What are the rules for ventilation in New Zealand? It depends on the house: whether you rent it out, are renovating it, or simply live in it. Jordan Statham, director of The Conduction Company and a registered electrician and electrical inspector, answers the questions clients ask about bathrooms, kitchens, laundries, and apartments.
In New Zealand, ventilation rules come from two places. The Building Code covers building work, such as a renovation that needs consent, and the healthy homes standards cover rentals. For a home you own and live in, The Conduction Company's advice is the same either way: extract bathroom and kitchen steam to the outside.
For an owner occupied home, what rules apply to bathroom and kitchen ventilation?
For an owner occupied home, the healthy homes standards do not apply. Jordan Statham, director of The Conduction Company, points out that they were written to protect tenants in rental and investment properties. The Building Code comes in when you do building work, which is the next question.
The reasons behind the healthy homes standards still apply to you. They were set up that way because wet areas need an extraction path for moisture to get out. A poorly extracted bathroom brings the same poor living conditions and poor health to whoever lives there.
"Regardless of being a tenant or a homeowner, you do need extraction in those areas to maintain a healthy and safe home environment," says Jordan Statham.
If the home is a rental, the healthy homes ventilation standard sets out fan sizes and ducting for every kitchen and bathroom. They are in regulation 23 of the Residential Tenancies (Healthy Homes Standards) Regulations 2019, so this page does not repeat them.
Does a renovation trigger new ventilation rules?
Yes, if the renovation involves a building consent. It depends on the type of renovation, but in The Conduction Company's experience, consented work will in the majority of cases need to comply with modern ventilation standards under the Building Code. The Building Code itself applies to building work whether or not it needs consent, as the G4 answer below sets out.
Does a new bathroom need a building consent for its fan?
In most cases, yes, depending on what the plans specify. When a new bathroom goes through building consent, The Conduction Company finds that the vast majority of the time it needs mechanical extraction to comply, so the fan is part of the consented work.
What does a council inspector actually check on ventilation?
A council inspector checks that the ventilation listed on the consented plans has been installed, or is ready to be. How closely they check is up to the individual inspector, The Conduction Company finds.
Normally the inspector looks at the consented plans and checks that each item of ventilation on them has been installed, is planned to be, or has its ducting in place. Some inspectors want to know the extractor fan is working. Others are happy to see the wiring in place and the ducting ready for the fan to be connected at a later stage.
Is an opening window enough for a bathroom in a new build?
No. Jordan Statham, director of The Conduction Company, says an opening window is definitely not enough for a bathroom in a new build.
A window does give some ventilation, but the air goes where the cross-draughts take it. If the bedroom side of the house is under negative pressure and there is positive pressure at the bathroom window, the airflow can force the steam from your shower back into the home. In some cases an opening window makes a high humidity problem worse.
Mechanical extraction makes the bathroom a negatively pressured room, so any steam you produce gets sucked out of the room instead of making its way into the rest of the building. That is why The Conduction Company recommends mechanical extraction over relying on a window.
What rules apply to a range hood in a kitchen?
In a rental, the kitchen needs a range hood, or at least an extractor, ducted to the outside for proper steam extraction. In an owner occupied home the healthy homes rules do not apply, but Jordan Statham of The Conduction Company says most owners want the same thing anyway: cooking steam and smells pushed outside the home.
The Conduction Company's advice is a range hood with enough extraction capacity to handle the steam and cooking smells your kitchen produces. If you are concerned about noise, we recommend a system with a separate fan located in the ceiling void, rather than a standard range hood with the motor and fan built in, which can be loud.
What happens when there is no rule, but the house is damp anyway?
Put the extraction in anyway. In an older owner occupied home, The Conduction Company always recommends installing range hoods and extraction fans, rule or no rule. It just makes sense.
Jordan Statham's view is that negative extraction is the most important part of home ventilation. Removing moisture at its source, as it is made, and not letting it into the rest of the home, is the key to solving high humidity. If you are also weighing up a whole-home system, The Conduction Company compares HRV, DVS and SmartVent home ventilation systems in a separate guide.
Where do you see people break the rules without knowing?
It is not always a broken rule, but The Conduction Company sees it in a lot of homes: a range hood or bathroom fan that ducts, or ports, straight into the ceiling void instead of outside.
It used to be really common, especially in bathrooms with large, wide extraction fan systems that pushed the moisture from the bathroom straight into the ceiling void. That causes all kinds of problems with high moisture levels in the ceiling void.
In every case, The Conduction Company's advice is to duct the steam from a bathroom or kitchen to the outside of the home, so it is not inside the building envelope. For a rental, the healthy homes standards settle it: the only extraction they accept vents to the outdoors.
What is different for apartments and body corporates?
