The invention relates to the use of a mineral having perovskite structure in vinyl aromatic polymer foam, i) for decreasing the thermal conductivity, ii) for increasing the mechanical properties (namely compressive strength and bending strength), or iii) for improving the self-extinguishing properties of the foam. The polymer foam further comprises one or more athermanous additives selected from a) powder inorganic additive selected from powders of silica and calcium phosphate, b) powder carbonaceous additive selected from powders of graphite, carbon black, petroleum coke, graphitized carbon black, graphite oxides, and graphene, and c) powder geopolymer and powder geopolymer composite.