Technological Assessment Of Council House 2 Melbourne Engineering Essay

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Council House 2 is a 10-storey office building housing approximately 540 City of Melbourne staff, with ground-floor retail spaces and underground parking. It's located at 240 Little Collins Street.

CH2 was officially opened in August 2006.

Gross floor area (GFA): 12,536m² comprising:

1995m² GFA basement areas

500m² net letable area (NLA) - ground floor retail

9373m² total NLA

1064m² GFA - typical floor

Bike spaces: 80

Showers for cyclists: 9

Car spaces: 20 plus one disabled space. The car park can be converted to office space or other uses.

CH2 costs

Total CH2 building cost = $51.045 million

Little Collins Street precinct development (including CH2 building costs), roadwork, upgrades to other buildings, professional fees, relocation costs, fit-out, art costs, footpaths, landscaping and other costs.

This includes:

$29.9 million for the base building (2,334$/m2 or 58.5 per cent of cost).

$11.3 million for sustainability features including a portion of the building cost of purge windows, light harvesting devices, precast ceilings, timber shutters, precast exhaust ducts, solar hot water collectors, photovoltaic cells, chilled water cooling system, shading screens, co-generation plant, air conditioning and beams and slabs. (884$/m² or 22.1 per cent of cost).

$2.8 million on education and demonstration including a portion of the cost of shower towers, multi-use water treatment plant, PCM modules, roof landscaping, and chilled ceiling panels/beams. (218$/m² or 5.5 per cent of cost).

$7.1 million on requirements specific to Council use including a portion of the cost of vertical landscape, balconies, access floors, lift finishes, communication cabling, stand-by generator, security system and building automation system. (553$/m² or 13.9 per cent of cost).

Fast facts

By opening the purge windows for four hours a night in summer, CH2 reduces its cooling requirements by 20 per cent.

CH2 office spaces have 100 per cent fresh air which is calculated to save Council over $2m a year in increased staff effectiveness and productivity.

Lower light levels (150 lux) supported by task lights, saves 2/3 of normal energy use and has a beneficial effect on staff.

CH2 replicates the leaf area of its original site through plantings on the north façade and roof terrace.

All fit-out materials are recycled and/or non toxic which is expected to improve the health of staff.

CH2 is projected to pay off its environmental features in approximately six years.

CH2's indoor plants are still alive and prospering - a typical indoor office plant gets replaced every two months.

CH2 was Australia's first '6 Star Green Star - Design' certified rated commercial office building by the Green Building Council of Australia. 

See CH2

CH2 is located at 240 Little Collins Street, Melbourne 3000. Since its completion in 2006, CH2 has changed the landscape of its local area, and inspired developers and designers across Australia and the world.

The building has generated substantial interest, with many people keen to see for themselves how its features appear and work.

CH2 is located at 240 Little Collins Street.  Given that CH2 is now a fully functioning workplace, it is not always possible for members of the public to see the building first hand which is why a virtual tour was commissioned and an image gallery created. In this section you will also find imagery, drawings, diagrams and plans of CH2. 

Image gallery: Visit our Media Centre to view and download images of CH2 at a high resolution.

Online tours: View a virtual tour and an online animation tour of CH2.

Drawings and diagrams: Architectural drawings and design related diagrams available to download for reference.

In 2004, the City of Melbourne was faced with an accommodation dilemma. Staff were housed in dated office buildings which although centrally located to the Town Hall, were nearing the end of their lifespan. 

Rather than relocate staff to alternative offices, Council embarked on an ambitious plan to construct a new office building, Council House 2 (CH2), that would meet its spatial requirements and lead the way in the development of an holistic green environment.

CH2 has been designed to not only conserve energy and water, but the quality of the internal environment of building has also been designed to improve the wellbeing of its occupants. CH2 demonstrates a new approach to workplace design, creating a model for others to learn from and follow.  

CH2 is located at 240 Little Collins Street, Melbourne.

How it works

Download the below document for details on how the building works. 

CH2 - How it works (PDF, 2.5Mb) This link opens in a new browser window

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Conserving energy and water

Energy efficiency in CH2 is achieved through an integrated set of features focusing on heating, cooling and water reuse.

