High performance and transparency: the challenge of the glazed envelope

The Shard’s plan is an irregular, eight-sided polygon, each segment, or ‘shard’, of glass sloping in a different direction, and each diversely exposed to the sun. The eight glazed façades gradually taper as they proceed to the tip of the building. They resemble a monumental castle of cards, each successive layer leaning inwards at various angles. The special feature of this glass castle is that the shards never touch each other, remaining independent to avoid the effects of wind load on large expanses of converging flat glass surfaces. An inner curtain wall wraps around the building ‘filling in’ the gaps left by the outer shards, and with these, creating a double-skin façade. Winter gardens and meeting rooms occupy the ‘fracture’ areas where the external shards do not meet.
The asymmetric design of the Shard’s volume meant a highly complex glazed envelope design. The eight ‘shards’ entailed the design, engineering, manufacturing, and installation of around 11,000 units, many of them one-off production elements.

The Shard’s envelope is a passive double-skin system. This was necessary to meet the extremely high transparency requirement, which would not have been possible with an active double-skin façade with a mechanical ventilation system. By no means a simple design, with no few execution challenges, the envelope’s beauty lies in its very complexity. The Shard has some fourteen different types of façade: Shard Cladding, Shard Skirt Cladding, Spire Cladding, Back-Pack Plant Cladding, Fracture Cladding, Winter-garden Cladding, Wing Wall Façade, Roof Steps and Soffits, Lower Level Façade Curtain Wall Systems, Canopies, Internal Wall System Lobby, Steel Framed Wall, Unitized Lower Level Cladding, Lower Level Louvre Cladding.
There are also special items that can be identified around the building and need extra attention in regard to operation and maintenance: Fracture Vents, Smoke Vents, Blinds in Shard Cladding Cavity, External Blinds in Lower Level Façade Curtain Wall Systems, Building Maintenance Unit (BMU) Doors in Shard Cladding, BMU Doors in Fracture Cladding, Doors and Revolving Doors.