The building that gives back

This Issue This is a part of the Energy efficiency feature

By - , Build 128

Australia’s first carbon-neutral office raises the bar for sustainable performance in commercial buildings worldwide and may be a foretaste of what’s to come in bigger urban projects.

Native grasses that filter rainwater cover 75% of the roof.
Façade with sunshades that let in light but keep out too much sun.
Figure 1: The Pixel building’s water cycle.

The $6 million, 4-storey, Pixel office building in Melbourne stands out, not only for its colourful appearance but also for its stellar environmental credentials. Australia’s highest-ranked sustainable building, Pixel was awarded a perfect 100 points by the Green Building Council of Australia (GBCA), achieving a 6-star Green Star rating. This denotes world leadership in environmentally sustainable design and/or construction. An additional 5 points were awarded for innovation.

Carbon neutral

Studio505 designed Pixel, working with sustainability and services engineers Umow Lai and structural engineers VDM Consulting on the building, which serves as the development and sales offices for a major inner city redevelopment. The brief from the developers, Grocon, was for a design that would achieve a 6-star rating, be carbon-neutral and would set performance and design standards for future buildings that would be constructed on the site.

Pixel achieves its carbon-neutral status by supplying its own energy needs and feeding surplus supply back into the grid. Over time, this will offset the carbon emitted during construction.

One notable aspect of the project is the way its systems are integrated so that few have only a single function. Another is the way the building uses products and materials that have not been specified in Australia before, including locally developed wind turbines, an environmentally friendly concrete that was specifically developed for the project and a gas fired heating and cooling system that uses ammonia as the refrigerant.

Façade with sunshades that let in light but keep out too much sun.

Self-sustainable water supply

Pixel is water balanced, so if Melbourne maintains its 10-year average rainfall levels from 1999–2009, the building will be self-sustainable in water supply (see Figure 1). Several systems help achieve this:

  • Rainwater is collected and stored in tanks before being treated by reverse osmosis to potable water standard, then it is distributed within the building.
  • The grey wastewater is filtered and directed to reed beds on the building perimeter. This means there is no greywater waste leaving the building, except for the wettest month of the year, dramatically reducing waste flow to the sewer.
  • The vacuum toilet system, similar to those used on aircraft, reduces water consumption to a minimum.
  • An anaerobic digestion tank system holds black waste from toilets and kitchens. Methane is extracted from the waste and used to power the hot water heaters on the building’s roof. These heaters provide hot water for the showers that subsequently produce the greywater that irrigates the reed beds. The black waste is then sent to the sewer in a liquefied form with reduced methane levels.

Good air

Air inside the building is distributed through the floor with individual controls located at each workstation, in much the same way vents work on a car dashboard. Outside air constantly circulates at rates 150% above Building Code requirements.

Exhaust air has its heat or coolth removed by energy capture systems before it is exhausted into the environment, reducing overall energy use.

Distinctive façade

Pixel’s distinctive façade includes perimeter plantings, fixed shading louvres, double-glazed window walls and solar panel shading. The sunshade system allows 100% daylight penetration while protecting from too much glare so that computers can be used without the need for blinds on windows.

Night purging – smart window technology that automatically opens the windows of the façade on cool nights, enabling air to flow into the building and cool the structure – maintains temperature levels.

Cooling and heating

Cooling and heating is provided by a gas-fired absorption chiller system that uses ammonia as the refrigerant source and gas as the energy source, dramatically lowering carbon emissions compared with electrical systems. The use of ammonia as the refrigerant gas means that there is no ozone-depleting potential in the gas nor any possibility of Legionella.

Exposed concrete ceiling slabs are cooled by pipes carrying cooled water embedded in the concrete, providing radiant cooling to areas below.

Renewable systems

A track-mounted photovoltaic (PV) array on the roof turns the panels in the direction of the sun at all times, increasing power outage by an average 40%. In addition, three roof-mounted wind turbines each provide up to 60% of a typical Melbourne household’s energy use.

Green roof and edges

The building is topped by a green roof – over 75% of the space is covered by four 3 × 4 m beds of native grasses that filter rainwater and insulate the building.

The reed beds at perimeter level on each storey – described by the architects as living edges – shade the office spaces inside and form a significant part of Pixel’s water cycle, utilising and evapotranspiring greywater harvested from the building.

Materials

A low-carbon concrete – Pixelcrete – was developed specifically for the project. The material uses 60% less cement and 100% recycled and reclaimed aggregate. It has half the embodied carbon of traditional concrete but the same strength and capabilities.

All the timber and timber products in the building meet Forest Stewardship Council (FSC) standards, meaning they are from FSC-certified forests, are recycled or are a combination of FSC-certified and controlled sources.

Native grasses that filter rainwater cover 75% of the roof.

Setting an example

The Pixel building has won a number of awards, the latest being the best of the best award in the 2011 BPN sustainability awards, when it was described by judge and principal of BVN Architecture Bill Dowzer as ‘illustrating the possibilities of future large-scale office buildings.’ Grocon says that the building is a prototype of the future and that all new office developments in a carbon-constrained environment will include some of the systems implemented in Pixel.

The building is now being assessed under the US LEED (Leadership in Energy and Environmental Design) and UK BREEAM (Building Research Establishment Environmental Assessment Method) rating systems, aiming to exceed the highest score yet achieved under either of these tools.

Figure 1: The Pixel building’s water cycle.

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Native grasses that filter rainwater cover 75% of the roof.
Façade with sunshades that let in light but keep out too much sun.
Figure 1: The Pixel building’s water cycle.

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