Ventilation

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Multi-dwelling ventilation

Individual dwellings in a multi-dwelling development

For individual dwellings in a multi-dwelling development, 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
  • central ducted
  • individual fan into central ducting plus Variable Speed Drive (VSD)
  • motorised damper into central duct plus VSD.

Similar to single dwelling developments, BASIX recognises the following controls:

  • interlocked to light – ventilation fan switch on/off is interlocked to the light switch
  • continuous – ventilation fan operates continuously (24 hours per day)
  • manual switch on/off
  • manual on/timed off.

Common areas in multi-dwelling developments

For common areas in multi-dwelling developments, BASIX recognizes the following types of ventilation:

  • no mechanical ventilation - that is, natural ventilation
  • ventilation supply only (mechanical supply only)
  • ventilation (supply and exhaust) (both mechanical supply and mechanical exhaust)
  • air conditioning system

NCC requirements

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.

Single dwelling ventilation

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

Operation controls available in BASIX are:

  • interlocked to light (ventilation fan switch on/off is interlocked to the light switch)
  • continuous (ventilation fan operates continuously ie. 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.

Internal ventilation options?

The most efficient option is natural ventilation, typically via windows that can be opened.

In general, individual fans without ducting are likely to be the most efficient of the mechanical ventilation options. However, moist air vented to the roof space by individual fans without ducting can increase the risks of building condensation, especially if the roof material is continuous (such as metal roofing).

Ducted individual fans are not much worse than those without ducting in terms of energy efficiency, as long as the intake, ducting and discharge are reasonably sized. Ideally, from a heating and cooling perspective, fans should have automatic dampers or shutters so that air does not leak through them when they are not operating.

A fan with some form of operation control such as manual on/off or interlocking to the light switch, will be considerably more efficient than a continuously operating fan.

 

An exhaust fan through a wall, individual fan not ductedIndividual fan not ductedDiagram of an individual fan - ducted to facade or roofIndividual fan - ducted to facade or roof