New Zealand’s HVAC&R sector must now use the Fifth Edition of G4/AS1 for building consent applications following the Acceptable Solution pathway. The transition from the Fourth Edition ended on July 31, 2026, with the Fifth Edition having taken effect on July 28, 2025.
Clause G4 of the New Zealand Building Code requires occupied spaces to have adequate ventilation consistent with their intended use and occupancy. G4/AS1 provides a recognised pathway for demonstrating compliance with these performance requirements.
The Fifth Edition restructures G4/AS1 as a standalone publication with updated terminology, clearer language and revised organisation. It covers natural, mechanical and hybrid ventilation systems in residential and commercial buildings and includes provisions for gas-fuel appliances and flue locations. The document also references current New Zealand and Australian standards and works alongside the Building Product Specifications framework introduced under the Building Act.
For HVAC&R professionals, the updated pathway requires designers, mechanical engineers, contractors and suppliers to ensure specification templates, design references and internal quality systems reflect the current requirements. Mechanical ventilation systems must address outdoor air, moisture and contaminants while integrating with increasingly airtight building envelopes and limiting unnecessary energy consumption.
Projects submitted for building consent from August 1, 2026 must reference the Fifth Edition when using the Acceptable Solution pathway. Projects lodged before that date can continue under the previous edition where applicable during the consent process.
