Most products and appliances sold today are expected to meet strict energy efficient standards. Air conditioning units are no exception, which is why research is underway to measure the impact of ducting on the energy use of ducted air conditioning systems.
Talk to the director of Ductair, Reuben Kelley, about thermal leakage and he is pretty forthright in his assessment of current installations. “There is still plenty of work to do,” he says.
In fact, Kelley believes there are serious flaws in the way Minimum Energy Performance Standards (MEPS) have been applied to air conditioners.
For more than a decade, MEPS provided a guide to the energy demand and performance standards for air conditioning units without taking ducting into account.
“It’s a bit like watering your garden with a leaky hose,” Kelley says.
“If your system has thermal or air leakage in the roof cavity due to poor quality duct and fixtures, then your air conditioning unit has to work even harder to get your living space to the right temperature.
“This in turn has a dramatic effect on your comfort levels, energy usage, peak power demand and of course your power bills.”
In the past there has been no independent testing or recorded data that measures the energy use and actual thermal loss or air leakage of fully installed systems.
“This meant that actual energy demand could be significantly different to performance standards set by MEPS,” Kelley says.
In 2010, the Australian Building Code Board took steps to address the issue by increasing the efficiency requirements of ducting.
At the same time Ductair prepared a formal submission seeking to include ducting and fittings in the MEPS rating to increase compliance of the current BCA regulations.
Between 1995 and 2008, the vast majority of ducted air conditioning systems in Australia were installed with 25mm (Rt0.6) polyester insulated duct and uninsulated plastic fittings.
Poor design and installation was affecting performance further, taking a MEPS-rated
6 star air conditioning unit to an operating efficiency of only 1.5 stars.
To address the problem, Ductair teamed up with the University of South Australia and local thermographers and began researching ways to improve the performance and energy use of ducted, reverse cycle air conditioners in Australian homes.
Over the past six months homes across Adelaide have been tested as part of a study investigating the impact of ducting on the energy use of ducted air conditioning systems.
“With over 50,000 ducted systems installed in South Australia and the highest energy prices in the country, we immediately recognised the potential impact of this study,” Kelley says.
Thermal loss due to ducting and fittings are a function of heat transfer through the duct and fittings into the roof cavity, known as thermal leakage.
Air leakage can involve roof space air being drawn into the air conditioner via the return air section or lost to the roof space via the supply air, both resulting in wasted energy.
Air can also leak past closed zone motors and condition parts of the house, unnecessarily wasting energy.
As a direct result of the research, Ductair has commenced an in-home testing and evaluation process that can measure and assess the performance of a home's existing ducted air conditioning system.
Kelley says the simple four-step process uses independent testing by trained professionals to identify potential issues. Sophisticated software developed by the university is then used to analyse the findings and calculate an energy rating.
Every home tested is also provided with an Energy Smart comparison report that details potential savings.
Kelley says upgrading an inefficient ducted system can significantly boost the performance of the unit and reduce running costs.
“We have been amazed at the dramatic improvements seen in our test results,” he says.
“By simply replacing old flexible ductwork and fittings with a new Energy Smart System, we have reliably proven savings of up to 45 per cent on heating and cooling running costs, nearly doubled the capacity of the total system and typically reduced greenhouse gas emissions by 857kg of CO2/yr.”
If all the systems Australia-wide were retrofitted with an Energy Smart system this would translate to a 0.6 per cent reduction in national emissions, equivalent to the savings delivered by a single nuclear power station.
“With domestic air conditioning representing more than five per cent of Australia’s greenhouse gas emissions the impact of these findings are significant,” Kelley says.
MEPS introduced more stringent standards for ducted systems on April 1, 2012 with Standard AS/NZS 3823.2.
The introduction of MEPS and energy rating tools (ERLs) was introduced to improve the energy efficiency of appliances and products.
The Equipment Energy Efficiency Program (E3) is expected to yield a cumulative economic benefit to Australia of $22.4 billion by 2024.
This reflects not only economic and environmental benefits, but also significant savings for households, businesses and industry.
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