Good afternoon All,
If I want to insulation the inside of external walls in an old French house, am I obliged by legislation to put in a specific type or R value of insulation? I’m interested in keeping the insulation reasonably thin (so as not to loose too much floor space in a room that is 3.3 metres wide) whilst still getting a reasonable ‘bang for my buck’. As in every aspect of things I do, cost is an important consideration also . . . .
I cant answer your question Mike, hopefully someone else can but I would like to say having had the same mindset years ago I put in at the time what was considered reasonable, also not wanting to reduce floor space. Now years later having not missed the 2" of floor space at all but facing ever increasing energy costs, I wish I had doubled it to 4" (100mm). I may yet add some more!
If its a bathroom and it will be tiled/wall panelled, I would use Wedi panel and leave out the placo element which would allow a bit more insulation and less issues with placo and water of any kind.
Wedi panels - available in France at Leroy Merlin:
https://www.leroymerlin.fr/marques/wedi/
Thanks Nigel, and similar types available at other Brico’s I have noted.
Wondered whether Wedi panels are installed on top of or instead of plasterboard?
I’d also like these in plain blue - unsure whether these are available of whether I’d have to paint them.
Instead of, you can create entire bathrooms out of wedi, curves, cabinets, bath panels etc. First introduced to it on a hotel refit we did and I laughed, it being used for foam based shower trays, the architect said hit it with a hammer, I did and its very strong. Used similar under a swimming pool liner base to insulate it from the concrete, that was Dow Corning in Spain and is almost identical except Dow foam is orange and Wedi is blue.
Its finished in a glassfibre and polymer cement coating (BASF) for tiling but it could be skimmed with a plaster finish.
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Hey! I’ve done some insulation work in older homes in France before, and from what I know, there’s no strict law on the exact R-value for internal wall insulation, though it’s always a good idea to check with local regulations just to be sure. If you’re looking to save space, I’d recommend looking into things like plasterboard with built-in insulation or even spray foam. I’ve used those before, and they give decent insulation without eating up too much of the room. Of course, balancing cost and effectiveness is key, but those options seem to offer a good compromise.
None at all.
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From a diagnostic, ok so they are not great, what level of insulation is needed to reach a good score? Ok without a heat pump you cant get an A or probably a B but they must have a tick box on their sheet which gets you pretty high up? Plus the shear comfort level you can obtain.
No need to check with anyone you can just paint, wall paper or install 3’ of insulation if you want. Only new builds are regulated.
I would n’t touch this stuff with a barge pole!
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Thanks everyone for your replies. Great to get your input 
I suggest 10+80 plasterboard with bonded on polystyrene insulation glued to the wall. Easy to install, great fun throwing dollops of adhesive onto the wall, suitable for direct decoration, keeps damp at bay, and will recover its cost very quickly via savings on heating / cooling bills.
If damp is an obvious problem, then use 40mm plain polystyrene panels first, then 10+40 insulated plasterboard with the joints of the two layers offset.
Result is a warm dry house that is cheap to run.
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Then some form of ventilation is required, an air gap between the damp wall and the insulation with ventilation to let it evaporate or it will become a nasty moldy wall.
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If it’s an old building, you might also want to look at a more sympathetic solution that works really well and allows the fabric to breath.
Subject covered before below (sorry, not sure how to paste the link properly but it talks to using insulating lime base plaster with hemp)
And:
I have an old 18th Century Farmhouse and in the process of improving the roof insulation with wood wool, replacing about 40 windows from single to double and replastering some walls will insulating plaster. The Wedi panels are really cool to use to form swish shower rooms but pricey if you need to straighten out walls with metal framing etc.
Good luck though!
Exactly, as we have discovered (but it was pretty obvious from the off) in our fixer upper in Kerry. Your man before us only went an installed Kingspan PU-backed plasterboard on the inside walls, and inevitably, the condensation has built up along the inside and gets driven with the heat differential to nearest outlet it can find, which tends to be the joints with the other pieces of plasterboard, e.g. around the windows…As a result, I’ve had to rip pretty much all of it out, and let the brick and plasterwork breathe again. If I could, I wouldn’t touch the $$$$$$ stuff with a barge pole ever again.
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Out of interest, how thick was the PU insulation?
From memory, I think it is about 40mm ?
Hmm, so that would allow warmth to gradually find the cool side and condense, a mustake I made years ago with 30mm of insulation. I wonder if much thicker insulation would result in not much temperature differential and therefore reduced mold? The last PU placo I put up was 80mm + 10mm but on a frame spaced to produce an air gap and with natural ventilation behind it.
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I’m pretty certain he did it because he was volume-constrained (the rooms aren’t massive) and it is a single skinned rubble and cement build from the 1920s, so he just went for (in his mind at least) the easiest and cheapest option. The expert appraisal (the equivalent to the surveyor’s report) that we had done before we bought the place said if it were him, he’d be ripping it all out and replacing it with some kind of silicate-based insulation panels that allow the overall structure to breathe and over which you’d put a skim coat. Unfortunately, the stuff costs an arm and a leg, and so not an option for us, so we’re reduced to making the best of it and trying to get as much air into the place as possible. At some stage in the very near future, I will have to put venting and ducts with a HVAC system in to ensure a reasonable air circulation. The whole rather annoying concern is that power supply generally is unreliable (as any of the recent storms have shown us), and the power can go down for several days, so electrically driven forced air circulation systems will always be subject to that weakness.
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