the building, Mike Hitchmough. The form was refined and developed, before being unveiled to the public in May 2009. The building's interior primarily consists of open plan space and can accommodate up to 4,000 staff. The building has 327,643 sq ft (30,439 sq m) of total space - approximately 29,000 sq ft (2,694 sq m) per floor. In keeping with the building's green credentials, employees will be encouraged to use public transport or cycle to work. Facilities have been created to encourage cycling by providing 105 cycle stands. Form The building has been nicknamed the 'sliced egg' because of its distinctive shape. A focal point is the diagonal slice which creates a nine-floor high atrium with its glass roof tilted towards the south, maximising daylight and passive solar gain. The structure has three internal concrete cores in the form of an equilateral triangle. Steel was utilised as the building main material; its strength allows for large column-free floors needed in an open plan building. The building's exterior has a double skin facade with a cavity between its inner windows and the outer glass panel structure. The double skin facade is for sustainability and aesthetic reasons - and allows for greater control of heating and ventilation, and accentuates the three curved corners of the building. To accentuate the form further, the exterior aluminium structure holding the glass panels in place has been anodised in a bronze-coloured finish, so it will shimmer in the sun. The facade was originally to be powder-coated but the client decided to spend an additional £120,000 on a bronze anodised finish. This excess was justified as being cheaper over 50 years than using a powder-coated finish which would require maintenance. The building's form has been compared with The Ark and City Hall in London. Sustainability The building is among the largest in Europe to have a BREEAM outstanding distinction as a result of its high, sustainable energy credentials. In December 2011, the building achieved the highest recorded BREEAM score, making it one of the most sustainable large buildings in the world. The open atrium faces south to collect heat from the sun, an example of passive solar building design. The diagonal slice is angled to the south to allow sunlight to pass into the upper floors and atrium. The sun emits electromagnetic radiation in the form of ultraviolet, but changes to infrared when it passes through glass.