Environmentally Sustainable Design (ESD) Objectives
The primary ESD design objectives for the ACE aim to:
- Provide enhanced thermal and visual comfort for building occupants
- Reduce energy consumption to levels well below current best practice benchmarks
- Reduce office greenhouse gas emissions to levels corresponding with a 4 to 5 star Rating
- Encourage social interaction between building occupants
- Encourage the effective use of recycling and waste minimisation
- Reduce water consumption from off-site storage resources
- Incorporate and maximise passive building design features.
Passive design, as opposed to active, is design that uses non-mechanical/electrical methods for heating, cooling, lighting and ventilation. Buildings that are passively designed take advantage of natural energy flows, airflows and daylight to give an acceptable internal environment for as much of the year as possible. They rely on passive design features to maintain the internal environment as much as possible, while only using active systems during extreme conditions. This approach typically allows for very low energy consumption and pleasant working conditions.
Design Features of the ACE Stage One
Building Fašade: Using computer modelling, the design team simulated the impact of daylight on the fašade of the building. They used this research to improve the design, increasing daylight transmission, while minimising heat transfer, improving views to the outside and avoiding direct entry of sunlight to minimise glare.
Building Automation System (BAS): The air conditioning, heating and exhaust systems control strategy have been designed to operate automatically using the BAS time clock function with manual override switches strategically located for after hours use. The BAS is also used to monitor energy and water consumption levels, allowing collection of data for operational management of energy and resource consumption.
Artificial Lighting: Lighting design is controlled in zones to reduce energy consumption. Local manual on-switches turn off via movement detectors and have manual override switches, giving the user full control whilst ensuring lights are only in use when necessary. Lighting near windows have automatic dimmers to use available natural light, thus reducing the lighting energy load.
Water Usage: Rainwater is captured, stored and reticulated into the building to reduce demand for mains water, using water tanks along with non-potable water reticulation to suitable areas. Rainwater is used in toilet flushing, irrigation, car washing and some paint shop supplies. Taps with flow restrictors limit the flow of water, particularly to showers and basins. The rainwater system integrates with the slab cooling system to provide night-time flushing of passive chilled water through the building. Water used for cooling slabs is naturally cooled by spraying it onto the roof at night and then recycling it. (See Cooling)
Passive Design Features in Stage One
Glazing: Improves views to the outside and increases daylight transmission, while minimising heat transfer through high-performance glazing that blocks radiant heat transfer and reduces damaging ultraviolet rays.
Shading: Shades glazing from direct summer sunlight, reducing summer temperatures, improving comfort and saving energy. With the building's prominent north orientation, the sun will be excluded in summer and admitted in winter using a large roof canopy on the northern fašade. The design omits glazing on the west fašade so that no shading was required there.
Ventilation: Provides natural ventilation flows through the building with operable louvres. Natural ventilation is provided through chimneys that take in air through the louvers at their base, which is then forced up the chimneys and dispersed from vents located throughout the building. Detailed modelling has determined the optimum areas for louvres to each part of the building. The Building Automation system controls the louvres in response to changes in temperature. The workshop areas have effective natural ventilation that moderates the temperature, removes airborne contaminants and provides for night cooling.
Insulation: Acts as a barrier to heat flow and is essential to keep the building warm in winter and cool in summer. The following insulation levels will be specified to optimise the passive design. Roof: R4.0 Walls: R2.5.
Natural Lighting: Provides as much natural daylight as possible. This involves the design of facades, glazing and skylights utilising computer modelling of various spaces to achieve good, even daylight distribution while avoiding the direct entry of sunlight to minimise glare.
Thermal Buffer: Reduces heat flow to the office spaces in the building. The east entry of the ACE incorporates a void designed to act as a thermal buffer. Floor heating and cooling is provided to this space, which also has temperature control through louvred windows. A similar system operates in the north entry space, with temperatures allowed to fluctuate in these two buffer zones.
Heating and Cooling Systems
Cooling: Provides the perimeter areas of the building with natural ventilation, allowing openings in the fašade to be used to cool and ventilate the building when external conditions permit. Openings into the entry atrium and the roof effectively discharge heated air. The building control system isolates the space air conditioning when running in this mode to save energy. Filter screens in air intakes provide natural ventilation while keeping insects out.
An innovative system of building climate control uses hydronic pipes within the building structure. A BATISTO active slab cooling system, embedded in the concrete floors, is used on the ground floor and Level 1. Water running through pipes in the exposed floor slabs are both cooled and heated to provide comfortable radiant heat exchange. Chilled beam technology allows cooled water to run through the floors and ceilings on Level 2. Night Sky Cooling uses recycled water sprayed onto the roof at night, which cools and is then redistributed through the building slabs to remove heat stored from the previous day. The cooled water is stored in underground tanks. Chilled water is supplied following nights which are not suitable for generation of night sky water. This reduces the size of the cooling plant required, and the energy required, to cool the building.
Chilled Water Plant: Is from an air-cooled chiller. The risk of Legionella originating from cooling towers, together with the high maintenance costs, far outweigh the energy savings expected of a water-cooled chiller. Water consumption is also very high, making this unattractive from an ESD perspective, even despite the improved energy efficiency they provide.
Heating: Is supplied by gas fired radiant tube heaters suspended at high level. This approach heats objects and people directly to provide comfortable conditions. The key benefit of radiant heating over warm-air heating is that it warms people and objects in the building, as well as the building fabric, not the air in the building. Hence, for the same comfort level the air temperature can be substantially lower, reducing heat losses.
Heating Hot Water Plant: As natural gas is the cheapest energy source readily available in Melbourne, and provides lower greenhouse pollution than electric fuelled water heaters, it is the fuel source for the boilers. A natural gas fire heating boiler has been installed at the ACE.