Thermoinsulating expanded articles with improved resistance to solar irradiation, which comprise an expanded polymeric matrix, obtained by expansion and sintering of beads/granules of a vinyl aromatic (co) polymer, in whose interior a filler is homogeneously dispersed, which comprises at least one athermanous material selected from coke, graphite and carbon black and optionally an active inorganic additive within the wave-lengths ranging from 100 to 20,000 cm
-1 . The polymeric matrix comprises a copolymer of styrene and at least one vinyl aromatic comonomer substituted in the ring or on the vinyl group and/ or a mixture of polystyrene and up to 10% by weight, with respect to the mixture, of a thermoplastic polymer compatible with polystyrene and having a Tg (glass transition temperature) > 100°C.