u ratings - 3.6N Aerated Celcon versus 50mm Cellotex

[Draughtsman]

I have a car port under the end of the house, the supports for the house are conc. blockwork, L shaped (in section) piers with a 2" cavity containing Rockwool or similar insulation. The car port is being converted to domestic/internal room.

BC says that original internal faces of car port piers need 50mm of insulation to achieve necessary u value, but I'd be happier just hiding them behind a standard 100 thick aerated Celcon/Thermalite wall (I don't mind losing the extra 50mm of space). I don't like stud walls and avoid them like the plague.

Is this likely to be acceptable? Will 100mm aerated blocks boost the u value as much as 50mm Cellotex?

 

[Nakajo]

Ah. Misread.

 

[^woody^]

Your wall will need to be 500mm thick

 

[Nakajo]

On my spectrum of things to avoid, it goes stud walls, then 500mm thick walls, and then the plague.

 

[cdbe]

Have you considered "glueing" celotex bonded plasterboard on? Will feel a bit more solid than a stud wall.

 

[^woody^]

On my spectrum of things to avoid, it goes stud walls, then 500mm thick walls, and then the plague.

Lightweight

 

[Nakajo]

Yep. Still trying to decide where to position Woody on that spectrum.

 

[^woody^]

 

[lt8480]

Is this likely to be acceptable? Will 100mm aerated blocks boost the u value as much as 50mm Cellotex?

No.

Insulation is about 10 times better at insulating.

 

[Draughtsman]

My list of things to avoid usually puts things that I can't do at the top.

Dot'n'Dab - I won't be able to do that.

Would a 50x75 (63 deep) CLS frame be ok? With 50thk Cellotex inserts. Faced with 12mm plasterboard. Only 12mm behind the boards for cables though.

Or maybe 100mm CLS (89 deep) would be more rigid, with more room behind the Cellotex for running cables.

@ what maximum ctrs?

Presumably I need a wider landing where the vertical edges of 2 boards meet, than the 38 wide edge of the CLS?

 

[lt8480]

Most insulation companies provide literature/brochures on this including whole wall build ups.

Try https://www.uvalue-calculator.co.uk/calculator/ for u-value calcs using Kingspan. Cellotex have a similar calculator you just need to register/log in.

 

[Draughtsman]

So, a 4" deep stud would let me run any pairs of socket cables well back from the face. Noggins adjust locally to back boxes so that they can be screwed in on 2 sides. Sole to sit on a length of that damp course that brickies use.

Does the membrane that's going under the flooring also run under the stud wall, up to and up the existing walls, with the the stud built on it? Or does the under flooring membrane just run up to the stud wall?

 

[Draughtsman]

BC says sheet membrane runs under the sole and up to the wall..

Any thoughts on sheet membrane, does it need any geotextile type protective matting above/below?