Wall insulation- porch

[Jake2021]

Evening ,

I’m just about to start extending my porch and between myself and next doors porch we have a double skin internal party wall which doesn’t have a cavity .

After fitting 12. 5 plasterboard on the wall I only have around 8mm to play with, which I would like to insulate. Most stuff comes a min of 25mm.

I was thinking of A- cement board(6mm) which has insulation stuff in the middle then board over that or6mm polystyrene with fire board over that?

Would this work or has anyone get any better ideas?
Thanks
Jake

 

[RandomGrinch]

Spacetherm WL? - ludicrously expensive, but only 13mm!

Spacetherm WL Wall Liner Aerogel Insulation - 600mm x 1200mm x 13mm | Insulation Superstore®

Spacetherm WL (Wall Liner) is a thin insulation system for difficult to treat walls, that can be fixed to the internal surface without the need for mechanic...

www.insulationsuperstore.co.uk

 

[^woody^]

I'm not sure of the value of thermally insulating a unheated porch that has another porch room on the other side of the wall.

What's the payback time of that expensive spacetherm? 100 years? More?

Don't forget that whatever you choose needs to be stuck on or fixed. Allow for that if space is limited.

 

[Jake2021]

Hey woody,
Hope you are keeping well.

I want to get building regs to remove the inner door so I need a thermal r value to match the building regs so I though since the rest is going to be double skin cavity I may as well put some insulation on this party wall, I just assumed as it was double skin there would be a cavity but unfortunately not !