Expert Advice
Frank DiStefano

Q: Hi Bill, I’m currently working on an extension to my home. I’m intending to use a vapour-permeable membrane, cladded with timber shiplap boards. Is there anything else I can do to help reduce condensation in the house? Thanks. (Mick, Eltham)

A: You can’t undervalue the importance of a vapour-permeable barrier, it is vital in creating a healthy home. The membrane is there to allow water vapour that has built up in the home to pass through walls and ceilings and exit the home. It doesn’t allow any moisture to enter and reduces the risk of condensation. Condensation build-up can lead to moulds, rot and early decay of structural timbers. Kitchen and Bathrooms are commonly susceptible to high humidity, which is unable to escape or dry and can result in mould stained areas and damp odours.

Changes to theNational Construction Code NCC2019 Volume 2-Ventilation of Roof Spaces’ have introduced a new section titled ‘Condensation Management’. It may not be enough to only vent your exhaust fans into your roof cavity. A compliant solution is to install Bradford Natural Ventilators in conjunction with Eave Vents. This has added benefits of heat and moisture management for the home. Alternatively, exhaust fans must be discharged directly or via a shaft or duct to the outdoor air.

I would also recommend fixing your external cladding to timber battens. This creates a cavity between the back of the cladding and the sarking membrane. It provides a drainage path for moisture and a ventilation area, allowing any condensation to dry. Don’t forget to install your timber cladding as per the suggested guidelines. This will ensure the best performance for your cladding.

For more information on Vapour Permeable Barriers and Roof Ventilators, please speak to your Bowens representative or visit your nearest Bowens store.

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