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Having completed in 2002 a carbon-neutral mixed-use development at Wallington, near London, BioRegional Development Group is planning one 25 times bigger with 2,000 homes called Z-Squared.

Hoping to find a site east of London this year, the firm has yet to appoint an architect for the zero-carbon development. Being site-dependent, energy systems have yet to be selected. But they will include cogeneration and use exclusively renewable sources, says project manager Nicole Lazarus.

Z-Squared’s predecessor, the $29-million BedZED, was zero-carbon until the firm providing its 130-MW prototype cogeneration plant, fueled by gasified wood, went bust. But even using mainstream power for the bulk of its needs, BedZED produces roughly half the carbon of a conventional development, says Jennie Organ, BioRegional’s spokeswoman. That’s partly because the thermally efficient five blocks need 88% less space heating, she adds.

BioRegional developed the BedZED concept and got the not-for-profit developer Peabody Trust, London, to hire Bill Dunster Architects, now ZEDfactory Ltd., to build it for $29 million. BioRegional and the architect are now based there.

For Z-Squared, the firm formed Bioregional Quintain Ltd. with a developer, which has funding. At an estimated $1.3 billion, the cost will be 8% above a conventional development because of additional infrastructure, says Lazarus. But that may be avoided by outsourcing energy services. Construction of Z-Squared could start in 2008.

special theme issue:   SUSTAINABILITY

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