Klober Permo® therm is a tongue and grooved rigid insulation board with integrated vapour permeable underlay and self-adhesive edge strips to seal laps. Unlike square-edged boards it prevents formation of air leakage paths and thermal bridges. Installed above the rafters, Permo therm provides added height within the roof space and can be laid either from left to right or right to left. No ventilation of the batten/counter-batten cavity is needed unless impervious or tight-fitting roof coverings are used. With LABC approval, boards are also CFC and HCFC-free.