Disclosed are methods of forming foam comprising: (a) providing a foamable composition comprising an isocyanate, a polyol and a physical blowing agent comprising at least about 50% by weight of trans1233zd and wherein the polyol comprises a polyol or mixture of polyols such that the trans1233zd(E) has a solubility in said polyol of 20 pphp or less and (b) forming a foam from said foamable composition.