"The modelling from IES enabled us to refine our strategy to gain six star world-leadership status and generate $450,000 a year in energy savings"
When MGF set about minimising the environmental impact of a Queensland government building, it had to find a way of achieving radical energy savings in a hot tropical environment typically requiring high levels of energy consumption to maintain comfortable conditions...
Carl N Gray, a sustainability consultant for MGF Consultants, explains, “Although our design for the building, William McCormack Place in Cairns, combines current best practices with a number of innovations to minimise its environmental impacts, we still wanted to be sure it would perform well in such a hot and humid environment. Not least so we could attain a Green Star rating for the design.”
He adds, “We wanted to see the theory in practice and to know, on a nuts-and-bolts level, how much energy was being consumed. That required knowing in advance not just how well the design was performing, but also how best to operate the various systems in place. For example, as well as ensuring that we had allowed sufficient water storage to chill enough cold water to meet air conditioning demands for the following day, we also wanted to establish how late we could turn the chiller on at night to avoid incurring peak energy tariffs.”
“We had some in-house software for modelling energy loading but nothing that would allow us to see the energy demands and comfort level of the building so we turned to IES, the energy software market leader for its technical and consulting expertise,” says Gray. “We wanted to model how our design would perform so we could refine it to make it as sustainable and comfortable as possible.”
IES created a number of models of MGF’s design to generate quality data on how the building was performing in the tropical location where it was based. “We were particularly interested in the thermal comfort of the building so IES created Computational Fluid Dynamics (CFD) models to demonstrate the effectiveness of the air movement,” says Gray. “This enabled us to see how fresh or stuffy our design made the building, both with and without ceiling fans.”
He adds, “In a typical office, breezes have little or no effect because they are most effective when directed over bare skin and the suit attire worn in warmer climates covers the skin. By taking into account that people wear less clothing, so have more skin exposed in the tropics, the modelling from IES showed that the use of ceiling fans would create a ‘physiological cooling effect’ simply not possible in a normal office.”
This approach actually improved comfort levels to reduce cooling energy use by 20% and eliminate the need for (wasteful) air conditioning after-hours.
When it came to leveraging demand tariffs, IES modelling again proved essential, “If we tapped into peak energy for just one hour, it pushed the energy tariff up for the rest of the year, so it was essential that the water for air conditioning was chilled between 6.30pm and 6.30am,” says Gray, “The model identified a potential problem on Sunday evenings in the summer, when a lack of air conditioning over the weekend meant the occupants needed to use the building generator for a few hours to make up the shortfall and avoid peak energy prices.”
Gray says, “Initially it was assumed that it simply wasn’t possible to achieve a six star Green Star rating in the tropics. However the modelling from IES was so robust that we were able to refine our strategy to pick up additional innovation credits, enabling us to gain six star world-leadership status from Green Star and generate $450,000 a year in energy savings. All of which enabled us to win the 2011 Premier’s ClimateSmart Award for best built environment.”
As well as becoming the first building in a tropical region to attain six-star status, the award-winning design achieves a 40% reduction in demand on the electricity grid and 60% reduction in CO2 emissions, compared to an average (2.5 star) building.
“The occupied building’s performance tracks very well with the IES modelling, so we’re confident of gaining a top NABERS rating as well,” concludes Gray.