I've seen some diagrams which depict a closer across the top of a cavity wall at eaves height. I'm assuming as a fire break and maybe to keep out vermin. On my single storey extension the insulation in the cavity will continue above this level to join the warm pitched roof insulation. Am I right in thinking that I will still need to use a closer, and if so, what type? The usual vertical closers with attached insulation would not be suitable as insulation will be in place already on both sides. It looks like the sort of thing they would have used slates for years ago, if they bothered at all, but I'm sure there is a modern equivalent with less of a thermal bridge etc. Thanks guys.