Quick answer
A rangehood that isn't extracting is nearly always a filter, a duct or an outlet problem — not a dead motor. The Healthy Homes ventilation standard requires a kitchen with a cooktop to have a rangehood venting to the outside, and anything installed on or after 1 July 2019 needs a minimum diameter including ducting of 150mm, or at least 50 litres per second. Every rental has had to comply since 1 July 2025. Wash the metal filters, follow the duct to confirm it reaches outside air uncrushed, and watch the external flap open. A recirculating hood doesn't meet the standard at all.
Key points
- The standard wants a rangehood venting outside, and for anything installed on or after 1 July 2019, 150mm including ducting or at least 50 litres per second.
- Every rental has had to comply since 1 July 2025 — the old 120-day runway is gone.
- Recirculating hoods don't meet the standard, however fresh the carbon filter is.
- Tenancy Services generally puts rangehood cleaning on the landlord where tools or technical knowledge are needed.
- A 150mm duct crushed flat across a truss still measures 150mm on the order form and still moves no air.
Extraction dies in four places, not one.
The call comes in winter. A tenant in a brick-and-tile in Papatoetoe reports black mould creeping up the wall behind the fridge, and the manager forwards a photo titled "ventilation?". The rangehood is there. It's ducted. It was ticked off on a compliance statement two tenancies ago. Somebody flicks it on, hears the motor, marks it working and moves on. Six weeks later the mould is back, because the motor was the only part still doing its job.
This is the servicing piece, not the buying piece. If you're still weighing a ducted hood against one pushing filtered air back into the room, the ducted versus recirculating question is settled before you reach this article. What follows is about the hoods you already own: what the regulations ask, why a compliant specification and a working extractor are different things, and what to check before a damp complaint becomes a Tribunal application.
What the ventilation standard actually asks for
The standard is short, and worth knowing by heart if you hold rentals. A kitchen with a cooktop needs a rangehood or extractor fan venting to the outside of the house. Anything installed on or after 1 July 2019 must have a minimum diameter including ducting of 150mm, or an exhaust capacity of at least 50 litres per second. Fans installed before 1 July 2019 have no minimum size, but must still vent outside and be in good working order — and when they pack it in, they're repaired or replaced to the current numbers.
Two details catch people out. "Including ducting" means the 150mm isn't the spigot on top of the hood — it's the duct. A 150mm outlet reduced to 125mm flexi above the cabinet is not a 150mm duct. The other is the openable window rule beside it: every habitable room needs an opening to the outside that fixes open, totalling at least 5% of that room's floor area. The kitchen counts. A sash painted shut in a Grey Lynn villa is not an openable window.
The deadline changed the mood. Every rental has had to comply since 1 July 2025; before that you had 120 days from the start of a new or renewed tenancy. That runway is gone. Across a portfolio, the wider Healthy Homes picture for kitchens covers the standards sitting around this one.
| Requirement | What the regulations ask | What to actually check |
|---|---|---|
| Extract to outside | Must vent outside. Recirculating systems don't qualify. | Follow the duct. Find the outlet from the ground; watch the flap move. |
| Installed on or after 1 July 2019 | 150mm minimum diameter including ducting, or at least 50 litres per second. | Measure the duct, not the hood spigot. Look for the reducer nobody mentioned. |
| Installed before 1 July 2019 | No minimum size, but must vent outside and be in good working order. On failure, repair or replace to current spec. | "Good working order" is the trap — it has to work now. |
| Openable windows | Every habitable room needs an opening to outside that fixes open, totalling at least 5% of floor area. | Test the stay. Painted-shut sashes are common in older stock. |
The paper test and the air test are not the same inspection
Here's the uncomfortable bit. The standard is written as a specification: duct diameter, litres per second, vents outside, installed after a date. You can satisfy every one of those with a hood moving almost nothing. Grease isn't mentioned in the regulations. Crushed flexi isn't mentioned. A specification test catches neither.
