Solar heaters and photovoltaic (PV) panels: Considering electrochemical compatibility with the protective coatings on cladding

The current fiasco pertaining to the supply of electricity has led to an increase in the number of solar heaters and panels of photovoltaic (PV) cells 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. The most important of which is that the materials used to manufacture the heaters and PV cell panels, together with their support system, components and all attachments, including fasteners are electrochemically compatible with the protective coating on the cladding.

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

Equally important is that the solar collectors and PV cell panels must not be attached directly to the surface of metal cladding. A gap of approximately one hundred millimetres (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, subsequent rapid drying by the wind plus removal of any accumulated 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 heater or PV panels is washed by rain, failing which the underside of the units and surface of the cladding will need to be regularly washed by hose. This is very important in marine and polluted environments. The gap will also provide access for the maintenance and replacement of fasteners. This point is to be taken into account when deciding how framed PV cells are to be positioned.

Solar heaters and PV cell panels need to be attached to concealed-fix cladding in such a way so as not to impinge on the movement and effectiveness of the anchoring system. Most manufacturers provide details of approved systems.

All piping, cables, etc. are to be mounted on suitable brackets so as to avoid direct contact with the surface of the cladding. The contact surface remains wet plus allows 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 rain water. Under no circumstances is any wood based product to be in direct contact with the surface of the cladding.

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.