Written by Mathias Aarre Maehlum, Engineering student from Norway
Both green roofs and solar panels have a wide array of benefits on their own. New research suggests that there is a synergistic effect when the two are used in combination. What exactly is this effect and what can I do to reap the benefits?
Green roofs, often called “living roofs”, are typically used to absorb rainwater, provide extra insulation, and to help mitigate the heat island effect. The end result is not only a vegetated roof that looks great (especially in non-urban off-grid homes), but in most cases also lower energy bills.
A 2012 study revealed that green roofs on their own were able to reduce the annual energy demand in some buildings by as much as 6%.
Not everyone is familiar with the benefits that come with residential solar power. With new smart financing plans, e.g. leasing and power purchase agreements (PPAs), homeowners can attach solar panels onto their roof for as little as zero upfront costs – and start saving from day 1. In an off-grid situation, solar panels are often not installed in order to lower energy bills, but sometimes the most feasible (or the only) means of generating power to fill electrical needs.
The neat thing about green roofs is lowering of ambient air caused by plants that through evaporation. Solar panels happen to perform better under cooler conditions, which is why several studies have been launched to investigate if green roofs were able to boost the power output of solar panels.
Researches from Bronx Design and Construction Academy are currently experimenting with smaller-scale green roof and solar panel systems in order to figure out how much of a synergistic effect there really is. According to their current data, solar panels yield as much as 3% higher efficiency rates if they are placed on top of green roofs.
Another way green roofs are thought to influence performance of solar cells is by removing pollutants and dust from the air. According to American Solar Energy Society (ASES), green roofs induce a total performance boost in solar panels of as much as 16%.
The thing with these numbers is that they are heavily reliant on what type of building, vegetation and solar panel is investigated – which is why the two studies have very different results. The bottom line is that green roofs help solar panels perform better at least to some extent, which will lower solar panels cost in the long run. This on top of all the other benefits of green roofs and solar panels will likely justify the extra costs.