Fabric first fundamentals

Architect Jon Boon's opening shot at the Fabric First conference at the National Motorcycle Museum in Solihull last week, was that the name of the event was wrong. "It should actually be Fabric Second," he said.

He hastened to add he wasn't questioning the premise of the conference. Organised by the UK Timber Frame and the UK Structural Insulated Panels (SIPs) Associations, the conference had as its central theme that the fabric of a building, rather than expensive renewable energy technology, is where construction should primarily focus to shrink its carbon footprint and satisfy green building codes and tougher Building Regulation targets on insulation and sustainability. In conjunction with that, the message is that timber and wood-based products and systems are the fabrics with most potential to help architects, structural engineers and builders do all the above.

Supply chain co-ordination Mr Boon did not take issue with this, but told the 180-strong audience of architects, engineers, timber construction specialists, contractors, housing association representatives and other specifiers, that the industry needed to go beyond fabric first, or rather further back. To work, the building approach needed more advanced preparation, right back to planning. It also demanded collaboration down the supply chain, to ensure components and materials worked together to best advantage.

"We need to adopt original 'Passivhaus' principles, where the initial focus for maximum energy efficiency is site and orientation," he said. "That means having principal rooms south-facing to maximise solar gain and siting to make optimal use of natural ventilation to avoid overheating. Planting and landscaping around buildings are also important. The fabric is key, but we must also get these fundamentals right, so we put less stress on it and further optimise its performance," he said. Others speakers also stressed the importance of supply chain co-ordination

"Frequently the performance gap between a building as designed and completed is due to how elements work, or don't work together," said architect Richard Partington. "We need to address the sequencing of how materials are brought together and the interaction of different elements. Frequently there are cold spots at conjunctions of walls, floors and ceilings. Recently on one of our projects, sealing tape used on timber panels in the roof came away because the adhesive reacted adversely with something in the board, and often there are unintended consequences from the interaction of different trades and suppliers - kitchen fitters drilling through the timber frame fabric, creating thermal bridges and bypasses, for instance. The UKTFA's guidance on timber frame structure and detailing is very helpful, but we also need better understanding among suppliers and trades about the interplay of different building elements and what each other does."

According to Professor Nick Whitehouse of Oxford Brooks University, the other key to getting the best results from a fabric first strategy is to combine it with offsite construction.

"Offsite prefabrication not only means improved performance in terms of energy efficiency because components and systems are put together in a controlled factory environment - and offsite buildings' energy in use is on average 20% better - it also results in significant health and safety improvement, 50-80% less energy used on site, up to 70% savings in transport to site, and 50-90% less waste," he said. "On a 2,000m2 building, waste reduction has been calculated at around £16,000, while faster construction on a £3m home saved £455,000."

Andrew Cook of LWT Contractors said that the use of SIPs in particular, which his company uses alongside timber frame, had major potential for increased take-up in conjunction with volumetric offsite approaches.

More housing for less money "The drive is for more housing for less money, delivering less waste and better performance," he said. "With SIPs we can offer that, with everything from raw material delivery, through prefabrication, engineering, assembly and interiors work done under cover."

Dhruv Sookhoo of housing association Home Group said it backed offsite, but cautioned that consumers did not want houses that look "overtly state-of-theart". "Offsite and other modern methods of construction (MMC) also entail more initial design time, as they're very unforgiving," he said. "Get something wrong, and you're not just fixing elements, you're fixing a system."

Other speakers said making the most of the fabric first approach, offsite and MMC generally also demanded greater standardisation of building components, including doors and windows.

"This comes up at every meeting of our industry think tank - and contractors are crying out for housing associations to adopt it," said UKTFA chief executive Andrew Carpenter. "We've been presented with an instance of a 160-dwelling development featuring 90 different window designs. We have to address this as an industry. "

"Adoption of Building Information Modelling (BIM) throughout the supply chain will also be key to embracing these approaches," said architect Stephen Lamb. "Some timber frame kit builders we've worked with have tended not to schedule windows and doors until the end of the design process in case of changes. But we need to fully integrate major component schedules from the outset."

"We all need to be looking at BIM," agreed Mr Carpenter. "It is the vehicle to drive collaboration."

Paul King of the UK Green Building Council acknowledged that in the current depressed market there was pressure from construction and government to push back the country's 2016 zero carbon housing target and water down Building Regulation eco demands. But he said the UK building industry should resist this as latest materials, technologies and techniques gave it the chance to achieve the highest performance standards and become a world leader in "cutting edge new [green] homes".

"The UK has set a goal of cutting greenhouse gas emissions by 80% by 2050, and construction can make a major contribution to achieving that," he said. "You helped deliver London 2012, the greenest Olympic Games ever, and you can build GB2050."