Council House 2, an administrative building for the City of Melbourne, is the first in the country to

achieve the highest possible rating of six stars in Australias Green Star environmental accreditation.
It is now influencing a new era of office design

Electricity consumption reduced by 85% and gas consumption reduced by 87% compared to
sister building Council House
The office is predicted to save the client 500,000 a year in saved sick leave costs
Gas fired co-generation plant provides 40% of electricity requirement. Recycled waste heat
supplies 40% of air heating/cooling requirements
Payback period for all of environmental features, including photovoltaics, of ten years or less
Healthy design
The somewhat unimaginatively named Council House 2 (CH2), in Melbourne, Australia (its
predecessor is Council House) is rather more innovative than its name would suggest.
Designed as a healthy workplace and environmental exemplar, the building is the greenest
urban office in the country. It has been operating now for two years and monitoring has shown
that it vastly outperforms even its nearest rivals in terms of carbon emissions, producing some
64% less CO2, and provides a working environment that is predicted to improve staff
effectiveness, partly through reduced sick leave, and save the City of Melbourne AUS$1.12
million (500,000) per annum.
The numbers sound almost too good to be true, so how does the buildings design achieve so
much? Although many perceive green building to be purely environmental, it is about people
too, says Su-fern Tan, of Advanced Environmental, a division of Lincolne Scott. The focus at
CH2 has been to give priority to the environment and to its occupants. Occupant needs
address fresh air, water, light and well being, while environmental needs address the
reduction of energy consumption, greenhouse gas emissions and water consumption,
reduced demand in public infrastructure and reduced dependence on energy and water
providers.

Cooling and heating

At ten storeys high and housing 540 staff, the 12,536m building includes multiple environmental
features. The design for the heating and cooling of CH2 has both passive and active measures.
Natural ventilation plays a large part both during occupied hours and to cool the thermal mass during
night-time and at weekends.

The concrete ceiling slab absorbs excess heat during the daytime and releases it at night. A chilled
ceiling air conditioning system and perimeter chilled beams provide radiant cooling during the summer
months. In cooler parts of the year an under floor convective heating system allows warm air to
percolate into the working environment without the use of fans. Much of this heat has been recovered
from waste heat produced by the cogeneration plant.

To date, the building has been adequately cooled by the passive thermal mass of the concrete
ceilings and fresh air supply in to the office. The building management system (BMS) has yet to
activate the chilled ceilings and beams.

Energy

A gas powered cogeneration plant provides 60kW of electricity, meeting 40% of the buildings power
requirements. Some 48m of roof mounted solar panels heat 60% of CH2s domestic hot water; a gas
boiler supplements them. Photovoltaics are also employed: a 26m array generates around 3.5kW of
electricity, which is used to power the sun-responsive shading devices on the western faade.
Potentially the most innovative part of the energy strategy is the free cooling of water for the chilled
beams and free ventilation of the ground floor retail spaces. After being circulated through the chilled
ceiling, warm water is passed through shower towers, top ventilated tubes running down the side of
the building. As it falls down the 13m drop, the water cools by up to 4oC, displacing air in front of it as
it goes. The water is then circulated through cool stores that employ phase change material, before
going round the chilled ceiling again. Additionally, the displaced air in the tower draws in fresh air at
the top and is passed into the retail spaces at the base, ventilating them for free.

Fresh air

At a circulation rate of 22.5 litres per person per second, CH2s fresh air intake is about three times
the minimum prescribed in Australian building standards. Fresh air is circulated through the work
space naturally. Entering at low level, the cool air displaces warm air that has risen to the ceiling; this
is exhausted through ceiling vents, negatively pressured exhaust plenums and shafts in the buildings
north faade. No air is reconditioned and circulated: it is all flushed out, providing workspaces with
fresh air every half hour.

It is encouraging to see that more and more property industry players are seeing the light and
realising that those extra dollars spent on green buildings do make sense

Su-Fern Tan, Advanced Environmental

Light

Extensive shading to the north, east and west facades eradicates glare and solar gain, while light
shelves and balcony floors bounce indirect natural illumination into the building to maximise natural
light levels. Artificial lighting is extensively T5 lamps, which are controlled via zone switching and
daylight sensors. Task lighting for occupants reduces the energy consumption further.

Water

All fixtures and fittings within the building are low consumption and extensive recycling reduces CH2s
water consumption by 72%, compared to its older sister building. A water mining plant draws black
water from the public sewer and recycles it. This, along with recycled rainwater, supplies all of the
buildings requirements for irrigation, toilet flushing and cooling. Any surplus is directed to other
buildings, fountains and street cleaning faucets.

Wellbeing

The naturally lit and ventilated workspaces in CH2 provide an optimum office environment or staff in
the building. In addition, individual control of fresh air vents and task lighting promote comfort. Finally,
break out space comes not in the form of a couple of sofas in a corner of the office but extensively
planted balconies and a roof garden, which create a real feel of being able to escape from the desk if
needs be.

A winning formula

CH2 is an unusual looking and innovatively designed office building. It has attracted much attention in
Australia and is making an impact on global design ideals. In achieving the highest possible Green
Star rating it has set a standard for urban design down under. CH2 leaves its older, similarly sized
sister building far behind, says Tan, consuming 15% of the energy and emitting only 13% of the
emissions of its counterpart, which still represents a majority of the buildings in the commercial
marketplace. However, it is encouraging to see that more and more property industry players are
seeing the light and realising that those extra dollars spent on green buildings do make sense.