Heading up to John O’Groats, the A99 takes a route through the small east coast town of Wick. Once home to a thriving fishing industry, the town is now a base for vessels supplying the North Sea oil rigs so the 8,000 or so inhabitants are used to the comings and goings on their harbour. However, in late October, it was a cargo of a very different nature that was offloaded onto the dock – a Tesco store.

Well, it wasn’t the completed product, but the huge glulam beams, plywood sheets, Kerto LVL, floor tiles and roofing – equivalent to 75 truck loads – were the bulk of the components for the supermarket giant’s first “eco store”.

Opened on November 27, the building is Tesco’s first notch in its aim to reduce the environmental impact of the construction and operation of its stores – and its first timber-framed and timber-clad building.

Tesco says the carbon footprint of the construction process was 20% smaller than the company’s conventional, steel-framed stores, and in operation its carbon output is expected to be halved. Work is now under way on a second timber frame store in Shrewsbury.

James Dorling, Tesco’s environmental project manager on the Wick site, said the building was a progression of the company’s energy-saving initiatives it had introduced at its Swansea store.

“We started off looking at energy reduction. Through various engineering initiatives – refrigeration, cold air retrieval – we reduced the energy consumption at the store by over 33%. We got to the end of Swansea and realised we wanted to take a more holistic view of the stores,” he said.

Material solution

Taking this approach, when it came to choosing the framing material, Tesco “scoured the world market” of timber commercial buildings and found it fitted the bill. “We felt that it’s a technology that is advanced enough for us to adopt quickly,” said Dorling. The frame of the 50,000ft2 building is glulam – 143 columns, ranging in height from 3.5 to 6.7m, crossed with 17 main glulam rafters and Kerto LVL purlins. Kerto also forms the framing for the 270mm-thick wall panels, which are finished with fire retardant-treated spruce plywood and filled with Warmcell. The exterior is clad with Finnforest’s durable, and thermally modified Thermowood (Timber Building Summer 2006), while spruce plywood features on the canopies at the store’s entrance. All the timber elements were supplied from its mill in Finland, and the company is also supplying the framing for the new Shrewsbury store.

The main Kerto LVL columns, from Finnforest, in place on the floor slab

Finnforest building solutions manager Kevin Riley described the building as “a whole new concept in retail”, referring not only to the building itself, but to the entire construction project. Tesco’s brief to Barr Construction, which designed and built the store, was to reduce the environmental costs of the construction transport and the building – hence the one shipment from Grangemouth to Wick carrying 1,500 tonnes of materials.

Keeping to schedule

While Barr is experienced in large timber frame projects such as sport stadia, schools and offices, the longer lead time required for the main glulam rafters being shipped from Finland called for an unusual approach. “We cast the floor slab and terrazzo tiling finish before there was any wall or roof up,” said Barr’s  Alyn Walsh. “All you could see on site at one point was a floor slab with columns standing up.“We did this to alleviate the time delay to the programme and so ensured the building opened on time and as per the original programme.” A micro factory was set up in a neighbouring building – the former Caithness glass factory – where the floor panels were put together and preparations made to the glulam beams to accept the steel fixings.

Strong winds on the exposed site also caused problems, particularly during the roof installation, and Barr employed a perimeter fall arrest system.

The store also features energy efficient cold-air retrieval instead of air-conditioning

In addition to its timber frame, the store’s other eco-credentials include five micro wind turbines and solar cells to help power the store, rainwater harvesting that will see around 1 million litres of rainwater reused in the store each year, north lights in the roof to reduce the need for artificial lighting, energy efficient refrigeration and ovens, and water-cooled refrigeration and cold-air retrieval systems instead of air conditioning units. Tesco also changed the material for its road signs so they’re now made from sustainably-grown wood. Eco performance was also included in the design: the roof is more than 1m lower than that of Tesco’s conventional stores, reducing the volume of air that requires heating, and the warehouse can accommodate the unloading of double-decker lorries which will cut delivery road miles.

Finnforest’s Kevin Riley described the flagship building as “a real departure from steel” but said the principles of using timber a now established. “Tesco has made a very bold move, a very commendable move and we hope they maintain that commitment,” he said.