There are times throughout the year when CH2 does not need supplementary heating or cooling to maintain thermal comfort. Air entering the building through floor vents, usually at a temperature of around 20 degrees, provides a basic ambient temperature control.
Heating system
Additional heating is provided by hot water through an underfloor hydronic system located around the perimeter windows. Given that air supplied to CH2’s office spaces is already heated to about 20°C, when heat is required, it is designed to be supplied at the points where heat loss is concentrated – the windows.
Hot water pipes are located in the underfloor space along the north and south walls, while beneath each window in the floor is a timber grille supplying radiant heat from the hydronic system. There are also small wall-mounted radiators along the south wall to assist with heat to areas restricted by full-height partitions.
The heat from the grilles under the forms a warm air barrier around the perimeters, which rises into the space naturally using buoyancy, not fans.
Cooling system
Even in Melbourne’s winter, office buildings require cooling. Heat is generated from two main sources:
- heat load from people, lighting, computers and other equipment
- heat gain or loss at windows or through the fabric of the building.
Conventional air-conditioned buildings deal with this heat load by re-chilling recirculated air. In CH2 the air is refreshed twice an hour, removing around 40 per cent of the heat load from the building.
The remaining 60 per cent of the heat load is stored during the day and removed at night:
- The thermal mass of the exposed concrete ceilings absorb the heat from the rising air during the day. The heat is later removed at night via a 'night purge'.
- During the day, the chilled water circulating in the chilled ceiling panels absorbs heat and transports it to storage tanks in the basement. At night the heat is removed through evaporative cooling by cooling towers on the roof.
- On particularly hot days, the cooling towers may be used, but this is kept to a minimum for energy efficiency.