Repair Systems — 07
Subfloor Ventilation
Technical product reference for terracotta airbrick, aluminium vent and mechanical subfloor fan systems for subfloor ventilation improvement and mould control in Australian Class 2 strata apartment buildings.
What are subfloor ventilation systems?
Subfloor ventilation is the supply of fresh air to the underfloor space beneath suspended timber floor buildings. Inadequate subfloor ventilation is a leading cause of mould growth, timber decay and deteriorating air quality in Class 2 strata and single-dwelling buildings in Australia. Failure most commonly occurs through blocked or missing airbricks in the foundation wall perimeter, insufficient number of vent openings for the subfloor area, or enclosed subfloor geometries that prevent adequate cross-ventilation regardless of the number of passive openings.
Passive airbricks and louvre vents rely entirely on wind-driven cross-ventilation and are adequate where the subfloor space is open and unobstructed and the number of openings meets NCC minimums. Mechanical subfloor fans are required where passive ventilation cannot achieve adequate air changes — typically in enclosed, compartmentalised, or L-shaped subfloor spaces, or where active mould remediation is necessary. Mechanical fans draw moist air from the subfloor and exhaust it to the exterior, creating negative pressure that draws fresh air through passive inlet vents on opposing walls.
NCC Housing Provisions Part 6.2 sets minimum aggregate subfloor ventilation opening area requirements per metre of external wall, varying by climatic zone (2,000 to 6,000 mm²/m). Free area per vent unit must be checked against the manufacturer specification to confirm compliance with the applicable zone requirement. Where passive ventilation is inadequate, a mechanical engineer or licensed building consultant should determine the required number of mechanical fans, their placement, and the minimum passive inlet free area required to support the fan airflow.
Do not confuse with:
- Roof vents (mushroom vents, whirlybirds) — ventilate the roof space above the ceiling, not the subfloor space below the floor
- Carpark ventilation — mechanical ventilation systems for underground carparks, not domestic residential subfloor spaces
- Exhaust fans — bathroom, kitchen and laundry exhaust fans that exhaust internal air to the exterior, not subfloor ventilation systems
Product Reference
3 products — 3 brands — subfloor ventilation systems — scroll to view all
Austral Terracotta Airbrick
Terracotta louvred airbrick for subfloor ventilation
System Description
The Austral Terracotta Airbrick is a louvred terracotta vent unit designed to fit the standard Australian 230×76mm brick course opening, providing passive cross-ventilation to domestic subfloor spaces. Terracotta construction is non-corrosive, UV-stable and visually compatible with heritage and standard brick veneer buildings. The louvred face allows free passage of air while providing protection against vermin and water splash-back from the adjacent ground. Airbricks are installed at foundation wall level at spacings that must achieve the minimum aggregate ventilation opening area required by NCC Housing Provisions Part 6.2 for the applicable climate zone. Blocked or missing airbricks are a primary cause of subfloor moisture accumulation and mould growth in suspended timber floor buildings. Confirm current product range and availability with Austral Bricks before specifying.
Technical Properties
- Terracotta construction — non-corrosive, UV-stable and suitable for exposed subfloor base course installations
- Standard 230×76mm brick course size — fits standard Australian brick veneer foundation wall openings without cutting or adapters
- Louvred face provides passive air passage while restricting vermin entry and direct water splash-back
Limitations
- Passive only — cannot overcome inadequate cross-ventilation in enclosed or complex subfloor geometries — mechanical supplementation may be required
- Terracotta is brittle — handle carefully during installation — replace cracked units before installation
- Colour and texture variation is inherent in terracotta products — confirm visual match with existing brickwork before ordering
PROCUREMENT SOURCES
Confirm suitability with the current manufacturer TDS before specifying or applying.
System Description
The Ventis Aluminium Subfloor Louvre Vent is a pressed aluminium passive ventilation louvre designed for installation in subfloor foundation wall openings at standard brick course dimensions. Aluminium construction provides superior corrosion resistance compared to steel alternatives and is well suited to coastal and high-humidity environments where terracotta is not specified or available. Available in mill finish or powder-coated colours to suit the building facade. The louvred face provides passive air passage and vermin exclusion. Ventis aluminium subfloor vents are widely used in residential and Class 2 strata remediation projects where existing terracotta airbricks have been damaged, blocked or removed. Confirm current product dimensions, free area ratings and available colours with Ventis before specifying.
