The present invention provides a process for the preparation of rigid polyurethane foams by reaction of a) at least one organic polyisocyanate with b) at least one polyol component in the presence of a blowing agent mixture comprising water and halogenated alkenes, wherein the amount of water is polyol component b) At least 1.40 mol per kg and the amount of the halogenated alkenes is at most 2.00 mol per kg of the polyol component b)] and for the production of this rigid polyurethane foam and for reducing the thermal conductivity and increasing the adhesion of the rigid polyurethane foam. It relates to the use of a blowing agent. The invention also relates to rigid polyurethane foams obtainable by the process of the invention.
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