It's a sign that a new build method is still relatively unusual when you arrive at a building site only to be told that you're in the wrong place, despite the system being right before your eyes.

In fact, the build method in question was being used on no fewer than three different sites in Petersfield during a visit by Timber Building.

The purpose of the trip was to check out Kingspan Century's TEK structural insulated panel (SIP) system, which has recently won its third site as part of the SIXTYK Consortium in the government's Design for Manufacture competition.

By securing the third site, the transformation of the former Rowan High School in the London borough of Merton, Kingspan Century became the most successful building system supplier in the competition.

The company will supply 227 low carbon, highly energy-efficient homes at Merton. In all, it will be building 441 units on competition sites – the others being at Maidstone and Newport Pagnell.

The success has given great confidence to the manufacturers of the German-made product, which see it as a validation to its approach to environmentally sustainable housing design, supply and construction.

With work due to start on the first competition site in October, national sales manager Jeff Tomlinson was in buoyant mood as Timber Building caught up with him at Petersfield.

Here Kingspan Century is replacing 1970s prefab

concrete houses with 148 TEK units for Drum Housing Association. The build programme for phase one (34 units) is 15 weeks.

“Six years ago this was a niche product, but I think we are past the shop window and past the cottage industry,” said Tomlinson.

With contracts for the likes of Lovell Partnership (550 units at Beswick, Manchester) and Crest Nicholson (all three Design for Manufacture sites), he clearly believes the TEK SIP system is becoming more mainstream.

Tomlinson said the off-site manufactured system, which comprises rigid polyurethane insulation sandwiched between OSB sheathing, was helping builders achieve their targets in terms of energy efficiency and build speed.

And he said residents were benefiting from features such as improved sound insulation and low fuel bills.

Tomlinson, a former director of the UK Timber Frame Association, said prior to moving into SIP manufacturing, Kingspan Century had looked at pre-insulating standard timber frame. However, it found this method problematic, so turned to composite panels and bought a German SIP manufacturing business.

The building envelope comprises 140mm TEK panels

The TEK facility in Berlin has a large capacity of about 17,500 houses a year but currently only about 1,000 are manufactured – the majority for the UK. Tomlinson believes low running costs are the real feature of the Design for Manufacture competition, which challenges the construction industry to design energy-efficient, good quality homes for a £60,000 build cost.

In itself, he doesn't believe the 60k figure is revolutionary. But he said providing energy-efficient and good quality homes under this price was a step forward.

“Already, many houses are being built for under a £60,000 build cost. But are they any good? Eco homes cost more.”

All the TEK homes planned on the three competition sites will have a U-value of 0.20W/m2K and incorporate renewable energy systems, such as photovoltaics and combined heat and power – plus rainwater harvesting.

Prior to the launch of Design for Manufacture, architects Sheppard Robson had already been working with Kingspan Century and engineers Arup on developing a housing concept which integrates the principles of sustainability, modern methods of construction and passive environmental systems. When the competition was launched it formed SIXTYK, inviting Crest Nicholson, quantity surveyors Davis Langdon and landscape architects Macfarlane Wilder to join the team.

The consortium's SIXTYK house concept, demonstrated at the Design for Manufacture exhibition in May, informs a portfolio of 35 house and apartment options to give flexibility to any housing development masterplan. It is also “future-proofed” to respond to projected climate change and to suit changing demographics and lifestyle choices.

The building envelope is formed of 140mm TEK panels, while the 300mm I-joist floors are in cassettes, with cement fibreboard added to ceilings to help minimise heat loss.

Sheppard Robson often works with traditional timber frames but the competition represents its baptism in SIPs.

“We selected SIPs because of the improved airtightness that can be achieved, therefore helping to reduce the carbon footprint,” said Sheppard Robson's head of sustainability Alan Shingler. “They also offer a unique structural benefit, negating the need for traditional roof trusses, enabling us to express the pitched roof internally.”

The SIPs construction allows the pitched roof to be expressed internally

Shingler said working with SIPs was neither easier nor harder, just different. “It is always enjoyable to work with new products. There is no question that they have a big future in the UK, the environmental benefits are an obvious advantage. “Public perception of MMC can often be the biggest hurdle but we only have to look to the rest of northern Europe to see that MMC can offer benefits in design and specification. The shell can still be dressed in traditional materials if preferred.”

The consortium's winning project at Newport Pagnell comprises 68 homes on a 1.5ha site within English Partnerships' Hospital Sites Programme. About 30% will be £60k homes.

The urban design solution is challenging and contemporary, with a variety of elevations and an “exciting roofscape”. Balconies, sun terraces, winter gardens and bay windows are intended to give a unique and identifiable streetscape.

At Maidstone, the consortium is providing 150 homes, maisonettes and flats at the former Linton hospital site, with affordable and £60k homes spread throughout so people of different incomes and tenures are mixed within the community.

Brick and timber façades will be used to reflect the local Kent vernacular, while a new public square will be created around a Grade II listed house.

The final and largest development will involve 227 homes on the former site of Rowan High School, Merton. For this scheme, the consortium formulated an energy use/environmental performance table comparing one of its typical house designs with previous, current and predicted Building Regulation requirements.

Annual CO2 emissions for the TEK house with photovoltaics are estimated at 60kg, compared with 1,664kg for a dwelling complying to current regulations. A key feature of all schemes includes designated service walls, which house heating, lighting and ventilation systems. These zones, situated alongside the party wall, produce a common solution to the layout of services across densities, enabling open plan living and creating space for future adaptations such as the inclusion of renewable energy systems.

Close up of the roof lantern

Central to the passive environmental design is Sheppard Robson's roof lantern. This allows the home to benefit from solar gain in colder months, while blocking the sun in the summer. It aids ventilation, allowing heat to rise and escape by stack effect and floods the centre of the house with daylight. It is designed to work like a south-facing conservatory, but its rooftop post enables flexibility in house orientation. Sheppard Robson believes these projects provide a platform to develop its designs and realise its ambition to create “design-led, sustainable, affordable, low density housing”.

Kingspan Century is also projecting ahead. “We’ll be looking at how to develop our approach and identify ways we can continue to drive forward change in the delivery of housing in the UK,” said Tomlinson.