Why the merits of the Heron Tower are so blindingly obvious
So great is the media prejudice against tall buildings that it has become more or less impossible to write in favour of KPF's Heron project without prefacing one's words with a lengthy restatement of the advantages of tall buildings in general - rather like being forced to explain the principle of the internal combustion engine before road-testing the new Mini. Nonetheless, I did my duty in this respect a fortnight ago and now I want to get into the meat of the case for 110 Bishopsgate.
To start with, it must surely be conceded that Kohn Pedersen Fox knows what it is doing when it comes to tall buildings. The firm reckons that, worldwide, it has built more than 40 high-rise office towers since its foundation in 1976, including in Europe the reconstruction of the 30-storey Martini Tower in Brussels and the 52-storey DG bank in Frankfurt, the latter of which pioneered the use of functionally asymmetrical facade treatments for tall buildings, a tradition that 110 Bishopsgate not only continues, but develops further.
Where the earlier building employed sun-shading and double facades in the German manner, the new one adds a planning orientation and structural design that offset the service core, from the centre of the building to the south elevation. There, banks of lifts and ancillary accommodation will not only reduce heat-gain within the building envelope using the lift shafts as warm air vents, but will provide the best location for a bank of photovoltaic cells, complete with self-powered cooling fans to increase their generating efficiency.
In these ways, the project raises itself above the so-called 'tall buildings debate', and can properly be seen as part of a worldwide technological development programme for 21st-century buildings. Thus, for example, the distinctive appearance of 110 Bishopsgate results not only from its advanced information technology capability, but from the way its key elevations, clad in highly transparent white glass, are mastered by a heavy diagonallybraced steel macrostructure from top to bottom.
This framework is not decorative, but reaches back into the building envelope to articulate the internal horizontal divisions that provide for flexible single- or multi-tenanting in three-floor office 'villages' 3,300m 2in area, each built around a triple-height atrium, and designed to accept a variety of energy-efficient servicing systems.
All these advanced measures grow out of the limitations of the Bishopsgate site, and the need to provide a structure capable of efficiently using its small footprint, while conforming to other design requirements.
The bottom line is that 110 Bishopsgate offers a platform only 1,900m 2of offices on 37 floors, rising to a height of 183m - in addition to retail, restaurant and bar accommodation.
This means a tower with the very high aspect ratio of 8:1 but, thanks to skilful structural engineering by Arup, one with floor-to-ceiling heights of 2.75m within slab-to-slab heights of 4.128m, leaving room for chilled beam cooling if desired. The tallest feature, the 39m mast that increases the building's height to 222m, carries a lightning conductor and aircraft light, as well as being large enough internally to house a number of microwave antennae.
The building is situated close to six Underground stations and three main line stations, the nearest of which at Liverpool Street are barely across the road.
The proposed Heron building will also benefit the public realm by facilitating the closure of Houndsditch, thus creating a new tree-lined public open space to enhance the setting of the adjoining listed church.