Modular glass unit in particular that for facing facades of buildings

A glazing unit 1 comprises two sheets of glass 2, 3 which are separated by a spacer bar 5. An outer secondary scal 10 extends around the periphery of the glazing unit. The seal 10 has a number of peripherally spaced-apart fixing inserts 50 extending around the periphery of the glazing unit for fixing the glazing unit to a support 17. Each fixing insert 50 has a base wall section 51, parallel side walls 52 and end wall sections 53 which define an arcuate slot 55 dosed at both ends. The configuration of the fixing inserts 50 allows simple fitting while ensuring the maximum bulk of material for structural strength. Opposed fixing inserts 50 are engaged, an assembly, by a toggle 60.