OFFSITE on target

The opportunities for timber-based construction created by the UK's push for more sustainable, affordable housing were underlined at OFFSITE 2007 last week.

The event at the BRE featured The Big Build, a mini 'village' demonstrating latest construction approaches, and four out of the six houses on show had timber and wood products at the core.

This was easily the most high profile OFFSITE to date. The biennial event was originally conceived as an industry conference with an exhibition attached. But the latter is now clearly stealing the limelight. With its focus on carbon neutral building, and its cutting edge prefabricated houses set in landscaped surroundings, complete with machined oak decking walkways from Arnold Laver, it pushed all the right media buttons. Most of the main TV channels turned up and BRE chief executive Dr Peter Bonfield was even interviewed for the Radio 4 arts show Front Row.

“The conference presentations are still key to the event,” said Dr Bonfield. “But out of the 6,000 people we expect to attend, 5,000 will be coming for The Big Build.”

OFFSITE targeted professionals from across the construction sector and was opened by housing and planning minister Yvette Cooper. She said the event chimed with the goal the government hopes to achieve, via its Code for Sustainable Homes (CSH), for all new build housing to be “carbon neutral” by 2016.

“A quarter of UK carbon emissions come from our homes and we need to build many more in coming decades – in fact, a third of all housing that will exist in 2050 is not built yet,” she said. “That's why standards for new homes are so important and why we set our 2016 zero carbon target. It's ambitious, but this exhibition shows it can be met.”

The highest ranked house under the CSH at Offsite was Kingspan Off-Site's chestnut-clad Lighthouse. This is billed as the first to achieve the CSH level 6 standard, which means zero net emissions of CO₂ from energy use. It is based on a glulam portal frame and Kingspan TEK structural insulated panels and has triple-glazed Nordan timber windows. The SIPs have a U-value of 0.11W/m²K and the building achieves airtightness of 1m³/hr/m² at 50pa. Combine this performance with energy-saving A++ appliances, a biomass boiler, photovoltaic and solar thermal panels and the fuel bill for the two-bed house would be just £30 a year.

“Admittedly this is a prototype and cost more than a conventional build,” said Kingspan Off-site regional managing director Gilbert McCarthy. “But costs will go down with economies of scale; by building multiple units around a shared heat and power plant for instance. ”

The Stewart Milne Timber Systems (SMTS) exhibit was its Sigma house, a four-storey semi-detached design. The SIPs and pod-based design achieves CSH level 5 and includes mechanical ventilation, solar thermal and PV panels, wind turbines and a “whole house thermal stack” which uses heat sensors to control vents to maintain optimum temperature and air quality.

“As well as achieving very low emissions in-use, Sigma is very quick and efficient to build,” said SMTS managing director Stewart Dalgarno, “a four-storey, four-bed house from grass to keys in four weeks.”

Built as part of a shared energy development, Sigma could achieve CSH Level 6. “We're now planning to build a Sigma village,” said Mr Dalgarno.

ecoTECH, a UK company which works with more than 30 Swedish timber panel construction specialists, presented a modular construction approach. Its “Organics” pod-based range comes in 21 designs and three sizes. The model on site was CSH Level 4, but, in shared resource developments could be Level 5 or 6, said managing director Christine Hynes.

Another SIPs home was presented by Osborne, in partnership with panel producer Vencel Resil. The building was watertight in a day and completed in 12 weeks. Mechanically ventilated, and equipped with a solar heating system, a final 'eco' touch was a mock slate rainscreen made from recycled tyres.

The other timber structure on show was a mini-school from Wilmott Dixon's “Re-Thinking” building consultancy arm, in association with architect White Design and timber specialist builder Eurban. The building was based on Lenotec cross-laminated solid larch panels from Finnforest Merk and finished with cedar cladding. “The school is designed to perform sustainably and provide a lesson in environmentally-sound construction for the children,” said Julian Cottrill of consulting engineer Max Fordham.

Dr Bonfield said the The Big Build exhibits showed the UK becoming a “world-leading innovator in design and construction of sustainable buildings”, and he added that the timber construction specialists had made particularly impressive progress since the last OFFSITE in 2005. However, he cautioned that the timber sector as a whole still needs to step up its efforts to meet the increasingly environmentally-driven demands of the building sector. “The [timber] supply chain has been pretty slow in reacting to the agenda,” he said. “It cannot rely on PR and spin about renewability. It has to understand what construction clients need and deliver hard facts and demonstrable evidence of performance and sustainability.”