Depron Foam Sheets. Designed for Underfloor heating but used by modellers Depron is a highly efficient extruded polystyrene insulation material suitable for use below wood, laminate or even carpets. White Depron is available in 2mm, 3mm or 6mm sheets. Grey is only available in 3mm or 6mm sheets. Also perfect for the Model maker, looking for a lightweight strong material that is easy to work with and inexpensive. See notes below for tec info. Depron is a millimetre thin insulation sheet manufactured of fully recycled material, free from Freon and Halogen. The sheet is produced of foamed polystyrene, a material that does not age. The cell structure in the sheet is built up of fine, closed cells that give Depron its excellent physical and mechanical characteristics. An insulation capacity that saves energy.