Just wondering what people's experiences are of insulation applied to the exterior of old stone walls? It's relatively new in the UK. It apparently totals 70mm in thickness, consisting of 3 different layers. In theory, it is the ideal solution to old stone houses that have no cavity, and where battoning and plasterboarding with insulation would lose too much space on the inside.
Has this product greatly increased anyone's thermal conservation, as well as removed the usual cold ingress problem? (cold wall surface + moisture in the air = damp and mould).
I'd be interested to hear any info at all on this, as we're considering it for our stone cottage.
The fact is, that heat always moves to cold, as indeed does water vapour. If you add insulation to the outside of a wall (or anything else for that matter) the walls will still soak up most of your heat. If you are retired, or live and work at home, and keep your heating on 24/7 thoughout the year, then putting the insulation on the outside, may help to keep you warm, but it won't do much good. Insulation needs to be on the warm side of your walls. Try putting your hand on a piece of polystyrene and feel the warm reflected back, then put your hand on your wall, the wall will always feel cold, even if you manage to get it up to 22C.
Your question on External Wall insulation, we are a weber approved installer of various systems and have just completed 29 houses for Lovell in Nefyn and Abersoch and can recommend this system for the cost saving in your heating bills of around 40 % and from a practical approach in reducing the Governments Carbon emissions as part of the Green Deal Program. The other requirements for you to also consider are your windows and doors,and Roof ? how old are they and what kind of thermal protection you are currently at, and your loft insulation, is it adequate? Remember for any system to work as per manufacturers Guarantee you have to have qualified and accredited installers, this type of system is a bit beyond your normal Plastering and rendering company, you need to be separately trained on how to install these systems. Check out weber I think they have the best product on the market and I know it definitely works.
The trouble with Dave's statement is that it is true, external insulation will save some heat from passing through a wall in a direct line, heat always moves in a straight line from hot to cold. Dave's sin is one of omission, what he doesn't mention is that a lot of the heat entering a wall also goes straight down the wall into the ground, and up the wall into the sky. Think of a Thermos flask, the contents stay hot/warm because the contents are surrounded by a vacuum the only point of contact with the outside is the thin amount of glass or stainless steel that makes up the neck - and of course heat leaks out of the neck by conduction.
If you want a room to stay warm, at the lowest heating cost, then the heat needs to be retained inside the rooms envelope, we cannot buy a vacuum the shape and size of a room, what we can do is to line the walls, ceiling and floor with polystyrene (not as good as Aerogel but one hell of a lot cheaper) by gluing polystyrene to the walls and then gluing plasterboard to the polystyrene, or buying the product ready made 8 x 4 sheets, screwing ditto to the ceiling joists, creating a fully floating floor, we get as close to perfection as we possibly can.
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