The Air Conditioning and Refrigeration Equipment Manufacturers Association (AREMA) has raised concerns about the whole-of-home approach proposed for the 2022 revision of the National Construction Code (NCC).
AREMA says it fully supports “sensible energy efficiency policy and legislation”, including incorporating energy efficiency into the NCC and using a whole-of-home calculation that includes heating and cooling equipment. But it noted that the methodology put forward may have unintended outcomes.
“The approach proposed by the Australian Building Codes Board does not ensure reductions in energy use,” says AREMA President Mark Padwick, “at least in relation to heating and cooling.”
According to AREMA, the methodology proposed only considers the efficiency of heat pump systems for heating and cooling, but not the size of the system. Most new systems are variable-speed or “inverter” units, and increase efficiency by running at less than rated capacity for much of their operation. AREMA points out that smaller systems are typically more efficient than larger ones, and the maximum efficiency of inverter systems typically occurs at around 50–70 per cent of rated capacity.
If a builder does not need to match an air conditioner’s cooling capacity to the building load, AREMA says, they may select a smaller system because it is lower cost and meets the “efficiency target”. The undersized air conditioner would operate mostly at maximum capacity, and its energy consumption would be higher than the figure projected by the NCC, with higher energy costs and decreased comfort.
“An undersized system operating at full load more often because it is undersized cannot deliver the efficiency, electricity costs or comfort as projected by the NCC,” says Padwick.
“Consider an analogy: a family might be thought of as environmentally conscious if it bought a highly efficient small four-seat car. But if the family had six children it would potentially require more frequent trips – not the efficiency the family would be expecting.”
AREMA says that equipment sizing is not overly complex, and uses factors such as area size, climate zone, building shell efficiency and window detail, that are already incorporated into the NCC.
“AREMA calls on the ABCB to incorporate sizing of heating and cooling equipment into the 2022 National Construction Code,” says Padwick.
“We would be delighted to help, but we cannot support the current approach that will lead to higher energy bills, increased electricity use and increases in greenhouse gas emissions.”