A composition comprising a formulation for preparing a polyurethane rigid foam, the formulation comprising at least one isocyanate component; at least one isocyanate-reactive component comprising: (a) from 30 to 50 weight percent, based on the total weight of components 2 through 6, of a first polyether polyol, having a hydroxyl value from 350 to 550 milligrams of potassium hydroxide per gram of the polyol and a functionality greater than 5; (b) from 5 to 25 weight percent, based on the total weight of the components 2 through 6, of at least one diol having a hydroxyl value from 100 to 300 milligrams potassium hydroxide per gram of the diol; and (c) from 15 to 35 weight percent, based on the total weight of components 2 through 6,of at least a second polyether polyol, having a functionality from 3 to 5; from 1.5 to 5 weight percent, based on the total weight of components 2 through 6,of a catalyst selected from dimethylbenzylamine, 1,2-dimethyl-imidazole, and combinations thereof; from greater than 0 to 1 weight percent, based on the total weight of components 2 through 6,of a catalyst selected from a glycine salt, tris(dimethyl aminomethyl) phenol, and combinations thereof; greater than 4.1 wt%, based on the total weight of components 2 through 6,of water as a blowing agent; and, optionally, any additional constituent or constituents; provided that the weight of components 2 through 6 totals 100 weight percent and, absent the at least one isocyanate component, the formulation has a dynamic viscosity from 540 to 864 millipascals*seconds at 20 degrees Celsius; which, when reacted under one-shot conditions, forms a polyurethane rigid foam having a ratio of molecular weight to crosslink from 380 to 420, as measured according to the method reported in Th. Broennumm, Proceedings of the Society of the Plastics Industry Conference 1991, p. 243. at least one isocyanate component; at least one isocyanate-reactive component comprising: (a) from 30 to 50 weight percent, based on the total weight of components 2 through 6, of a first polyether polyol, having a hydroxyl value from 350 to 550 milligrams of potassium hydroxide per gram of the polyol and a functionality greater than 5; (b) from 5 to 25 weight percent, based on the total weight of the components 2 through 6, of at least one diol having a hydroxyl value from 100 to 300 milligrams potassium hydroxide per gram of the diol; and (c) from 15 to 35 weight percent, based on the total weight of components 2 through 6,of at least a second polyether polyol, having a functionality from 3 to 5; (a) from 30 to 50 weight percent, based on the total weight of components 2 through 6, of a first polyether polyol, having a hydroxyl value from 350 to 550 milligrams of potassium hydroxide per gram of the polyol and a functionality greater than 5; (b) from 5 to 25 weight percent, based on the total weight of the components 2 through 6, of at least one diol having a hydroxyl value from 100 to 300 milligrams potassium hydroxide per gram of the diol; and (c) from 15 to 35 weight percent, based on the total weight of components 2 through 6,of at least a second polyether polyol, having a functionality from 3 to 5; from 1.5 to 5 weight percent, based on the total weight of components 2 through 6,of a catalyst selected from dimethylbenzylamine, 1,2-dimethyl-imidazole, and combinations thereof; from greater than 0 to 1 weight percent, based on the total weight of components 2 through 6,of a catalyst selected from a glycine salt, tris(dimethyl aminomethyl) phenol, and combinations thereof; greater than 4.1 wt%, based on the total weight of components 2 through 6,of water as a blowing agent; and, optionally, any additional constituent or constituents;