Spacer for an insulating glazing unit, at least comprising: a polymeric main body, at least comprising two parallel side walls (1,2) that are connected to one another by an inner wall and an outer wall, wherein the side walls (1,2), the inner wall, and the outer wall surround a hollow chamber, wherein the main body - has a glass fiber content of 0 wt.-% to 40 wt.-% and - has, due to hollow spaces, a weight reduction of 10 wt.-% to 20 wt.-% and wherein - the hollow spaces are obtained by addition of at least one foaming agent and - the amount of the foaming agent added is 0.5 wt.-% to 1.5 wt.-%, wherein the spacer has, at least on the outer wall, an insulation film, which contains a polymeric carrier film and at least one metallic or ceramic layer, the thickness of the polymeric carrier film of the insulation film is from 10 μm to 100 μm and the thickness of the metallic or ceramic layer of the insulation film is from 10 nm to 1500 nm and wherein the insulation film contains at least one more polymeric layer with a thickness of 5 μm to 100 μm and the metallic or ceramic layer of the insulation film contains at least iron, aluminum, silver, copper, gold, chromium, silicon oxide, silicon nitride, or alloys or mixtures or oxides thereof and wherein the polymeric carrier film of the insulation film contains at least polyethylene terephthalate, ethylene vinyl alcohol, polyvinylidene chloride, polyamides, polyethylene, polypropylene, silicones, acrylonitriles, polymethyl acrylates, or copolymers or mixtures. a polymeric main body, at least comprising two parallel side walls (1,2) that are connected to one another by an inner wall and an outer wall, wherein the side walls (1,2), the inner wall, and the outer wall surround a hollow chamber, wherein the main body - has a glass fiber content of 0 wt.-% to 40 wt.-% and - has, due to hollow spaces, a weight reduction of 10 wt.-% to 20 wt.-% and wherein - the hollow spaces are obtained by addition of at least one foaming agent and - the amount of the foaming agent added is 0.5 wt.-% to 1.5 wt.-%, - has a glass fiber content of 0 wt.-% to 40 wt.-% and - has, due to hollow spaces, a weight reduction of 10 wt.-% to 20 wt.-% and wherein - the hollow spaces are obtained by addition of at least one foaming agent and - the amount of the foaming agent added is 0.5 wt.-% to 1.5 wt.-%, wherein the spacer has, at least on the outer wall, an insulation film, which contains a polymeric carrier film and at least one metallic or ceramic layer, the thickness of the polymeric carrier film of the insulation film is from 10 μm to 100 μm and the thickness of the metallic or ceramic layer of the insulation film is from 10 nm to 1500 nm and wherein the insulation film contains at least one more polymeric layer with a thickness of 5 μm to 100 μm and the metallic or ceramic layer of the insulation film contains at least iron, aluminum, silver, copper, gold, chromium, silicon oxide, silicon nitride, or alloys or mixtures or oxides thereof and wherein the polymeric carrier film of the insulation film contains at least polyethylene terephthalate, ethylene vinyl alcohol, polyvinylidene chloride, polyamides, polyethylene, polypropylene, silicones, acrylonitriles, polymethyl acrylates, or copolymers or mixtures.