Elements that work together to achieve this goal include:

Design based on ecology and climate

Natural light

Cooling system

Heating system

Vaulted concrete ceilings

Western timber shutters

Window treatment

Water conservation

Energy generation

CH2 waste management

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Internal environment

CH2 was designed on the principle that a quality internal environment, complete with fresh air and carefully selected materials, can have a positive impact on the wellbeing of its occupants.

Find out more about CH2's:

Air quality

Indoor environment quality

Materials selection

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Art is integrated into the fabric of CH2, complementing and extending the building beyond its engineering and architectural aspirations. 

Artists were selected to participate in the project via a formal selection process held in October 2003. Selected artists worked closely with the design team during 2004 while developing and finalising their designs. Three artists were also invited to participate in the design charrette at the concept stage. Their challenge was to express a vision that reflected, complemented, and/or questioned the design team's commitment to sustainable design.

CH2's project artists were:

Cara Jones, Hoardings

Janet Laurence, Waterveil

Cameron Robbins, Double Vortex

David Wong, Roof landscape

David Emery & DesignInc, Concierge desk

Tom Carment, Documentation

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Facts and figures

Visit Facts and figures for more information on CH2. You can also download the below document for details on how the building works.

CH2 - How it works (PDF, 2.5Mb) This link opens in a new browser window

Design based on ecology and climate

CH2 has been designed to reflect the planet's ecology, which is an immensely complex system of inter-related components. 

The first focus of the design process for CH2 was to gain an understanding of Melbourne's climate and weather patterns. An ecosystem responds to its environment, and its ability to adapt to take advantage of changing weather conditions contributes greatly to the success of the system.

The design team found that responding to the site's climactic conditions highlighted a range of opportunities for energy efficiency, and in doing so gave rise to some of CH2's most innovative features.

Melbourne is well known for its 'four seasons in one day'. This variability could be viewed as a problem, but in the case of CH2, it was viewed as an opportunity to design the building around the concept of cold energy storage.  The building therefore operates in two seasonal modes (winter and summer), as well as day mode and night mode.

CH2's many parts work together to heat, cool, power and water the building, creating a harmonious environment. More detail about how the building works as an ecosystem is contained within the below document:

CH2 - How it works (PDF, 2.5Mb) This link opens in a new browser window

Natural light

CH2 targets and maximises the penetration of natural light within the building, reducing the requirement for artificial lighting. 

The building's north and south facades are comprised of alternate vertical bands of glass and thick concrete walls containing supply-air ducts (on the south side) and exhaust-air shafts (on the north side). The shafts widen towards the upper levels in order to facilitate air supply and exhaust. 

Conversely, the windows are at their widest at street level, narrowing at the upper levels. This enables more light to be admitted to the lower levels of the building, where light access is restricted by surrounding buildings and there is less air demand at the end on the air ducts.  

CH2 takes advantage of natural light by:

locating windows at the highest point of the curved concrete ceilings

an external 'light shelf' on the northern windows that, while protecting the windows from the direct rays of the sun, also bounces natural light into the building

moveable timber shutters that remain open to catch the morning sun, closing when the sun is in the western sky in the afternoon

careful positioning and use of blinds to the northern windows. These windows are divided into upper and lower sections, each with its own blind. The upper blinds are only needed when the sun is low in the sky in winter. The lower blind is a partial blind (900mm high), to protect from the direct rays of the sun, while still letting in natural light.


Cooling system


Radiant cooling

Thermal mass and the night purge

Chilled ceiling panels and Phase Change Material

Shower towers


A key consideration in the design of office buildings was how to cool the space. Even in Melbourne's winter, cooling is required. Heat load is generated from two main sources: 

heat loads 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. Typically, air chilled to about 13°C is introduced into the office at a high level and velocity in order to mix with the existing hot air, to create the desired temperature across the office floor.

The air entering CH2 is approximately 20°C (the lower end of the comfort range). The process of refreshing the air approximately twice every hour means that air leaving CH2 removes 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. This is done in two ways:

Through the use of the thermal mass of the exposed concrete ceilings. The concrete absorbs the heat from the rising air which is later removed from the ceiling at night with a 'night purge'

By using the chilled ceiling panels to circulate chilled water. The chilled water absorbs the heat and transports it to tanks in the basement containing Phase Change Material (PMC). The PCM tanks store any heat collected during the day, which is then removed at night through evaporative cooling by cooling towers on the roof.

