Condensation build-up in roof and wall cavities can cause long-term aesthetic, health and structural problems in buildings if not managed properly.
The problem is caused by changes in temperatures. When the surface temperature falls below the dew point of the surrounding air, condensation in the form of water vapour will take place on the colder surface.
Generally, small quantities of condensation can be tolerated so long as it is given the opportunity to dry out. If not kept in check, condensation causes mould build-up on surfaces and in HVAC systems, and can result in plaster deformities. In severe cases it can cause damage to framing in the form warping and rotting.
Provisions under the National Construction Code (NCC) 2019 have removed ambiguity and outlined minimal requirements for residential buildings covering how much ventilation is needed and where it should be placed (Clause F6.4 NCC 2019 Volume One and 220.127.116.11 of NCC 2019 Volume Two).
A key ingredient in minimising condensation is to provide adequate ventilation to help extract moisture or allow it to escape naturally. In areas like kitchens, laundries and bathrooms, where water, steam and cold hard surfaces most often meet, extraction systems are important, particularly those that duct the moist air outside rather than into the roof.
While ducted extraction systems do a great job in removing steam from wet areas, installing roof-cavity ventilation will further reduce condensation, providing additional peace of mind.
As a leading producer of steel building products, Lysaght offers several roofventilation solutions, ranging from traditional turbine ventilators through to the VENT-A-ROOF® system. VENT-A-ROOF® is a concealed roof-ventilation system that uses the power of natural airflow. It’s installed under traditional ridges, hips and barges, making it extremely versatile and inconspicuous.
The use of insulation and how it’s installed can also assist to minimising condensation. In the roof space, insulation and membrane should be fitted so it doesn’t block ventilation paths. Roof-level insulation such as blanket and foil is also useful, particularly in cooler climates.
For architects, engineers and builders, Lysaght can assist in developing effective moisture-management solutions for buildings that will be clad with LYSAGHT® products.
Lysaght has produced a comprehensive Technical Guide and a supporting Product Application Bulletin as useful design and construction references for buildingindustry professionals.
The detailed recommendations contained therein take into account the building location’s climate zone, as well as the type of cladding used – this covers supported or unsupported cladding (ie: does the cladding need continuous support such as plywood, or can it free span between batten or purlin supports?) and whether it’s open or closed profile. ‘Open’ profile claddings are those that allow airflow; ‘closed’ profiles typically have closed ribs that won’t allow easy airflow.
Style of roof construction is also addressed: trussed and skillion roofs with self-supporting metal claddings or trussed and skillion roofs with supported metal claddings. NCC 2019 condensation requirements are also applicable to walling cavities, with similar principles applying, and are also covered in Lysaght’s reference materials.
To download Condensation Control in Australian buildings constructed with LYSAGHT® claddings visit https://professionals.lysaght.com/resources/manuals