Influence of substrate on green roof thermal performance

Abstract

Green roof (GR) substrates can be improved, seeking to increase the thermal characteristics, which influence the heat transmission on this layer. This article presents the results of one year of thermal monitoring of four modular GR with different substrates. The substrates assessed were local soil, commercial peat-based, and two alternative substrates obtained from the improvement of the local soil amended with the addition of biochar obtained through the Carbonized Rice Husk (CRH) and other components including construction waste. The local soil substrate presented lower thermal performance than the others, in relation to all evaluated indices: thermal amplitude, thermal damping, thermal delay and External Temperature Ratio. The substrates with the addition of CRH showed better results than the local soil and lower thermal performance than the commercial substrate being a potential alternative to more expensive substrates, as well to allocate and add value to this environmental liability. The results indicate the importance of the appropriate choice of substrate to improve GR’s thermal performance, as well as the observance of the state of development of the vegetation. The need for studies is pointed out for the development of substrates with properties that contribute to the better thermal performance of GRs.