Roof integrated solar replaces the tiles or slates on the roof so the panels sit lower down in the roofline to look more like an intended part of the house and less like a bolt-on afterthought than above-roof rack-mounted systems.
The aesthetic benefits of roof integration are clear, but there are other benefits from going in-roof.
Solar panels should last thirty years or more. In this time it is highly likely that the roof covering will need either maintenance or replacement. An on-roof system will have tiles or slates behind the panels, so the solar system would need to be decommissioned and removed before a single tile can be replaced. A simple job that can be carried out from a roof ladder by a roofing contractor has become a significant task that requires scaffolding and the involvement of an electrician or solar installer. With roof integrated solar, there are no tiles behind the panels, so all roofing repairs can be carried out while leaving the solar system in place.
For new roofs or extensions to existing buildings, new regulations require that all tiles are fixed with nails or clips. This makes the task of fitting an above-roof solar system afterwards very difficult. Tiles may need to be broken to access the roof structure below and attach fixing brackets. Replacing removed tiles in accordance wiht the roof fixing specification is likely to require an adhesive bond between the replaced tile and the surrounding ones.
By contrast, roof integrated solar panels can be installed easily in a new roof. Solar specialists can fix the panels and flashings before the roofing contractors fix the roof covering around them.
When installing to an existing roof, integrated solar is often seen as more work than above-roof systems. However, the task of weathering around numerous fixing hooks can be time consuming. Removing a patch of tiles or slates does not take much longer, and provides spare roof tiles that are a perfect match for any future roof repairs.
Solar panels fixed above the roof offer a safe, sheltered area behind for birds to roost or nest. While this may at first sound like a good thing to do, householders with solar installations that have been colonised in this way have reported a number of drawbacks including noise and fouling of the panels, walls and paths below the nests. A small industry has sprung up to bird-proof above roof solar installations with spikes and mesh around the outside, further reducing their aesthetic appeal.
Clearly nests below the panels will reduce the free passage of cooling air behind solar PV panels increasing operating temperature and reducing energy yield (see next point).
A reason that is commonly given for opting for above-roof solar PV ahead of roof-integrated solar PV is that above-roof systems will operate at a lower temperature due to better ventilation (although see section above). Since solar PV power output falls as panel temperature rises the argument goes that roof integrated solar will have a lower energy yield. Viridian Solar and researchers from Cambridge Univeristy have examined this effect.The published research found that the reduction in energy yield was very small, of order only 3%.