Cold-formable, thermally stable, rigid polyisocyanurate foams having a density of 10 to 100 kg/m 3 (as determined in accordance with DIN 53420), a breaking extension (as determined in accordance with DIN 53430) of 12 to 35%, an open-cell content (as determined in accordance with DIN ISO 4590-86) of 51% to 98% and a storage modulus for the rigid polyisocyanurate foam (as determined in accordance with DIN EN ISO 6721 B:1996-12) in the temperature range from 160° to 190°C of on average not less than 0.1 MPa, characterized in that the rigid polyisocyanurate foam is the reaction product of the components consisting of A) a polyol component A) consisting of a. 130 to 95 wt%, based on said polyol component A), of one or more polyalkylene oxides having a number average equivalent weight of 700 to 2500 g/mol and a number average functionality of 1.8 to 2.3, b. 10.1 to 4 wt%, based on said polyol component A), of polyalkylene oxide-modified siloxane polymers, e. blowing agents comprising not less than 95 mol%, based on blowing agent, of carbon dioxide, and B) at least one isocyanate component B) from the group consisting of i) a mixture of a) 75 to 100 wt%, based on said isocyanate component B), of 2,4'-diphenylmethane diisocyanate, 4,4`-diphenylmethane diisocyanate and 2,2'-diphenylmethane diisocyanate, b) 0 to 25 wt%, based on said isocyanate component B), of isocyanate components other than a), and ii) NCO prepolymers based on said mixture i) and one or more polyether polyols having an ethylene oxide content of not more than 5 wt% and a number average functionality of 2 to 3, wherein the molar ratio between the isocyanate groups from said component B) and the isocyanate-reactive groups from said component A) is between 1.8:1 and 3.0:1. A) a polyol component A) consisting of a. 130 to 95 wt%, based on said polyol component A), of one or more polyalkylene oxides having a number average equivalent weight of 700 to 2500 g/mol and a number average functionality of 1.8 to 2.3, b. 10.1 to 4 wt%, based on said polyol component A), of polyalkylene oxide-modified siloxane polymers, e. blowing agents comprising not less than 95 mol%, based on blowing agent, of carbon dioxide, and a. 130 to 95 wt%, based on said polyol component A), of one or more polyalkylene oxides having a number average equivalent weight of 700 to 2500 g/mol and a number average functionality of 1.8 to 2.3, b. 10.1 to 4 wt%, based on said polyol component A), of polyalkylene oxide-modified siloxane polymers, e. blowing agents comprising not less than 95 mol%, based on blowing agent, of carbon dioxide, B) at least one isocyanate component B) from the group consisting of i) a mixture of a) 75 to 100 wt%, based on said isocyanate component B), of 2,4'-diphenylmethane diisocyanate, 4,4`-diphenylmethane diisocyanate and 2,2'-diphenylmethane diisocyanate, b) 0 to 25 wt%, based on said isocyanate component B), of isocyanate components other than a), and ii) NCO prepolymers based on said mixture i) and one or more polyether polyols having an ethylene oxide content of not more than 5 wt% and a number average functionality of 2 to 3, wherein the molar ratio between the isocyanate groups from said component B) and the isocyanate-reactive groups from said component A) is between 1.8:1 and 3.0:1. i) a mixture of a) 75 to 100 wt%, based on said isocyanate component B), of 2,4'-diphenylmethane diisocyanate, 4,4`-diphenylmethane diisocyanate and 2,2'-diphenylmethane diisocyanate, b) 0 to 25 wt%, based on said isocyanate component B), of isocyanate components other than a), and a) 75 to 100 wt%, based on said isocyanate component B), of 2,4'-diphenylmethane diisocyanate, 4,4`-diphenylmethane diisocyanate and 2,2'-diphenylmethane diisocyanate, b) 0 to 25 wt%, based on said isocyanate component B), of isocyanate components other than a), and ii) NCO prepolymers based on said mixture i) and one or more polyether polyols having an ethylene oxide content of not more than 5 wt% and a number average functionality of 2 to 3,