Hi, I am looking for advice on the best kind of insulation for a cathedral ceiling.
Existing roof is not great - it has tiles on top, blue/foil lining and then not much space between that and the pine lining shown on the inside for the bulk insulation that's crammed in there. It's a skillion roof angled approx 13 degrees to the South.
Seeing as I'm getting the room walls plastered (not by me) I thought I'd get a flush ceiling done too, creating a decent size space to better insulate.
Bear in mind this is an upstairs bedroom with recently fitted timber d/g windows and in insulated cavity brick wall. It faces North with Clerestories with some passive solar gain, so the bigger problem is more going to be overheating in summer. All windows are shaded on the outside in summer, but I'm hoping to reduce heat gain a bit through the roof.
Main questions are:
Should there be an airgap between pine lining and the plaster or should it be filled with insulation, e.g earthwool or similar?
Is there any benefit in having some type of reflective insulation to reject heat, that would sit above any bulk insulation, right below the pine lining?
Image showing the ceiling: