (which is booked in for repair)
If the thermal properties of the wall are improved, again hopeful that the mould will be kept at bay.
@dirksdiggler, I'm a novice at this sort of thing and likely wrong but don't want to have the ballache of replacing the sill and trimming around the frame, along with the rad pipes possibly needing to be spaced
I'll look out details of the vents. They seem to work; both in tenants' houses who aren't slow in coming forward if things aren't right so I'm glad I made the investment.
The mould is almost certainly linked to cold walls, not the paper.
You have 2 options. Dry line with insulted plasterboard with built in vapour barrier and lose some of your room space, or get exterior wall insulation.
I've got single skin of bricks on a C19th building. Just had bonding put on, then fibre glass mesh then silica. Noticeable improvement in insulation and sound too and would do it again. Comes in at around £52pm.
Are you looking to do the whole house or just one room?
If whole house, consider external wall insulation as you get better performance. If you are going to be replacing windows soon - do this first before insulation otherwise you have to break the insulation to change the windows later.
If you use thermal laminate board everywhere internally then you can no longer fix heavy things to the wall as you can’t anchor into the brick. And technically you shouldn’t put any fixtures into thermal laminate as you puncture the vapour control layer,
So no shelves or anything.
Historic England provide some good guides on how to insulate solid walls.
you have mould because you have damp walls.
unless you have a leak, you have damp walls because they are colder than the dew point temperature (a function of temperature and relative humidity) so water vapour will condense on them.
you can either raise the skin temperature of the wall above the dew point temperature with insulation or reduce the humidity to get the dew point temperature below the temperature of the wall.
I live in a old (1880's) house with thick stone walls, adding internal insulation would have robbed too much internal space plus the window reveals are 'organically' shaped and would have been a nightmare.
So i have a positive pressure ventilation unit in the loft. it dried up the damp/mould problems we had in the house within a week or so. Average humidity in the house now sits around 50-55% depending on the external conditions, whereas it used to be more more 70-75%
in terms of dew point, at 18 deg C, 50% RH gives a dew point of 7.4 deg, 70% is 12.4 deg.
I
Wallrock Thermal Liner
We've used this in a room.
It helps, but isn't anything like as well insulating as proper insulated plasterboard, woodfibre or hempboard.