On particularly hot days the cooling towers might be used during the day, but this is kept to a minimum for energy efficiency. 

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Radiant cooling

CH2's comfortable temperature is achieved primarily by radiant cooling rather than by cooling the spaces with chilled ventilation air.

Radiant cooling is based on the principle that individuals are primarily cooled by body heat being radiated towards cooler surfaces. In CH2's case, cooler surfaces are provided in the form of exposed concrete ceilings and chilled ceiling panels. In contrast to conventionally air-conditioned buildings, CH2 is not cooled via the influx of large volumes of cold air. The CH2 system recognises that air temperature is not the only way to measure and achieve thermal comfort within a building. CH2 acknowledges that humans sense a combination of environmental conditions such as temperature, humidity and draughts to gauge their thermal comfort. Feeling cold is not based on air temperature alone.

Physiologically, humans possess cooling systems that are sensitive to air humidity, air movement and surface temperatures. Also, human skin is more responsive to the cooling or heating effects of radiant surfaces within a room than to direct contact with the air surrounding the body.

CH2 is designed to maintain the office at a temperature of 21°C-23°C, which is the mean of air and radiant temperatures. To control the indoor comfort level, the ceilings are kept cooler in summer than in winter by regulating the temperature of the concrete ceilings and the operation of the chilled ceiling panels.

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Thermal mass and the night purge

At night, when the external temperature has fallen below that of the internal concrete ceilings, windows beneath the low points of the vaulted ceiling automatically open. Cool night air flows in and across the ceiling's underbelly, removing the previous day's heat by cross ventilation and by being drawn up through the exhaust air shafts. Exhaust air in the flues is propelled upwards by the chimney or 'stack' effect, assisted by the roof-mounted wind-driven turbines (when wind conditions are right).  This process is known as the 'night purge'.

The night purge is controlled by CH2's computerised building automated system (BAS).  Using information gathered from temperature sensors in the concrete at two locations on each floor and combining this with an external temperature reading (from the weather station on the roof) the BAS automatically opens the windows at the coolest part of the night - usually between 2am and 6am.

If the outside temperature is at least two degrees lower than the temperature of the concrete an effective night purge can occur. This occurs on a floor-by-floor basis, meaning that some floors may have a night purge while others do not.

Whether a floor conducts a night purge is also determined by the temperature of the concrete ceilings. If the temperature of the concrete falls below a set level (usually about 20°C in summer) the windows will close and cease the night purge. This is to prevent the ceilings becoming too cold.  In winter this set point is raised to approximately 24°C.

In very high-wind situations, the purge windows on one side of the building remain shut and the wind-driven turbines maintain the purging air flow.

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Chilled ceiling panels and Phase Change Material

In the most passive mode, the chilled water to the ceiling panels is supplied by three large tanks in the basement. Each of the tanks contains nearly 10,000 small stainless steel balls filled with a form of Phase Change Material (PCM). CH2's PCM's are a salt suspension which freezes at 16°C.

The water in the tanks is chilled by the frozen PCM balls to about 16°C and is then pumped around the building to the chilled ceiling panels when cooling is required. The water that returns from this circulation is usually about 2-3 degrees warmer. Heat from the water is transferred to the 16°C PCM balls re-chilling the water. The PCM balls continue to absorb heat (which is energy) enabling the material to have enough energy to break-down the molecular bonds and move from solid into liquid phase. Essentially, the balls absorb heat until they melt.

By this process the PCM acts as a thermal storage battery. When the PCM has melted into liquid phase, and can no longer absorb heat, the PCM system is shut down and the chillers on the roof are used to chill the water required to run the cooling system. This occurs more frequently in summer.

As with the night purge process, cool nights are used to dissipate the heat contained in the water. Water is put through the cooling towers on the roof. Using a trickle evaporative cooling process heat is dissipated to the night air, and cool water brought back down to the basement. In winter, when the night air is very cool, the water that returns to the basement is cold enough to re-freeze the PCM balls without the need for chillers. In warmer months the chillers (in the rooftop plant room) provide chilled water to the basement to freeze the PCM balls.

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Shower towers

Located on the buildings south façade, CH2's shower towers comprise five tubes of durable lightweight fabric, 13-metres tall and 1.4-metres in diameter, inside which a water shower induces air movement and cooling. The ensuing evaporative cooling process cools both air and water. 

