Wood/Coal burner (insert type not free standing with a back boiler unit unused) pre-existing when we moved in. Sitting in a standard fireplace with about 2" all round it between the actual fire back and the hearth/chimney brickwork. Draught from chimney is excessive so need to insulate between the sides and back. (Already has a plasterboard type face with tiles on which the unit sits against) and possibly over the top Question is do I use vermiculite and pour around the spaces to fill the gaps and reduce the downdraught or use fibreglass insulation and pack between the sides of the fire and the brickwork. or Set a plate in the chimney and pass the flue through that (Will make sweeping it a lot harder) and seal the face to the front of the fireplace.
Anyone ????