Personal touch

“The CIPD is a highly enlightened client and was already on the path to an energy efficient building,” explained Terry Brown senior design partner for architect GMW. Timing was to take this a step further.

The revision of the planning policy in the London Borough of Merton where the new headquarters of the Chartered Institute of Personnel Development (CIPD) was to be built meant that to get the green light the use of renewable energy sources had to be added to the design. This mix of low energy design and renewable sources brought some interesting aspects to the m&e installation.

The building was the first to come under Merton’s renewable energy policy adopted in October 2003. This states that all new non-residential developments above 1000 m2 will be expected to incorporate renewable sources to provide at least 10% of the predicted energy requirements. Merton was the first borough to implement the new London Sustainable Development Framework.

The timing of the policy’s introduction was far from ideal for the CIPD team. “We were quite far down the design of the building when Merton started to discuss 10% on site renewables. We’d already embarked on a low energy design with [m&e consultant] Rybka – that was part of the brief from CIPD,” explained Brown. Perhaps more importantly: “On an urban site it’s quite difficult to do,” he stressed.

The building sits on the site of a former Odeon cinema. It is squeezed tightly between a restaurant and local job centre on Wimbledon High Street, south-west London, with a residential area immediately to the rear. Although purpose-built for the CIPD, one of the specifications was of flexibility for possible future renting.

Structure plays a part

Visually the building has created quite a stir, reports Michelle Watts of the CIPD, and has attracted local jobseekers. Around 4700 m2 of flexible office space is encapsulated behind a dramatic bulging glass facade that stretches over the full five-storey height. On the ground floor visitors are greeted by a wide, open atrium, which conceals a dining room, member library and offices; the upper floors comprise primarily of open-plan offices, breakout areas and staff facilities.

The design of the structure plays a key role in the energy strategy. This begins with the main external envelope. The glazed facade that styles the building is north facing, so allows maximum penetration of natural daylight, with minimum solar heat gains. On the south and east facades, the structure is virtually solid brick to minimise any solar gains. A semi-circular, open-galleried atrium expands in size as it climbs the full height of the building’s west facade within the office space. This allows the deep prenetration of natural daylight into the office areas, reducing the need for artificial lighting. It is also integral to the ventilation system.

The exposure of the concrete structure internally is vital to the low energy strategy. This enables the structure to act as a thermal flywheel: essentially the concrete mass cools naturally during the night, reducing the mechanical cooling load during the day. Brown explains: “This came from the design team working together to produce the most energy efficient building...it dictates the idea of a concrete frame.” It also meant the early co-operation of those in the construction team.

Inviron won the contract for m&e installation in a two-stage competitive tender, this included design packages such as solar heating, bms and security, which were completed prior to starting work on site. Preconstruction work began in October 2003 and the firm was on site in February 2004 after the floor slab was poured.

The servicing strategy

Mechanically, the majority of the plant is on the roof, concealed behind a glazed panel that runs the width of the building.

Two supply and extract air handling units (ahus) feed conditioned air into the offices via an underfloor displacement system. Each feeds one half of the building. Air is ducted through the two main risers from the roof and into 450 mm-deep floor voids. From here it vents into the working areas via displacement grilles in the floor. The extract fans on the ahus pull the exhaust air back through the atrium out of a roof level vent.

“There is quite a lot of emphasis on energy conservation, which was part of the planning requirements,” explained Inviron project manager Bob Wilson. “Both ahus have spray coils for free cooling. They’ve also got thermal wheels to take advantage of any heat they can use in the extract.”

Some local control over the air conditioning has been added in cellular offices, with underfloor boost fans installed to overcome any issues of overheating. These are manually operated by the occupant, with pir control to minimise energy waste. “[The building] almost could have been fully natural ventilated, but the client wanted more control,” added Brown. This was to maximise the commercial viability of future letting.

The electrical installation began with a new substation. This proved to be a relatively complex task as, in addition to feeding the hq, the substation must also supply the surrounding network for Wimbledon High Street. “There was an existing substation which fed all the network in Wimbledon High Street,” explained Wilson. “We put a temporary transformer at the front of the building which was connected prior to removing the old transformer.”

This enabled the demolition of the existing and construction of the new substation at the rear of the building. The changeover period was carefully managed to ensure a constant power supply to the surrounding area. This was critical, stressed Wilson, as the work was carried out during the Christmas shopping period – the busiest time for many of the local businesses. The process was managed by Inviron with ABB Utilities and local energy provider EDF. Once the new substation went live in July 2004, the temporary one was removed.

