Hi, I would like to insulate small roof that is above a partial extension in which my kitchen is. Similar to the 1 and 3A insulation in the picture below. I think I am clear and understand what should be done where 1 meets 3 and where 1 meets 3A, however I am not sure about start and end of 3A insulation. Should 3A go all the way from kitchen's ceiling plasterboard as high as it can go to the roof and touch/seal if possible? Additional info: insulation 1 will be roll of mineral wool insulation, 3A I plan to use kingspan or similar. Red line is an external wall. Wall between arrows does not exist. Space above 1 is ventilated through soffits. Small roof has flashing to the red wall.