As a permeable membrane of an air conditioning system that performs as supply to a space to be air conditioned through the permeable membrane and/or gas discharge from the space to be air conditioned through the permeable membrane, an asymmetric membrane is used. The asymmetric membrane is made of a cyclic olefin addition polymer obtained by addition polymerization of a cyclic olefin functionality siloxane, or by addition polymerization of the cyclic olefin functionality siloxane and a cyclic olefin compound, and in which a rate of a structural unit derived from the cyclic olefin functionality siloxane is 5 to 100 mol % of the addition polymer, and a number average molecular weight (Mn) is 10,000 to 2,000,000 in terms of polystyrene conversion measured by a GPC using tetrahydrofuran as a solvent.