The Belgian U suite's main difference from the standard Belgian suite is an increase of 15mm in depth from 33mm to 48mm. It substantially increases structural strength for larger spans, sashes, and doors.
The U series resulted from calls from the building industry for steel profiles able to take 24mm of double-glazing with glazing beads without diminishing the elegance of the original Belgian profile.
A 5mm increase in the glazing leg from 11mm to 16mm gives boosted edge support for larger spans of glass and also helps general rigidity.
Belgian U glazing
The profile commonly uses inside 24mm glass with an internal snap-on glazing bead. It can be double glazed up to 24mm in operable products, and up to 26mm in fixed windows, with snap-on beads.
It can also take double-glazing with structural silicon glazing, without a glazing bead. The use of 24mm or greater double-glazing gives great flexibility for glass thicknesses and inter-glass spacing when larger spans demand thicker glass.
Also, double-glazing of 24mm or more allows for additional in-frame glass for boosted performance where the glass is thinner or has a greater space between panes.