Submitted by admin on Fri, 23/09/2011 - 3:52pmIn this montsh renewable installer magazine Brice Cross from GB Sol highlights the importance of best practice when it comes to Solar Pv Mountings
The majority of PV systems being installed at present are simple over-roof systems. The mounting systems will probably have been subjected to many loading and durability tests by the manufacturer and are likelyto perform well over the life of the system. However, there are many potential pitfalls with the fixings that attach to the structure, the structure itself and the weatherproofing of the penetrations in the roof covering.
There has been some recent media publicity highlighting dubious selling practices by some PV companies, so imagine the harm caused to our industry by stories of water running down the walls, or, even worse, PV panels falling into the gardens of houses. We must be vigilant to early signs of trouble to come, and act immediately as an industry to stamp out any bad practices.
The roof structure
An over-roof system attaches to the roof structure at a small number of discrete points. It is vital that the structure is suitable to takethese loads. The MCS 3002 installation standard specifies that the contractor must ensure the structure is capable of supporting the loads and most MCS assessors will want to see evidence of how the installer has verified this. There are indications that many installations are done ‘on the nod’ because the salesman/installation company wants to reduce cost rather than pay for a structural survey, yet MCS requires a structural survey if there is any doubt. The roof types ofmost concern are modern trussed roofs where they are designed down to the minimum factor of safety, and roofs that are old and may have had many modifications and repairs or may suffer from decay. The requirements are all clear to see, but there is some empirical evidence that the combination of inexperience, cost and time pressure is
leading to short cuts being taken.
Weatherproofing of penetrations
MCS 3002 requires that all penetrations are durably sealed. Worryingly there are reports of fixings being made by drilling through the slates/ tiles and using a sealant around a screwed fixing. This is explicitly forbidden under MCS, yet there is no policing of the practices being used by the installers, or indeed their sub-contractors. The focus of the assessment / surveillance visits is primarily on the documentation and processes, should we be considering some methods of regularly checking how installers are meeting this important requirement?
Integrated PV panel mounting systems and solar tiles/slates have significant advantages over the bolt-on systems in these respects.
The installer has the ability to verify the integrity of the roof structure during installation and also there is a much reduced chance of water ingress through the engineered flashing systems rather than site sealing of penetrations.
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