Panel curtain walls for commercial high-rise façades have been popular for some time. Stefan Brey, senior engineer with BGE Facades, says the main reasons are to minimise site labour and to speed up installation. “There’s a great deal of design freedom with panelised systems because panels can be made into many different shapes and forms with various attachments and treatments that you can work with,” he says.
While there is a general trend towards the increased use of glass in commercial high-rise façades, panel cladding systems are typically used in low-rise commercial buildings. “But often, it isn’t going to be an either/or decision. Both panelised cladding systems and energy efficient glazing options can work together in the same building,” Brey says. “A polyurethane sandwich panel 100 mm wide is always going to perform better than a window which normally has, at best, two pieces of glass. But this isn’t comparing apples with apples. You need windows in a building.”
Abhi Qazi, consultant engineer with HH Roberston, says the use of panel façades instead of glass comes down to architectural decisions based on the application, and aesthetics. “Trespa panels provide a colourful appearance and privacy, while glass provides transparency for light and views,” Qazi says.
“Generally, 8 mm, 10 mm and 13 mm panels are used, depending on the design and application. The panels are usually screwed to the secondary structure (top hats, etc) or installed using a proprietary concealed fixing arrangement. In either case, panels can be easily removed and replaced,” he says.
Trespa has a range of finishes incorporated into its products at the time of manufacture. The panels are not designed to be painted and are rigid, but some curved panels are available to provide three dimensional effects and rounded corners. Trespa has ISO 14001 accreditation for its integrated environmental management, with Trespa Meteon made from wood chips impregnated in thermosetting resins. Eighty-five per cent of the raw materials used are renewable.
CSR developed Commercial ExpressWall for commercial and industrial buildings. Its lightweight panel-based system, ExpressPanel, is a 9 mm thick, primarily compressed fibre reinforced cement sheet which has a mass of 17 kg per m2 and comes in sizes up to 3m. ExpressWall panels are fixed to the building frame on ExpressWall top hats at the vertical edges and by intermediate top hats between edges. Gaskets are used to seal vertical and horizontal joints and to accommodate building movement. The system can be used to conceal most common structural materials such as masonry, pre-cast concrete or steel and timber stud framing.
Michael Ryan, manager of CSR’s Designlink service, says the system uses durable gaskets, and the framing has wide surfaces for generous fixing tolerance. “The system has great design flexibility. The lightweight panels can be arranged in stack or stretcher bond patterns, can be rotated from vertical and are suitable for curvatures down to a 10m radius,” Ryan says.
James Hardie’s ExoTec and ComTex are lightweight commercial façade panel and fixing systems. Both have been added to the Ecospecifier database and use sustainable plantation grown timber and low toxicity materials (they are composed of Portland cement, ground sand, cellulose fibre and water).
Anthony Milostic, national technical support manager at James Hardie Australia and Asia, says the boards are screw-fixed to zincalume top hats. ExoTec provides an expressed joint panel appearance for building façades, fascias and soffits and can coated with a variety of finishes, including site-applied textures. “ExoTec has exposed fastener and concealed options available. As the sheet joints are expressed and not set, the panels can be easily removed if damaged,” Milostic says.
“While ComTex has only the concealed fastener option, ComTex façade panels can also be removed. However, as the sheet joints are set, it may mean having to texture coat the affected area. ComTex accepts a high build acrylic coating which is applied using a trowel by an approved texture coat applicator to produce a lightweight rendered look. It can be used to hide building elements such as concrete columns and slab edges.”
Weathering and maintenance considerations
Ryan says part of the CSR ExpressWall façade’s appeal is its durability. “ExpressWall has been tested in cyclonic wind conditions, so it's suitable for exposed applications. It also has excellent weather resistance, having passed the Australian standard tests for water penetration by static and cyclic pressure.
“It’s immune to permanent water damage over long-term exposure. It won’t rot, burn or corrode and it’s unaffected by termites, air, steam, salt and sunlight. It’s a low maintenance system, but even if a panel is damaged, the simplicity of the system means that it can be easily replaced.”
According to Milostic, ExoTec and Comtex have been tested to withstand wind pressure up to 7 kPa, and the ExoTec façade panel has demonstrated resistance to permanent moisture-induced deterioration by passing tests in accordance with AS/NZS 2908.2.“The ExoTec façade panels are fully sealed on all six sides to help create a stable board, while the ComTex façade panel is coated with a high quality primer on all six sides to help minimise moisture ingress into the board prior to texture coat application,” he says.
While panel systems are generally a low-maintenance option, the extent and nature of maintenance required will depend on the product, the climate and the exposure of the building. Some panel types will absorb moisture, but installing them on top hats creates an air gap between the cladding and the sub frame. This is considered best building practice, and with adequate air flow, it can allow trapped moisture in the cavity to dry out.
