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Sustainable construction: One team one roof

Every aspect of Scottish Water’s new headquarters is designed to minimise its impact on the environment and bring together its employees. In the latest of NCE’s series on British Construction Industry Award winners, Katherine Smale finds out more.

Energy incentive: The contractor shared savings resulting from energy efficiency measures

Source: Andrew Lee

Energy incentive: The contractor shared savings resulting from energy efficiency measures

Spread across multiple low grade buildings in various locations, the employees of Scottish Water led largely separate lives working in disparate teams, resulting in inefficiencies across the business.

To try and turn this around, the company decided to hold a competition to design a new headquarters building which would address these issues. Social interaction was at the forefront of its requirements and there was a strict sustainability policy and cost efficiency target.

The resulting building’s innovative sustainability aspects helped it to win last year’s British Construction Industry Award for sustainability.
Judged by its own rigorous standards for excellence in sustainability, Scottish Water stipulated that the building should be as efficient as possible.

However, perhaps one of the most innovative aspects of the project was not to do with the building process, but part of the contractual agreement.

Under the contract between the client, Scottish Water, the winners of the competition and main contractor, Bam Construction, there was an energy share agreement.

“There is a building management system, which opens windows if people aren’t opening them”

Lyle Chrystie, Reiach and Hall

“If Bam could deliver the building and Scottish Water could operate it at better than their energy targets, Bam gets some money back,” explains Reiach and Hall architect Lyle Chrystie.

The energy share agreement lasts for five years and so the shift of the design process was changed to ensure that the building was designed with this in mind.

“We worked very hard with Bam to make sure they understood where energy losses happen in buildings,” says Chrystie.

The main issue was air tightness. “They [Bam Nuttall] were very careful about the construction of the air tightness detailing to make sure that the facades and the building envelope weren’t leaking energy.”

Control panel

One of the other positive impacts of the energy share agreement was that Scottish Water was left with clear directions for how to run the building to get the best out of the installed features.

“When a new owner takes possession of a building, quite often they’re shown how all the dials work on the control gear and then left to it,” says Chrystie.

“Instead, Bam worked with Scottish Water for quite a long time to make sure all the systems were working as efficiently as possible and that Scottish Water knew how to work them as efficiently as possible, because it was in the interest of Bam to do so.”

The building was packed full of ways to maximise its potential.

“It has solar photovoltaics on the roof, solar thermal, water recycling, it has biomass [boilers], an exposed concrete frame acting as a heat sink and it’s naturally ventilated,” says Chrystie.

“There is a building management system (BMS), which opens windows if people aren’t opening them. There are actuators on the windows that will open them so that the air quality levels and the temperature is moderated by the BMS.”

The Bridge: Smart shading: External precast concrete columns help limit solar gain

Source: Andrew Lee

Smart shading: External precast concrete columns help limit solar gain

The building also had to enable social interaction, promoting the values which had been previously lost.

The atrium space was designed for people to mill around, break away from their desks and meet colleagues for informal conversations. Because of the modest budget, the team worked hard to make the layout of the building as regular as possible.

The grid of columns was kept to a strict pattern, which enabled a post tensioned concrete floor slab to be used. This reduced the thickness of the slab to just 275mm, saving concrete, weight on the foundations and reducing the overall height of the building, which had a big effect on the cost of the cladding.

“Bam Nuttall was very careful about the construction of the air tightness detailing”

Lyle Chrystie, Reiach and Hall

Precast concrete fins at 4.5m centres on the external elevation act to shield the building from solar gain in the summer.

Using precast concrete columns also reduced construction time on site. The actual construction programme was only 14 months and cost a total of £15M, including fit out costs.

The building also features Scotland’s first adopted detention basin for storm water management.

The detention basin itself is effectively a giant pond where the levels are allowed to fluctuate. When the level in the basin reaches a certain point, the water flows away through the overflow pipe.

To control the settlement of the basin on the very compressible peaty soil, a stable base underneath had to be built. During construction of the basin, traditional concrete foundations, were replaced with a geogrid and stone solution.

This eliminated the need to excavate and remove large quantities of the peat underneath the basin’s location, saving on excavation costs. The geogrid, which is formed from a geosynthetic material and used to reinforce the soil, was laid in layers in the soil, interleaved with layers of aggregate.

One of the challenges presented by the project was that the data centre had to be built and completed two to three months before the rest of the building and this was an immovable deadline.

This was to allow the centre to be commissioned in time for the completion of the rest of the building.

Interactive: The building’s central space was designed to encourage staff to communicate more informally

Source: Andrew Lee

Interactive: The building’s central space was designed to encourage staff to communicate more informally

Testing of the new data centre had to be carried out in parallel with the old to make sure that the systems were in place to cope with the company’s 24 hour, 365 days a year work cycle.

The data centre also contributed to the building’s sustainability features, with heat recovery from the servers used to supplement the solar thermal heating of its water system.

Scottish Water did not apply for a Breeam rating for the building, preferring to adhere to its own, stricter criteria instead.

“It was very particularly tuned to Scottish Water’s requirements, rather than the blanket industry [Breeam] rating,” says Chrystie. “Scottish Water didn’t see a value in the process as their requirements are actually in excess of what would be delivered to you. It does have an A+ energy performance certificate, though, which is the best it can be.”

In the end, the hard work and commitment of the architect, contractor and client has paid off and the results have been positive. After the first year of use, the building has out-performed its energy predictions and consequently Bam has received an energy payback from Scottish Water.

BCIA Judges’ comments

The BCIA judges said this was a stand-out building with excellent delivery through an integrated delivery team and an innovative benefit sharing energy contract.

They said: “The project team delivered a well-considered and impressively low cost solution to Scottish Water’s HQ. Sustainable features include a biomass boiler, PV and solar thermal as well as rainwater harvesting throughout and a demonstration SUDS pond. The benefit-sharing, long term maintenance contract is particularly innovative.

“The design of the building atriums is well handled, with the achievement of a social, open and relaxed environment - a delightful place to work.

“Handover of the bomb proof data at 43 weeks is very impressive. There was also an interesting procurement method with all team on board throughout. A simple, elegant, low cost and highly sustainable solution with a very satisfied client.”

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