Could you make the external wall a trombe wall?
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I dread to think what’s behind the plaster board. My first guess is very mouldy Victorian wallpaper on the original plaster.
You definitely need forensic suits and breathing equipment to clear the room.
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I love this idea! I had to Google it and found the following link.
Our gable end wall is south facing, but it’s externally covered in a network or piping and wiring . How would the heat in the cavity affect all of this ?
https://www.sciencedirect.com/topics/earth-and-planetary-sciences/trombe-walls#:~:text=The%20Trombe%20wall%20is%20a,enter%20the%20indoor%20[4].
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I’ve been wondering if someone might like the larger Vent Axia I have and swap me for a smaller one .
And buy an Aereco for the bedroom.
Definitely will have mask and coveralls. We don’t want to breathe in any nasty particulates.
I realised another potential problem - the ceiling in this room is also plasterboard with a moulding attaching attached. Above that is 30 cm of sheep wool.
If we’re going to all the trouble replacing the gypsum wall coverings with lime - what do I do about the ceiling. The old lath and lime plaster ceiling is completely gone on this side of the house. What is our best approach with the ceiling?
I’m starting to wonder about the lime with aerogel board or clay board options mentioned.
@Tim_Gilbert
@zapaman
@Clive_Durdle .
When I think about costing and how much more labour intensive one option might be to the other - versus cost of materials ??
On another note , I went to visit my neighbour last night. Her house still has all the original lime plaster upstairs. I went into the same little bedroom with the same external wall situation as ours. Her bedroom, also with a storage cupboard ram jammed full of assorts in plastic bags and boxes is as dry as a bone. She stated she never has had a damp problem . In fact - her upstairs was noticeably, far more temperate and comfortable than ours.
I couldn’t have been more impressed and I’m certain that vapour open lime is the way to go.
Other things I may have overlooked .
This bedroom was originally part of one large room with two windows, which was split into two rooms by a stud wall also covered with gypsum plasterboard.
In my mind , the plans for the room were to replace only the vapour closed gypsum plaster wall coverings on the two external facing walls - then it occurred to me - will we actually create a thermal envelope by only changing the wall coverings of the external two walls and the ceiling? 
Are there problems or benefits still to be had with our focus area?
When you installed the insulated ceiling did you cut the aligned wall plaster back to the brick (to reduce thermal bridging) and run your vapour control layer down the exposed brickwork. No? I would probably not have done either.
I fear that you are going to need to disturb the edges of your ceiling. Any IWI can then be taken up to the top of the wall and the two insulations overlapped and abutted to remove thermal bridges. The old plaster needs to be removed anyway, unless you believe that there is no dampness that high on the wall.
Changing your proposed insulation and/or wall finish won’t alter the above.
It is fortuitous that you were able to visit the same room in the “same” house in a different time zone. I take it from your description that it is also split be a partition wall.
You may have the answer by copying the past or maybe you could be inspired by the past for the answers of the future. Perhaps a lime based plaster with integral insulation? You could look into Diathonite.
Hi Carla, we had a similar small bedroom, with South & East solid brick 1910 external walls, one party semi neighbours wall & one internal lath & plaster. Gaps round window where sashes had been removed & some pointing issues.
Was definitely the coldest room in house in winter.
But we didn’t have persistent damp or mould & mostly the original lime plaster was in good condition so were able to retain it.
Didn’t want to loose much internal space as room only 2.7 x 2.8m.
Our retrofit assessment recommended a target u value of 0.4 W/m2K .
We compared prices & overall build up thickness for PIR, aerogel, wood fibre & cork.
Aerogel spacetherm wallboard was the thinnest but is very expensive & not easy to fix/work with (we don’t have a nail gun!)
PIR/plasterboard is next thinnest but with cost of battening & membrane the price mounts up.
Cork & woodfibre/lime plaster are similar build ups but cork is more expensive.
We’ve been trying to use breathable natural fibres where possible so went for 80mm wood fibre (stieco therm) with lime plaster (Adaptavate) & mechanical fixings (ejot) (basically a hybrid of the ecomechants/back to earth/Ty mawr recommended methods).
