Green Roofs May Boost Efficiency Of Solar Panels

It’s no surprise that having both a green roof and a solar panel array on a building is a great way to double down on reducing energy bills for property owners. Two recent studies, however, raised some eyebrows by indicating that the plants on a green roof may actually improve the performance of the photovoltaic solar cells themselves.

By absorbing rainwater and on rooftops and enhancing water evaporation, the plants in a green, or “living,” roof can reduce the ambient air temperature and mitigate the heat island effect on rooftops. In addition to providing natural insulation for buildings, the plants also create a better environment for solar cells, which perform best at lower temperatures.

Green Roof Solar

Image via Bronx Design and Construction Academy

According to preliminary research being conducted by the Bronx Design and Construction Academy, the efficiency rates for a solar array on a green roof are 3 percent higher than a solar array on a conventional rooftop.

The students and a professor at the Bronx Academy who conducted the Green Roof Integrated Photovoltaic Canopy experiment submitted a $100,000 grant through the Zayed Future Energy Prize last summer and are currently one of the top two finalists in the Americas region. The students have been invited to Abu Dhabi to present their findings at the annual World Future Energy Summit. The winners of the Zayed Future Energy Prize will be announced on Jan. 15, 2013.

Meanwhile, a separate study conducted by the American Solar Energy Society (ASES) suggests an even more synergistic relationship between green roofs and solar panels. Living roofs, the ASES researchers found, can also improve solar cell performance by filtering out pollutants and dust from the surrounding air that can interfere in the photovoltaic process. Operating a green roof in conjunction with a solar array, the study found, can boost solar panel performance by as much as 16 percent.

The wide variation in the results of the two studies has to do with differences in the types of solar cells being used, the plants that are included in the green roof ecosystem and the materials in the rooftops. However, both studies provide encouraging data that suggest a synergistic connection between living roofs and solar panels.

Randy Woods is a Seattle-based writer and editor with 20+ years of experience in the business publishing world. A former managing editor of Seattle Business, iSixSigma, Claims and Waste Age magazines, he has covered topics that include newspaper publishing, entrepreneurism, green businesses, insurance, environmental protection and garbage hauling (yes, really). He also contributes to the Career Center Blog for The Seattle Times and edits a photography magazine called PhotoMedia. When not working, he likes to hide out in Seattle movie theaters and attend film festivals—even on sunny days.


  • Reply December 9, 2012

    Anjum Husain

    Wonderful!…thinking green on green

  • Reply January 9, 2013

    Joerg Breuning

    Combining Solar/PV is not new for European
    Countries. I personally installed my first project of this kind in 1995 on the
    Zeppelin Carré in Stuttgart, Germany. This combined system is still performing
    well. The currently largest Green Roof Solar project (over 400,000 sft) is also there and a year ago we reported about
    that on our blog at

    The system in the picture above is a Sun-RootTM
    system and this project is not in the Bronx. This system is the only system on
    the market that actually utilizes the run-off of the solar panels for
    irrigation under the panels and additional evapotranspiration. In other words
    this is the only combined system where both systems have a synergetic effect of
    each other.

    The system will be installed without roof
    penetration and is eligible for stormwater credits AND Solar credits at the
    same time. The costs are comparable and in same case lower than other ballasted
    Solar systems without Green Roof.

    As a matter of fact there is only one fully functioning,
    non-penetrating and synergetic integrated Solar-Green Roof project in entire
    North America. Green Roof Technology /
    Green Roof Service LLC are the market leader in this technology in Northern
    America. Note: Some of the links in the article of Randy Woods are potentially misleading.

Leave a Reply