An interesting approach to reduce building energy consumption is to use green roofs as a part of building envelope. However, many building designers ignore this opportunity as it is quite difficult to estimate the resulting energy saving. This paper provides results from an ongoing experimental research project that focuses on the thermal performance of extensive green roofs when buildings are in the cooling mode. The paper discusses the importance of green roofs and reviews previous research studies. In particular, this paper focuses on the role of plants for the heat flux reduction through the roof structure. The performance of the plant material was assessed in an environmental chamber by experiments with two samples, one with the plant material, and another one without the plant material. Overall, plants reduced the measured heat flux through the green roof sample by 40-50% compared to the roof sample without plants. In conclusion, plants have an important role in reducing the heat flux by regulating: (1) latent heat flux through better water management and additional water storage in the plant leaves/roots, and (2) sensible heat flux through additional shading provided by the plant leaves. Based on these results, future research will focus on thermal modeling of green roof including the role of plants.

Units: Dual