Technical Properties
- Pressed aluminium construction — corrosion-resistant — suitable for coastal, high-humidity and subfloor environments
- Available in standard brick course sizes — replacement for terracotta or existing aluminium subfloor vent openings without structural modification
- Louvred face provides passive airflow and vermin exclusion simultaneously
Limitations
- Passive ventilation only — does not overcome inadequate cross-ventilation in enclosed or compartmentalised subfloor spaces
- Mill finish aluminium will oxidise in aggressive coastal environments — powder-coat finish recommended within 500m of saltwater
- Free area per unit must be checked against NCC and AS 1684 subfloor ventilation requirements — do not assume one vent per opening is sufficient
PROCUREMENT SOURCES
Confirm suitability with the current manufacturer TDS before specifying or applying.
System Description
TODO: owner confirm model name — Fantech offers 150mm mixed-flow inline fans for subfloor ventilation (current AU model: TD-500/150SIL per Fantech website). A 150mm mechanical fan designed for active subfloor ventilation where passive airbrick ventilation alone is insufficient to achieve adequate air changes. The fan draws moist air from the subfloor space and exhausts it to the exterior, creating negative pressure that draws fresh air through passive inlet vents on the opposite side of the subfloor. Suitable for installation in an existing 150mm vent opening in the foundation wall or through a new penetration cored through the perimeter wall. Mechanical subfloor ventilation is specified where subfloor geometry prevents adequate cross-ventilation by passive means — including enclosed or partially enclosed subfloor spaces, split-level configurations, or where mould growth is active. Confirm current product specifications, model name, wiring requirements and control options with Fantech before specifying.
Technical Properties
- 150mm centrifugal fan — provides active mechanical ventilation to subfloor spaces that cannot achieve adequate air changes by passive means
- Installs in standard 150mm subfloor vent opening or new core-drilled penetration — minimal structural impact on foundation wall
- Low-wattage motor — suitable for continuous or timer/humidity-controlled operation — low running cost
Limitations
- Electrical connection required — must be installed by a licensed electrician — add to cost plan accordingly
- Mechanical fan does not resolve moisture entry from plumbing leaks, rising damp or groundwater — address moisture source before installing fan
- Fan creates negative pressure in subfloor — passive inlet vents on opposing walls must be clear and adequate in free area to support airflow
PROCUREMENT SOURCES
Confirm suitability with the current manufacturer TDS before specifying or applying.
System Comparison
Side-by-side technical comparison of subfloor ventilation products for domestic and Class 2 strata buildings. Confirm current product specifications with manufacturer TDS.
| Product | Brand | Type | Material | Vent mode | Size standard | Primary use |
|---|---|---|---|---|---|---|
| Austral Terracotta Airbrick | Austral Bricks | Louvred airbrick | Terracotta | Passive | 230×76mm brick course | Subfloor ventilation — heritage and standard brick veneer buildings |
| Ventis Aluminium Subfloor Louvre Vent | Ventis | Louvred vent | Pressed aluminium | Passive | Brick course sizes | Subfloor ventilation — replacement and new — coastal and standard environments |
| TODO: confirm — Fantech 150mm subfloor fan (model name TBC) | Fantech | Mixed-flow fan | Polymer / metal | Mechanical (active) | 150mm vent opening | Active subfloor ventilation — enclosed spaces, mould remediation |
Brand Equivalents
Subfloor ventilation product equivalents across brands active in Australian Class 2 strata remediation.
| System type | Austral Bricks | Ventis | Fantech |
|---|---|---|---|
| Terracotta airbrick (passive) | Terracotta Airbrick | — | — |
| Aluminium louvre vent (passive) | — | TODO: confirm product name | — |
| Mechanical subfloor fan | — | — | TODO: confirm model name |
Free area and mould risk
- Minimum subfloor ventilation free area must comply with NCC Housing Provisions Part 6.2 — minimum aggregate opening area varies by climate zone (2,000 to 6,000 mm²/m of wall) — confirm free area per unit against manufacturer data and the applicable zone requirement before specifying
- Mechanical fans are required where passive ventilation alone cannot achieve adequate cross-ventilation — for example, in enclosed subfloor spaces, L-shaped configurations, or where internal subfloor walls obstruct airflow
- Always address the source of moisture (plumbing leaks, rising damp, groundwater) before installing additional ventilation — fans alone will not resolve moisture entry from leaks and may accelerate corrosion of affected framing
Disclaimer
Information is general only. Subfloor ventilation design must comply with NCC and AS 1684. Product selection must be confirmed against subfloor area, air change requirements and the current manufacturer technical data sheet. Do not rely on this reference as a substitute for a mechanical engineer or licensed specialist.