From a simple shower rose at the top of the tower, water falls through the three-story tube, pulling air in from openings at the top. Both the water and the air are then cooled by this evaporative cooling process.

The cool air is fed into the ground floor lobby, shops and arcade, to assist with the cooling of these spaces.

The cool water is used to assist with the cooling of the office spaces by pre-cooling water returning from the chilled ceiling panels and improving the performance of the phase change material. Some of the heat absorbed by the water circulating through the chilled ceiling panels is dissipated through the shower towers (about 0.5-0.7°C is removed). This 'pre-cooling' of the water before it enters the phase change tanks assists the phase change material to last longer before melting.

Heating system

The temperature of the air entering CH2 through the floor vents is usually around 20°C. This provides a basic ambient temperature control which is supplemented by additional cooling via the chilled ceiling panels and heating (through hydronic heating).

There are times throughout the year when the building does not need any supplementary heating or cooling to maintain thermal comfort.

When CH2 is in heating mode, 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, that is the windows.

Hot water pipes are reticulated in the underfloor space along the north and south walls. In the floor beneath each window is a timber grille supplying radiant heat from the hydronic system. There are also small wall-mounted radiators along the south wall designed to assist with heat to areas restricted by full-height partitions.

The heat from the grilles under the windows acts to protect the office area from the cold by forming a warm air barrier around the perimeters, which rises into the space naturally using buoyancy, not fans.

Vaulted concrete ceilings

CH2's distinctive vaulted concrete ceilings perform a variety of functions including providing thermal mass.

CH2's main floors feature distinctive pre-cast concrete ceilings which bring a number of benefits, including:

enhancing air stratification in the offices by keeping warmed air further away from occupants

optimising natural light by locating windows at the highest point of the vault

increasing the surface area of the ceiling, thereby increasing the thermal mass of the concrete and improving the heat absorption characteristics

providing a void for the collection of the exhaust air, avoiding the need for an array of surface-mounted metal ducts.

The vaulted ceilings are pre-cast concrete and the floors above are poured in-situ, with both tied to form the structural floor system for the building.

Western timber shutters

CH2's western façade features a system of recycled timber shutters that protect the building from the late afternoon sun while enabling views out of the building and natural light to enter the building. The shutters are open when the sun is in the eastern or northern sky, closing only when the sun is in the west.

One aim of the shutters was to provide a responsive sun shade system for the office. By constructing the shutters from reused scraps of timber that would otherwise go to waste, they also show how materials age over time and weather at different points on the façade.

The timber was sourced from Nullarbor Timbers from two hundred derelict and demolished houses. The timbers are Australian native hardwood species, such as jarrah, ironbark, red gum and blackbutt. Untreated, the shutters will be left to age and go grey naturally.

The shutters move automatically to a pre-set program based on the seasonal position of the sun. Therefore the movement occurs daily, regardless of whether the sun is hidden by overcast skies.  

The shutters are slatted to maximise the amount of daylight that can be admitted while still performing their protective function. In summer, the shutters fully close fairly quickly and, when the sun is nearly square-on to the building, they then open slightly to stop the sun from penetrating through the slats.

In winter, the shutters close more slowly and do not need to close completely as the sun does not get square-on to the building. In winter, the main purpose of the shutters is to protect staff from the glare of the sun's rays.

The movement of the shutters is hydraulically operated using vegetable oil. The power required to operate the shutters is produced by the solar photovoltaic cells on the roof of CH2.

Window treatment

The windows to the north and south elevations have a number of features that assist in the heating and cooling processes in the building. Simply, the treatment is designed to provide a barrier to 'heat gain' into the building in the summer and 'heat loss' from the building in winter. 

The following features contribute to this process:


timber window frames, which are a low conductor of heat when compared with aluminium, reducing the 'heat bridge' effect

external sunshade from balconies (from the floor above) and from fabric shades above the door to each balcony

chilled beams over the window cooling the air and creating a protective curtain of falling cold air across the window when heat gain is an issue

underfloor hydronic heating grilles, located adjacent to the window, providing a protective curtain of rising warm air when heat loss is an issue.

