A warm roof abutting a cold roof

[imo]

I am doing a loft conversion with a dormer with a flat roof. I am upgrading the insulation on the existing sloping roof on one side, this will be a cold roof, but I want the flat roof to be a warm roof as from what I gather this is the better option in regards to condensation.

My question is, would there be a problem where the warm roof and cold roof meet?

Thank you

 

[noseall]

My question is, would there be a problem where the warm roof and cold roof meet?

No problem. It will not matter if the cold moist air within the main roof space enters the flat roof void as protection is there, nor would it matter in reverse.

However, to get the best of both worlds, isolate any air movement with a wad of fibreglass to prevent air movement as this will alleviate any unnecessary cooling within the flat roof void.

 

[tkmax]

I'd definately ensure continuity of the insulation by filling in the gap between the flat roof and the rafter insulation, there is a potential cold spot there. Cold air infiltrating between the flat roof joists could cause condensation imo.