Going to eco town

Stewart Milne Timber Systems (SMTS) has been awarded the design order to help create the UK's first eco town, North West Bicester (NW Bicester), and is in final negotiations for the production and supply of the Sigma II timber frame on the first Exemplar phase.

The company is working with lead developer A2Dominion, and main housing contractor Willmott Dixon, to provide highly-sustainable timber frame houses as part of the UK's only eco town still to adhere to the government's original Eco Town Policy Planning Statement designed to achieve high standards of environmental sustainability. The first phase of the timber frame element is worth around £1m.

"Timber frame is the most energy-efficient building material available and therefore is a perfect fit for NW Bicester's design as the UK's first eco town," said Alex Goodfellow, group managing director of SMTS.

"We employ more than 100 people in the local area and have extensive experience in delivering energy efficient homes quickly and cost effectively and this made us an ideal local partner for the developers."

The Exemplar phase of the scheme will provide 393 homes, which meet the Code for Sustainable Homes Level 5. Each home will have a true zero carbon rating, with heat and hot water being generated on-site by a highly-efficient, gas-fired combined heat and power plant.

The development will also feature the UK's largest domestic solar panel array, with 17,500m² mounted across the rooftops of all homes to generate electricity. This includes freestanding photovoltaic (PV) panels, overlaid PV panels and inset PV tiles.

The homes at NW Bicester are designed to be 'future proofed' against climate change and rising temperatures. Some homes also have future-adaptable roofs, which can be transformed with ease into increased working or living space to improve the life cycle of the buildings and reduce travel requirements. Incorporating renewable technologies and future-adaptable roofs is all part of a day's work for SMTS.

"All of our timber system product range is fully customisable for each project, depending on the design intentions and performance standards specified by our clients, so incorporating additional technologies and design features is never a problem," said Mr Goodfellow. "We also work closely with our client project teams to enhance performance and suggest more cost-effective material integrations or build processes where appropriate," he continued. "Sigma II is highly customisable in terms of being able to integrate with additional materials."

Aiding the energy efficiency is the type of wall being used to construct the homes, which is SMTS's proprietary Sigma II build system, 195 C-Stud. The system delivers a U-value of 0.15W/m²K through the external walls, and 0.13W/m²K through the roof. The external walls will also have a PSi value of 0.04W/m²K, which is achieved through the Sigma II unique C-Stud, ensuring minimal member crosssection between the external and internal sections of the panel. The project's airtightness will be 3m³/hm² @ 50pa, which will be tested after the erection of the timber frame and before the handover of each plot. Airtightness in the external walls is achieved within the Sigma II panel itself, rather than at a site fit level, allowing a higher quality of finish.

The party walls and roof will be site insulated and made airtight with membranes. This, along with pre-assembled roof modules and insulated floor cassette edges, means a pair of semi-detached homes can be weathertight, airtight, secure and fully insulated within 72 hours, providing a safe and efficient means to complete the homes on site.

"Being able to build the timber systems before they're brought to the site to be erected with mobile cranes allows a significant time advantage over standard construction methods," said Mr Goodfellow. SMTS's 'fabric first' approach is a critical element of achieving high levels of environmental performance, with energy efficiency built into the building's fabric.

"Low-carbon homes and other buildings are going to take on growing importance in the future, and timber's inherent energy efficiency and structural integrity can play a key role in helping achieve those objectives," said Mr Goodfellow