Our Ballarat design has a bedroom with mostly fixed glazing and one small awning window. The building surveyor says the room fails ventilation. How much openable area does a habitable room need, and can a door to the hallway or a ceiling fan make up the difference?

The surveyor is right, and the reason is that your fixed glazing counts for nothing. A habitable room needs an openable ventilating area of at least 5% of its floor area, and only the part of a window that actually opens is counted. [1]

How the 5% is measured. The ventilating area must be provided by openings, windows, doors or other devices that can be opened. [1] For a window, only the openable sash counts, whatever the window type (awning, casement or sliding) and regardless of any restriction on the sash. [2] So your large fixed panes add nothing, and the single small awning sash has to reach 5% of the bedroom floor area on its own, or you borrow ventilation from next door.

The hallway door can make up the difference, under three conditions. Ventilation may come through a door to an adjoining room, your hallway, if all of these hold: [1]

• neither the bedroom nor the hallway is a sanitary compartment;
• the door or opening between them has a ventilating area of at least 5% of the bedroom's floor area; and
• the hallway has its own window, opening or door with a ventilating area of at least 5% of the combined floor area of both rooms.

Where the bedroom also gets some direct ventilation from the awning window, the borrowed areas may be reduced to suit, using the method in Figure 10.6.2. [2] The catch is that the hallway must ultimately open to outside air, such as a court, a space open to the sky or a verandah. A door into an internal hallway that dead-ends does not satisfy the chain. [1]

A ceiling fan cannot. The only mechanical alternative in this Part is for a sanitary compartment, laundry, kitchen or bathroom, not a bedroom, and it means exhaust or mechanical ventilation, not a fan. [1] Ceiling fans sit under the thermal comfort provisions in Part 13.5, which do not count as a ventilation device for a habitable room. Nothing in the ventilation provisions lets a fan make up a shortfall. [1]

One exemption, which does not help here. The rule does not apply to specialised spaces occupied neither frequently nor for long, such as a pantry, walk-in robe or store. [2] A bedroom is a habitable room occupied for extended periods, so it is not exempt.

Edition note. Victoria is on NCC 2025 as the sole edition since 1 May 2026. The 5% figure, the openable-sash measurement and the borrowed-ventilation method are materially unchanged from NCC 2022; NCC 2025 adds the explicit specialised-room exemption. [3]

Practical next step: get the openable sash area of the awning window and compare it with 5% of the bedroom floor area. If it falls short, either enlarge the openable sash or detail a compliant hallway door path, with the hallway's own opening sized to 5% of both rooms combined.