Photovoltaic Panels

( this is a complex subject and there are multiple issues - we will be adding other points as time and circumstance permit )

Simply adding PV Panels to your existing roof is not as simple as just instructing an installer. Sadly, many have jumped on this band wagon without having any technical knowledge or fully comprehend the implications of what they are doing.

We are already seeing some very costly nightmares occurring, Some resulting in new roofs having to be installed which is further extended by having to comply with Current Building Regulations..

 

PLANNING & BUILDING REGS

Do you require A planning application and Building regulation approval -- chances are the answer is ~ YES. Beware, some installations have not gone through this process.

The implications of adding PV Panels to your roof are covered in many sections of the building regulations.

 

Structural

The first and probably main consideration is one of the existing structure to support the additional weight. A PV panel system will add circa 20 kg/ sq m to your roof. Very few existing buildings can accept this without major structural modifications. Remember, we are not just considering purlins here, but also the main portal members too. Some roof build ups may not support the additional weight either. ( e.g. spacer systems )

It is essential that a Structural Engineer is used to establish the suitability of your building. These calculations will ( should ) be sought by the AI / BCO anyway.

 

Invalidating Warranty

There is every chance that by installing PV panels on a roof that you may invalidate A confidex ( or other ) warranty. If is essential to clarify with the supplier if their or their suppliers warranties are effected.

 

Rooflights

These can cause a serious H&S problem for your installers. Even if your rooflights are described as " Walkable " or " Non fragile " they should not be stepped upon.

Many " Non Fragile" rooflights are only non fragile when new. Even those that are non fragile for 25 years, must be installed correctly. The Longevity of the fixing screws will also have a part to play. If carbon screws are used ( warranty 10 to 12 years ) and your roof is say 15 years old -- you are taking a very big risk.

If the installer has allowed the lower sheet to provide the non fragility, then the outer sheet is unlikely to support a person and will at the very least break. Probably giving the installer a serious scare - if not heart attack

When designing the PV Panel layout consider also how maintenance is to be undertaken. Can your workman walk from eaves to ridge without walking over a rooflight or PV Panel? Will not having access to your main roof prevent you from inspecting your roof and thereby invalidating any manufacturer's warranty ? ,

 

Type of Roof and how the PV system is fixed

There are many types of profiles and build ups of industrial roofs. For now we will only deal with the metal forms. i.e Composite, Standing seam and Built up

Mostly of these are also available in steel and aluminium, but other metals complicate the issue further.

The type, profile and material of the roof will greatly determine how your PV panels should be fixed. Most PV supporting members are fabricated in aluminium, This should not come into contact with steel sheet ( even if it is coated )

Subject to wind loading calculations these supports should be fixed through to the purlins or spacer bars ( This is not practical with aluminium sheets ). Some systems are designed to attach the outer skin only - but be aware they are usually designed for 0.7mm thick sheets. Not all roofsheets are a minimum of 0.7mm thick, most especially those used with composite panels.

The fixings used must be sealed. Simply allowing the screw to penetrate a roofsheet will not usually form a water tight attachment. (the thread of a screw will allow water to pass) and under no circumstances would we recommend that such fixing is used on a rooflight of any type.

 

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