Internal solid wall insulation - What's best?

fix

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Hi I'm renovating a terraced house which with the way it's built the downstairs is basically detached and all four walls aren't joining another house (only upstairs joins another house).

The entire house needs plastering so I thought while I was at it, it would be best to insulate the living room before plastering as it gets pretty cold in there.

Ideally I would like the simplest method, attach insulated plasterboard to the walls and skim over, however from reading up it doesn't seem that straight forward, there needs to be a vapour barrier on the internal side, and if using foil backed plasterboard it cant really be dot and dabbed.

What's the best way to do this please?

I know another way to do it is to build a timber frame, but I have a few questions about this method:

Can I use a wool type of insulation in the middle, then a vapour barrier over the top then normal plasterboard? If so what about cutting into the vapour barrier for plug sockets etc?

I know I can use kingspan in the middle of the timber, but I guessed wool insulation will be cheaper!

Thanks
 
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The plaster+paint/wallpaper will make a good-enough vapour barrier. It's not like it's a bathroom or sauna.
 
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Insulated plasterboard tends to have a vapour barrier built in. I have used both insulated plasterboard and celotex between battens with the joints foil taped and then normal plasterboard in different rooms and have been happy with both approaches.
 
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Framing in 4 x 2 (or whatever) gives you plenty of hard points in the wall to fix things to (radiators, skirting boards, anything else you might fancy) but filling the gaps with Celotex or equivalent solid insulation is a pain - the insulation needs to be a tight fit between the battens to achieve the thermal performance so you'll get a certain amount of wastage and a lot of dust and swearing while you cut the stuff up. And yes wool is cheaper (rockwool etc) but you need it thicker to achieve the same notional performance- think 100mm solid is equivalent to 150mm wool but check that.

Bonus with solid insulation is (a) built-in vapour barrier (b) if the outside does become damp it is fairly non-porous so the damp won't percolate through the boards.

Cabling- if you can spare an additional 25mm on wall thickness, the easiest way is to do your insulation however you do it then add 25mm vertical battens to create a service void (you then fix your plasterboard to the battens). Bonus of this void is it makes retrofitting extra stuff feasible (if you have access to top or bottom of void).
 
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In my stone built part of the house I used roofing battens and put 22-25mm insulation boards between then the same insulation over the top of the battens to give me approx 50mm of insulation the plasterboard on top, this was not the quickest way but it did allow me to pre plan cable runs and voids to allow TV cables to be used on brush plates etc so cables can be changed at later dates. Rooms although only 50mm of insulation are a lot warmer compared to the stone and plaster of before and only a small amount of space was lost in each room.
 

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Thanks everyone for your replies, has anyone found a sensible/effective way of attaching insulated plasterboards directly to the outside wall then skimming over, and having a vapour barrier in place? This although probably not being as effective as building a frame, would be quicker and cheaper.

Thanks!
 
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Thanks very much I'll have a read of that, after I put the post above I came across this website which seems to explain things pretty well: http://www.superhomes.org.uk/resources/internal-wall-insulation-1/

If I did go down with creating a frame, where they say about placing the kingspan on the wall then attaching the frame on top of that so there's a cavity sounds plausable, however they then say to fill the cavity with more insulation which seems overkill.

Foil backed kingspan, then a frame creating a cavity, then plasterboard sounds good, then there would be space for plug sockets etc, with less fear of damaging a vapour barrier with the cavity there.
 
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The kingspan doesn't have to be foil-backed, it is - unless you are a physicist- impervious to water and will therefore form your vapour-barrier if you either tape the joints or if it is available T+G.
 

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