A method for making a rigid polyurethane foam by reacting a polyisocyanate and a polyol in the presence of a urethane catalyst, a blowing agent and a silicone surfactant characterized by employing a blowing agent comprising a C4 or C5 hydrocarbon, or mixtures thereof, with an average molecular weight of .ltoreq.72 g/mole and a boiling point in the range of 27.8 to 50.degree. C., and a silicone surfactant comprising a polyether-polysiloxane copolymer represented by the following formula: (CH.sub.3).sub.3--Si--O--(Si(CH.sub.3).sub.2--O).sub.x--(Si(CH.sub.3)(R)O- ).sub.y--Si(CH.sub.3).sub.3 where R=(CH.sub.2).sub.3--O--(--CH.sub.2--CH.sub.2--O).sub.a--(CH.sub.2--CH(CH.- sub.3)--O).sub.b--R'', and where R'' is H, (CH.sub.2).sub.zCH.sub.3, or C(O)CH.sub.3; x+y+2 is 60 130; x/y is 5 14; z is 0 4; the total surfactant molecular weight, based on the formula, is 7000 30,000 g/mole, the wt % siloxane in the surfactant is 32 70 wt %, the blend average molecular weight (BAMW) of the polyether portion is 450 1000 g/mole, and the mole % of ethylene oxide in the polyether portion is 70 100 mole %.