Biosolar roofs: a sustainable solution for modern architecture
In an era where sustainability and energy efficiency are at the forefront of building design, architects and building owners are constantly looking for innovative solutions to meet environmental goals while offering economic advantages.
One such solution consists of “biosolar roofs”. This hybrid approach combines green roofing and solar energy generation, resulting in a versatile and eco-friendly roofing system. By integrating vegetation and solar panels, biosolar roofs provide energy production, thermal insulation, stormwater management and aesthetic appeal—all while contributing to the fight against global warming.
What are biosolar roofs?
A biosolar roof is basically a flat roof where a green roof (usually an extensive green roof) and a solar roofing system are both present. The solar panels can be installed either directly onto the green roof structure or alongside the vegetative layer.
The synergy between the two systems allows them to work together more effectively. For instance, the vegetation on the green roof helps cool down the surrounding air through evapotranspiration, mitigating what is known as the “urban heat island effect”. This also enhances the efficiency of the solar roof, as solar panels perform better in cooler temperatures. Conversely, solar panels provide partial shading to the vegetation, reducing the likelihood of plant stress due to excessive sun exposure. This mutual benefit helps create a more resilient and productive roofing system which can increase the longevity of the roof by 20 to 30 years, compared to traditional exposed flat roofs.
Enhanced solar performance
Biosolar roofs combine the numerous benefits of green roofs and solar roofing in one system. Green roofs cool down the urban microclimate, reduce air pollutants, improve biodiversity, enhance thermal insulation, protect the waterproofing membrane and improve stormwater management. Solar rooftop systems, on their side, offer an excellent way to generate clean, renewable energy.
In addition to these benefits, by combining solar panels with a green roof, the solar system can potentially produce more energy compared to traditional rooftop solar installations. How? The cooling effect of the vegetation layer helps maintain the efficiency of solar cells, which can become less efficient in high heat. Recent research* has shown that the presence of a green roofing system can significantly improve PV efficiency.
Design considerations for biosolar roofs
Generally speaking, a biosolar roof requires a stronger structural base than a standard flat roof due to the combined weight of the green roof and the solar roof. The type of green roof—extensive (lightweight with shallow, sedum style vegetation) or intensive (deeper soil with larger plants)—will also influence the load requirements.
Roof waterproofing membranes used in biosolar systems should be durable, lightweight and root-resistant to prevent damage from plant roots, and drainage layers should be installed to maintain proper moisture levels while avoiding waterlogging.
The type and orientation of the solar panels is also crucial in biosolar roof design. The arrangement must also consider the placement of the vegetation to ensure that the green roof receives adequate sunlight for plant growth. Some designs incorporate adjustable or raised solar panels, allowing for flexibility in angle and orientation. This approach can ensure that both the green roof and the solar panels function efficiently without one element negatively impacting the other.
Maintenance and access
A biosolar flat roof requires regular maintenance to ensure both the vegetation and the solar roofing system perform effectively. Incorporating safe access points and walkways into the roof design is therefore important to facilitate maintenance tasks.
Economic impact
The adoption of biosolar roofs offers significant long-term benefits. While the initial investment may be higher than a traditional flat roof, the combination of energy savings, reduced stormwater fees and potential incentives can result in a faster payback period. Additionally, a biosolar roof can contribute to increasing the property’s value.
Biosolar roofs represent a forward-thinking solution that allows the creation of buildings that are not only energy-efficient but also contribute to urban biodiversity and aesthetic enhancement. They also provide building owners a long-term investment in sustainability, and energy savings. As cities continue to grow and evolve, biosolar roofs stand as a testament to the potential of innovative design in creating a greener, more sustainable future.
Our EPDM and TPO single-ply roofing membranes are fully compatible with biosolar solutions. Get in touch with our roofing experts for specific advice.
*Green Roof & Solar Array, University of Technology Sydney (2021)