A gas-filled insulating glazing unit comprising: • a first and a second glass panes, • an edge spacer assembly extending between the first and second glass panes along their edges for holding them at a certain distance from each other and for sealingly coupling them so as to form a hermetically sealed interspace between them, • an insulating gas filling said interspace, wherein said edge spacer assembly has at least one transparent side along one of the glass panes edges, and said at least one transparent side is characterized in that it comprises at least two piled and connected transparent parts comprising: • at least one transparent stiffening part comprising a transparent rigid material having a Young's modulus of at least 0.5 GPa, • one single transparent sealing part comprising a transparent viscoelastic polymer having a Young's modulus lower than 0.5 GPa, wherein the top surface (S1) and the bottom surface (S2) of the piled and connected transparent parts are connected respectively to the first and the second glass panes, and wherein at least one of the top (S1) or bottom (S2) surface belongs to a transparent stiffening part and is rigidly connected to the first or the second glass pane. • a first and a second glass panes, • an edge spacer assembly extending between the first and second glass panes along their edges for holding them at a certain distance from each other and for sealingly coupling them so as to form a hermetically sealed interspace between them, • an insulating gas filling said interspace, wherein said edge spacer assembly has at least one transparent side along one of the glass panes edges, and said at least one transparent side is characterized in that it comprises at least two piled and connected transparent parts comprising: • at least one transparent stiffening part comprising a transparent rigid material having a Young's modulus of at least 0.5 GPa, • one single transparent sealing part comprising a transparent viscoelastic polymer having a Young's modulus lower than 0.5 GPa, wherein the top surface (S1) and the bottom surface (S2) of the piled and connected transparent parts are connected respectively to the first and the second glass panes, and wherein at least one of the top (S1) or bottom (S2) surface belongs to a transparent stiffening part and is rigidly connected to the first or the second glass pane. wherein said edge spacer assembly has at least one transparent side along one of the glass panes edges, and said at least one transparent side is characterized in that it comprises at least two piled and connected transparent parts comprising: • at least one transparent stiffening part comprising a transparent rigid material having a Young's modulus of at least 0.5 GPa, • one single transparent sealing part comprising a transparent viscoelastic polymer having a Young's modulus lower than 0.5 GPa, • at least one transparent stiffening part comprising a transparent rigid material having a Young's modulus of at least 0.5 GPa, • one single transparent sealing part comprising a transparent viscoelastic polymer having a Young's modulus lower than 0.5 GPa, wherein the top surface (S1) and the bottom surface (S2) of the piled and connected transparent parts are connected respectively to the first and the second glass panes, and wherein at least one of the top (S1) or bottom (S2) surface belongs to a transparent stiffening part and is rigidly connected to the first or the second glass pane. <EOS>