Hi, Hope some of you can help, I'm currently removing old insulation from the loft with a view to putting down new stuff and using loft stilts to create storage space. The roof has an odd design (at least I've never seen it) in that the plaster in the corners of the rooms is affixed directly to the rafters in the roof. The rafters look about 2*4 so there's only a 100mm gap in the loft. This area is currently uninsulated but I'm thinking about the heat loss in the 1ft or so section in the rooms below this area. Any advice on how it could be insulated without compromising ventilation in the loft space-there are air bricks in the external walls which don't go into the house (as well as others that do) so I'm guessing they vent the cavity and from there the loft space, there aren't vents in the soffits .It's a semi with a hip roof and the rafters do this on all three sides. Looking down between the rafters I can see the top of the bricks so guess it's like the sketch. Would it be ok to put say 50mm insulation board down there or should I just get some insulated plaster board and do it in the rooms below instead? Whether the ventilation is by accident or design the timbers look original circa 1930 with no damage.