Flat roof make up

[Mike]

4 hours ago, -rick- said:

I thought the air sealing externally was for hot climates where you ran AC inside and want to stop the moisture getting in. With our climate we generally want to seal from the inside out.

In that kind of build the air sealing won't end up being external; external insulation goes over the top of what you see there. Or at least the majority would go on the outside. You could put some between the studs but, following the UK rule-of-thumb, it would be no more than 1/3 of it avoid the risk of condensation within it and hence the need for a separate internal VCL.