When insulating a roof, the objective is to cover the entire area, i.e, every nook, cranny and gap whilst ensuring that the wooden timbers within the roof maintain their ability to breathe. This is achieved by installing a breathable card membrane or Vent Card between the rafters.
Open cell insulation is then sprayed onto the membrane of the vent card to the appropriate depth ensuring that an adequate level of heat retention is achieved.
This card creates the 50mm air gap required by building regulations.