Vaulted roof insulation over dividing walls?

[Digmixfill]

I have a few dividing walls that go up to roof level between rooms. They all need some attention.

 

The whole top floor will be vaulted (thanks @George) and the roof will have insulation between and under the rafters. I've been thinking about how to fit the insulation and VCL at these wall points.

 

Do I shorten the wall a little and run the insulation and VCL over the wall?

Do I take the wall up to the rafter level and insulate under the rafters up to the wall and VCL a down stand at the wall?

 

My google fu has failed. I can't find a similar circumstance.

 

[JohnMo]

 

 

13 minutes ago, Digmixfill said:

I have a few dividing walls that go up to roof level between rooms. They all need some attention.

 

The whole top floor will be vaulted (thanks @George) and the roof will have insulation between and under the rafters. I've been thinking about how to fit the insulation and VCL at these wall points.

 

Do I shorten the wall a little and run the insulation and VCL over the wall?

Do I take the wall up to the rafter level and insulate under the rafters up to the wall and VCL a down stand at the wall?

 

My google fu has failed. I can't find a similar circumstance.

 

You really need all the insulation above the wall otherwise the wall will just be huge thermal bridge. I would take the airtight vcl over the mid walls and down the end walls and join with a primed wall and airtight mastic/adhesive designed for joining airtight vcl to wall.

[Digmixfill]

2 hours ago, JohnMo said:

You really need all the insulation above the wall otherwise the wall will just be huge thermal bridge.

 

This was part of my thinking. It worried me that I couldn't find a single instance of someone insulating over a masonry internal wall.