Timber window frames

All of the window frames to the north, south and east elevations are timber, rather than aluminium. When resourced correctly timber is a more sustainable material than aluminium and also enables the window system to contribute to the thermal performance of the building. Timber window frames are a low conductor of heat when compared with aluminium, and therefore reduce the 'heat bridge' effect that occurs with metal frames. Other features of the timber frames include:

timber was chosen on the basis of being a product with low embodied energy and well understood performance and maintenance regimes

finger-jointed construction was used for less waste

the windows were designed for repair and disassembly (screw construction) and have an anticipated life-span of over 100 years

laminated fabrication was used to ensure a well-sealed and air-tight system.

Upper and lower windows and use of blinds

Each window has an upper and lower section, each with a separate blind, which has the following benefits:

the use of blinds can be optimised. The upper section is well protected from the sun by the balcony above and blinds are only needed in the winter when the sun is very low in the sky. The upper blind also is raised rather than lowered and can therefore be set in an optimum position

the lower blind is required for sun protection more often than the upper blind. In this instance the use of the blind is optimised by having only a partial blind, 900mm high. The blind can therefore be set at the optimum level up the window to protect from the direct rays of the sun, without unduly reducing the amount of natural light entering the building.

Staff can control the use of the blinds to optimise the protection from the sun's rays and the amount of natural light entering the building at any time.

Glare control

Glare is caused by sharp contrasts and is often treated by brightly lighting inner walls or using blinds. Both of these methods waste energy. CH2 reduces glare while using energy by framing external views with leaves on the northern balconies and on the south with vertical planters.

Additionally, CH2's window treatment incorporates features to control glare:

Use of reveals: the air supply and exhaust ducts are located either side of the windows on the south (supply air) and the north (exhaust air) facades. These ducts give the external wall enough thickness to form reveals to the windows. The window reveal is a splayed framing to the window which mitigates the contrast between the very bright outside light and the internal relatively dark wall. Glare is caused by sharp contrasts and the half light on the reveal helps to reduce glare. This is an old device used particularly in Georgian interior architecture. 

External plants: each of the windows on the northern façade has a balcony with trellised planting on each side, running the full height of the building. These plants provide both lateral protection from the sun's direct rays and help control glare by diffusing light.

Internal plants: plants were successfully trialled in the existing Council House for glare control and have been installed in moveable internal planters on each side of the most windows on the south elevation. The south-facing windows can be subject to glare reflected from buildings across the street.


Water conservation

CH2 reuses water, using less in the process. Find out more about:

Strategy for water efficiency

Water recycling and sewer mining

Re-use of fire sprinkler test water

Rainwater harvesting

Vertical garden watering systems

Shower towers and cooling towers

Strategy for water efficiency

The overall water conservation design strategy for CH2, including water saving impacts of the cooling and ventilation systems, has established a total water consumption design performance target of just under 31 litres per day per person. Water management measures implemented by CH2 fall primarily into four categories:

water efficiency

water recycling by sewer mining

water reuse (rainwater harvesting and fire sprinkler test water)

innovative water saving techniques.

CH2 has the following features:

'AAAA' fittings and fixtures, throughout the building

taps and showerheads of low water flow rate of approximately 2.5 litres per minute and nine litres per minute respectively

water flow to all hand basin taps is controlled by electronic sensors

4L/3L dual flush toilets and 2 litre flush urinals.

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Water recycling and sewer mining

Central to the water reuse strategy in CH2 is the Blackwater Treatment Plant located in Basement 3. As well as treating both the blackwater (toilet) and greywater (showers and basins) waste produced by the building, the system is also treating sewerage 'mined' from the sewer in Little Collins Street, adjacent to CH2. Sewerage is usually made up of 95 per cent water and the system in CH2 is demonstrating that sewers can be a source of useable water.

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Re-use of fire sprinkler test water

The fire sprinkler system in the vast majority of buildings is connected to mains water and during the regular testing process the water is normally discharged to the sewer. In CH2, the fire sprinkler test water is collected and re-used, mostly in conjunction with mains water for showers and taps. It has been calculated that over one year this will save about 9000 litres of water per week.

Most of this water is saved from the fire pump testing. The fire pumps are connected directly to mains water, so the discharge during testing is collected and placed into the Potable Water Tank in the basement.

The water in the reticulated sprinkler pipes is considered to be potentially contaminated and this is collected and put through the Blackwater Treatment Plant.

