USB REFLEX PLUS is a heat welded 4 layer reinforced membrane. The penultimate outer layer is made of a pre-perforated aluminium film, protected by another rust proof PE film; the aluminium film serves to reflect the infrared rays coming from outside which carry heat by radiation. Emissivity is the ability of a material’s surface to emit energy in the form of radiation depending on its surface temperature. It is a value which falls between the following interval: 0 < ε < 1. The lower the emissivity value the lower the energy radiated from its surface. SUB Reflex Plus has an emissivity coefficient of 0,168 (16.8%); this means that 16.8% of the incident energy is emitted (it passes inwards), whilst 83.2% is reflected. Consequently, this minimal passage of energy translates into a lower heat input on the underlying insulation and therefore a considerable improvement in the performance of the insulation package both in summer and in winter.