Is a flexible, diffusion-open separation layer. It can be used on all pitched roofs with metal, flat roofing and on metal facades. It consists of a carrier foil integrated with an 8 mm high profiled, openwork structure of tangled polyamide fibers. DELTA-TRELA ensures permanent ventilation of the underside of the metal cover. In addition, thanks to the carrier foil, which is open to water vapor diffusion, residual moisture from the roof structure and thermal insulation can be drained out. Mutes rain and hail sounds by 8 dB. Due to the high density of the profile structure, it guarantees that the panels can move without braking friction when temperature changes.