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Rainwater harvesting

The building has been designed for the total roof area to be used for capturing rainwater. The rainwater collected is used in conjunction with the recycled water from the Blackwater Treatment Plant for toilet and urinal flushing, landscape watering, cooling towers and for off-site uses such as fountain top-up and street tree irrigation. A storage tank with a capacity for one week's capture at 15 kilolitres is located in the basement.

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Vertical gardens watering system

Another concept in CH2 is to provide vegetation equivalent to that if the site was still in its natural state. This is achieved with both horizontal and vertical plantings: the roof landscape and the northern green façade of the building. In addition, there are internal plantings in the office areas and on the summer and winter terraces at the west end. Recycled water is used to water the external plantings.

The challenge for CH2 was to get the water to the plants efficiently, and the solution is a self-watering system in the recycled plastic planter boxes. This water-sufficiency based system provides the ideal wet-and-dry cycle required for healthy plants.

This system comprises a watering device and a soil additive. Each planter box is filled with Fytogen Flakes, a soil additive that looks like polystyrene flakes but acts like water crystals, storing water until the soil needs it. The planter box is also connected to a system functioning in a similar way to a toilet cistern, which is triggered to refill with water when the crystals dry out. 

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Shower towers and cooling towers

The shower and cooling tower systems use water as the cooling media, allowing for an energy-efficient cooling system.  Recycled water is used in the cooling towers while the shower towers use mains water. These two features are a good example of the efficient use of a value added product, recycled water, to improve the energy efficiency of a building while reducing greenhouse gas emissions. This is a significant factor considering drought conditions and Melbourne's current permanent water restrictions, where the use of a limited resource may not outweigh savings in energy use and greenhouse gas emissions.

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Energy generation

CH2 generates its own energy.

Micro-turbine: Co-generation

A gas-fired micro-turbine located in the roof plant room is used to generate electricity thus reducing reliance on the public electricity grid. The process produces waste heat (the water-cooling of the turbine produces steam) which is used to assist the building's air-conditioning plant. The co-generation plant has much lower CO2 emissions than coal-fired electrical generation and provides 60kVA of electricity, meeting up to 30 per cent of the building's needs.

In CH2, the waste heat is also used for heating hot water for the building and also for cooling via an absorption chiller.

Solar Power - Photovoltaic cells

CH2 includes 23 solar panels, which are equivalent to about 26 square metres of photovoltaic cells. These are located on the roof and generate close to 3.5kW of electricity from the sun's energy. The amount of energy generated is approximately equivalent to that required to power the movement of the Western timber shutters. 


The lifts in CH2 generate power in the braking mode.

Solar hot water

About 60 per cent of the building's domestic hot water supply is provided by 48 square metres of solar hot water panels on the roof. This is supplemented by a gas boiler.

Green power

The City of Melbourne pays for accredited green power. CH2 is 100 per cent green power.

CH2 waste management

Waste generated during CH2's construction was recycled wherever possible.

During construction the builder was contractually required to produce and implement a comprehensive waste management plan and to achieve a minimum of 80 per cent recycling of all waste produced on site (as required by the Green Star credit).

The final recycling of building materials amounted to over 87 per cent of all waste produced in site.

CH2's commitment to recycling has continued with a comprehensive recycling program adopted within the building. All kitchen facilities incorporate waste separation.

Air quality

The temperature of the air supplied to each floor vent in CH2 is approximately 20°C. Fresh air is released from the floor, with swirl diffusers located on movable floor tiles allowing individual placement to suit workstations. Air is only used once and is exhausted by natural convection to the atmosphere.

CH2's air:

is treated by filtering, heating or cooling and drying (if needed) in the plant room on the roof

is pumped from the roof plant room down the supply-air ducts (on the south side) and into the sub-floor space, which is a raised access-floor about 300mm high

is brought into the office space via the circular outlets ('swirl' diffusers) located across the floor on the moveable floor tiles. These diffusers mix the air at low level

rises as it heats up (from the heat generated in the office from people, lights, computers and so on), so the hot air is moved to the top of the office space

finds its way, by natural convection, into the void formed by the 'belly' of the curved concrete ceiling. This void is connected to the exhaust-air shafts (located on the north side) by a short metal duct

is exhausted to the atmosphere from vents at the top of the exhaust shafts beneath the yellow wind turbines on the roof.

