BowZed
Client: Yorklake Homes
Architect: BDA/ZEDfactory
Structural engineer: Ellis and Moore
Main contractor: Toweregion
Masonry’s thermal mass is a vital weapon in the battle for energy efficiency, as this zero-carbon project shows
The BowZed apartment block at Tomlins Grove in east London exploits the benefits of masonry’s thermal mass. Completed in 2004 by Bill Dunster Architects’ ZEDfactory, the four-storey building can store solar heat gains for up to five days in winter. In summer, this time lag means internal temperatures can be up to 10ºC cooler than outside.
Dunster has frequently warned that houses with lightweight construction do not have sufficient thermal mass to cope with ever increasing solar heat gain. By the middle of this century, many will require air-conditioning or could even face demolition. The zero carbon project at Tomlins Grove, Bow, shows a way forward. Project architect Steve Harris says: ‘It has such high levels of insulation and thermal mass that no central heating is required. It generates as much energy from renewable sources as it consumes over a year, half from photovoltaic cells and the rest from the wind generator.’
The £500,000 building is orientated to maximise its solar potential. Two flamboyant roof-mounted ventilation cowls with integral heat recovery track the wind, and the roof is further animated by a wind generator.
‘The finish is to the high levels expected of a modern urban private sales development,’ Harris says. ‘Windows are triple glazed, high quality sustainable softwood and the building is airtight to Scandinavian standards.’ Each of the four apartments has a south-facing living room, a terrace and a conservatory tucked beneath the dramatic 30° PV slope.
Heating is derived from the occupants themselves, solar gains on the south elevation and from cooking and appliances. A 15kW wood pellet boiler provides back-up for a single radiator in each flat, which only comes on when flats are unoccupied and the temperature drops below 18ºC
Clay blocks and bricks articulate the elevations. Yellow London stocks were sourced from the brickworks that supplied the area in the 19th century. Projecting by 120mm, the clay blocks are supported on an exposed C-channel at first-floor level, designed to allow a future change of use on the ground floor
Typical wall sections are 100mm clay block or brick, 300mm rock fibre insulation and an internal 140mm leaf of dense concrete block. Finished with a dense wet gypsum plaster, the wall construction is more than half a metre thick and achieves an impressive U-value of 0.1. Thermal mass is enhanced by precast floor slabs supported on the reclaimed steel frame.
Tomlins Grove makes fine use of masonry in an integrated solution to environmental, technical and architectural demands. Harris adds: ‘It also shows how a zero fossil energy scheme can be done on a tight site as part of a conventional development opportunity.’