Best thin internal insulation

[Dusty]

Hi all

 

I have an old solid wall brick cottage. On one side an internal breezeblock skin has been built and the exterior walls have all been cement rendered. The property is cool in summer and freezing in winter. I am tight on space as externally the building is only 4m wide. Whilst I appreciate external insulation would be better, I am in a conservation area and I may need to alter the roof to accommodate this. Is there a good, high performance thin internal insulation which would be suitable please? I have seen Kingspan Optim -R advertised an wondered if it was any good?

 

Cheers

[TonyT]

Aerogel?

[Thorfun]

Kingspan Optim-R (other makes are available) is a vacuum sealed insulation board that is made to measure. they cannot be cut and if they get nicked by anything then there goes your insulation value. plus they are stupidly expensive. I probably would look down the Aerogel route that @TonyT mentioned.

[RobLe]

Digikey looks like they sell the similar Panasonic U-vacua.  Please check my maths - I think the largest 610mm by 610mm by 25mm thick panel (link below) at £53 each is equivalent to about 125mm of celotex.   So it’s much better performing than an aerogel blanket(which only just beats celotex), but pricey for a whole house - and don’t hammer in any nails!

I think these panels are actually used in high end fridge freezers.

 

https://www.digikey.co.uk/en/products/detail/panasonic-industrial-devices-fbd/CNRZZB78400/9558502

[Temp]

Be careful because although pure Aerogel is the best insulation material the blanket stuff sold for house insulation isn't always massively better than cheaper insulation. In terms of the thermal conductivity lower values are is better...

 

Aerogel blanket

      GORE Aerogel Blanket - about 0.020 W/mK

      Thermablok Aerogel - about 0.015W/mK 

      Proctor Spacetherm - approx 0.015W/mk

 

Phenolic board

Kooltherm K5 - approx 0.021 W/mk 

 

Polyisocyanurate (PIR) board

Celotex GA4000) - approx 0.022 W/mK.

 

So i would expect.

150mm of an Aerogel blanket to be equivalent of 210-220mm of Phenolic or PIR.

75mm of Aerogel blanket to be equivalent of 100-110mm Phenolic or PIR.

 

 

[JohnMo]

57 minutes ago, Temp said:

150mm of an Aerogel blanket

Would cost a small fortune, I doubt its even available at that thickness.. No one would buy it that thick

 

10mm thick 1.2m2 is £230!

 

Old buildings you need to be careful with condensation also.

[SteamyTea]

Insulation is a strange thing, and often misunderstood.

For every doubling in thickness, you generally only get a 50% improvement.

While not ideal, you may find that adding just 25mm of just about any sheet insulation greatly improves the place.

Before you do, start by finding all the air leaks. Sorting them will make the biggest difference.

[Dusty]

Ok thanks everyone for your invaluable advice. It seems fitting the house out with the ultra-thin vacuum blanket stuff could be prohibitively expensive. 

 

The advice to fit 25mm of sheet insulation would be affordable. If this greatly improves the house then I will be very happy. Would this just dot and dab over the existing plaster or would I need to go back to bare brick please?

 

Many thanks

[bmj1]

I've had to solve this problem for cavity walls... if you want something for your walls, look at this: https://www.mannokbuild.com/pir-insulation/mannok-therm-laminate-kraft-mlk/

 

Insulated plasterboard, you choose from 17mm of PIR + 9.5mm plasterboard (26.5mm total), up to whatever thickness you want.

 

Has paper facing for dot + dab, for ease of application.

[SteamyTea]

39 minutes ago, Dusty said:

Would this just dot and dab over the existing plaster or would I need to go back to bare brick please?

If you take the plaster away, you get another 12mm or so.

Edited September 26, 2023 by SteamyTea

[Dusty]

10 minutes ago, SteamyTea said:

If you take the plaster away, you get another 12mm or so.

Yes that's what I thought thanks. Upstairs that extra 12mm  will be very helpful. I presume they will be fitted to wooden batons? 

[SteamyTea]

49 minutes ago, Dusty said:

I presume they will be fitted to wooden batons

Not necessarily, you can get insulated plasterboard that can be glued to the wall.

One thing to remember is all your sockets may need to be adjusted as the cable may not be the correct length, and you may need to get some rating calculations done on them.