What catches them is everything around the standard — the duty to keep it in good working order, a tenant reporting condensation, an inspection report with a photo attached. Tenancy Services has published Tribunal outcomes where landlords paid exemplary damages over the healthy homes standards, including properties with no extractor fans at all. Missing is the easy case. A hood that's present and doing nothing is still a damp house.
Filters: the bit that's always the problem
Filters fail first and cost least to fix, which is exactly why they get ignored. Metal filters — aluminium mesh in most rental-grade hoods, stainless baffles in the better ones — are made to be washed and put back. They don't wear out. They clog, slowly, and the drop is gradual enough that nobody notices.
Manufacturers typically ask for a wash every month or three depending on the cooking, and a house that fries most nights sits at the short end. Most metal filters go through a dishwasher. There's a fire dimension too: Fire and Emergency New Zealand says one in four house fires start in the kitchen, unattended cooking is the leading cause, and its advice is to clean rangehood filters regularly. Grease-soaked mesh above a gas burner is a fuel load in the worst place.
| Filter type | Where you'll find it | Servicing | How it fails |
|---|---|---|---|
| Aluminium mesh | Most rental-grade slide-out and canopy hoods | Wash monthly to quarterly; usually dishwasher-safe | Packs solid with grease; airflow falls away unnoticed |
| Stainless baffle | Better canopies, commercial-style hoods | Same cycle, more forgiving between washes | Grease pools in the channels and drips onto the cooktop |
| Carbon / charcoal | Recirculating hoods only | Can't be washed; replaced every few months | Saturates silently; the hood runs and removes nothing |
Now the part most landlords have wrong. Tenancy Services' guidance is that where technical knowledge or specific tools are needed, or the filters aren't easily accessible, the landlord is generally required to maintain the device, including cleaning it. Tenants still owe reasonable cleanliness, and a slide-out mesh you can drop in the dishwasher is fair to expect them to handle. A fixed canopy filter needing a step and a screwdriver is your problem. Build it into the inspection cycle like any other item across a rental portfolio's maintenance programme.
Ducting: where extraction quietly dies
Filters are visible. Ducts aren't, which makes them the more expensive failure. The 150mm gets specified correctly on plenty of jobs that then get built badly. Flexible duct is the usual culprit — cheap, fast, and routinely installed at half its stretched length, coiled above the cabinet, or squashed flat across a truss.
None of that shows up in the kitchen. Laboratory work on compressed flexible duct has found the compression seen routinely in real installations can multiply the pressure drop several times over, with heavier compression pushing it close to ten times. Take the point rather than the exact figure: a hood rated well past 50 litres per second at the fan can deliver a fraction of that at the outlet. Rigid or semi-rigid duct, short and straight, is the difference between a spec sheet and air leaving the building.
Termination is its own category of sin. Ducts stopping short in the roof space. Ducts pointed at a soffit vent and left unattached. External flaps painted over, nailed by a gutter installer, or blocked by a bird's nest. Any of these means the fan works and the moisture stays — a defect to catch before handover, not eighteen months into a tenancy. It belongs on the checklist when you're refreshing a rental between tenancies.
Half the hoods I pull down are still running. They're just not connected to anything that ends outside.
Compliant on paper is not extracting in fact.
How to check a hood in five minutes
None of this replaces a proper airflow measurement. But five minutes finds most of what's wrong, and it beats ticking a box because you heard a motor.
- Pull the filters and hold them to the light. If you can't see through the mesh, the hood isn't extracting, whatever the spec says.
- Run it on high with a sheet of tissue against the filter opening. It should hold on its own. Flutter and drop means something downstream is choked.
- Find the external outlet from outside while it runs, and watch the flap. No outlet is the finding — write it down.
- Look at the duct above the top cupboard or through the ceiling hatch. Coiled flexi, sharp bends and reducers all cost airflow.
What goes wrong
- **The reducer nobody mentioned.** A 150mm spigot stepped down to 125mm flexi because that's what was on the van. Specified compliant, built non-compliant.
- **The duct that goes nowhere.** Terminated in the roof space, or aimed at a soffit vent and never fixed to it. Every hour it runs it pumps moisture into your ceiling.
