A process for producing rigid polyurethane foams by reacting a) organic polyisocyanates with b) compounds having at least two hydrogen atoms which are reactive toward isocyanate groups in the presence of c) blowing agents, d) catalysts and optionally, e) auxiliaries and additives, wherein a mixture of b1) from 20 to 60 parts by weight of one or more high-functionality polyether alcohols having functionalities of from 3.9 to 5.0 and a hydroxyl number of from 400 to 500 mg KOH/g and having hydroxyl-comprising high functionality compounds as starter substances, b2) from 5 to 25 parts by weight of one or more polyether alcohols based on aromatic and/or aliphatic amines and having functionalities of from 3.5 to 4.5 and a hydroxyl number of from 350 to 500 mg KOH/g, b3) from 5 to 25 parts by weight of one or more polyether alcohols having functionalities of from 3 to 4 and a hydroxyl number of from 150 to 200 mg KOH/g, b4) from 1 to 15 parts by weight of one or more low molecular weight chain extenders and/or crosslinkers having functionalities of from 2 to 3 and a molecular weight M w of < 400 g/mol and optionally b5) from 1 to 5 parts by weight of water is used as component b), where the parts by weight of b1) to b5) in the polyol b) do not exceed 100 parts by weight. a) organic polyisocyanates with b) compounds having at least two hydrogen atoms which are reactive toward isocyanate groups in the presence of c) blowing agents, d) catalysts and optionally, e) auxiliaries and additives, wherein a mixture of b1) from 20 to 60 parts by weight of one or more high-functionality polyether alcohols having functionalities of from 3.9 to 5.0 and a hydroxyl number of from 400 to 500 mg KOH/g and having hydroxyl-comprising high functionality compounds as starter substances, b2) from 5 to 25 parts by weight of one or more polyether alcohols based on aromatic and/or aliphatic amines and having functionalities of from 3.5 to 4.5 and a hydroxyl number of from 350 to 500 mg KOH/g, b3) from 5 to 25 parts by weight of one or more polyether alcohols having functionalities of from 3 to 4 and a hydroxyl number of from 150 to 200 mg KOH/g, b4) from 1 to 15 parts by weight of one or more low molecular weight chain extenders and/or crosslinkers having functionalities of from 2 to 3 and a molecular weight M w of < 400 g/mol and optionally b5) from 1 to 5 parts by weight of water is used as component b), where the parts by weight of b1) to b5) in the polyol b) do not exceed 100 parts by weight. b1) from 20 to 60 parts by weight of one or more high-functionality polyether alcohols having functionalities of from 3.9 to 5.0 and a hydroxyl number of from 400 to 500 mg KOH/g and having hydroxyl-comprising high functionality compounds as starter substances, b2) from 5 to 25 parts by weight of one or more polyether alcohols based on aromatic and/or aliphatic amines and having functionalities of from 3.5 to 4.5 and a hydroxyl number of from 350 to 500 mg KOH/g, b3) from 5 to 25 parts by weight of one or more polyether alcohols having functionalities of from 3 to 4 and a hydroxyl number of from 150 to 200 mg KOH/g, b4) from 1 to 15 parts by weight of one or more low molecular weight chain extenders and/or crosslinkers having functionalities of from 2 to 3 and a molecular weight M w of < 400 g/mol and optionally b5) from 1 to 5 parts by weight of water