HFO/WATER-EXPANDED HARD FOAM SYSTEMS

The invention relates to a method for producing polyurethane rigid foams by reacting a) at least one organic polyisocyanate with b) at least one polyol component in the presence of a blowing-agent mixture containing water and halogenated alkenes, wherein the amount of water is at least 1.40 mol/kg polyol component b) and the amount of halogenated alkene is at most 2.00 mol/kg polyol component b), and to the use of such a blowing-agent mixture to produce corresponding polyurethane rigid foams and to increase the adhesion and to reduce the thermal conductivity of corresponding polyurethane rigid foams. The invention further relates to a polyurethane rigid foam that can be produced by the method according to the invention.