This one-way air flow is called a 'displacement' air flow, which is of great benefit to staff because air that is exhaled rises and is, in turn, displaced by rising fresh air. This means that staff are always breathing fresh air rather than the mix of used and fresh air found in conventionally air-conditioned buildings.

There are two complete air changes every hour in CH2, which means there is about two and a half times the amount of fresh air coming into the building than compared with most conventionally air-conditioned buildings.

This air system also means that the output from coughs and sneezes is being taken straight out of the building rather than being spread around the floor, and around the building.  This creates a healthy workplace.

Indoor environment quality

A key focus of the design for CH2 is the indoor environment quality. In CH2 the air intake is 100 per cent filtered outside air, instead of being recycled as it is with traditional air-handling systems in most office buildings.

In addition, materials have been selected for qualities that minimise the harmful effects of off-gassing and indoor pollutants, such as Volatile Organic Compounds (VOCs).

Indoor plants have a proven role in the improvement of indoor air quality in office environments. There is at least one indoor plant per person in CH2.

CSIRO has undertaken indoor air quality tests during summer and winter conditions and in both assessments the indoor air quality in CH2 for the weeks of assessment was rated as very good.  The reports are available by visiting Staff wellbeing.

Indoor environment quality

A key focus of the design for CH2 is the indoor environment quality. In CH2 the air intake is 100 per cent filtered outside air, instead of being recycled as it is with traditional air-handling systems in most office buildings.

In addition, materials have been selected for qualities that minimise the harmful effects of off-gassing and indoor pollutants, such as Volatile Organic Compounds (VOCs).

Indoor plants have a proven role in the improvement of indoor air quality in office environments. There is at least one indoor plant per person in CH2.

CSIRO has undertaken indoor air quality tests during summer and winter conditions and in both assessments the indoor air quality in CH2 for the weeks of assessment was rated as very good.  The reports are available by visiting Staff wellbeing.


CH2 was fully operational and occupied in late 2006. Since then staff have enjoyed the benefits of a workplace designed with their health and wellbeing as a prime concern.

Now that CH2 has been completed and actively in use for several years, it is possible to evaluate the performance of the building's systems.  As with any innovative project, evaluation of the success of elements is an ongoing process. 

Staff wellbeing

CH2 has now proven that the productivity of office building occupants can potentially be enhanced through good building design, and provision of a high quality, healthy, comfortable and functional interior environment, that takes account of basic occupant needs. 

The first full year of operation was evaluated independently by the CSIRO and the report is available for download below. The CSIRO report includes analysis from independent consultant Adrian Leaman of Building Use Studies in the UK, and indicates that productivity has improved by an impressive 10.9 per cent.


Janet Laurence, Waterveil

'Waterveil' forms the glass wall behind the concierge desk in the CH2 ground floor reception area. The glass foyer wall creates a site for a permanent artwork that has evolved through project-specific research and design collaboration with the CH2 architects.

The artwork creates a transparent atmospheric membrane that expresses and reveals hydrology processes, in particular the blackwater recycling treatment utilised in CH2.

A series of vertical overlapping glass panels form the Waterveil wall of the foyer. Over these are hanging or standing glass panels scripted with metallic texts of the chemical symbols indicating the elements removed in the black water treatment.

These panels carry a series of poured fluids in colours of water and chemistry overlaying the chemistry images on the white starfired glass panels beneath In the work, glass is a metaphor of the fluidity and transparency of water and its purification. Blackwater treatment is usually a hidden process.  However, this work expresses, reveals and interprets the process; thus educating in a playful and poetic way, whilst connecting to the total concept of the building.

The work expresses an open and fluid reading, through an alluring and veiling language, that is allusive rather than a fixed didactic expression. This is to draw the viewer into the work, in order to engage with the ghosted chemical images and texts screened into the glass.

This work bleeds the boundary between the inside and the outside of the building's skin.  It can be viewed from both within the building, and the public space outside. One sees through it and reflects into it in varying light.

The Waterveil is consistent with other works Janet has completed, revealing our interconnection to the natural environment and the elemental world.

Double Vortex

Cameron Robbins, Double Vortex

Located in the ground floor reception, just inside the main entry doors, Double Vortex forms part of the wall between the CH2 foyer and the café.

Cameron Robbins is committed to recycling materials where feasible, working with small-scale local industries, frugality, and with themes revolving around our place in the natural world.

