Ventilation Requirements

Ventilation requirements

Introducing outside air is a requirement set by the Australian standard AS 1668.2 Mechanical Ventilation for Buildings. Its purpose is to maintain contaminants (body odours, VOC, CO2, etc) below concentration levels that have the potential to cause adverse health effects.

There are multiple ways to determine the amount of outside air needed for a building based on its use and needs.

  • The calculation for the minimum amount of outside air required to be introduced into a building will need to consider the floor area, the amount of people in the space and use of the area.
  • The National Construction Code 2019 references this standard and has the following requirements:
  • As per NCC Volume 1 (2019), modulating control and energy reclaiming systems are a requirement if the outdoor air flow exceeds a specified range in each climate zone. Required measure for each climate zone is as seen in the table below.
  • Table J5.3 Required outdoor air treatment
    Climate Zone Outdoor Air Flow (L/s) Required Measure
    1 >500 Modulating control
    2 - No required measure
    3 >1000 Modulating control
    4 and 6 >500 Modulating control of energy reclaiming system
    5 >1000 Modulating control of energy reclaiming system
    7 and 8 >250 Modulating control of energy reclaiming system
  • Note - Energy reclaiming system can be achieved using Daikin’s Heat Recovery Ventilation (HRV) which can also perform modulating control with an optional CO2 sensor.


Indoor units with outside air with no treatment guidelines

  • For Daikin DX FCU’s the following is the limit for no outside air treatment
    • For cooling mixed air needs to be below 32°C db and 24°C wb
    • For heating the mixed air must be above 15°C db

Indoors units with outside air treated by Outside Air Processor (OAP) FXMQ-MFV1

  • OAP unit pre-treats outside air to a set supply temperature. The OAP is required to temper the outside air so that the mixed air result is lower than 32°C db and 24°C wb in cooling and or below 15°C db in heating.

Indoor unit with outside air treated by HRV (VAM)

  • Daikin HRV (Heat Reclaim Ventilation) transfers heat energy between the outside air and the exhaust air. When outside air temperatures are higher than the indoor temperature, heat is removed from the outside air and transferred to the exhaust air meaning a reduced amount of heat enters the conditioned space. When outside air temperatures are lower than the indoor temperatures, the warm air that would normally be exhausted out of the building passes through the HRV and the heat is transferred to the outside air warming it up. This allows for the conservation of energy and to temper the outside air so that the mixed air result is lower than 32°C db and 24°C wb in cooling and/or below 15°C db in heating for the indoor unit.
  • HRV can be interlocked with Daikin’s VRV and Sky Air systems for night purge and bypass mode. The supply and exhaust fans can be operated at different fan speeds to allow for external exhaust or supply fans.
  • Daikin HRV units can be equipped with CO2 sensor to prevent over-ventilation, therefore preventing further energy losses. Having CO2 control will reduce the ventilation amount when the CO2 amount reaches the setpoint. This will increase the energy-saving potential in building where occupancy fluctuates throughout the day.


  • Standard AHU – return air only temperature control. Designed for air on conditions below 32°C DB in cooling or above 16°C DB in heating. Able to handle small amounts of outside air.
  • Outdoor Air Series –is equipped with the Microtech 3 controller that can control the supply or return or room temperature. Can either condition full outside air or vary the amount of outside to return air ratio via dampers.


  • CO2 control is one of the options available for the Microtech 3 controller of the Outdoor Air Series.
  • CO2 can be controlled by either by dampers or fan speed.


FiltersHEPA Filter
  • A range of filters are available from American Air Filters.
  • Different filter options available - standard pre-filter (G4), bag/pocket filters (F7-9) , cartridge/pleated filters (F7-10).
  • HEPA filters also available, HEPA filter is a high-efficiency particulate air filter which forces air through a fine mesh, trapping small particles in the air.

Energy Recovery

Energy RecoveryEnergy Recovery-1
  • Plate heat exchanger (HRV) can be optioned for the VRV AHU’s.
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