Beyond the Code

RuralZED takes zero-carbon housing to new levels, writes Hattie Hartman

Bill Dunster claims his RuralZED house, which will be shown at the Ecobuild exhibition (26-28 February at Earls Court), meets the unprecedented (and non-existent – he invented the term) Level Seven of the Code for Sustainable Homes, with a wind turbine producing energy to make up for the embodied energy in the materials and construction of the structure.
While this may appear a gimmicky claim, Dunster says the project is all about myth-busting. 'Anybody can build to Level Six,' he says [witness the Sheppard Robson and PRP houses at BRE innovation park], 'but the key is to keep it affordable'. The basic kit of parts for a RuralZED house costs £116,000. Dunster says a typical house can be built in a month; Ecobuild's prototype will be assembled in thee days.
RuralZED is a box which can be wrapped with a variety of elevations and roofing configurations. Units can be grouped to form a terrace or stacked to form a multi-unit building. The house can accommodate upgrades of technologies such as a wood pellet burner and photovoltaics.

The house combines 200 x 200mm glulam timber post-and-beam construction with thermally massive walls and ceilings. CNC technology enables all setting out and cutting of the timber structure to take place in the factory. Dunster, in collaboration with Aggregate Industries, has developed a stacking system of 1.9m-long precast, eco-concrete planks for the walls and, with Ibstock, has developed a specially extruded 13kg arched terracotta 'coolvault', which forms the ceiling to the ground floor and the floor of the upper storey.
The RuralZED house is a result of more than 10 years of research, beginning with Dunster's BedZED project, completed in Beddington, near Croydon, in 1998, and developed through a prototype house in Cambourne, Cornwall in 2004, and Jubilee Wharf in Penryn, Cornwall, in 2006.
With this project, Dunster proposes a new business model for house-building. RuralZED emerges from a consortium comprising Danish window manufacturer Rationel, Rockwool (for insulation), and Aggregate Industries.
Dunster's practice, rechristened ZEDfactory in 2004, is now in the business of supplying everything from extralong wall ties for super-insulated walls to small-scale wood-pellet boilers, which are sold to architects and homebuilders alike. These products are distributed by Dunster's new brand ZEDfabric.
Dunster explains that all the suppliers of RuralZED have earned their place. He says the UK has yet to manufacture a triple-glazed window that can compete with Danish supplier Rationel. Dunster visited all the major PV factories in China who were supplying the European and PV supplier for ZEDFactory. All ZEDfabric products have been tested on Dunster's own home or on the homes of his staff . 'We
never inflict products on our clients until we know exactly how they work', he says.
But why RuralZED, I ask Bill. Surely this building's natural home is suburbia? Dunster is quick to point out that Countryside Homes is not really building in the country. 'It's nostalgia for the rural idyll,' he says, acknowledging that the ideal site for RuralZED is suburban infill or a village extension at approximately 50 homes per ha. According to Dunster's calculations, this is 70 per cent of the UK – a huge potential market for ZEDFactory products.


Click here for a detailed, labelled diagram of a RuralZED house