With people becoming more and more aware of the scarcity of resources, as well as the importance of sustainable building, large numbers of solar collectors and photovoltaic (PV) panels are being installed on metal clad roofs.
“In order to ensure the continued performance of the cladding system and the durability of its protective coating, there are a number of points to be considered,” advises Dennis White, director of the South African Metal Cladding and Roofing Association (SAMCRA).

Here are his top tips:

1.    Compatible materials
The materials used to manufacture the heaters and PV panels, together with their support system, components and all attachments, including fasteners, must be electrochemically compatible with the protective coating on the metal cladding.

These units should not be installed on unpainted galvanised roofs. Runoff from components containing copper, lead, nickel and their alloys is incompatible with all metal cladding materials such as aluminium, stainless steel and all forms of painted cladding, and will result in premature perforation of the cladding.

2.    Leave a gap
The solar collectors and PV panels must not be attached directly to the surface of metal cladding. A gap of approximately 100mm (which will also be beneficial to the performance of PV panels) needs to be maintained to ensure the washing of the cladding beneath the units, rapid drying by the wind, plus removal of debris and airborne contaminants that accumulate between the units and cladding.

Units need to be located sufficiently downslope from the ridge to ensure the surface of the cladding covered by the solar collector or PV panels is washed by rain, and if not, the underside of the units and surface of the cladding will need to be regularly washed by hose. This is especially important in marine and polluted environments.

The gap is also necessary to provide access for the maintenance and replacement of fasteners. This point should be taken into account when deciding how framed PV cells are to be positioned and attached to roofs.

3.    Allow movement
Solar heaters and PV cell panels need to be attached to concealed-fix cladding in such a way that they don’t impinge on the thermal movement and effectiveness of the anchoring system of the cladding. Where panels are attached to the cladding via an aluminium support system provision has to be made to accommodate the differential in thermal movement between the two metals. Most cladding manufacturers provide details of approved systems for attaching items to their cladding profiles.

A rail installation on a metal roof. Courtesy of Safintra

4.    Use suitable brackets
All piping, cables and more are to be mounted on suitable brackets in order to avoid direct contact with the surface of the cladding. The contact surfaces remain wet and allow for the accumulation of corrosive elements, both of which will lead to the premature failure of the protective coating on the cladding. They may also affect the free flow of rainwater.

Under no circumstances can any wood-based product be in direct contact with the surface of the cladding. Failure of a coating due to such conditions is normally excluded from performance warrantees.

5.    Inspect the cladding and fasteners
Prior to the installation of a solar heater or PV cell panels, it is advisable to check the condition of the cladding surface plus all fasteners.

Full thanks and acknowledgement are given to SAMCRA for the information provided.

Caption main image: PV panels must not be attached directly to the surface of metal cladding. Courtesy of SAMCRA

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