My Building Regs submission, which is approved and work underway, contains info on windows stating that they would be uPVC with a U-value of 1. We are in fact going with aluminium and are getting a U-value of 1.6, which is pretty much standard for aluminium.
I believe that I can just agree this as part of a flex with the building control officer. Is that right or should I amend the Building Regs submission (I’m not even sure if that is possible)?

thanks