In many apartments, the extraction is not in your unit at all. Jordan Statham, director of The Conduction Company, says a lot of apartments have a building management system with central extraction: one large fan, usually in the plant room at the top of the complex, ducted to multiple units to provide their extraction and ventilation.
So in larger apartment complexes, the ventilation is sometimes handled by the building itself, rather than each unit having its own extractor fans ducted to the outside.
These units may also have a recirculating range hood in the kitchen. Its purpose is to cut cooking smells, usually with a carbon filter, and to capture grease. Any steam passes straight through it and back into the home. So you are relying on the building management system, and the ventilation that is part of the whole complex, to remove the moisture from your unit.
If you are a landlord and a fan cannot go in, the healthy homes regulations deal with that in regulation 24, for a fan that is not reasonably practicable to install, and regulation 32, for a landlord who does not own the whole building. Both come with conditions.
What does building code clause G4 actually require, in plain words?
In plain words, clause G4 of the New Zealand Building Code requires every space in a building to get enough outdoor air for how many people use it and what it is used for. It also requires a way to remove cooking fumes, and moisture from laundering, washing up, bathing and showering, from the spaces where they are made. The Conduction Company has read it at the source: Schedule 1 of the Building Regulations 1992, where it has stood unchanged since 1997.
G4 itself never mentions fans, windows, flow rates or duct sizes. It says what has to be achieved, not how. The how is in MBIE's Acceptable Solution G4/AS1, fifth edition, effective 28 July 2025, which a council must accept as compliance. It is the standard route, not the only one.
For a new home, this is what G4/AS1 asks for, as The Conduction Company reads it:
Bathrooms and kitchens. A room with a shower, bath or cooktop must have a mechanical extract fan. Paragraph 2.2.1.5 sets a flow rate, including the ducting, of at least 25 litres a second for a shower or bath and 50 litres a second for a cooktop.
Windows. MBIE's own comment on that paragraph says natural ventilation on its own is not adequate to remove the moisture from cooktops, showers and baths. That matches Jordan Statham's answer on opening windows above.
Laundries. A laundry with no external wall must be mechanically ventilated (paragraph 2.1.1.3).
One more rule sits behind all of this. Section 17 of the Building Act 2004 says all building work must comply with the Building Code, "whether or not a building consent is required in respect of that building work." So skipping consent does not mean skipping the Code.
Do any rules apply to garages and laundries?
For a garage, The Conduction Company's answer is a recommendation rather than a rule: we definitely recommend an extractor fan in a garage, so any moisture brought in on vehicles is not carried into the home.
For a laundry, The Conduction Company always recommends mechanical extraction, whether or not you are renovating. The dryer should be ducted directly to the outside of the home. We also recommend a separate extractor fan on the laundry ceiling if you do a lot of washing, or dry clothes on racks in there, so it can pull that moisture outside.
In short
The rules for ventilation in New Zealand depend on the house. A rental follows the healthy homes standards, and building work follows the Building Code, which for a new bathroom almost always means mechanical extraction. In a home you own and live in, the healthy homes standards do not apply, but the reasons behind them do. The Conduction Company's advice, in Jordan Statham's own words above, is to extract steam from bathrooms, kitchens, and laundries at its source and duct it to the outside, never into the ceiling void.
If you would like to know what your bathroom or kitchen needs, The Conduction Company fits range hoods and extraction fans across Auckland . What a whole-home system costs is covered in The Conduction Company's guide to home ventilation system costs . Happy to help.
Frequently asked questions
What ventilation do gas appliances need?
It depends on the type of gas appliance, says Jordan Statham, director of The Conduction Company. A flued gas fire ducts to the outside through its flue, a gas hob needs ventilation in the form of a range hood, and an outdoor gas califont vents straight to the outside. The Conduction Company does not do gas work, so check what a particular appliance needs with your gasfitter.
What are the ventilation standards in New Zealand?
For homes there are two. The Building Code, through clause G4 and MBIE's Acceptable Solution G4/AS1, applies to building work, and the healthy homes standards apply to rentals. The Conduction Company's advice for any home, rented or not, is extraction to the outside in bathrooms and kitchens.
What are the requirements for ventilation?
Under clause G4 of the Building Code, every space in a building needs enough outdoor air for how it is used, and the building needs a way to remove cooking fumes and moisture from bathing, showering, washing up and laundering from the rooms where they are made. The Conduction Company's practical version is to extract steam at its source and duct it outside, not into the ceiling void.
What are the requirements for ventilation in a building with NZ building code G4?
Clause G4 requires adequate ventilation for each space's occupancy and use. MBIE's Acceptable Solution G4/AS1, fifth edition, requires a mechanical extract fan in any room of a new home with a shower, bath or cooktop: at least 25 litres a second for a shower or bath and 50 for a cooktop, ducting included. The Conduction Company notes it is the standard way to comply, not the only one.
