double glazing unit(A double glazing unit is a combination of two panes of glass spaced apart with a spacer bar and sealed with a primary and secondary sealant to form a single airtight unit with an air space in between. 'More); double glazed unit(A double glazing unit is a combination of two panes of glass spaced apart with a spacer bar and sealed with a primary and secondary sealant to form a single airtight unit with an air space in between. 'More)