In order to maximise the flow of air across the concrete surfaces, the majority of services were installed in the floor void. Tight space here meant careful planning and co-ordination: “Generally the ductwork was installed first as it was the bulkiest item, so had to take precedence,” explained Wilson. “The pipework was fitted at around the same time as the bulk of it was around the perimeters, so away from the main installation area. After this the electricians would move onto the floors.”

The lighting is primarily contained on lightweight ‘rafts’ suspended from the ceiling, again to minimise any interference to the flow of air across the structure. These panels were designed by GMW and manufactured by Barratt Ceilings specifically for the project. Within the restaurant they are mainly circular in shape, with Erco light emitting diodes around the edges. In the offices they take more of a concertina-type form and comprise high frequency, fluorescent lamps that are pir controlled, so switch off when the office empties.

“Installation was difficult, as everything has to come from above,” stressed Wilson. “There was quite a bit of preconstruction work to do.” The lighting is powered via cabling contained in the floor void above and fed through metal-sleeved holes and conduit in the floor slab. “While the structure was going up we had to get all these holes cast into position before the slabs were cast,” he explained. “A lot of co-ordination work went into that. One of the biggest problems was stopping everything from being trampled underfoot,” he explained. “There was a lot of protection and segregation needed.” It was essential these were correctly positioned to prevent time-consuming drilling through the slabs afterwards.

From a safety stand, this method was beneficial as any working at height was minimal and restricted to the second fix.

Meeting renewable demands

While the strategies above satisifed the energy efficiency demands of the client, the need to meet the renewable target proved more difficult.

Strictly speaking, the target has not been fully met by on-site renewable production equipment, relying in part on a green electricity tariff. This was primarily due to the site constraints, explained Brown: “Renewable energy on site in an urban site for a one-off building is quite difficult. On a building that is less urban and has more space, it is easier to include renewables. Ones in the city centre haven’t got the space – you’ve only got the surfaces of the building to work with. Also, wind turbines work best in open spaces, so the efficiency would be much lower.”

This did not deter the design team from trying to find solutions. “In the development of the design we explored all possibilities for on-site renewables, including ground cooling and wind turbines, but on an urban site these were not possible. We found that we could also not use photovoltaics in any sensible way,” stressed Brown.

The cost of the photovoltaics and payback period could not be met within budget. In addition, the best position for them would have been on the south-facing wall, which the architect had deliberately designed in red brick to minimise the building’s impact from the residential side. “This left the roof,” said Brown. “It worked out more efficient to provide solar collectors for the hot water provision.” This makes up 4% of the 10% target.

The system required four solar panels and associated plant to be installed at roof level. Inviron subcontracted Solar Services for the task (see box, ‘Solar water heating system in detail’). “There’s not a lot to them,” stressed Wilson. “You’ve got four collectors and they are all linked with copper pipework, nothing any bigger than 22 mm, plus a circulating pump and a controller.”

So why subcontract the work when it appears so simple? The answer is warranties. “All these panels are under licence,” explained Wilson. “You can’t buy them direct from Stiebel Eltron, you have to buy them from their distribution network. They are very much like certain refrigeration kit. You have to be an approved installer to maintain the warranties,” he added.

Solar Services is the sole UK distributor for Stiebel Eltron solar water heating products and has been installing solar products for 24 years. MD Ian Clark commented: “Basically, it’s plumbing, but there are a lot of pitfalls if you don’t know what you’re doing. Balancing the system depends on the pipe runs, size of collectors and vessels, which affect the flow rates.

“It’s not an easy market to break into contractor-wise,” he commented. Most installations are completed with Government funding under the DTI’s Clear Skies project, and installers must be registered with the organisation before grants will be awarded. “But installers can’t register [with Clear Skies] unless they have had experience installing solar heating,” Clark explained.

To counter this Catch-22 situation, Clear Skies now has a ‘Student’ level (see box, ‘Getting started with solar power’). With the number of installations likely to increase throughout the UK to meet government renewables and carbon emission targets, now may be the time for contractors to get involved.

The remaining 6% of the renewables target will be met by the uptake by CIPD of a green electricity tariff.

As well as reducing the CIPD’s energy costs, the new building has brought other positive changes. CIPD’s Watts explains: “It’s actually made a huge difference to the way we work as a company...it’s much easier to work cross-functionally, and with the breakout areas it’s much easier to establish levels of communication internally.” This was a desire at the design stage and apt for the professional body of those specialising in the management and development of people.