Its High Density Foam on foil. This is the stuff they use on sheds and to insulation roofs of warehouses and of cos performance insulation in engine bays
Measurements
Type A (Most popular)
1200mm X 1000mm X 15mm ( This stuff has adhesive backing)
Type B
1200mm X 1000mm X 10mm (Thinner but more flexible, no adhesive backing)
Type A $50, 2 lots of it $80
Type B $30, 2 lots of it $50