Economy class

King’s Cross was once a byword for dirty buildings, congested roads and shady characters doing drug deals in dark alleys. Today, it is the location of the stylish St Pancras International Terminal and scene of a huge £3bn regeneration project. King’s Cross Central, led by developer Argent, is at the start of a 15-year programme to fill a 67-acre brownfield site with 52 retail, residential and office buildings set in landscaped open spaces.

But one of the first completed buildings in the development is on a more modest scale. The King’s Cross Construction Skills Centre is just two storeys high and its build cost was a mere £2.7m. It’s been designed to be light on energy use and resources, and to achieve the ultimate sustainable goal of recyclability: when King’s Cross Central is finally completed, it will quietly be taken down.

Until then, it will have a crucial role in transforming King’s Cross from a place to leave to a place to linger. As a state-of-the-art facility built by Carillion, it will train local apprentices and adult learners to work on King’s Cross Central and other local projects. Offering courses funded by ConstructionSkills and the Learning and Skills Council and taught by Carillion, the centre is part of Argent’s section 106 commitment to the local community.

The centre is a highly sustainable building that incorporates energy efficient design, low-carbon technologies and renewable energy. These are immediately visible to visitors on the building’s exterior, where sleek slats of timber brise soleil project from the main facade, and the saw-tooth profile of the roof lights juts into the sky.

The building can also be completely dismantled and rebuilt elsewhere – a real possibility as the site is earmarked for a residential block at the end of the King’s Cross development.

Much of the building’s structure is also exposed, providing a daily lesson in sustainable construction for the 120 apprentices who will use the centre each year.

‘Sustainability was always embedded in the brief and the design team’s approach,’ explains Ruth Butler, associate at designer David Morley Architects. ‘We saw it as the core of what the building was all about, not just in the ecological sense, but also in terms of the education helping improve social and economic sustainability.’

When designing the centre, DMA first focused on what Butler terms ‘light green’ environmental technologies: techniques to minimise wasteful energy consumption such as orientation, increasing natural daylight, and ventilation and insulation. Only then did the design team consider the use of ‘dark green’ technologies, such as renewable energy.

We wanted to recreate an outside environment by minimising the use of artificial light

Ruth Butler, DMA

The building centres on a large double-height workshop space, which is bordered on one side by classrooms and administrative offices and overlooked by a balcony on the upper ground floor from which assessors can view apprentices’ work.

On CM’s visit, the workshop was a brightly lit hive of activity. ‘We saw the quality and brightness of natural light as extremely important. Many of the trades being taught, such as bricklaying and joinery, tend to be outside, so we wanted to recreate that environment by minimising the use of artificial light,’ says Butler.

This was achieved by installing large north-facing vertical roof lights. ‘This is by far the best training facility we have in terms of lighting levels,’ says Andrew Shapland, regional operations manager at Carillion Training Services. ‘The assessors can see very clearly what students are doing from the balcony, and students can also go up there and view their progress from a different perspective.’

Lighting in the classrooms beside the workshop is also good, due to large double-glazed windows, partially covered by panels of timber brise soleil. These project out at an angle from the facade to reduce glare from the west and cut down solar gain, while still permitting uninterrupted views to the north. DMA worked closely with services consultant Scott Wilson on the design.

Recreating site conditions in the workshop space allowed heating requirements to be cut significantly. ‘The apprentices are usually kitted out in PPE gear, which keeps them warm, so we reached an agreement with Building Control to minimise heating in that area,’ explains Butler. Heating for the rest of the building is provided by a high-performance condensing boiler. A biomass option was considered too expensive for such a small building.

Natural ventilation is provided by a combination of low-level ventilation in the workshop, which draws in cool air, while at roof level the north light windows are fitted with actuators that automatically open when the internal temperature rises above a preset level, allowing warm, stale air to be vented to the outside.

DMA had planned to install Monodraft ventilation units – 300mm pipes that project from the roof and use wind energy to drive stack-effect ventilation – but these were considered a ‘nice to have’ rather than a necessity, although they may be installed at a later date based on post-occupancy evaluations.

Photovoltaic panels have been installed on all the south-facing slopes of the roof lights to help Argent meet its obligations under the Merton Rule, which requires buildings to provide 10% of their energy needs through renewable sources on site. A total of 68 1.3m2 Sharp NU series 180W panels were fitted covering an area of approximately 88m2. The panels have exceeded expectations by delivering 13% of the building’s power.

Everything came cut to size. The reduction in waste was significant

Alistair Mitchell, Carillion

Other ‘dark green’ systems include a flat sedum green roof on the classroom block, designed to improve air quality, increase biodiversity and help rainwater attenuation.

‘It was also in vogue at the time we were designing the building,’ says Alistair Mitchell MCIOB, project director at Carillion, who has been impressed by the client’s commitment to push through sustainable features. ‘Argent and DMA were adamant about creating something that makes a statement on sustainability. We suggested things like removing the brise soleil or the green roof, but they stuck to their guns.’

Mitchell’s main challenge was keeping to the tight 29-week programme. This relied on off-site manufacture for many of the structural components – which also had the sustainable spin-off of reducing waste on site. The structural steel frame is mostly clad with Kingspan long-span insulated metal panels on the walls and roof, chosen to provide an insulation and weathering layer in a single sheet.

‘Installing the cladding took one month, which allowed us to get on with the windows and internal fit out,’ says Mitchell. ‘The reduction in waste was significant. Traditionally sites deal with cladding offcuts, but here everything came cut to size, so we only needed a few skips.’

Off-site prefabrication also helped create a demountable structure that can be easily taken apart when the building’s use expires. All the Kingspan panels can be easily detached, while the steel work was bolted together, rather than welded. Features such as connections, joints, cladding rails, electrics, cable trays and ceiling soffits are all designed to be exposed and open to view, assisting in the future dismantling.

‘The design and build contract provided an ideal opportunity to get Carillion and the subcontractors involved very early with this design concept,’ says DMA’s Butler. ‘The M&E guys first raised an eyebrow when they heard that all their work would be exposed to view, but soon they fully bought into the idea.’

Since the building opened in January, the trainees have been taking an active interest in the design. According to Andrew Connor, construction employment manager at the Construction Skills Centre: ‘The apprentices love it. Trainers have been explaining to them how the building works and it’s a big talking point for visitors considering applying for courses.’