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Revision of NZS 4303:1990 Ventilation for acceptable indoor air quality

NZS 4303:1990 Ventilation for Acceptable Indoor Air Quality is a key compliance standard for indoor air quality (IAQ) in New Zealand buildings.

Why is the standard being revised?

Published in 1990, NZS 4303 has served as the benchmark for ventilation design and operation for 35 years. However, the standard is now overdue for a comprehensive update to reflect modern building practices, address emerging health and environmental challenges, and align with international good practice.

The current standard was originally based on ASHRAE Standard 62-1989 and provides prescriptive guidelines for ventilation. While it has been widely used, it does not adequately address issues such as new contaminants, post-pandemic health risks, natural ventilation strategies, moisture management, and energy efficiency. These gaps limit its relevance in today’s building environment.

The Ministry of Business, Innovation and Employment (MBIE) Building System Performance (BSP) team has commissioned this revision as part of its programme to update standards cited in the New Zealand Building Code. A scoping exercise led by Standards New Zealand identified multiple areas for improvement.

NZS 4303 is currently cited within MBIE solutions under G4/AS1 and H1/VM1.  This makes it an important reference for designers, engineers, and building consent authorities.

What changes are in scope?

The revision will address significant developments in ventilation and indoor air quality since 1990. Key areas include:

·         Non-residential ventilation

  • Updated airflow requirements and compliance pathways.
  • Potential referencing of more current Australian standards such as AS 1668.2 (Mechanical ventilation in buildings) and AS 1668.4 (Natural ventilation of buildings).

·         Residential ventilation

  • A new section providing guidance on continuous ventilation, purge ventilation, and natural ventilation for homes.
  • Consideration of UK and Irish regulations for moisture management, overheating, acoustic performance, and airtightness.

·         General indoor air quality

  • Review of international benchmarks such as ASHRAE Standard 62.2-2022 to ensure alignment with global good practice.

What's next?

The standards development committee is being formed with the first committee meeting scheduled for 11 February. The project is expected to take up to 20 months to complete.