A process for preparing an insulating unit comprising at least two side walls, a back wall and a top wall wherein each wall comprises a polyurethane foam between an inner lining and an outer lining and the side walls are connected to the back wall and the top wall at an angle between 85 and 95°; the back wall and the side walls have a height of between 0.5 and 3 meters and the side walls have a width of between 0.5 and 1.5 meters and the back wall has a width of between 0.5 and 2.0 meters and wherein the polyurethane foam disposed between the inner and outer liner has a thickness of 20 to 120 mm and is produced from a reaction mixture comprising; (a) preparing a reactive foam-forming system comprising as components at least an organic polyisocyanate; a polyol formulation comprising a polyol component containing from 5 to 85 weight percent of at least one amine-initiated polyol, an nominal average functionality of 3 to 8 and an average hydroxyl number of from 200 to 850, from 1 to 5 parts by weight of a catalyst system per 100 parts by weight of the polyol component wherein the catalyst system comprises at least one amine catalyst, a non-chlorofluorocarbon physical blowing agent: and an amount of water that is less than 2 percent by weight based on the polyol formuation, wherein the weight percent of nitrogen in the formulation, excluding the weight of the blowing agent, derived from the polyol component (Npol) is from is from 1 to 5 and the ratio of Npol to the weight percent nitrogen from the catalyst system (Ncat) is from 2 to 8; (b) injecting the reactive foam-forming system at or above atmospheric pressure into a cavity, wherein the reactive foam-forming system forms a gel in no more than 30 seconds (c) subjecting the cavity to a reduced atmospheric pressure; and (d) maintaining the reduced atmospheric pressure at least until the gel forms a closed cell rigid polyurethane foam, the foam having a density of from 28 to 40 kg/m 3, an average cell diameter of less than 250 microns, a thermal conductivity of less than 19 mW/mK at 10°C average plate temperature, according to ISO 12939/DIN. 52612. (a) preparing a reactive foam-forming system comprising as components at least an organic polyisocyanate; a polyol formulation comprising a polyol component containing from 5 to 85 weight percent of at least one amine-initiated polyol, an nominal average functionality of 3 to 8 and an average hydroxyl number of from 200 to 850, from 1 to 5 parts by weight of a catalyst system per 100 parts by weight of the polyol component wherein the catalyst system comprises at least one amine catalyst, a non-chlorofluorocarbon physical blowing agent: and an amount of water that is less than 2 percent by weight based on the polyol formuation, wherein the weight percent of nitrogen in the formulation, excluding the weight of the blowing agent, derived from the polyol component (Npol) is from is from 1 to 5 and the ratio of Npol to the weight percent nitrogen from the catalyst system (Ncat) is from 2 to 8; a polyol formulation comprising a polyol component containing from 5 to 85 weight percent of at least one amine-initiated polyol, an nominal average functionality of 3 to 8 and an average hydroxyl number of from 200 to 850, from 1 to 5 parts by weight of a catalyst system per 100 parts by weight of the polyol component wherein the catalyst system comprises at least one amine catalyst, a non-chlorofluorocarbon physical blowing agent: and an amount of water that is less than 2 percent by weight based on the polyol formuation, wherein the weight percent of nitrogen in the formulation, excluding the weight of the blowing agent, derived from the polyol component (Npol) is from is from 1 to 5 and the ratio of Npol to the weight percent nitrogen from the catalyst system (Ncat) is from 2 to 8; (b) injecting the reactive foam-forming system at or above atmospheric pressure into a cavity, wherein the reactive foam-forming system forms a gel in no more than 30 seconds (c) subjecting the cavity to a reduced atmospheric pressure; and (d) maintaining the reduced atmospheric pressure at least until the gel forms a closed cell rigid polyurethane foam, the foam having a density of from 28 to 40 kg/m 3, an average cell diameter of less than 250 microns, a thermal conductivity of less than 19 mW/mK at 10°C average plate temperature, according to ISO 12939/DIN. 52612.