Insulation detail around replacement bow window

[embra]

Hi folks,

 

As part of a renovation project on my home, I’ve asked my joiner to replace the bow window in our living room, and would like to ensure the make up of surrounding materials is matched to the thermal properties of the new windows.

 

I’ve narrowed down the search for windows and am settling on triple glazed timber units with a whole unit window u-value of ~1.0 W/m²K. I’m using this value as a worst-case upper limit to guide design for the surrounding structure.

 

After scratching my head and doing a bit of reading, I believe something like the below sketch would be suitable.

 

Interested in any guidance or pointers to help keep discussions with the joiner on track. I’m most interested in simple / pragmatic solutions – we’re improving what we can but will be nowhere near Passivhaus etc standards.

 

Thanks as aways 🙏