An alkenyl aromatic polymer foam comprising a polymer matrix containing one or more polymer and defining a plurality of cells having an average cell size wherein: (a) the alkenyl aromatic polymer foam has: (i) an average cell size according to ASTM method D-3576-04 that is in a range of 0.02 and 5 millimeters; (ii) a density of 64 kilograms per cubic meter or less according to ISO method 845-85; (iii) an open cell content less than 30 percent according to ASTM method D6226-05; and (iv) a cell size variation of 30% or less as determined by taking the absolute value of the difference between the average cell sizes for the entire cross section and the circular portion of the entire cross section, dividing that value by the average cell size of the entire cross section and multiplying by 100; and (b) 50 weight-percent or more of the one or more polymer consists of one or more polymer selected from a group consisting of alkenyl aromatic polymers; and wherein the alkenyl aromatic polymer foam further comprises one or more fluorinated alkene blowing agent at a concentration of 0.1 moles or more and 0.3 moles or less per 100 grams of polymer foam, the one or more fluorinated alkene blowing agent being selected from: hexafluoropropene; 3-fluoropropene, 2,3-difluoropropene; 1,1,3-trifluoropropene; 1,3,3-trifluoropropene; 1,1,2-trifluoropropene; 1-fluorobutene; 2-fluorobutene; 2-fluoro-2-butene; 1,1-diffuoro-1-butene; 3,3-difluoro-1-butene; 3,4,4-trifluoro-1-butene; 2,3,3-trifluoro-1-butene; 1,1,3,3-tetrafluoro-1-butene; 1,4,4,4-tetrafluoro-1-butene; 3,3,4,4-tetraffuoro-1-butene; 4,4-difluoro-1-butene; 2,4,4,4-tetraffuoro-1-butene; 1,1,1,2-tetrafluoro-2 butene; 1,1,4,4,4-pentaffuoro-1-butene; 2,3,3,4,4-Pentafluoro-1-butene; 1,2,3,3,4,4,4-Heptaffuoro-1-butene; 1,1,2,3,4,4,4-Heptafluoro-1-butene; and 1,3,3,3-tetrafluoro-2-(trifluoromethyl)-Propene. (a) the alkenyl aromatic polymer foam has: (i) an average cell size according to ASTM method D-3576-04 that is in a range of 0.02 and 5 millimeters; (ii) a density of 64 kilograms per cubic meter or less according to ISO method 845-85; (iii) an open cell content less than 30 percent according to ASTM method D6226-05; and (iv) a cell size variation of 30% or less as determined by taking the absolute value of the difference between the average cell sizes for the entire cross section and the circular portion of the entire cross section, dividing that value by the average cell size of the entire cross section and multiplying by 100; and (i) an average cell size according to ASTM method D-3576-04 that is in a range of 0.02 and 5 millimeters; (ii) a density of 64 kilograms per cubic meter or less according to ISO method 845-85; (iii) an open cell content less than 30 percent according to ASTM method D6226-05; and (iv) a cell size variation of 30% or less as determined by taking the absolute value of the difference between the average cell sizes for the entire cross section and the circular portion of the entire cross section, dividing that value by the average cell size of the entire cross section and multiplying by 100; and (b) 50 weight-percent or more of the one or more polymer consists of one or more polymer selected from a group consisting of alkenyl aromatic polymers; and hexafluoropropene; 3-fluoropropene, 2,3-difluoropropene; 1,1,3-trifluoropropene; 1,3,3-trifluoropropene; 1,1,2-trifluoropropene; 1-fluorobutene; 2-fluorobutene; 2-fluoro-2-butene; 1,1-diffuoro-1-butene; 3,3-difluoro-1-butene; 3,4,4-trifluoro-1-butene; 2,3,3-trifluoro-1-butene; 1,1,3,3-tetrafluoro-1-butene; 1,4,4,4-tetrafluoro-1-butene; 3,3,4,4-tetraffuoro-1-butene; 4,4-difluoro-1-butene; 2,4,4,4-tetraffuoro-1-butene; 1,1,1,2-tetrafluoro-2 butene; 1,1,4,4,4-pentaffuoro-1-butene; 2,3,3,4,4-Pentafluoro-1-butene; 1,2,3,3,4,4,4-Heptaffuoro-1-butene; 1,1,2,3,4,4,4-Heptafluoro-1-butene; and 1,3,3,3-tetrafluoro-2-(trifluoromethyl)-Propene.