BASIX assesses the energy for air-conditioning based on:
- whether it is a single-phase system or three-phase system;
- for cooling, the cooling star rating or the Energy Efficiency Ratio (EER);
- for heating, the heating star rating or the Coefficient of Performance (COP);
- for systems that serve both the living areas and bedrooms, whether the system is day-night zoned between the areas.
If a reverse-cycle air-conditioner is to be installed for heating and cooling, the system needs to be described in both the heating and cooling sections of BASIX. The air conditioner may have a different energy efficiency rating for heating and cooling.
Air conditioning ducting needs to be installed in accordance with the relevant insulation and sealing requirements of the Building Code of Australia.
Some ducted air conditioning systems have the capacity to be zoned to function between "day-night". This means, the air conditioning will only be able to be used in the living areas during the day and in the bedrooms at night.
By incorporating a zoning feature the required size of the air conditioner is reduced and its use is reduced, since it either cools/heats one area or the other, and not both at once.
The larger an area to be cooled or heated, the larger the surface area between the conditioned space and the environment so, the more heat will flow and the more energy will be used to maintain comfort.
Zoning a building may also reduce the air leakage rate, saving more energy, as walls form barriers to internal air flow.