As this blog has outlined before, heat loss from buildings is big problem. Not so much since the means to stop it exiting doesn’t exist, but the difficulties in retro-fitting it and the expense. Another issue is breathability and therefore damp.
Some means of keeping the heat in such as roof insulation, lagging pipes, hot water tanks or stopping drafts not only make economic sense but not surprisingly are usually easy to carry out. As I’ve written on before I’ve done the floors of our house and I reckon the payback on that is probably 4-5 years. (I combined this other work and did when we were going to get the floors sanded and vanished.) Floors are easier than people think, but not as easy as bunging stuff in the roof.
Walls however are different matter. Do you insulate on the inside and therefore potentially make the room smaller, or the outside in which case you will probably need a building warrant and or planning permission? Or the inside with all the disruption? There’s no simple answer to this and the solution will depend on particular situation.
We had a room with a daughter in it and a lot of her stuff. When she and her partner moved out we discovered two areas of damp. (Which to be fair we were aware of in the past but had forgotten about.) We had two damp surveys – one free and one we paid for. Both agreed there was no rising damp issue and both agreed about the damp patch associated with the old chimney, but disagreed about the second on the wall against the underside of the stairs. This wall is technically inside the house, but the same time external because the next stop is the external wall.
I searched on-line for a solution and found one. Insulating lime. All the steps are shown in the images below.
First I removed a rectangular section of the 170 year old lime bigger than the patch. I took maximum care doing this since I suspected the old lime would have horse hair added as binder in it. Due to the risk of anthrax I wore a face mask and gloves.
Then I re-pointed the brick work with some lime mortar where necessary and applied the insulating lime. This stage isn’t easy, or at least I didn’t find it so. I fixed two wooden battens to the wall at depth I wanted the insulating lime. Then you’re supposed to flick the lime at the wall using a trowel so it sticks between the wood. I’ve since found throwing it underhand works better. This is different to normal lime plaster which you push on with a float. The reason for throwing it is so the structure is more open and therefore insulating. Frustraingly the lime kept falling off so in the end I had to push it in. Its not very open looking (there are pictures and videos on-line to compare it with). After applying the lime I ran a straight edge (I used a piece of wood) to level the surface using the battens as guide.
I let it set then removed the battens and filled those in with lime.
After this had set I applied to very thin layers of topcoat lime (specific to the insulating lime) at about 1mm thick each. This is to protect it and make it look nice. Again not easy but after some sanding it wasn’t bad (see picture below).
Next we paper over it and painted over it. This you are not supposed to do since it won’t be breathable. The worst case scenario was that we would have to remove all the paper from that wall and paint it with breathable paint. I knew this would work since when we stripped the paper back from that area before removing the original lime it dried very quickly.
In any event the problem has been solved. We were very lucky that the depth of the original plaster was 25mm. This is the minimum depth you use. I put about 23mm on plus the top coats. In some places it was deeper than that due to the wall not being vertical and the bricks being recessed etc.
We sorted out the problem with the chimney damp (this is another post since I threw the book at it), insulated under the floor leaving gaps and had sanded and vanished. The floor company left some gaps between the boards so the room would breathe. Its drier and warmer than it was.
Is this stuff the solution in historic buildings? I look at the plaster wall in our church which is a bit older than our house and also stone. Yes technically – but cost wise its not cheap.
I’m currently insulating with another brand of insulating lime elsewhere and will at least put this up on Facebook when it’s finished.
Neil



