FraserD

Hi, I'm looking for advice. We live in a converted farm Steading, built in 1830 with 450-600mm tick stone walls with a pitched slate roof. (No external insulation and minimal insulated plasterboard internal walls. In the attic space there is an air gap (2 inch in places!) between where the wall stops, roof rafters meet the wall and ceiling joists all come together. I've had multiple wasps nests and mice in my attic (and it heats up/cools down a lot!) due to these gaps. I should also say we live in a very windy area and the flat area of the roof is 17 x 7 m is size with the 16m west/east facing (prominent wind direction). I'm looking at upgrading my loft insulation as its currently 100mm at best but also stop the wasps and mice getting in these gaps. My understanding is that these air gaps are needed for attic ventilation. However, practically speaking... Our roof construction consists of slates nailed straight onto sarking boards (no liner inside or out). With visible gaps - 1-3mm between sarking boards. Would it be safe to use mineral wool or a "breathable?" expanding foam to seal these gaps between the rafters and wall? Obviously the last thing I want is condensation in my attic space. If I should fit some kind of vents in this area, could anyone recommend the type and how often they should be spaced? Access from outside the property isn't possible so any vents will need to be fitted internally. Many thanks and looking forward to hearing from you. Kind regards FraserD