A process for preparing a rigid polyurethane foam, comprising a) forming a reactive mixture containing at least 1) an amine-initiated polyol, or mixture thereof with at least one other polyol, provided that such a mixture contains at least 5% by weight of the amine-initiated polyol, wherein the amine-initiated polyol has an average functionality of from 3.3 to 4.0 and a hydroxyl equivalent weight of form 75 to 560, and the amine-initiated polyol is a reaction product of at least one C 2 -C 4 alkylene oxide with an aminocylohexanealkylamine initiator compound; 2) at least one polyether polyol having a functionality of from 4.5 to 7 and a hydroxyl equivalent weight of 100 to 175; 3) at least one different amine-initiated polyol having an average functionality of from 2.0 to 4.0 and a hydroxyl equivalent weight of from 100 to 225; 4) at least one hydrocarbon, hydrofluorocarbon, hydrochlorofluorocarbon, fluorocarbon, dialkyl ether or fluorine-substituted dialkyl ether physical blowing agent; and 5) at least one polyisocyanate; and b) subjecting the reactive mixture to conditions such that the reactive mixture expands and cures to form a rigid polyurethane foam. a) forming a reactive mixture containing at least 1) an amine-initiated polyol, or mixture thereof with at least one other polyol, provided that such a mixture contains at least 5% by weight of the amine-initiated polyol, wherein the amine-initiated polyol has an average functionality of from 3.3 to 4.0 and a hydroxyl equivalent weight of form 75 to 560, and the amine-initiated polyol is a reaction product of at least one C 2 -C 4 alkylene oxide with an aminocylohexanealkylamine initiator compound; 2) at least one polyether polyol having a functionality of from 4.5 to 7 and a hydroxyl equivalent weight of 100 to 175; 3) at least one different amine-initiated polyol having an average functionality of from 2.0 to 4.0 and a hydroxyl equivalent weight of from 100 to 225; 4) at least one hydrocarbon, hydrofluorocarbon, hydrochlorofluorocarbon, fluorocarbon, dialkyl ether or fluorine-substituted dialkyl ether physical blowing agent; and 5) at least one polyisocyanate; and 1) an amine-initiated polyol, or mixture thereof with at least one other polyol, provided that such a mixture contains at least 5% by weight of the amine-initiated polyol, wherein the amine-initiated polyol has an average functionality of from 3.3 to 4.0 and a hydroxyl equivalent weight of form 75 to 560, and the amine-initiated polyol is a reaction product of at least one C 2 -C 4 alkylene oxide with an aminocylohexanealkylamine initiator compound; 2) at least one polyether polyol having a functionality of from 4.5 to 7 and a hydroxyl equivalent weight of 100 to 175; 3) at least one different amine-initiated polyol having an average functionality of from 2.0 to 4.0 and a hydroxyl equivalent weight of from 100 to 225; 4) at least one hydrocarbon, hydrofluorocarbon, hydrochlorofluorocarbon, fluorocarbon, dialkyl ether or fluorine-substituted dialkyl ether physical blowing agent; and 5) at least one polyisocyanate; and b) subjecting the reactive mixture to conditions such that the reactive mixture expands and cures to form a rigid polyurethane foam.