Also, if you use polystyrene insulation, it must not touch PVC cables.

Also, also, think about any pipework, shirting and coving, and window cills.

[Iceverge]

You could blow EPS beads into the side with a cavity wall. 

[TonyT]

The OP advises it’s a solid wall

[Iceverge]

On 24/09/2023 at 14:02, Dusty said:

On one side an internal breezeblock skin has been built

 

I assumed there was a cavity here for some reason. My bad.

[Dusty]

11 hours ago, Iceverge said:

 

I assumed there was a cavity here for some reason. My bad.

Yes there maybe a very narrow cavity behind the breezeblocks on one side? Thanks for the advice.

Edited September 27, 2023 by Dusty

[Redbeard]

I would normally advise not to remove plaster (though that applies particularly to lime, and I would normally remove Gypsum) and NOT to use 'pure' dot-and-dab. Preferably full adhesion of the boards, or at very least full perimeter beads with cross-hatchings. If you get air movement behind with D&D you may thermally separate the original wall and the insulation ('thermal by-pass'). With D&D that movement is almost completely unfettered. Removing the plaster (what was advised 40 years ago -along with D&D - when I started IWI) loses you a valuable air-tightness layer.

 

Slim solutions as suggested are unlikely to meet the 0.3W/m2K wall U value target for Bldg Regs. Many would say simply do not apply for B. Regs, but it can potentially come back to bite you when a future purchaser feigns horror at your failure to get approval but agrees to be less horror-struck if you drop the price by £10k. If it is impracticable to meet the target waivers are available.

 

[Mike]

Not sure how affordable or available it is, but there is at least one company that produces an insulating plaster/render that incorporates polystyrene granules - Vimark Thermointonaco. It could be useful if/when you need to re-render the outside. In Europe I've come across one or two similar products incorporating aerogel, but not in the UK.

[Dusty]

21 hours ago, Redbeard said:

I would normally advise not to remove plaster (though that applies particularly to lime, and I would normally remove Gypsum) and NOT to use 'pure' dot-and-dab. Preferably full adhesion of the boards, or at very least full perimeter beads with cross-hatchings. If you get air movement behind with D&D you may thermally separate the original wall and the insulation ('thermal by-pass'). With D&D that movement is almost completely unfettered. Removing the plaster (what was advised 40 years ago -along with D&D - when I started IWI) loses you a valuable air-tightness layer.

 

Slim solutions as suggested are unlikely to meet the 0.3W/m2K wall U value target for Bldg Regs. Many would say simply do not apply for B. Regs, but it can potentially come back to bite you when a future purchaser feigns horror at your failure to get approval but agrees to be less horror-struck if you drop the price by £10k. If it is impracticable to meet the target waivers are available.

 

Thanks for the heads-up. There is internal lime plaster on one side of the building, however there is cement external render. Would this keep the wall airtight? I don't care about meeting any targets or building regs. I just want a warmer home and I am sure any future purchaser would be happy there is some insulation in such an old property. It will be me fitting the wall insulation, I just want to make sure I achieve a decent improvement and it not be a waste of money.

  

Edited September 28, 2023 by Dusty

[Iceverge]

Have you had a look at the floor and the ceiling? 

 

Is there any ventilation etc installed as is?

 

 

[Redbeard]

On 28/09/2023 at 08:21, Dusty said:

Thanks for the heads-up. There is internal lime plaster on one side of the building, however there is cement external render. Would this keep the wall airtight? I don't care about meeting any targets or building regs. I just want a warmer home and I am sure any future purchaser would be happy there is some insulation in such an old property. It will be me fitting the wall insulation, I just want to make sure I achieve a decent improvement and it not be a waste of money.

  

The cement render may limit the wall's ability to pass water vapour to and fro, and the lime plaster, existing as it probably doesn't (!) behind the skirting boards, may not be wholly airtight.

 

I take your point re Building Regs but I also note the increasing tendency for buyers' solicitors to pick up on any 'failings' (such as not having BC approval for works), note how dreadful this failure is, and then the buyer agrees to overlook the failure if the asking price is reduced by 'x' (where x = an indeterminate number of thousands of pounds). I am sure they may be grateful for the insulation, but potentially even more grateful for the 'cash bonus'. If I can wave a completion cert and avoid this sort of behaviour I will.