For single dwellings, BASIX recognises the following types of ventilation system:
- no mechanical ventilation, that is, natural ventilation
- individual fan, not ducted
- individual fan, ducted to façade or roof
Individual fan not ducted
Individual fan ducted to façade or roof
Operation controls available in BASIX are:
- interlocked to light (ventilation fan switch on/off is interlocked to the light switch)
- interlocked to light with timer off
- continuous (ventilation fan operates continuously, that is, 24 hours per day)
- manual switch on/off
- manual on/timed off.
All ventilation systems must be designed in accordance with the National Construction Code (NCC), which in turn requires compliance with Australian Standards 1668.1 and 1668.2 for mechanical ventilation systems.
BASIX calculations are based on AS1668.2 minimum airflow requirements and generally assume fan efficiency higher than the NCC minimum.
If your dwelling is designed and constructed in accordance with the Passive House standard to satisfy the BASIX thermal comfort requirements, you must install mechanical ventilation with heat recovery (MVHR) in the dwelling.
To improve efficiency of both the system and the dwelling:
- The system should have an external outlet
- Keep duct runs as short as possible, limiting the number of bends
- Size the duct and outlet appropriately
- Install back draft dampers
- Install automatic shutters and dampers to reduce indoor air leakage (as they are closed when the system is not operating)
A fan with some form of operation control such as manual on/off or interlocking to light switch, will consume less energy than a continuously operating fan.