- **The coil.** Three metres of flexi on a one-metre run, looped above the cabinet. Resistance rises, airflow falls, nobody sees it.
- **The over-specced hood on an under-specced duct.** A canopy sold on its extraction rate, hung on a long, tortured run. That number was measured at the fan, not your outlet.
- **The recirculating swap.** A dead ducted hood replaced with a cheap recirculating unit because it was in stock. That kitchen fails from that day.
What to ask before you sign anything
- Is the duct 150mm the whole way, or only at the hood? Get it in writing.
- Rigid, semi-rigid or flexible? If flexible, who confirms it's stretched and uncrushed at handover?
- Where does it terminate — soffit, wall or roof? Is there a photo from outside?
- Run length and how many bends? Short and straight beats big and rated.
- Are the filters washable metal, and is a spare set available across your models?
- Does the install date get recorded somewhere you'll find it in three years?
That last one sounds like admin, and it is — but it's the admin that settles an argument. Landlords must keep the records showing how they comply and produce them on request. A dated photo of the outlet beats a confident memory at a hearing. The same logic drives low-maintenance rental kitchen specification: pick what survives being ignored.
Where MTN fits
We're a kitchen manufacturer in East Tamaki, twenty-three years and better than two thousand kitchens in, and we supply and install under one contract and one invoice. That matters more here than it sounds. Ventilation is the classic seam between trades — the joiner hangs the hood, someone else runs the duct, someone else does the flashing, and each assumes the next owns the bit in the ceiling. Under one contract that gap doesn't exist.
Send the address list, the unit count and a rough scope — even a phone photo of the hood and the cupboard above it tells us most of what we need. You'll get a trade-priced number back inside 24 hours, no showroom loaded into it, and if the honest answer is "wash the filters and re-run the duct" rather than "replace the kitchen", that's the answer you'll get. Batch the properties and the economics shift again, as with a West Auckland portfolio upgrade. Confirm anything consent-related with your council or LBP; the Tenancy Services guidance is the source that counts.
Frequently asked questions
How often should rangehood filters be cleaned in a rental?
Manufacturers typically ask for metal filters to be washed between monthly and quarterly, and a household that fries most nights sits at the short end. Tie it to your inspection cycle rather than a calendar nobody reads. Aluminium mesh and stainless baffles are almost always dishwasher-safe, while carbon filters in recirculating hoods can't be washed and need replacing every few months.
Does a recirculating rangehood meet the Healthy Homes ventilation standard?
No. The standard requires the rangehood or extractor fan to vent to the outside of the house, and Tenancy Services is explicit that recirculating systems aren't suitable. A carbon filter takes some odour out and puts the moisture and heat straight back into the room, which is the opposite of the point. If a ducted hood has been swapped for a recirculating unit, that kitchen has been non-compliant since the day it happened.
Who has to clean the rangehood filter — the landlord or the tenant?
Tenancy Services' guidance is that the landlord is generally required to maintain ventilation systems, including cleaning, where technical knowledge or specific tools are needed or the filters aren't easily accessible. Tenants still owe reasonable cleanliness, so a slide-out mesh that drops in the dishwasher is fair to expect them to manage. A fixed canopy filter needing a step-ladder and a screwdriver is on you.
My rangehood is ducted but the kitchen still gets condensation. What's wrong?
Almost always the duct or the filter, in that order of expense. Check the duct is 150mm the whole way rather than reduced to 125mm flexi above the cabinet, that it isn't coiled or crushed where it crosses framing, and that it terminates outside rather than in the roof space. Then pull the filters and hold them to the light. A motor that runs perfectly can still move very little air.
Do I have to replace a rangehood installed before 1 July 2019?
Not automatically. Fans installed before 1 July 2019 have no minimum size or performance requirement, but must vent to the outside and be in good working order. The catch is what happens when one fails: it then has to be repaired, or replaced with a fan meeting the current requirements of 150mm including ducting or at least 50 litres per second. An old hood that still extracts can stay; one that's stopped working is a decision point.