BOXTHERM plenums are designed for mounting in diffusers in air conditioning installations and connection in flexible circular duct. The maximum operating temperature is 55 ° C in air supply. These plenums are suitable for diffusers series AXO, RXO, PLAY, OTO and NEX. The plenums BOXTHERM are made of expanded polystyrene (EPS), material that acts as thermal and acoustic insulation. With a thickness of 22 mm and a transmission coefficient of 0.0297 w/mk, thermal insulation of theses plenums complies with the thermal insulation specifications. The insulation of the plenum BOXTHERM reduces between 2 and 3 dB(A) the acoustic power, respect to a metallic plenum box. BOXTHERM plenums, with pyramidal shape, are are stackable to save space in its transport and storage. Thanks to a reduced weight of 1,7 kg the BOXTHERM plenum facilitates its handling and installation.