Stirotermal Duo 30 is a very compact panel, which allows a uniform load of up to 3000 kg/m2. It consists of hard polystyrene and a hard corrugated polystyrene film. The panels join solidly and waterproof with each other longitudinally and transversely according to the principle "knob into knob", therefore they are suitable for installation under cement mortar, as well as under floating screed in spaces, where the height of the floor is limited. The shape of the knobs allows for a very firm grip of pipes in diameter of 14 to 18 mm at an interval of at least 50 mm.