Hello. I have a 1.5 storey chalet type property. I’m looking to add additional insulation to the first floor rooms that adjoin the loft space. I’m planning on adding PIR insulation between the uprights of the wall, however I notice there is no insulation between the ground floor ceiling and first floor, and there is space for cold air to come in through the soffits, into the loft space and then straight through the space between the ground floor ceiling and first floor. Should I fill this gap with insulation or leave it open to air flow?
Thank you
