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Eco-Buildings

Climate change has many causes, but most people wouldn’t guess that buildings are among the biggest culprits. Luckily, the technologists are on the case and many countries have started building Eco-buildings

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These are the usual suspects when we think of energy guzzlers and climate change culprits. But the buildings that silently line the streets of every city on the planet the structures in which we live and work turn out to be among the biggest offenders of all. Including operation and construction buildings consume 30 to 40 percent of all energy used globally and produce a similar percentage of carbon dioxide emissions. Over the past decade promoters of green buildings have worked to transform them from environmental villains into saviours.

"Ten years ago people put up solar panels on their roofs and said they were green buildings but there was nobody to check and substantiate those claims" says Tom Hicks vice-president of international programmes at the United States Green Building Council. Today to be considered green a building needs to meet objective standards of energy efficiency water efficiency responsible use of materials and indoor environmental quality.

Architects and engineers who have risen to the challenge still include the odd solar panel in their designs but they've gone further. They've reduced energy use through better insulation more efficient lighting and water conservation. They've replaced air-based cooling and heating systems with new technology. They've harvested waste water for reuse. And they've saved money.

Many of these measures offer real savings too. On average they drive up design and construction costs by less than 5 percent – and often pay back the initial outlay through energy savings in a few years.

"Sustainable buildings have almost become mainstream" says Tony Arnel chair of the World Green Building Council and the Green Building Council of Australia. "If you are not building a green building in 2009 then you are building in obsolescence." Here are some of today's most ambitious and innovative building designs both green and efficient.

Location: Australia
Melbourne's Council House 2 or CH2 is a finely tuned organism as ingeniously adapted to its environ- ment as any creature subject to the forces of evolution. Its windows for instance are carefully designed to help it thrive. Those on the northern and southern faces start out wide at the building's base and grow nar- rower as they approach the top of its ten storeys where less exposure is necessary to provide natural light to the interior. The windows on the western face are equipped with solar-powered shutters made from salvaged wood. The shutters start the day wide open and gradually close to minimise glare as the sun descends through the afternoon. "They open and shut rather like a flower opens and shuts" says princi- pal design architect Mick Pearce.

As with many green buildings CH2's cleverest features are hidden from view. During the day thick undulating concrete ceilings chilled by cool water flowing through pipes absorb excess heat. When the out- side temperature drops at night the windows open automatically letting cool air flow through and shuttle away accumulated heat from the ceilings. This "night purge" reduces by 20 percent the energy necessary to cool the building. Pearce first employed this method in a shop- ping centre in his native Zimbabwe inspired by the way African termites opened holes in their mounds at night to draw in cool air.

The water used to cool the build- ing falls through 14-metre "shower towers" on the building's south façade. As the water falls some of it evaporates leaving the rest cooler. The water is further cooled in basement tanks containing 31500 stainless-steel balls the size of cricket balls filled with a Phase Change Material (PCM) solution that freezes at 15 degrees Celsius. This solution is approximately 40 percent water mixed with a combination of naturally occurring salt hydrates.

These form crystal complexes incorporating water molecules and can be mixed together in set proportions to give a crystallis- ing (freezing) temperature of as high as 117 degrees Celsius. This salt solution can be frozen at night using a water- or air-based free- cooling system through the towers on the roof then used as a cooling reservoir during the day. To freeze an equivalent amount of pure water would require a tremendous amount of energy. In fact if CH2 used plain water to get the same amount of cooling power it would take a volume of water ten times that of the salt solution.

"We have developed a building that responds to nature; it doesn't try to conquer it" says Pearce.

In drought-prone Australia water conservation is a perennial concern. CH2 employs typical water-saving methods – low-flush toilets low-flow taps and showers – and has pioneered a novel way to supplement its water supply: "mining" and purifying 100000 litres of water per day from the municipal sewer system running beneath the street outside. This provides all the water necessary for irrigation the toilets and for the building's cooling system.

Solar panels on the roof supply 60 percent of the building's hot water requirements. The rest of the hot water is heated by a gas boiler and by waste heat from a gas-fired co-generation plant on the roof which additionally provides about 30 percent of the building's electricity with much lower emissions than a conventional coal-fired plant.

Compared to a typical building CH2 is designed to cut electricity consumption by 80 percent and produce 87 percent less greenhouse gas emissions.

According to City of Melbourne figures the employees in CH2 are 10 percent more productive than workers in other buildings – perhaps because the air is replenished twice an hour rather than recycled as in a conventional building. The office plants seem to be happy with the building as well.

"Normally in an air-conditioned building you replace the plants every three months" comments Pearce "but in CH2 they grow too well and have to be cut back to keep it from becoming a jungle." That is he observes a very good indicator that the designers have got the air quality right.

The combined savings from reduced energy use and increased productivity mean that CH2 is set to pay off its increased sustainability costs in just five years – twice as fast as initially projected – demonstrating that a green building can be handsome innovative and thrifty at the same time.