Recently stuffed in acoustic insulation foam & butyl throughout the car, mostly foam, doors, trims, boot, ceiling, ABCD pillars. The foam has a bit of thermal benifit for the car, from Carbuilders. In the ceiling there was plenty of space so shoved in some polybatts while at it, probably equal thickness to about R0.8 but with acoustic foam best guess about R1. Makes a difference with heat from outside even though I haven't tested it in summer.