Footprint

David Henderson of Bennetts Associates presented the practice’s BREEAM Excellent New Street Square project as part of the ‘Concrete Elegance’ talks at the Building Centre last week.

Beginning with the orientation of the New Street Square development, the practice’s holistic approach to the site’s environmental, social and economic issues was clear. By designing five separate buildings, as opposed to one, and by keeping the concrete floor slabs at constant heights throughout the development, the buildings are flexible and allow the possibility of links between the buildings in future should the need arise.

Building heights  were dictated by sun paths and the desire to maximise sunlight in the public open spaces.

Locating the low-rise Building 3 to the east allows morning sun to reach the inner square while the 18-storey tower to the north casts its shadow outside the development.

Detailed shading solutions include louvres which vary in response to sun conditions in specific areas of the site. In contrast with the shaded north facades, the buildings facing east are fitted with solar-control glass and fritting to screenout the morning sun.

By devising three options for ‘internal comfort control’, Bennetts Associates’ prepared the building for future tightening of energy regulations. Alongside the currently favoured fan-coil air-conditioning, air can be supplied from the floor void in tandem with passive chilled beams as well as at high level through an active chilled beam.

The building itself is only part of the story. It is the occupants who will have to make the effort to remember, for example, to purge the building at night by opening windows to allow air flow ( this has yet to be put into action by tenants). Bennetts Associates hope that, with decreasing noise levels predicted for the City, this purging will take off, but old habits die hard.

New Street Square’s annual CO2 emissions are not far off the original predictions (in buildings with fan-coils, 46-66kg CO2/m² per annum, in buildings with active chilled beams, 40-60kg CO2/m² per annum. The typical City office: 134kg CO2/m² per annum). This is largely due to the firm’s dedication to reducing embodied CO2 and transportation of materials. Bennetts Associates was involved in monitoring construction transport.

David Henderson believes that if the design were to be submitted today the predicted annual CO2 emissions would be even lower, at 30kg CO2/m² per annum or less.

Imogen Holden