A rigid polyurethane foam-forming composition comprising: (a) a diisocyanate and/or polyisocyanate; and (b) an isocyanate-reactive component comprising: a polyol blend comprising: (i) 60 to 98% by weight, based on the total weight of the polyol blend, of a saccharide-initiated polyether polyol having an OH number of from 200 to 600 mg KOH/g and a functionality of 4 to 6; (ii) 1 to 20% by weight, based on the total weight of the polyol blend, of an aliphatic triol-initiated polyether polyol having an OH number of 100 to 500 mg KOH/g and a functionality of from greater than 2 to 4; and (iii) 1 to 20% by weight, based on the total weight of the polyol blend, of a polyalkylene oxide glycol having a functionality of 1.9 to 2.0 and an OH number of from 40 to 225 mg KOH/g; a halogenated olefin; a surfactant; water; and a tertiary amine catalyst composition comprising: (i) 80 to 99% by weight, based on the total weight of the tertiary amine catalyst composition, of a morpholine; and (ii) 1 to 20% by weight, based on the total weight of the tertiary amine catalyst composition, of an imidazole. (a) a diisocyanate and/or polyisocyanate; and (b) an isocyanate-reactive component comprising: a polyol blend comprising: (i) 60 to 98% by weight, based on the total weight of the polyol blend, of a saccharide-initiated polyether polyol having an OH number of from 200 to 600 mg KOH/g and a functionality of 4 to 6; (ii) 1 to 20% by weight, based on the total weight of the polyol blend, of an aliphatic triol-initiated polyether polyol having an OH number of 100 to 500 mg KOH/g and a functionality of from greater than 2 to 4; and (iii) 1 to 20% by weight, based on the total weight of the polyol blend, of a polyalkylene oxide glycol having a functionality of 1.9 to 2.0 and an OH number of from 40 to 225 mg KOH/g; a halogenated olefin; a surfactant; water; and a tertiary amine catalyst composition comprising: (i) 80 to 99% by weight, based on the total weight of the tertiary amine catalyst composition, of a morpholine; and (ii) 1 to 20% by weight, based on the total weight of the tertiary amine catalyst composition, of an imidazole. a polyol blend comprising: (i) 60 to 98% by weight, based on the total weight of the polyol blend, of a saccharide-initiated polyether polyol having an OH number of from 200 to 600 mg KOH/g and a functionality of 4 to 6; (ii) 1 to 20% by weight, based on the total weight of the polyol blend, of an aliphatic triol-initiated polyether polyol having an OH number of 100 to 500 mg KOH/g and a functionality of from greater than 2 to 4; and (iii) 1 to 20% by weight, based on the total weight of the polyol blend, of a polyalkylene oxide glycol having a functionality of 1.9 to 2.0 and an OH number of from 40 to 225 mg KOH/g; (i) 60 to 98% by weight, based on the total weight of the polyol blend, of a saccharide-initiated polyether polyol having an OH number of from 200 to 600 mg KOH/g and a functionality of 4 to 6; (ii) 1 to 20% by weight, based on the total weight of the polyol blend, of an aliphatic triol-initiated polyether polyol having an OH number of 100 to 500 mg KOH/g and a functionality of from greater than 2 to 4; and (iii) 1 to 20% by weight, based on the total weight of the polyol blend, of a polyalkylene oxide glycol having a functionality of 1.9 to 2.0 and an OH number of from 40 to 225 mg KOH/g; a halogenated olefin; a surfactant; water; and a tertiary amine catalyst composition comprising: (i) 80 to 99% by weight, based on the total weight of the tertiary amine catalyst composition, of a morpholine; and (ii) 1 to 20% by weight, based on the total weight of the tertiary amine catalyst composition, of an imidazole. (i) 80 to 99% by weight, based on the total weight of the tertiary amine catalyst composition, of a morpholine; and (ii) 1 to 20% by weight, based on the total weight of the tertiary amine catalyst composition, of an imidazole.