Freak power

London’s Olympic park is going to be powered by a dedicated energy centre. More often than not these utilitarian buildings are tucked away out of sight, but the Olympic Delivery Authority (ODA) decided to place this building halfway up the western edge of the park, right in the public eye. 

To be fair, short of burying it underground, this building was impossible to hide. It is 70m long, 30m wide and 16m tall, with a flue stack the height of Nelson’s column; this makes it one of the largest energy centre schemes to be built in the UK. Instead, the ODA picked a design that celebrated the building for what it is. A big element of the winning scheme was its cladding, but this gives it far more than just a pretty face, as Arran Pexton, associate with John McAslan + Partners, explains.

How did you get involved in the scheme?

In 2007 we were approached by Cofely East London Energy which was interested in winning the concession to build and install the energy centre. As well as serving the Games it will provide heating, cooling and power to the developments that are rolled out in the area after 2012. We teamed up with Cofely and submitted a design bid that won. In October 2007 we began the design in earnest and in May 2008 received planning permission. Work started on site the following September. It was incredibly fast track.

What did you think when you first saw the proposals?

The first thing that really struck us was that this building needed to be flexible. The client has a 40 year concession and will need to add and replace elements of plant over time. These are huge bits of kit, some weighing up to 60 tonnes and they have to get them in and out of the building.

We also wanted this to be a modern-looking building. Normally when you think of power generation you think of buildings like the Tate Modern, Lots Road and Battersea, which are all heavyweight brick buildings on a huge scale built at a time when coal was the main source of power generation. This building will use state-of-the-art combined cooling, heat and power plants so we wanted to convey that modern approach in the building’s exterior.

What were your main concerns?

We were conscious of the aesthetics because this building is highly visible - it can be seen clearly from the central land bridge in the park which will be crossed by about 200,000 people a day during the Games. But it’s not just about designing for the long range camera shot; people will also walk past this building so a key consideration was how it looks close up.

How did the design develop?

Site constraints dictated that we go for a two-storey structure. Adjacent to the northern side of the building is the railway line that runs from Stratford Central to Hackney Wick so it was decided to put all the large items of plant along the southern edge of the building. On the ground floor there are five massive gas engines and their boilers; on the first floor are the waste heat boilers and chillers. This means that if we want to get one of these pieces of plant in or out we can simply demount part of the facade and take it through.

What look were you going for?

We decided to go for a neutral box and keep it simple by cladding it in one colour. Then came the idea that it should be a black box and coincidentally at the same time Nord, who designed the adjacent substation, decided to use black bricks.

This worked out well because the ODA wanted a family of utility buildings and it dawned on us that the link could be made using colour.

Why black rubber?

We didn’t want a shiny finish or to use something like metal panels that have echoes of an industrial shed. Plus it also needed to be robust. We settled on an EPDM membrane partly because you can cut a hole in it, take the piece of plant out and then reseal it. It’s 1.2mm thick and can be lapped and jointed so you won’t see the joints when it’s sealed back up. It’s also stable in terms of ultraviolet light, so it won’t turn light grey in a few years. And it’s durable; there are examples of it being on roofs for 60 years.

How are you making it demountable?

The building is a steel frame on an 8m grid with 8m floor-to-floor heights. Our initial idea was to use a metal stick system to infill the facade and fix sheathing board to this with the EPDM on top. But we were uncomfortable with the demountability of this design. Metal stick systems are so thin they tend to twist when they’re dismantled and there was the danger that it would just end up being scrapped and the whole thing redone.

Instead we came up with the idea of using structural insulated panels with the EPDM layer factory-applied to the outer face. These are 150mm-thick and self-supporting and are fixed in position with coach screws.

The joints on the outer face are masked over with a strip of EDPM to give the uniform finish we wanted. If you need access to replace plant you can cut through this joint and remove the panels. On replacing them you simply go back over the joint with a new 75mm strip of EPDM.

Do you really need the insulation?

Because this building is classed as a plant room, it doesn’t have to comply with Part L of the Building Regulations. However, the insulation is an integral element of the structural insulated panels (SIPs).

Were there any technical issues to overcome?

Because the air inside the centre is laden with a lot of moisture there were concerns that condensation might form between the orientated strand board sheathing on the panels and the EPDM. To overcome this we have covered the inner face with a 1mm steel sheet. This also adds to the panel’s durability.

Noise was also an issue. In general the SIPs meet the requirements but for special cases, such as the gas engines and chillers, two inner leaves of 100mm-thick medium density blockwork were used. In these cases the EPDM is mounted on sheathing attached directly to the blockwork.

You’ve added a Corten steel veil to two facades - why?

When we came up with the idea of a black neutral box we thought maybe it needed some sort of screening element to make it a bit more interesting; that’s when we came up with the expanded metal mesh and we quickly settled on Corten steel partly because of the colour contrast with the black but also because of the variation you get with the pattern. But we liked the idea of keeping the east and west elevations exposed.

How is this fixed in place?

Stainless steel fixings hold the Corten panels 100mm off the face of the EPDM. These are drilled directly into the timber frame of the SIPs at 450-600mm centres.

You’ve paid a lot of attention to detail …

Yes, particularly around the ventilation openings. Here we have lapped the EPDM into the louvres and painted them in RAL9004, which is the closest match you can get to the EPDM. We also looked at heat welding the joint between the EPDM but this leaves a residue so we’re gluing it on site instead.

Why did you install a large window?

So passers-by understand what’s happening in the building and so it isn’t just seen as alien box. The window gives a view right into the ground floor and all the plant. There is another large window at first floor level on the north facade which gives a view out for the occupants in the control room.