Looking for some advice on what would be the best material and way to insulate these. Looking at the build up I have about 25 mm this includes the skim coat, this will take it to about halfway across window frame and I wouldn’t want to go any further than that.

Regards. James

Do the cheeks not have insulation in them already ..?

There is a little, wasn’t sure how much ld need to prevent cold bridging. Was thinking some sort of material over the full triangle area to prevent to much heat loss in rooms.

Anyone ?

I think the only material that's of any use at that thickness would be aerogel.

This problem is the main reason I did not want dormers on my build, aesthetically i like them but well insulated dormers can be very chunky and ugly. Although a cold bridge it’s not a huge area

Was looking at the aerogel but I have six cheeks to do and that stuff is very expensive, was hoping for something a little cheaper.

Celotex do a 12mm PIR board

XPS would do it too, I used some 10mm in our bathroom reveals just to get a wee bit more condensation protection.

Trying to find 12mm celotex near me and in stock not a chance. Been looking at XP’s and other makes of thin foam some on amazon and tile places,as you say anything is going to give it better protection.

Regards. James

20mm wood fiber covered directly with skim?

 

So with this there is no need for plaster board? Plaster straight to it. Have you had any experience using this material and have you any links to it, wouldn’t want wrong stuff so many likeness/ copies of things nowadays.

 Regards. James 

Polystyrene wallpaper? It's a couple of mil thick, you could stick up a few layers then plaster board. Not as good as the other stuff mentioned, but might be available

No experience with this., just seen it online. 

 

You can defiantly render onto it directly, with breathable plasters and paint ideally,althought you might be ok with conventional materials given the placement in the structure.