The Healthy Homes ventilation standard, explained

A New Zealand household puts litres of moisture into its air every day, cooking, showers, breathing, drying washing. The ventilation standard is about giving that moisture a way out before it becomes mould on a ceiling. It has two halves: openable windows in the living spaces, and extractor fans in the rooms that make the most steam.

Windows that open

Habitable rooms, bedrooms, living rooms, dining rooms, kitchens, need windows or doors that open to the outside, with a total openable area meeting a minimum proportion of the room's floor area. The details and figures sit on tenancy.govt.nz; the practical check is simpler: does every habitable room have openings to outside air, and do they actually open, or has paint, swelling or a broken latch quietly sealed them?

Fans where the steam is

Kitchens and bathrooms need mechanical extraction venting to the outside. Two failure modes cover most non-compliance. The first is the fan that vents into the roof cavity, moving the moisture problem somewhere worse, extraction has to reach outdoor air. The second is the fan that spins without extracting, clogged, undersized or dead. Newer installations also carry minimum performance requirements, sized in the official guidance by duct diameter or flow rate.

• Run every fan and confirm the flap or vent outlet moves on the outside of the building.
• The toilet-paper test is honest: a square held to the grille should hold itself there while the fan runs.
• Check range hoods are ducted outside, recirculating hoods that just filter and return air do not vent moisture anywhere.

The habits half

Hardware is the landlord's half of ventilation; habits are the household's. A compliant house can still grow mould if it is never aired and washing dries in the lounge all winter. The most durable setup pairs compliant extraction with a short, friendly note in the tenancy pack about running fans and cracking windows, and a maintenance channel where a dead fan gets reported the week it dies rather than the month mould appears.

Evidence worth keeping

Fan make, model and specifications, installation invoices, and a simple dated note of which rooms have which openable windows. If a fan is replaced, file the new invoice against the property, the ventilation section of a compliance statement is exactly these facts in order.