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Why Roman know-how is a cool solution

Verry Construction’s work on a technology park in Luton draws on an ancient heating system to meet green building targets

ProjectButterfield Business and Technology Park
Value £9 million
ClientEaster Group
Main contractorVerry Construction
ArchitectHamiltons Architects
Environmental designerAtelier Ten
Concrete frame subcontractorModebest
Contract type Design and Build

For large images of the project click here

At first glance Steve Jellis, contracts manager, and Geoff Taylor his director at Verry Construction are not what you would consider to be tree-hugging environmentalists.

But the two ex-carpenters are part of a new generation within the industry that debunk the myth that you have to be a hippy to be sustainable.

Having delivered high quality, successful projects such as the new City and Islington College campus on Holloway Road in north London, the two are well versed on what level of excellence can be achieved.

And so it seems is the team which assessed the company’s project at the Butterfield Business and Technology Park development in the Bedfordshire town of Luton for its environmental impact.

External inspectors have awarded the project an ‘Excellent’ rating under researcher BRE’s environmental assessment method - or BREEAM - and that level of success is thanks to the continued buy-in from everyone throughout the contractors supply chain, says Mr Taylor.

“We had to look at our supply chain and sift through it to see who would be able to meet some of the requirements which would enable us to reach the BREEAM excellent rating. We took a shortlist from our general supply chain and sifted through that,” he says.

Hitting that excellent rating was a prerequisite set by developer client Easter Group, according to Mr Taylor. Its managing director Peter Taylor set his stall out to make sure the Butterfield development delivered sustainable, green buildings for the office letting market.

“Fair play to him for that,” says Geoff Taylor. “He has set his path out along that route and we have had to follow. The carbon footprint for these offices is probably about 80 per cent less than standard office buildings of this size and type.”

The first phase of the Butterfield master plan is a low rise two-storey development of five buildings. These offices owe much of their excellent sustainability credentials not just to supply chain changes but to technology developed from ideas brought into the country by the Roman Empire.

Verry has installed an under floor ‘earth duct’ heating and cooling system which, just as the Roman army’s first attempts at central heating did 2,000 years ago, draws warm air around the building through a series of ducts and vents set in the walls and floor.

Instead of using artificially heated air, environmental designer Atelier Ten used the natural heat in the ground to warm up air drawn through a series of large diameter ducts and then into the building.

Buried 1,200 mm below ground level these ducts can use the consistent temperature of the ground at that depth to warm up the air during -winter and also cool it down in the summer.

Temperature control

“It’s a really simple system,” says Verry Construction’s contract manager Steve Jellis. “The temperature is very constant at that depth. In the summer the system will pull in air at around 12 deg C which will help cool the building and then in the winter these temperature levels will obviously help heat it.”

About 90 m of 900 mm diameter precast concrete ducts are buried beneath the ground at a depth to crown of 1,200 mm stretching from air intake points located around the development.

Each of the project’s four smaller buildings boast one air intake point each while the largest building features two intake points and two ducting systems.

Sitting in trenches on a pea gravel bedding the only difference between the precast concrete ducts and similar runs of precast drainage pipes is the lack of fall and the plastic rubber seal at each joint.

They also had to be air tested at every joint, a process which would take approximately 20 minutes to complete.

“You know immediately when there is some leakage,” says Mr Jellis, “The ducts had to be bunged up at the end and then air pumped into them. Initially it was difficult but our concrete frame and groundwork’s subcontractor Modebest eventually got it down to a fine art.”

The building also uses other clever tricks to help regulate the heat within it. Despite looking like a heavily glazed structure the architects have managed to limit the use of glass to just 50 per cent of the overall outer surface of the building.

The super energy efficient double glazed glass panels are manufactured in the Republic of Ireland and are capable of reflecting light and heat.

Automatically opening windows and both internal and external sun blinds, which react to the sun and increases in temperature, help regulate the heat in each of the five buildings.

In addition, the exposed concrete walls and ceilings throughout the buildings take advantage of concrete’s ability to store and absorb heat.

Limit wasted energy

Office lighting controlled by passive infra-red sensors help limit wasted energy by flicking banks of four low energy bulbs into life only if there is some level of movement in the area.

“There are no switches at all - everything runs on the PIRs. Each bank of four lights has a sensor and a timer which ensures they are all automatically switched off as the offices empty,” says Mr Taylor.

Even the storm water drainage systems have been designed with environmental impact minimisation in mind.

Hidden behind the concrete parapets and wall cladding rainwater and surface water run-off from the site’s car park is directed into a huge attenuation tank buried beneath its surface.

Here storm water can be held until it drains into the watercourse through 200 mm diameter boreholes drilled directly into the underlying chalk rock strata.

It is the level of detail and planning that has gone into the construction of the building that is striking. The environmental aspect of every point has been assessed.

From site staff’s journeys to work to the locality of suppliers - the Verry team went through the pros and cons of every aspect before hitting on the final construction.

It’s a move which will help propel Verry into the environmental building big league according to Mr Taylor.

“We have experience in constructing buildings of note. I think in just a few years time this sort of approach will very much become the norm.

“The younger generation is driving the change, they are buying into the environmentalism message. It’s good to be there with them,” he says.

Getting the staff on board

Crucial to the delivery of a top-end environmentally friendly development is getting staff on site involved.

Without the buy-in of the workforce it can be easy to let things slip.

At Butterfields the workforce peaked at 120 but it was the level of involvement and enthusiasm of site manager Layla Harper that pushed the project on, according to Verry Construction’s contract manager Steve Jellis.

“She was a bricklayer for eight years and decided to go down the site manager route through our training programme.

“Her enthusiasm for the concept and her determination to see it through won the respect of everybody on site,” he says.

Attaining a Breeam rating

Gaining an ‘Excellent’ rating under the BRE environmental assessment method was a prerequisite for client Easter Group.

As part of the project specification the Verry Construction team had no alternative but to embrace the BREEAM assessment and hit its targets.

Under the assessment Verry had to look through its supply chain, sifting through those which it felt could supply the project and those that could not. As a rule of thumb most of the materials were as locally sourced as possible, cutting back on vehicle mileage.

“We made sure all our concrete and imported fill was coming in from within a 20 mile radius of the project. Obviously you have to weigh the practicalities up and if there is a sound argument against this limit – for instance the glazing systems which came from Ireland – then we would take that into consideration,” says Geoff Taylor.

Throughout the project BREEAM assessors would visit the site and the project team would be continually feeding information through to them.

“We had a site waste management plan although they weren’t mandatory at the time,” says Mr Taylor.
“There was no MDF used on the site and we would take into consideration the fuel usage of staff to and from site, encouraging them to car share where ever possible.

“Getting an ‘Excellent’ rating on a greenfield site like this is very difficult,” he says. “On a brownfield site you are already at an advantage just because you are redeveloping an area. You get a bit of a head start.”

For large images of the project click here