What changed in AS 1668.2:2024?

The 2024 edition replaces non-quantified performance requirements with precise prescriptive values, introduces borrowed ventilation for adjacent spaces, updates carpark ventilation rates to reflect modern vehicles, and significantly revises healthcare facility requirements including doubling isolation room air changes from 6 to 12 ACHR.

Does AS 1668.2:2024 affect my current project?

If your project is in early design, adopt the 2024 edition now. Projects with documentation already issued under the 2012 edition can typically continue under that edition until certification. Check with your certifier on which edition applies to your project timeline.

Will the updated carpark ventilation rates save money?

Yes, potentially. The revised contaminant generation rates reflect modern low-emission vehicles, which can allow reduced fan sizes and duct sizes in carparks. This reduces both capital cost and ongoing energy consumption. The savings are most significant in large multi-level carparks.

AS 1668.2:2024 Update: What Changed for Ventilation Design

Section 1

What You Need to Know

AS 1668.2:2024 replaces the 2012 edition of Australia's primary standard for mechanical ventilation in buildings. The standard is referenced by the National Construction Code for Deemed-to-Satisfy compliance, which means it affects every building type that requires mechanical ventilation.

The 2024 edition makes 6 significant changes to how ventilation systems are designed, calculated, and documented. The most notable: non-quantified performance requirements have been replaced with precise prescriptive values, carpark ventilation rates now reflect modern low-emission vehicles, and healthcare facility ventilation has been substantially rewritten.

If you are designing, certifying, or constructing a mechanically ventilated building in Australia, these changes apply to you.

Section 2

Key Changes

1

Prescriptive Requirements Replace Non-Quantified Performance Criteria

The 2012 edition included performance requirements that lacked specific numerical values, leaving interpretation to individual engineers. The 2024 edition replaces these with precise, prescriptive requirements. This removes ambiguity and produces more consistent designs across projects and consultancies.

This is the most fundamental change in the standard. Designs that previously relied on engineering judgement for certain provisions now have defined values to meet.

2

Simple and Detailed Calculation Methods for Outdoor Airflow

Both a simple calculation method and a detailed calculation method are now available for determining minimum outdoor airflow rates. The simple method suits straightforward projects. The detailed method allows engineers to account for specific occupancy profiles and contaminant sources, which can result in more efficient system sizing on complex buildings.

The dual-method approach gives flexibility. Use the simple method for standard commercial fitouts. Reserve the detailed method for projects where optimising airflow rates materially affects equipment sizing or energy consumption.

3

Borrowed Ventilation Introduced

The 2024 edition introduces the concept of "borrowed ventilation," where outdoor air can be drawn from an adjacent room under specific conditions. This is new to the standard and has practical implications for spaces that are difficult to duct directly, such as internal rooms adjacent to naturally ventilated corridors or perimeter zones.

Borrowed ventilation is conditional. The source room must have adequate outdoor air supply, and the transfer path must meet the requirements set out in the standard. It does not apply universally.

4

Carpark Ventilation Updated for Modern Vehicles

Contaminant generation rates for carparks have been revised to reflect modern low-emission vehicles. The 2012 rates were based on older vehicle fleet profiles with higher per-vehicle emission outputs. The updated rates can allow reduced ventilation rates, which translates directly to smaller fans, smaller ducts, and lower energy consumption.

The savings are most significant in large multi-level carparks where fan and duct sizing drives substantial capital and operational cost. On a small basement carpark, the difference may be marginal.

5

Healthcare Facility Ventilation Substantially Revised

Healthcare ventilation provisions have been significantly updated. Key changes include new HEPA filter requirements, isolation room air changes increased from 6 to 12 ACHR, and new room pressure categories covering birthing suites and anaesthetic rooms. These changes align the standard with current infection control practices and international healthcare ventilation guidelines.

Healthcare projects in design should review their ventilation schedules against the 2024 requirements immediately. The doubling of isolation room air change rates will affect equipment sizing, ductwork capacity, and energy modelling.

6

Kitchen and Healthcare Provisions Aligned with Contemporary Practice

Kitchen ventilation and healthcare ventilation provisions have been revised to align with how these spaces are currently designed and operated. The 2012 edition had provisions that lagged behind industry practice in these areas. The 2024 edition closes that gap, reducing the disconnect between what the standard required and what engineers were already doing to meet real-world performance expectations.

Section 3

What This Means in Practice

For new projects: Adopt AS 1668.2:2024 from the start of design. The prescriptive requirements give you clearer targets, the dual calculation methods give you flexibility, and the updated carpark rates may reduce system costs.

For healthcare projects: The changes are not minor. Isolation room air changes doubling from 6 to 12 ACHR affects AHU sizing, ductwork capacity, and energy consumption. New HEPA filter requirements and pressure categories for birthing suites and anaesthetic rooms need to be incorporated into ventilation schedules. Review these early.

For carparks: Re-run your ventilation calculations using the 2024 contaminant generation rates. On large multi-level carparks, the reduced rates may allow you to downsize fans and ducts, saving on both capital cost and ongoing electricity.

For commercial fitouts: The borrowed ventilation provision may simplify ductwork layouts for internal rooms. The simple outdoor airflow calculation method is straightforward for standard office, retail, and hospitality fitouts.

Section 4

Transition Considerations

Check which edition your certifier requires. Projects with documentation already issued under AS 1668.2:2012 can typically continue under that edition until certification is complete.
New projects entering design should adopt the 2024 edition. Starting with the current standard avoids re-work if the certifier or authority having jurisdiction requires it.
Review existing ventilation schedules on healthcare projects. The isolation room air change increase from 6 to 12 ACHR will affect equipment and ductwork already sized to the 2012 edition.
Re-calculate carpark ventilation on projects in early design. The updated contaminant generation rates may allow system optimisation that was not available under the 2012 rates.
Update your calculation templates. If your firm uses standard spreadsheets or software templates referencing AS 1668.2:2012 clause numbers and values, update them to the 2024 edition.
Communicate changes to the project team. Architects, contractors, and certifiers should be aware of which edition is being used and any implications for ceiling void space, plant room sizing, or energy modelling.

Section 5

Who Needs to Know What

Section 6

References

AS 1668.2:2024, The use of ventilation and airconditioning in buildings – Mechanical ventilation in buildings, Standards Australia
AS 1668.2:2012, The use of ventilation and airconditioning in buildings – Mechanical ventilation in buildings, Standards Australia
National Construction Code 2022, Volume One – Deemed-to-Satisfy Provisions, ABCB
Standards Australia, AS 1668.2:2024 Publication Notice