We had a new triple glazed window and sealed & insulated the lintel, sill & reveal with a combination of tape, diathonite, Pir & plasterboard to fill up the ‘sash boxes’ (ok, not so natural or breathable!)
We couldn’t find any window manufacturer who would supply without trickle vents either.
We used parge coats of diathonite (~2mm thick) around floor joists to ceiling below and above up into wall in loft. The woodfibre continued up through ceiling into loft about 100mm.
When we did the loft we similarly parged around edges & left excess intello which we were able to bring down and join with tape/plaster to the wood fibre.
Around perimeter of external walls we infilled between joists with natrahemp batts approx 600mm into room under floor.
If/when we insulate walls in room below we should hopefully be able to join up contiguously through the diathonite layer.
We did the work ourselves except for the lime plastering, cost of materials was around £700 inc. woodfibre, fixings, tapes, plaster, clay paint, delivery & government diy insulation penalty charge.
It was completed just last month so haven’t had a winter yet, it’s been so hot in last week that hard to say if we’ve cracked the decremental heat - but the room does have a good ‘feel’ about it!
Hope this helps. D&H
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That looks like a well researched and planned job. Well done. Please post an update in the spring, if not sooner, with your winter experience.
I think we might have to look into replacing the lime plaster base layers ourselves.
I’m not confident we’d be good with the final finishing coat though.
I briefly mentioned brise soleil above. If summer overheating remains a problem this link could be useful.
Thanks Tim. I’m rather delayed responding to all this great feedback, but I I did take a little look at this and just read some more .
About the Brise soleil - looking at it I read about orientation and how the the effectiveness of brise soleil can be reduced - our front is approx 130 Southeast facing.
*Horizontal brise soleil ‘shelves’ will not work as well on east or west elevations as the angle of the sun is lower ― sunlight will pass underneath. In these situations, a system that uses multiple vertical blades in front of glazing may be more effective.
Another factor is when it’s hot in the room in question. Even throughout the night when it’s considerably cooler and the sun has long before gone around the side to the back, the room remains sweltering.
I think the bricks are heated through the day and then release the heat into the room throughout the night. I wonder if improving the u-value of the wall with good lime parge layer / lime cement and lime finishing coat lime will be sufficient to enable a more temperate room - or if wall insulation may also be needed.
A brise soleil across the window would help somewhat too it seems.
The ceiling in the bedroom is also just flimsy layer of plasterboard, with 30cm of sheepwool on top. I’m considering lowering the ceiling to add in more insulation too.
Interestingly and a boost to my confidence around replacing the gypsum with lime , was a recent trip to my neighbour who still has all her lime walls in tact - there is no sign of damp and the rooms are lovely and temperate. It has convinced me to restore the lime walls as completely as I can.
Indeed her house and my house together are the perfect example of what goes wrong when a Victorian house built to be breathable has the layers replaced with non breathable and moisture becomes a problem.
Her home is my envy !!!
Although a brise soleil is usually associated with windows, I know of one family that fitted one along their entire south wall. The brickwork remains cool. The slats of a brise soleil can be vertical if you prefer but should pass left to right rather that to and from a window.
You can build shades for east or west facing walls/windows and they will have some effect but if you have serious overheating then vertical blinds will be best. Something looking like a Venetian blind would be good for windows and vegetation can shade the walls. In winter the blind can be removed but vegetation is generally fixed.
Lowering ceiling height will help make a room warmer, whatever the time of year, however purge ventilation to expel hot air at night will be improved.
I have nothing to add to your lime plans, apart from “
”.
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I am about to fit a shade for my WSW back wall. [Edit: ground floor only.] To avoid thermal bridging it will not be fixed to the house but freestanding 20cm from it. The depth will be 1.75m. That is the length of the solar panels that I’m going to fit above my ground floor windows.
As you can see, I’m killing two birds with one stone. I should get an extra kW output, to contribute to my heat pump requirements.
That is a great plan Tim ! I love it 
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