Avoiding thermal bridge behind external insulation

[Andrewb]

Good evening,

I wondered if anyone could critique my design of a particular junction on the garage conversion project I am doing. The project adds a first floor and brings out the front of the old garage by 500mm.

 

The existing cavity walls have small cavities and I plan to externally insulate them.

The new front wall will be wooden clad, and due to fixing issues and potential fire risks I am not externally insulating this front wall.

I'm therefore left with a potential issue of a cold bridge from the front outer skin down behind the external insulation of the side wall. My solution currently is to use blocks with improved thermal properties on the outer skin of the new front wall.

 

Could there be other ways, such as a thermal break at a wall starter where we extend the existing side wall? I'd be keen to get any of your thoughts.

 

In the image below, the red lines show the position of the existing garage wall and garage door.

[Andrewb]

I might look at fixing compacfoam to the existing wall and then fixing a wall starter (possibly with thermally broken fixings) through the compacfoam to build the new wall from. This would hopefully reduce the cold bridge behind the new ewi. Then I could revert to standard blocks, which I'd prefer as I'm worried about mannok blocks being more prone to cracking. Any opinions?