Catalyst composition for water blown, low density, rigid polyurethane foam

3A method for preparing a water blown, low density, rigid polyurethane foam which comprises contacting at least one polyisocyanate with at least one polyol, at an Isocyanate Index of 70 to 200, in the presence of a blowing agent composition comprising at least 75 wt % water and an effective amount of a catalyst composition comprising a gelling catalyst which is bis-(N,N-dimethylaminopropyl)amine and a blowing catalyst which is N,N-dimethylaminoethyl-N′-methyl-ethanolamine, the foam having a density of 6 to 16 Kg/m.