Improved condensation management in NCC 2022

We’ve introduced new provisions and made improvements to the existing provisions. It’s important you know what will impact your work.

This article outlines the changes in NCC 2022, which impact some of the Verification Methods and Deemed-to-Satisfy (DTS) Provisions.

These Verification Methods (F8V1 of Volume One (2019: FV6) and H4V5 of Volume Two (2019: V2.4.7)) provide flexible approaches to manage condensation in buildings.

Additional details are included to help practitioners complete condensation risk analyses. Specifically, the referenced Design Application Manual AIRAH DA07 provides modelling details that specialists can use to assess condensation risk in a building.

The Verification Methods now includes quantified targets for allowable condensation risk. A Mould Index of 3 (a measure of mould growth potential) must not be exceeded.

Well-sealed buildings with poor ventilation can have increased condensation risks.

However, buildings that are both well-sealed and adequately ventilated can be very effective at managing condensation.

Because of this, the building envelope sealing Verification Methods (H6V3 of Volume Two (2019: V2.6.2.3) and J1V4 of Volume One (2019: JV4)) are updated to include requirements for continuous ventilation in homes that are well-sealed.

These homes also need extra ventilation openings for combustion appliances, such as gas and wood-fired heaters.

Some materials used in walls can inadvertently trap moisture. To reduce this risk, the DTS Provisions are updated to require additional vapour permeance of some wall materials, such as building wrap or secondary insulation, depending on climate zone.

This may be achieved, for instance, by ensuring that a building wrap used in climate zone 5 is a class 3 vapour permeable membrane.

Exhausting air directly from areas where moisture is generated, such as kitchens, bathrooms and laundries, is one of the most effective measures for managing condensation in a home.

The DTS Provisions for exhaust systems include several new requirements:

1. Many exhaust systems commonly used in homes must be discharged to the outside of a building (e.g. instead of discharging into a roof space).
2. Exhaust systems installed in bathrooms or sanitary compartments, which don’t have sufficient access to outdoor air (e.g. via windows), must be controlled to turn on when the lights in the room are turned on. They are also required to continue to operate for 10 minutes after the lights are turned off.
3. Exhaust systems installed in bathrooms or sanitary compartments that don’t have sufficient access to outdoor air must be provided with make-up air from an adjacent room, like having an undercut to a separating door.

Roof spaces, particularly in cool climates, are often at increased risks from condensation. NCC 2022 requires roof spaces in climate zones 6, 7 and 8 to be provided with ventilation openings.

Concrete roofs and roof spaces in bushfire flame zones (BAL-FZ in AS 3959:2018) are not required to be provided with ventilation openings under the provisions.

The ABCB has published an updated “Condensation in Buildings” handbook that is available from the ABCB website. This provides further support to practitioners to use the new condensation management provisions in NCC 2022.

We’re also continuing to explore what other improvements can be introduced in the future.

This article was updated on 19/06/2023