Pitched roof- required U-value for new extension pitched roof

[ab12]

What is the required U-velue to be achieved for pitched roof for new extensions according to thhe building regs applicable pre October 2024?

 

Architect has specified 150mm Rockwool laid between joits and 150mm  laid at right angles to joist to a give a U-valuenof 0.15 for the roof.

 

Can I use Knauf 44 loft roll instead of Rockwool.

 

I take it will need to use total thickness of 300mm as well to achieve U value of 0.15?

 

Thanks