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Solar PV Knowledge Bank

Introduction to Solar PV Mounting Systems

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solar pv mounting systems

Which solar PV mounting systems does Spirit use?mounting_1.jpg

To give you and us peace of mind, we always use high quality accredited products. We do not buy pre-assembled kits; instead we source components individually ensuring we can always buy at the best prices. The following should be taken as a guide only; if you are set on one particular mounting system we can usually source and install it for you.

Compliance: Building Regulations and MCS 

It is important that your mounting systems lasts as long as your solar system - in other words 20 to 30 years minimum. For this to be the case it needs to weatherproof, durable and utilise secure fixings. Furthermore, it is important that the system complies with Building Regulations. The installation must not compromise the structural integrity or the fire safety of the building.

In order to qualify for the Feed-in Tariff, solar systems sized below 50kWp have always had to comply with the Microgeneration Certification Scheme (MCS).  In 2016, MCS also introduced a specific mounting system certification standard (MCS012) to set standards for Building Regulations compliance (durability, weather tightness and fire resistance).  

As part of our product selection process, we check our mounting systems acheive the necessary compliance.

Sloping Roofs: On-roof, in-roof or solar tiles?

There are three ways of installing solar on a tiled roof:

  • by attaching solar panels to the roof using “on-roof” mounting brackets which sit above the tiles;
  • by removing tiles in the area in which the panels are to go, and mounting the panels directly onto the battens and rafters using “in-roof” mounting brackets;
  • by installing solar tiles directly onto the roof.

In addition a system can be installed on a flat roofor it can be ground mounted.  For more information on in-roof solar PV mounting systems, see our dedicated in-roof page.

Most people are installing systems to their existing house (‘retrofit’) and choose to attach panels onto the roof using mounting brackets.

For new build or re-roof situations, or where there may be an issue with planning (e.g. a conservation area), an in-roof mounting system or solar roof tiles may be the solution of choice.

In-roof systems use the same panels as on-roof systems. The only difference is that the panels are mounted on the battens/rafters, not on the tiles (usually with a metal tray backing between the panels and the rafters). The roofer will then tile up to the panels, often using lead flashing to make a tight seal around the panels.

In general we don’t recommend in-roof systems for existing roofs, for several reasons:

  • Customers often believe the top of the panels will sit flush with the tiles. This is not the case – usually tiles are a few centimetres thick whereas the brackets and panels stand 11cm off the rafters. So unless the rafters around the PV system have been deliberately built up (as could be the case with a new roof) the tiles will not sit flush with the roof.
  • The performance of the system will be reduced by around 3% relative to an on-roof system due to the fact that to operate more efficiently, panels need a gap behind them for ventilation. The in-roof system doesn’t provide this ventilation and the performance of the system is compromised as a result.
  • In order to create a watertight seal between the system and the surrounding tiles, lead flashing usually needs to be used. This is often ugly and defeats the point of using an in roof system in the first place which is usually to create an unobtrusive system blending with the rest of the roof.

If you want your system to sit flush with the surrounding tiles and to blend seamlessly into the roof, you may prefer to use solar roof tiles. These are much more expensive than an on-roof or in-roof systems, but could be a better bet if you are particularly worried about aesthetics.

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Solar panels with on-roof mounting brackets

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Roof intergrated solar tiles

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Solar panels with in-roof mounting brackets

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Ground mounted installation

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Flat roof installation

 

Flat roof solar

We have written a page dedicated to solar panels on a flat roof.

To many people it seems that flat roofs should offer a far simpler starting point for a solar system than sloping roofs. In some ways that's true, but there are a number of issues that need to be taken into account:

  • Requirement for planning permission.
  • Flat roof systems take up more space per kW than sloping roof system.
  • Flat roof solar mounting is usually 'free-standing' on the roof. The mounting frames are not secured to the roof and therefore the system has to be weighted down using ballast. The structure of the roof needs to be able to support the ballast.
  • If the system is fixed to the roof, it is important to check the impact on the roof warranty and to ensure water tightness is maintained. 
  • Optimal mounting angle and orientation.

Click here to read more.

 

Which should I choose: roof mounted or ground mounted?

Roof mounted systems work well because the space cannot be used for any other purpose and planning permission is either unnecessary (see planning requirements) or is relatively easy to obtain, unless the building is listed or in a conservation area.

However roofs can be problematic from a structural point of view as the loads imposed by the system can be significant (both down weight and ‘wind uplift’). Many roofs are not over engineered: they are not made to take additional loads that were never envisaged at the design stage. In addition the roof structure or covering may present a problem. Warm roofs are sometimes problematic, as are roofs containing asbestos.

Ground mounted systems are ideal where space is not limited and there is an easy cable route back to the incoming electricity supply. They can be orientated for maximum output and are often looked on favourably by planning departments where a roof mounted system might fail (for example on a listed building).