The vortex is a natural form which has fascinated many artists, scientists, and alternative thinkers. Scientist and writer Fritjof Capra has said that it is a 'dissipative structure', a class including all living organisms and also fire. As in living organisms, a vortex creates and sustains structural order from the flow of energy through one end to the other.

The vortex occurs on all scales, from galaxies with their central black holes to nano-scale superconductors. They are also fascinating and obviously complex dynamic structures which engage the imagination. As a primal focus of energy, they can be unsettling, beautiful, and even frightening.

Double Vortex comprises a pair of hand-blown glass water-vortex chambers, stainless steel framework, recycled Kauri pine table-top and cedar ply, cast bronze pieces, water, plumbing lines, pumps with electric timers, and low-voltage lighting. It holds 120 litres of tap-water in a reticulating system, which will be periodically changed.

By spinning the water and extracting it through the bottom, the piece produces both clockwise and anticlockwise spinning vortices. This alludes to the philosophical idea of binary opposites (such as +/-, male/female, north/south) and to the old-and-new-school alternative energy subtext of the CH2 project.

The twin chambers draw an analogy to the human respiratory system, positively reinforcing the idea of CH2 as a living system.

Double Vortex also refers to 'the experiment' - a process of exploration and invention, both in the artwork and in CH2.

Three cast bronze pieces draw the eye from the vortices to their table-top base. The two cone-forms which allow the vortex outlets down through the table are hyperbolic cones- the mathematical curve which describes the line drawn by a vortex- and both have opposing movements.

The central bronze element is a direct casting of two interacting magnetic fields, echoing the opposing polarity of the vortices, the lessons of natural forms, and the interaction with primary forces.


Roof landscape

David Wong, Roof landscape

David Wong's work blurs the boundaries between art and horticulture. David worked with the City of Melbourne's landscape design team to develop a concept for the roofscape of CH2. The intention is that garden and art blend uniformly - it is not obvious where one begins and one ends.

Using a mixture of indigenous and non-indigenous plants suited to the light and climate conditions on the roof, the garden transitions between the formal built urban environment to less formal patterns echoing the bush.

Large organic stainless steel mesh climbing forms along with a lyrical flowing mesh curtain along the plant room wall on the south side of the building provide climbing frames for the plants.  Stainless steel rings of varying sizes are attached to the mesh to create vortex shapes, echoing the organic forms and cycles occurring in nature.

A very large bluestone boulder has been sliced into flitches to create two installations - again provides spaces for plants to grow, in between and around the flitches.

In the overall roof design, the East Core wall is considered to reflect the bush - David has designed a stylised representation of the bush using bluestone rock caps and rusted steel columns. The west face of each of the turbine walls have the same treatment so that if one is at the urban end looking towards the bush end there is a series of 'bush'/'dreaming' walls.

These blend harmoniously with the patina of naturally aged timbers, the neutral finish of concrete and the collection of climbers, foliage and grasses.

Concierge desk

David Emery & DesignInc, Concierge desk

The elliptical was designed by DesignInc, managed by City of Melbourne and was made by furniture maker, David Emery.

The timber was salvaged from elm trees being replaced in Swan Street, as part of Council's replacement program.

Full size drawings were prepared showing the inner and outer profile of each of the fifty levels of the desk, each level in a different colour ink. These profiles were traced onto small sections cut from the partly decomposed timber, which were then bandsawn, sanded and finished, and then dry screwed into the desk.

Design and delivery

CH2's collaborative design process explored and challenged every aspect of a contemporary office design. The result was the creation of a highly energy-efficient environment, with an emphasis on the wellbeing of occupants.

Council's CH2 journey began with the assembling of an expert team of consultants from around Australia and beyond. Firms were selected for their credentials and potential to work as part of a team. Working collaboratively with Council's own designers and project managers, the CH2 project team began by attending a two week workshop, followed by a series of weekly design meetings across an eight-month period.

This focus on collaboration was critical to the achievement of an integrated design concept for CH2. The CH2 design and development process was documented to enable others to learn from the experiences.

This section contains information on the following items:

Design reports document key aspects of the design.

Design snapshots.

Research undertaken during the design phase via the AusIndustry program and other references.

CH2 team details for the organisations responsible for CH2's design and delivery.