The updated Condensation Management provisions in NCC 2025 include new requirements regarding wall ventilation. Building in Victoria is now covered under the new NCC 2025 provisions. Other states are following in mid 2027. Section 10.8.1 was previously focused solely on insulation – but now includes ventilation requirements for walls which have been impacted adversely in some situations in cooler climate zones.
One of the new requirements is the inclusion of mandatory drained and vented wall cavities in the cooler climate zones 6, 7 and 8 in external walls without a pliable building membrane. The cavity must be a minimum of 12mm in depth – using cavity battens, spacers or the like. There are some exclusions – such as single skin brick or panel walls, in insulated sandwich panels are used – or if the wall does not form part of the building envelope.
Additionally, in order to provide drainage and ventilation, open areas of at least 1000/mm2 must be provided at the top and bottom of a wall cavity – or at each storey if the cavity is closed off.
For brick masonry walls, there are several options for architects and builders. Weep vents is one – however with small openings from weep vents, depending on the vent it may be required to insert weep vents almost between every brick in a layer of bricks. If the building is in a bushfire zone, BAL rated vents will be required and will further reduce open area. Another option is traditional stainless steel or galvanised steel sub floor vents. This is probably the easiest and most cost efficient approach. Vents come in different sizes and designs and come with and without mesh. Many BAL-40 compliant models are available.
The sub floor ventilation requirements specified in 6.2.1 have not changed between NCC 2022 and NCC 2025. These would apply in addition to the new 10.8.1 provisions should a building with a sub floor be located in climate zone 6, 7 or 8.
Additionally, there are changes to the 10.8.3 provisions which covers ventilation of roof spaces. This also only applies in the same climate zones (6, 7 and 8) that have new regulations regarding wall venting detailed above. We will cover this in more detail a future article.