To provide stiffness, shading and privacy with daylight and a feeling of openness for restaurant extensions and an entrance canopy to a London hotel, we used glass sandwich panels with aluminium honeycomb core. Similar construction had been used on smaller scale for interior decorative panels and for some interior floor panels. Exterior glass sandwich panels need durable strength and stiffness with continuing clarity, so we developed a detailed set of tests and acceptance criteria for all aspects of the appearance and performance of the panels with a specialist façade contractor. The panels were over twice the area of previous examples and too large for the established sandwich panel manufacturers so the contractor developed a new production method.
When sealed sandwich panels are exposed to the weather, they experience changes of pressure in the entrained air, so need to be allowed to equalise. We proposed to ventilate the panels through canisters of silica gel desiccant to dry incoming air sufficiently to avoid condensation. The technique is commonly used to condition the expansion airspace above oil in electrical transformers and gearboxes but was not known in the glazing industry. The technique has wide potential for façade applications.