Building form and construction
The building height was determined by St Paul's Cathedral and the basement depth by the Post Office railway tunnel systems. These constraints heavily influenced the M&E plant location and form. Careful attention had to be paid to external noise as there are sensitive buildings adjacent to the site and the plant operates continuously.
The first and second floors are for trading and have a high occupational density and electrical and cooling loads that are three times the load of a normal back-office floor. They have a higher floor to floor height and a deeper raised floor void. The building fabric has a high thermal performance, confirmed by extensive full-size testing. Double-glazing is used throughout and internal blinds are used to reduce glare.
The building can operate independently of the external power network. An early decision was taken to use diesel-driven rotary UPS sets capable of cleaning the power supply under normal conditions and providing generator and UPS back-up in an emergency. An attenuated plant room weighing 300 tonnes sits on six anti-vibration spring supports to isolate it from the building frame.
All business-critical equipment is electrically dual-fed from different electrical substations. Trading desks are served on a 'salt and pepper'basis whereby every other desk is served from a different electrical riser. Each trading floor distribution panel has a 'no-break'changeover to an alternative sub-station in the event of a riser fault. In office and trading areas, a pre-wired electrical distribution system and lighting management system has been installed on a modular basis to allow for future change.
Cooling needs are met by seven roof-mounted air-cooled chillers, each of 1.2MW capacity.Chillers are located around the UPS/generator plant room to suit the roofline required by the planners. The ground, third, fourth, fifth and sixth floors use conventional overhead variable air volume air conditioning with the air plant at lower basement level. The air-supply diffusers are of the swirl type to give good mixing and have been formed in the metal ceiling tiles.
Trading floors use the deeper raised floor void for a through-the-floor air conditioning system. Attenuated floor-mounted AC units supply air to the floor void from where it enters the room via floor grilles. The trading desks have been designed to allow cooling air to pass over the heat producing IT equipment. All IT rooms are cooled with through-thefloor air systems with duplicated plant.
The IT strategy was developed in close conjunction with Merrill Lynch's IT team. This was Arup's first large example of a building where flat screen technology dominated the IT design and the design and layout of the trading desks from day one.
The location of the main and sub IT hub rooms was determined by issues such as security and riser distribution. IT rooms and risers have been sized to allow for future expansion.
This is one of the largest buildings to use the IT network for linking the control, monitoring and management of the M&E systems. This proved very beneficial during the installation of the BMS, lighting controls, security systems, power monitoring, load shedding and air sampling and will prove efficient during future layout changes.