Process for producing rigid polyurethane foams by reacting a) polyisocyanates with b) compounds having at least two hydrogen atoms which are reactive toward isocyanate groups in the presence of c) blowing agents, wherein the compounds having at least two hydrogen atoms which are reactive toward isocyanate groups comprise at least one polyether alcohol bi) which can be prepared by reacting aromatic amines with ethylene oxide and propylene oxide, with firstly propylene oxide and then ethylene oxide or a mixture of ethylene oxide and propylene oxide being added on in a first process step and the remaining amount of propylene oxide being added on in a second process step using a basic catalyst.