Insulation in Georgian

[atlasfever]

Just to dig deeper on insulation.

Background: georgian flat, 1st floor, solid brick walls

Question:
Because the exterior walls had to largely have the brick exposed b/c of engineering repairs, the contractor has suggested that I can insulate. Does anyone have an opinion on this? He said the insulation is damp proof, or something like that. I am just trying to double check if this makes sense? As in, maybe you should afix an insulation to brick of an old georgian? i.e. any kind of technical/damp, etc issue that my contractor does not realise? The slabs would fit between the wood (vertical) beams/joists and then the lathe plaster thing on top. Some walls would be brick then insulation, then plaster.

Feedback please? hope I'm clear.

 

[Owain]

gap between the brick and the insulation, i.e. brick - gap - studs - insulation - vapour barrier- plaster.

If you are using, ahem, plasterboard, you can get it ready made with a layer of insulation foam stuck on the back.

 

[Nigel Watts]

When you say the exterior walls do you mean the interior side of them, or are you talking about external render?

Assuming you are talking about the interior sides of the external walls, which would all be brick, my advice would be to use traditional lime plaster and forget about insulating or damp proofing layers. Damp proofing the external walls on the first floor of a substantial, well built 18th/19th C townhouse in a sheltered urban environment makes no sense at all. Damp will not be a problem unless there is something wrong on the outside, such as defective rainwater goods or a later impervious external render which is starting to fail and allowing water to get trapped behind it, in which case the solution is to fix it on the outside, not the inside. If the outside treatment is right (exposed brick or lime-based stucco) then the wall will be semi porous, or "breathable", like unglazed terracotta; when it rains it will absorb some moisture, but when it stops the moisture will evaporate. This system works best if the whole wall is breathable (inside and out). This means you should avoid using any impervious materials such as cement based render, gypsum based plaster, plasterboard, damp proof insulation etc. Lime plaster is breathable and the best solution. You contractor may not like this however because lime plastering is seen as specialist work and needs more time to apply (eg leaving a week between coats and not letting in dry out too fast).

As for internal studwork walls, I can't see much point in insulating these and even less point in damp proofing them.

 

[atlasfever]

Update:

Let me a bit more clear:

The front walls where I have the oversized sash windows, and have shutters, there are vertical wood joists or maybe you call them studs, built on the brick, which allow the wall to appear thicker than they really are, in order for the shutters (when closed) to fit the depth. The lathe/plaster was built onto these studs. On other exterior walls, there are no vertical wood studs, it's just brick, and there was plaster applied directly to it it seems.

So, my contractor said we could insulate. For the walls with the studs (depth), I guess it could go behind the lathe/plaster and on the brick itself. There would be an air gap it would seem. For the other walls, it would go directly on the brick, and I'm not sure how or where you afix the plaster.

The comment above about the plasterboard having insulation is interesting, and likely would apply to one of my rooms at the back which (after the previous owner renovation) doesn't have any lathe/plaster left.

Hope that's clearer.

 

[atlasfever]

Hi All,

I found this link, might be of interest to others. i admit, makes me more nervous though

http://www.climatechangeandyourhome.org.uk/live/content_pdfs/779.pdf

 

[Nigel Watts]

How much of the lath and plaster have you had removed on your external wall? If it was my flat I would try to conserve as much as possible and repair using traditional materials eg haired lime plaster over the laths.

The conservation officer may also have something to say about wall treatment. With my grade 2 listed house one conservation officer insisted we use lime for a second floor bedroom ceiling. A few years later a different CO said we didn't have to use lime on a staircase wall, although there might have been an additional fire regulations requirement here. I personally wouldn't insulate the gap behind the lath and certainly wouln't put in anything watrerproof because if the void does get damp for any reason you dont want to prevent it from drying out.

 

[Nigel Watts]

From your leaflet:

"in the majority of cases it would not be worth considering the insulation of external walls until the full range of easier and more immediately rewarding upgrades to traditionally-constructed buildings have been carried out. These would include actions such as repairing and draught-stripping windows and doors; insulating roofs and suspended ground floors, and possibly even installing condensing boilers. Significantly, most of these upgrades will also have considerably fewer detrimental effects on the character and cultural significance of historic buildings."

Sound advice I think.

 

[JoceAndChris]

Excellent advice Nigel and EH.

This treatment would be odd in atlasfever's case, but the French like fabric. Board, cut to size, cover in bump (interlining), cover in thick fabric, screw up. That's what we'll be doing with the cold North wall in the spare bedroom.

 

[atlasfever]

Nigel, agree with your use of the quote. Check, check, check

I only have one opportunity to do the insulation now, b/c of those works that had to be done. So, now or never. The thing about central london (at least, in my humble opinion), is that many folks do refurbishments to their flats, but they do the bare minimum b/c it's either a rental and 'shabby but liveable' is the goal, or you just muster up some repairs and then sell on. That's not the approach I want to take -- so it's investigate and try to do the best possible, though of course, within a budget. There's always the budget