ARCHITECTURAL EXEMPLARS

Pennie Varvarides discovers the benefits of localised task lighting at the Woodland Trust’s BREEAM ‘excellent’-rated headquarters in Grantham

The Woodland Trust’s headquarters in Grantham, Lincolnshire has become one of the first task-lighting projects in the UK to win a Breeam ‘Excellent’ certification.

The energy strategy for the 2,800m2 building – which houses 200 staff – includes widespread use of natural ventilation, daylight, solar shading and light shelves.

Building services consultancy Max Fordham worked with architects Feilden Clegg Bradley Studios to come up with an open design brief for the trust. They wanted to create an environment that was well lit and energy efficient, with localised control.

The client was initially sceptical about the floor-standing fittings

Controlling surroundings

Nick Brown, an engineer with Max Fordham, says: ‘The client said they’d like to control their own surroundings and we decided, through conversation, that floor-standing fittings would be most suitable. We gave a presentation with different fitting types concerned and sold them the idea.

‘They weren’t sure to begin with, because they didn’t see any examples of these lights used in the UK. But we showed them a few examples deployed successfully in Germany and they loved the idea.’

The local controls give employees at each set of desks the power to decide whether the light needs to be on or off. This idea hasn’t been widely employed in the UK but can cut energy use because empty areas need not be illuminated.

Ups and downs

About 100 iGuzzini Ground Y Light lamps were installed for direct and indirect illumination. The rectangular fittings consist of four T5 fluorescent sources fixed on top of a pole, with a switch built in. Two ratios of up and down lighting are available. Brown says: ‘We wanted as much downlight as possible as it’s more efficient than uplighting. We went for the 65:35 indirect/direct option over the 90:10.’

Each set of desks has its own luminaire with local manual controls and the working plane has levels of over 500 lux. Fixed lighting illuminates the corridors at a low level. The workspace needed to be brighter than the walkways so focus was directed towards the tables.

The 15-metre-wide floorplan takes advantage of daylight, saving energy. Simple fluorescent battens have been fixed between the concrete slabs on the ceiling. The slabs are radiators that provide passive air conditioning, absorbing heat during the day and releasing it at night.

The building is designed to allow easy access to natural light. There is a void in the floorplate that encourages natural ventilation, using the stack effect, as well as helping distribute daylight. Internal light shelves also help distribute daylight to the centre of the building.

Wall washing

Wall-washing lights have been installed around the perimeter of the space.They are switched by photocells and illuminate the walls when the room gets dark. Alternatively they can be switched by a timer.

Brown says that the separation of lighting in this way is more energy efficient than conventional uniform lighting. By making the most of the available daylight, the localised lighting doesn’t need to be switched on during bright hours of the day, driving down energy bills.

The overall install load is 17.5W/m2. Max Fordham is monitoring the energy bills and will soon work out the average energy use.

Brown says: ‘Max Fordham was asked by architects Feilden Clegg Bradley Studios to help put in a bid to design the building. We wanted to create a comfortable workspace that was energy efficient.’ The project took two and a half years from conception to completion and cost in about £5 million.

The outer courtyard leads directly to the large entrance area, which leads directly to the high sunlit ceiling.

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