BedZED is the UK’s largest mixed use, carbon-neutral development. When it was built in 2002, it set new standards in sustainable building. BedZED comprises 82 affordable dwellings in a mixture of flats, maisonettes and town houses, and approximately 2500 m2 of workspace/ office, and is built on a brownfield site.
The BedZED urban system reconciles high-density with amenity, providing each dwelling with a sky garden or terrace. A combination of passive measures and proven, cost effective active technologies form the strategy of an integrated, sustainable development. A rigorous specification process helped reduce the environmental impact of the construction process.
The scheme includes a biomass combined heat and power plant, an onsite sewage treatment and rainwater recycling system, and natural wind driven ventilation.The idea was to show how it was possible to combine workspace with housing whilst matching the residential densities of the surrounding dormitory suburb, and actually increasing overall standards of amenity - particularly gardens and public open space. This was achieved by matching south facing rows of single aspect residential terraces with north facing live / work units or workspace. By placing gardens on the workspace roof, it was possible to give almost every home a garden or terrace, whilst achieving high levels of cool northlight within the office space.
Five years after full occupation, there has not been one complaint from residents about workers on the site, indicating that the combination of different uses has been complimentary on the whole. The design team tried hard to do the right thing in the right place. A complex mixed income residential brief from Londons' oldest housing association - the Peabody Trust asked for one third of the homes to be social rent, one third shared ownership and one third private for sale. A requirement for a mixture of both large and small family homes as well as one and two bed flats, led to a wide variety of different plan unit types, each changing to suit the position within the masterplan and cross section. North facing workspace can be divided up into small units each with its own front door to the street, or knocked through to create one large workspace the length of an entire terrace, with enough deskpace for a thirty to forty person office.
This enables a mixture of fairly sizable and micro start up companies to integrate themselves in this community. BioRegional reclaimed were very successful at reclaiming structural steelwork and softwood walling studs from local demolition sites for remanufacturing into useful new structural components.
Most bulk materials and labour were sourced within a 50 mile radius of the site, enabling the completed embodied carbon to compare favourably with that of a volume housebuilder's industry standard product - despite having thicker walls and considerably higher thermal mass.
BedZED is just about large enough to merit its own on site water treatment plant and woodchip fuelled combined heat and power plant. Although the plant can be accurately sized to meet demand, staff maintenance costs on an isolated island site of this size can become prohibitive, although this problem will be overcome as both these community scale technologies become more commonplace in south London. Biomass chp works very well on mixed use zero heating specification developments, as the thermal demand is for hot water only, and remains consistent all year, withoversize hot water storage tanks that can meet peak demands whilst still allowing trickle recharging throughout the day. This allows the power plant to more or less match average electrical demand, exporting to grid when surplus power is generated on site - and importing to meet peak demand.
On balance over a year, if the plant performs reliably, with only its planned maintenance downtime - then slightly more power is generated than is actually required on site. If this surplus power is between 5 and 15 % of annual demand, it should be possible to pay off both the embodied initial construction carbon and the planned maintenance / replacement carbon footprint.
The advantage of the biomass chp system is that very similar amounts of biomass are burnt compared to a conventional heat only boiler, as the electricity is generated from flue gases that would be unlikely to have been harnessed to the same efficiency in a more conventional combustion process. This make it much easier to stay within the national biomass quota, whilst still inhabiting higher density urban infrastructure