Thermal Insulation help please!

[michu70]

Just had dorma extension built upstairs which will house extra bedroom and bathroom.
All finished outside - need to finish (more like start) inside now.
The wooden structure is still exposed inside, with thermal Recticel block insulation between the woodwork on the walls, and (deeper) Kingspan thermal block insulation between the flat roof joists, with vents on the soffits or airflow over that insulation. New building regs say I have to now have a thermal barrier on the inside of the wall woodwork before it's plasterboarded as the cold can creep through the wood! Seems I can either a) put a thermal backed plasterboard so only one fix or b) line with something thermal then board over with dryliner board.

Anyone got any experience of this or got any recommendations?

Want to retain as much space as poss so the thinner the better - and cost-effective too!

 

[r896neo]

The quickest method is to over board with insulated plasterboard which you can get down to about 22mm thick i think.

The other option is to overboard with 25mm kingspan type board and then just plasterboard as you say. This may be more suitable because it will allow you to tape the joints giving you better airtightness and also a full vapour barrier. Its also only coming out at 40mm once plastered so not a big difference in size lost.

You can't get Insulated plasterboard with a foil back as far as i know.