Image source: Optigreen.
Those looking to make the greatest environmental benefit from their roof space may feel they should choose between solar panels and green roofs - but can you combine the two? Yes - though both systems need to be designed properly.
What is a green roof?
A green roof is a surface of living vegetation that sits in place of a traditional roof covering like tiles. While they provide added insulation for the building (both noise and heat), their main benefit is increasing local green space and biodiversity, which is particularly important in urban areas.
Green roofs are made from a layered system:
- a waterproof and root-resistant membrane,
- growing medium,
Typically they’re planted with sedum, a light and water-retaining plant that spreads outwards rather than upwards as it grows. A brown roof is left with bare soil, in which local plants can seed themselves. In the UK we get enough rainfall that extra watering isn’t required.
Can you have solar panels on a green roof?
You can install solar panels on a green roof. It’s called green roof PV or a biosolar roof system, where solar is designed to fit into the roof with specialist mounts. Compared to a regular flat roof PV installation, the panels are at a steeper angle (15° rather than 10°) and raised higher from the ground (about 0.5m at the lower end). This extra space allows vegetation to spread underneath the panels with access to light and moisture.
The PV mount is placed underneath the modules containing the growing medium (usually a mixture of gravel and soil). This provides enough weight to ballast the mount, without needing fixings that would penetrate the roof or waterproofing. For this reason the solar really needs to be installed alongside the green roof itself.
Benefits of green roof PV
A biosolar roof reaps rewards for both the bio and solar parts of the roof. Solar panels work more effectively at lower temperatures, and as plants release moisture through their leaves in a process called transpiration, they lower the ambient temperature!
On the other side, panels can actually increase biodiversity. They create areas of shade and concentrated moisture (though rain running off them), conditions which encourage varied plants across the roof. In turn this supports more diverse insect life.
Is a biosolar roof right for you?
If you’ve been weighing up green roofs vs solar panels, hopefully we’ve convinced you of the benefits of having both. But the system must be well designed - you don’t want plants overgrowing and shading your array or panel placement which hinders growth. Plus there are all the regular factors in play for maximising the potential solar generation through good design.
Luckily we have the experts you need here at Spirit. Get in touch today to discuss your project.