A process for producing rigid polyurethane foams or rigid polyisocyanurate foams comprising the reaction of A) at least one polyisocyanate, B) at least one polyetherester polyol obtainable by esterification of b1) 10 to 70 mol% of a dicarboxylic acid composition comprising b11) 50 to 100 mol%, based on the dicarboxylic acid composition, of one or more aromatic dicarboxylic acids or derivatives thereof, b12) 0 to 50 mol%, based on said dicarboxylic acid composition b1), of one or more aliphatic dicarboxylic acids or derivatives thereof, b2) 2 to 30 mol% of one or more fatty acids and/or fatty acid derivatives, b3) 10 to 70 mol% of one or more aliphatic or cycloaliphatic diols having 2 to 18 carbon atoms or alkoxylates thereof, b4) 2 to 50 mol% of a polyether polyol having a functionality of not less than 2, prepared by alkoxylating a polyol having a functionality of not less than 2 in the presence of an amine as catalyst, wherein the aminic alkoxylation catalyst remains in the polyetherol b4), all based on the total amount of components b1) to b4), wherein said components b1) to b4) sum to 100 mol%, C) optionally further polyester polyols other than those of component B), D) at least one polyether polyol, and E) optionally flame retardants, F) one or more blowing agents, G) catalysts, and H) optionally further auxiliaries or admixture agents, wherein the mass ratio of total components B) and optionally C) to component D) is at least 7. A) at least one polyisocyanate, B) at least one polyetherester polyol obtainable by esterification of b1) 10 to 70 mol% of a dicarboxylic acid composition comprising b11) 50 to 100 mol%, based on the dicarboxylic acid composition, of one or more aromatic dicarboxylic acids or derivatives thereof, b12) 0 to 50 mol%, based on said dicarboxylic acid composition b1), of one or more aliphatic dicarboxylic acids or derivatives thereof, b2) 2 to 30 mol% of one or more fatty acids and/or fatty acid derivatives, b3) 10 to 70 mol% of one or more aliphatic or cycloaliphatic diols having 2 to 18 carbon atoms or alkoxylates thereof, b4) 2 to 50 mol% of a polyether polyol having a functionality of not less than 2, prepared by alkoxylating a polyol having a functionality of not less than 2 in the presence of an amine as catalyst, wherein the aminic alkoxylation catalyst remains in the polyetherol b4), all based on the total amount of components b1) to b4), wherein said components b1) to b4) sum to 100 mol%, b1) 10 to 70 mol% of a dicarboxylic acid composition comprising b11) 50 to 100 mol%, based on the dicarboxylic acid composition, of one or more aromatic dicarboxylic acids or derivatives thereof, b12) 0 to 50 mol%, based on said dicarboxylic acid composition b1), of one or more aliphatic dicarboxylic acids or derivatives thereof, b11) 50 to 100 mol%, based on the dicarboxylic acid composition, of one or more aromatic dicarboxylic acids or derivatives thereof, b12) 0 to 50 mol%, based on said dicarboxylic acid composition b1), of one or more aliphatic dicarboxylic acids or derivatives thereof, b2) 2 to 30 mol% of one or more fatty acids and/or fatty acid derivatives, b3) 10 to 70 mol% of one or more aliphatic or cycloaliphatic diols having 2 to 18 carbon atoms or alkoxylates thereof, b4) 2 to 50 mol% of a polyether polyol having a functionality of not less than 2, prepared by alkoxylating a polyol having a functionality of not less than 2 in the presence of an amine as catalyst, wherein the aminic alkoxylation catalyst remains in the polyetherol b4), C) optionally further polyester polyols other than those of component B), D) at least one polyether polyol, and E) optionally flame retardants, F) one or more blowing agents, G) catalysts, and H) optionally further auxiliaries or admixture agents,