A storage stable isocyanate-reactive composition for forming a rigid polyurethane foam, the composition comprising: a reactive component including, based on the total weight of the reactive component, from: (a) 5 wt% to 30 wt% of at least one Novolac-type polyoxypropylene polyether polyol having a nominal hydroxyl functionality from 2 to 5 and a hydroxyl number from 130 to 450 mg KOH/g, (b) 20 wt% to 60 wt% of at least one high functional polyether polyol having a nominal hydroxyl functionality from 6 to 8 and a hydroxyl number from 300 to 700 mg KOH/g, (c) 2 wt% to 30 wt% of at least one low functional polyether polyol having a nominal hydroxyl functionality from 2 to 5 and a hydroxyl number from 50 to 400 mg KOH/g, (d) 2 wt% to 30 wt% of at least one amine initiated polyol prepared from an alkylene oxide and having a hydroxyl number from 250 to 600 mg KOH/g, the amine initiated polyol being an aromatic amine initiated polyol, a cycloaliphatic amine initiated polyol, or an aromatic and cycloaliphatic amine initiated polyol, and (e) 1 wt% to 25 wt% of one or more additives selected from a catalyst, a chemical blowing agent, and a surfactant; and a hydrocarbon physical blowing agent component present in an amount of at least 10 parts by weight and less than 20 parts by weight for each 100 parts by weight of the reactive component, wherein the isocyanate-reactive composition does not exhibit phase separation, as determined by unenhanced visual inspection, for a period of at least 7 days at ambient conditions. a reactive component including, based on the total weight of the reactive component, from: (a) 5 wt% to 30 wt% of at least one Novolac-type polyoxypropylene polyether polyol having a nominal hydroxyl functionality from 2 to 5 and a hydroxyl number from 130 to 450 mg KOH/g, (b) 20 wt% to 60 wt% of at least one high functional polyether polyol having a nominal hydroxyl functionality from 6 to 8 and a hydroxyl number from 300 to 700 mg KOH/g, (c) 2 wt% to 30 wt% of at least one low functional polyether polyol having a nominal hydroxyl functionality from 2 to 5 and a hydroxyl number from 50 to 400 mg KOH/g, (d) 2 wt% to 30 wt% of at least one amine initiated polyol prepared from an alkylene oxide and having a hydroxyl number from 250 to 600 mg KOH/g, the amine initiated polyol being an aromatic amine initiated polyol, a cycloaliphatic amine initiated polyol, or an aromatic and cycloaliphatic amine initiated polyol, and (e) 1 wt% to 25 wt% of one or more additives selected from a catalyst, a chemical blowing agent, and a surfactant; and (a) 5 wt% to 30 wt% of at least one Novolac-type polyoxypropylene polyether polyol having a nominal hydroxyl functionality from 2 to 5 and a hydroxyl number from 130 to 450 mg KOH/g, (b) 20 wt% to 60 wt% of at least one high functional polyether polyol having a nominal hydroxyl functionality from 6 to 8 and a hydroxyl number from 300 to 700 mg KOH/g, (c) 2 wt% to 30 wt% of at least one low functional polyether polyol having a nominal hydroxyl functionality from 2 to 5 and a hydroxyl number from 50 to 400 mg KOH/g, (d) 2 wt% to 30 wt% of at least one amine initiated polyol prepared from an alkylene oxide and having a hydroxyl number from 250 to 600 mg KOH/g, the amine initiated polyol being an aromatic amine initiated polyol, a cycloaliphatic amine initiated polyol, or an aromatic and cycloaliphatic amine initiated polyol, and (e) 1 wt% to 25 wt% of one or more additives selected from a catalyst, a chemical blowing agent, and a surfactant; and a hydrocarbon physical blowing agent component present in an amount of at least 10 parts by weight and less than 20 parts by weight for each 100 parts by weight of the reactive component, wherein the isocyanate-reactive composition does not exhibit phase separation, as determined by unenhanced visual inspection, for a period of at least 7 days at ambient conditions.