G4/AS1: Ventilation

G4 VENTILATION ACCEPTABLE SOLUTION G4/AS1 Spaces within buildings 2.3 Mechanical ventilation 2.3.1 Mechanical ventilation systems 2.3.1.1 Mechanical ventilation systems must satisfy the following conditions: a) outdoor air supply shall be designed and equipment installed to comply with NZS 4303, or AS 1668.2 (excluding Table A1 and Sections 3 and 7), and to provide outdoor air to occupied spaces at the flow rates given in NZS 4303 Table 2; and b) air-handling systems shall comply with Section 7.2.2 of the Building Product Specifications; and c) extract ventilation shall: i) be constructed so that any products listed in Clause G4.3.3 are removed, collected or diluted by ventilation rates and methods set out in AS 1668.2 Section 5, and COMMENT: Commercial kitchen extract ventilation is included in AS 1668.2 Section 5. ii) where provided to remove moisture and other contaminants from kitchens, bathrooms, toilet spaces and laundries in household units, exhaust the air to the outside at flow rates given in AS 1668.2, Table B1, and COMMENT: Extract ventilation systems that pass through fire rated building elements must be designed to maintain the fire performance of the building. Refer to Building Code Clauses C1-C6 Protection from Fire. iii) exhaust air to the outside at a flowrate not less than 50 L/s, when intermittent mechanical extract ventilation is used to remove moisture and other contaminants from spaces in household units and accommodation units that contain cooktops; and d) outdoor air intakes shall be located to avoid contamination from any local source in accordance with AS 1668.2 Clause 4.3.1 and NZS 4303 Clause 5.5; and e) recirculated air systems shall comply with AS 1668.2 Clause 4.5; and f) contaminated air discharge systems shall discharge contaminated air in a way that complies with AS 1668.2 Clause 5.10; and g) filtration shall comply with AS 1668.2 Clause 4.4; and h) commissioning shall comply with CIBSE Code Series A. 2.3.2 Car park ventilation 2.3.2.1 Mechanical ventilation of car parks shall comply with the mechanical ventilation part of AS 1668.2 Section 7. 2.3.3 Positive and negative pressure 2.3.3.1 Building interiors ventilated by mechanical systems incorporating filtration shall be maintained at a positive pressure except where Paragraph 2.3.3.2 applies. COMMENT: Positive pressure allows good control of intake air filtration, whereas under negative pressure, unfiltered air may be drawn through gaps and openings in building elements. MINISTRY OF BUSINESS, INNOVATION AND EMPLOYMENT 28 JULY 2025 Page 11