Have finally reached the stage of roof on and all interior walls built.My query is ,how much and what type of unsulation should i put above the ceiling downstairs,as its a dormer bungalow my builder has suggested 100 mm of fibrewool,i think this is ok between the ceiling and upstairs but what about the voids around the 2 sides of the bungalow any idea of whether i need celotex or just another layer of fibrewool.