Insulation recommendations please

[AJB Temple]

The main living area in our house is about to have a major revamp, including dumping the carpets and laying a limestone floor. The living room area has a north wall 10 metres long and an east wall section 6 metres long both of which are going to be panelled and painted by me.

I plan to stand these either 100mm or 200mm off the existing walls using C16 stud, and back fill with insulation. Cost is a factor. Could use kingspan (celotex) - expensive :shock: , rockwool, natural wool bales (if I can find it), loft insulation etc.

I seem to recall a thread on here which used some sort of blown loft insulation but can't find it now.

Any recommendations for insulation for this job? I realise that insulation efficiency may be less with a cheaper product, but this is really beefing up what is there already, not a new build. The primary motivation is cosmetic revamp and get rid of remaining carpets in this house. Must not increase fire risk.

 

[sunnybob]

Why would you take 8" (200mm) off your floor area?
Make the effort to find rockwool if you dont want to buy the rigid celotex, 100 mm of rockwool behind foil backed plaster board will do the job.

 

[Mike G]

What's the build-up of the existing wall, Adrian, say working from the outside inwards?

 

[Lurker]

I’m sure I read somewhere that wool can be a nightmare.
Moths and sags and damp?

 

[Mike G]

Jim.......yes, no, yes. Last time I looked (a while ago, admittedly), wool doesn't have a BBA certificate for use in walls. Only in lofts.

 

[AJB Temple]

Mike, out to in:

Painted timber cladding (Bedec)
Batten
Membrane (not sure what make)
6" concrete block infill to oak and steel frame set on brick piers. Low down is brick, then heavy concrete up to a point, then some sort of thermalite I think to top
Thin insulation layer (not more than 30mm celotex or 1980 equivalent, no idea if foiled
Plasterboard
Horrible rippled render in thin coat on that.

Old barn as you know but hacked about and converted by bodger the builder long before my time here. Not listed. Some walls are brick double skin and outer clad, but the north wall on this part of the building isn't.
No airbricks, no damp.

 

[sunnybob]

I've had two houses infilled with blown rockwool into the cavity in England, and never had a single problem. But that was almost 40 years ago now so I expect theres a lot more legislation.

 

[AJB Temple]

In my case that would be an imaginary cavity Bob.....

It's an old barn. Frame allegedly dates from 1680. In my opinion that is probably a made up fact by some estate agent of yore though. But is certainly documented as pre 1900 and cavity walls were not really a thing in barns and oasts. No idea what planning policies were in 1980 ish, but based on the work exposed, I doubt the developer had compliance with regs at the top of his list.

I don't care about losing space. In a room 10m by 6m, 200mm along two walls will make no difference and will look radically better.

 

[Mike G]

How do you feel about pulling the plasterboard off? Or at least a patch or two. Ideally the new insulation you add internally would be hard up against the existing insulation, with no gaps, and no vapour barrier between. Therefore I'd try to avoid having foil-backed plasterboard left in place, if that's what it might be. Also, the gypsum plaster that is presumably on there at the moment acts as a partial vapour barrier.

I would certainbly suggest you go for a soft insulation such as mineral wool, Rockwool, or fibreglass, so that there are no air-gaps. Trying to press a board such as Celotex up against existing would inevitably leave gaps.

Inside your new studwork you should then either have a vapour barrier (polythene) or use foil-backed plasterbaord.

The other thing to consider is what happens at the margins. There's not much you can do about the bottom of your new studwork, but the top and the ends need thinking about. This is in the 2 storey element of your house, isn't it? In which case, are you proposing to do the same upstairs? If so, you should also fill the floor void with insulation for at least the width of your new wall. And the ends. Will the new studwork abut internal walls?

 

[PAC1]

Adrian, Have a look at this: https://www.soprema.co.uk/en/product/in ... lair-multi
or this one
https://www.soprema.co.uk/en/product/in ... re/pavadry
My local Listed Building officer suggested it to me. I have used it in my lounge and bathroom against a solid brick wall. I am very impressed and much warmer.
Obviously a solid wall is different to your construction but it is definitely worth considering.

 

[AJB Temple]

Thanks Peter. Most helpful, I will look into that.

Thanks Mike.

Yes, this is in the two storey plus loft part of the house. The drawing room is on the ground floor and is to the right of the triple height inner hall, separated by solid double brick wall. From there is a 10m wall that ends with a short turn of a metre that is now (after I altered it) a double thickness wall that then becomes the fully insulated all round piano room.

Above the drawing room is the master bedroom and bathroom. That north wall will become a bathroom and dressing room all along the north side, and I will build a new interior wall as well. I've already insulated under the floor (oak not laid yet) as I did that when we put the plumbing through to the kitchen building. That is with foam around insulated pipe etc gaps and then 200mm rockwool.

Thinking about it from when we did the piano room oak framed abutment, there is no foil in the original barn wall. At least on the East side and I see no reason why the North side should be different.

The textured (not artex and not asbestos) gypsum plaster is going to have to stay there. It makes a hell of a mess to get off as it is extremely hard. Possibly cement based. I was going to smooth plaster it, but then I thought it makes a lot of sense to add 200mm insulation and panel the room. This of course will completely hide the oak posts and beams. I will take photos for any future buyer, but in my opinion the idiot developer ruined the lower part of the oak frame when he did his original conversion work, so to me although it is the posts and original beams, it is hacked about to much to be desirable and so we will now go for a clean look that is more modern. It can be taken back to original if a future owner wants.

Noted re additional vapour barrier. Thanks for that - I had forgotten that but I have a roll in stock.

 

[Mike G]

How have you arrived at 200mm for the additional wall thickness?

 

[MattS]

I have no idea about building regs and what a good wall make up is! But do have an interest in sustainable building materials - how about something this company offer? Fairly local in Lewes

https://kindsupply.co.uk/products/savol ... ool-boards

 

[AJB Temple]

How have you arrived at 200mm for the additional wall thickness?

That depth fully covers the old oak posts and the brick plinths. It's also readily available as a thickness.

I think to go any thicker is going to give me disproportionately deep window reveals. The double glazing becomes the weak point, and any thinner leaves a void as the panelling needs to cover the bricks.

............

Matt - thanks for that. But the material is not useful in this application, where I already know how I will make the panelling and I am mainly looking to insulate.

 

[Mike G]

I wondered if it was to get over a projecting plinth. That's an extremely generous depth of insulation. You'll get much the same benefit with 150mm, which is also a standard thickness/ multiple of thicknesses. Bear in mind that you'll probably end up doing it in 2 layers......one behind the studwork, and one between the studs.

 

[AJB Temple]

Thanks Mike. Yes, I have to get past the brick plinth. I may as well pack everything with insulation as cost difference for extra 50mm is trivially small. I will check prices for roll thicknesses as I plan to do two other wall sections at 100mm just to avoid having a drum effect on the paneling as the TV will probably be hidden in this plan.