Space heating is provided by a system of Low Pressure Hot Water that is distributed throughout the building. The heat source is provided by Sheffield City Centre’s district heating system with their heating mains terminating in the basement. The LPHW system serving the building is coupled to the district heating system by way of a heat exchanger and pumping plant.
Ancillary areas that are exposed to outdoors (corridors, toilets etc.) are to be heated to an internal temperature of 18ºC when the outdoor temperature is at -4ºC. Heating is provided by radiators, fitted with thermostatic radiator valves and lock-shield valves. Pressure control valves are provided, where necessary, on each radiator circuit to protect the thermostatic radiator valves.
Central air-handling units in the roof level plant room supply ventilation air to the office accommodation. The air-handling plant is designed to heat, cool and filter the incoming air which will be supplied to the offices at approximately room temperature.
Exhaust air from the offices is removed by central extract air handling fans at roof level. The office ceiling voids are used as extract plena, and stub-duct branches on the rising builders work extract ducts draw air from the ceiling voids. The rating of the extract fans will allow for some slight pressurisation of the offices.
The air-handling unit supply and extract sections include a heat exchanger to recover energy from the exhaust airstream.
The ventilation systems are designed to provide an average ventilation rate of 1.45 litres per second per square metre of nett lettable floor area. This is designed to be distributed evenly over the open plan floors. The ventilation rate provides a 17% margin of overcapacity when offices are occupied to a density of one person for each 10 m² of nett lettable floor with each person receiving, on average, 12 litres/second of outdoor air. The overcapacity within the system is available for redistribution to Meeting Rooms, Conference Rooms and Staff Rest Rooms as appropriate by the incoming tenants.
Ventilation to Fire-Fighting Staircase Lobbies
This is provided using mechanically assisted smoke extract fans at roof level. The fans are coupled to a smoke extract shaft which is fitted with Automatic Opening Vents (AOV’s) which in turn open on to the Fire Fighting Lobbies at each floor level. The AOV’s are individually controlled by the fire alarm system to vent only the lobby which is smoke filled. There is also an AOV at the top of the Fire Fighting Stair shaft, opening directly to atmosphere and motorised to open and close by the fire alarm system. The staircase is not provided with mechanical ventilation and is not pressurised.
Ductwork and pipework for the supply of ventilating air, chilled water and heating water to service the fan coil system is housed within the service risers in the main core.
The heating, cooling and ventilation plant is controlled and monitored by a purpose-designed Building Management System.
All principal plant controls are housed in control panels. The control panels contain a B.M.S. outstation and a touchscreen/display for interrogation of data and adjustment of set points, etc.
Motor trips, chiller trips, incorrect L.P.H.W. and chilled water system pressures and shutdowns are monitored.
Warnings or Alarms (according to the significance of the problem) are relayed to the Ground Floor Reception Area.
The B.M.S. controls temperatures, etc. of the central systems and the operational hours of all systems.
The control system includes a supervisory computer located on the reception desk within the Ground Floor foyer.
The system also includes a facility for remote monitoring, by way of a telephone line, to an “off-site” supervisory computer.
There is not a Fire Brigade override panel. However the control panels are linked to the fire alarm system to shutdown all main fans in the event of an emergency.
There are 2 control panels on each typical office floor plate to allow the occupants to adjust room temperature, as sensed by each fan coil unit controller. The control panels also allow the tenant of that floor (or half floor) to extend the hours of operation of the plant.