Hi to all and thanks to anyone who can help me with my question.
I have done many hours researching and just cannot find the correct information.
I live in a 1970 semi detached house and we have just started to renovate the house, I know there is no insulation in the flat roof and exterior upstairs walls.
Here's what I have on the walls from outside in: Tile-batten-felt-75x50mm stud work then 12.5mm plasterboard. Should I leave a 50mm air gap between the felt and insulation boards the same as I would do inside the ceilings. Many thanks guys
