Façade engineering Cooling canvas Tilting
Looking to design a high-performance single-skin façade, engineers turned to the classic bay window for inspiration. And the successful results underlined the importance of early-stage collaboration, writes Dr Mikkel Kragh
M
y firm belief is that façade engineering (FE) is an essential component of integrated design. By looking at two new- build projects where FE was applied, I
hope to show how bringing FE in at the early stages of the process can help deliver ambitious designs and high performance. Ropemaker Place is a commercial development near
Moorgate in the City of London, developed by British Land and designed by Arup Associates. The façade plan was set up with input from specialists in Arup Façade Engineering as a repeat of a successful formula adopted in connection with the Plantation Place project a few years earlier. The concept was developed in close collaboration across the disciplines – covering architecture, environmental strategy, façade detailing, buildability, building physics, and procurement including costing. The Ropemaker design team, however, was not
in a position to adopt the advanced façade concepts developed for the same client’s Plantation Place project a few years earlier. The challenge for the team was to deliver high performance and appealing architecture to suit Ropemaker’s more limited budget, while also meeting the sustainability targets.
Plantation Place The Plantation Place development features a series of advanced façade solutions. The lower levels are ‘sealed’ (no openable windows) with stone fins, to fit into the urban fabric of the City of London. The massing of the buildings is informed by planning policies, including rights to views of St Paul’s Cathedral. The result is that the buildings step back and the floorplates of the top levels are less deep. The façade to the upper floors is a double-skin system, with openable windows in the inner façade and an automated solar shading device in the cavity between the two skins.
24 CIBSE Journal August 2010 The fully-glazed outer skin is shingled, which means
that the glass panels are tilted slightly with open joints between them. The inner curtain wall façade is not highly glazed by London standards, but the outer skin gives the top storeys of the building a highly glazed look and feel, with reflection of the sky bringing to the big elevations a certain ‘lightness’ when seen from the streets below. The outer skin also serves to shield the shading device
from the wind. Without the outer screen the automated external venetian blinds would have been exposed to the wind, and there would have been situations where they could not be deployed when needed. The double skin arrangement solves this problem and the control system is fairly sophisticated with zoning according to solar exposure and shadowing (see Figure 1). The double skin also serves to shield the openable
windows from the wind and deals with the problem of natural ventilation at height. The openable windows have been built in as a future proofing-measure or an optional environmental feature. The building is currently fully air conditioned but can be operated in mixed mode.
Ropemaker Place The Ropemaker façade design is an exemplar of the integration of architectural treatment with environmental performance. The design team created a bespoke tilting façade
system, which reduces energy for cooling by up to 27% compared with a reference flat façade. The subtly changing colour and rhythmic expression of the façade present a dynamic canvas of reflectivity and tone, while the projecting arrays also provide the integrated solar shading as the windows ‘turn their backs’ to the sun and thereby significantly reduce solar gain and consequent cooling loads. The building is composed of six large-scale >
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