Structural Glazing and Thermally Broken Curtain Walling

BDF Architectural fabricates and installs insulated, thermally broken curtain walling for commercial façades across London and the UK, in capped and structurally glazed (SG) versions, from low-rise offices to high-rise towers, on Schüco FWS 50, including the highly insulated FWS 50.SI and the structurally glazed FWS 50 SG, and on Jansen VISS SG where a steel façade is specified.

There are two ways to hold the glass in a curtain wall. Capped systems clamp it mechanically with a pressure plate and a visible cover cap, which gives a crisp grid on the outside. Structural glazing bonds the glass to the frame with structural silicone instead, so the outside of the building reads as a near-continuous plane of glass. We fabricate both on Schüco FWS 50, including the structurally glazed FWS 50 SG and SG.SI variants for flush or semi-structural all-glass façades, and install Jansen VISS SG, which supports structural glazing and large glass formats, where a steel façade is specified.

Thermally broken curtain walling has an insulating break between the inner and outer parts of each profile, so heat cannot conduct straight through the metal. That keeps the inside face warm, cuts condensation risk and lowers heating and cooling loads, with U-values down to about 1.0 W/m²K depending on the glass. The systems take solar control, low-e and triple glazing, with integrated opening vents and smoke ventilation where needed, all designed to BS EN 13830.

An insulated curtain wall is more than its profiles. The thermal performance of the whole wall depends on the glass, the spacer at the edge of each unit, the proportion of frame to glass and the opaque zones, so it is calculated for the actual façade, typically to BS EN ISO 12631, rather than taken from a profile or glass figure alone. Where the thermal target is demanding, the highly insulated FWS 50.SI, which has Passive House-certified configurations, and triple glazing are the usual options.

Not every part of a curtain wall is vision glass. Where the wall passes slab edges, columns, ceiling voids and plant, the same mullion and transom grid carries opaque infills: insulated spandrel panels with a metal or glass outer face, or a shadow box, where glass sits in front of an insulated back panel to give the elevation depth. These opaque zones carry much of the wall's insulation, so their build-up, vapour control and condensation risk are designed together with the thermal calculation, and glass in front of a spandrel, which runs hotter than vision glass, is normally heat-strengthened or toughened. Insulation and other materials in the opaque zones are specified against Approved Document B and the fire strategy, including the restrictions on combustible materials in the external walls of relevant buildings with a storey 18 metres or more above ground.

As curtain walling fabricators and installers, we process, machine and assemble the Schüco profiles in our West Drayton facility and install the finished wall, so the thermal and spandrel details on the drawings are the ones built on site.

To price, send elevations and sections, the performance specification including thermal targets, glass and any opaque or spandrel zones, the fire strategy, and programme dates.