Method of producing a foam material product

A method of producing a foam product, whereby a body of expanded closed-cell foam, the expanded closed-cell foam being expanded polystyrene particle foam, is subjected to a non-melting heat treatment at a temperature above the glass transition temperature of plastic used to form the expanded closed-cell foam,

• wherein the temperature during the non-melting heat treatment is selected from a range with a lower limit of 90° C. and an upper limit of 120° C., and
• wherein a volume of the foam product is uniformly reduced by the non-melting heat treatment compared with an initial state of the body prior to the non-melting heat treatment by a value from a range with a lower limit of 50% and an upper limit of 97%.