Thermal characterization of different substrates under dried conditions for extensive green roofs

Extensive green roofs have been consolidated as good tools for passive energy saving systems in buildings,providing a more sustainable trend in the building field. However, as the growth of vegetation is variable depending on external factors such as weather conditions, disease, etc. the coverage of plants cannot ensure uniformity and consequently the 'shadow effect' cannot be considered as a constant parameter.On the other hand, materials used in substrate and drainage layers should provide a constant 'insulation effect' depending only on their physical properties and water content. In spite of this, the complexity of disaggregated materials used in internal layers of extensive green roofs implies a lack of real data about their thermal properties. The main objective of this study is to determine experimentally the physical properties of different disaggregated materials from the internal layers of extensive green roofs commonly used in Mediterranean climates. The experimentation presented in this paper allows to calculate the thermal transmittance in steady-state (U-value), the heat storage capacity (Cp), and the dynamic thermal response under a daily thermal oscillation.This work was partially funded by the Spanish government (ENE2015-64117-C5-1-R (MINECO/FEDER) and ULLE10-4E-1305), in collaboration with the company Buresinnova S.A (C/Roc Boronat 117-125, baixos 08018 Barcelona). Moreover, the research leading to these results has received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreement n° PIRSES-GA-2013-610692 (INNOSTORAGE) and from European Union’s Horizon 2020 research and innovation programme under grant agreement N° 657466 (INPATH-TES). The authors would like to thank the Catalan Government for the quality accreditation given to their research group (2014 SGR 123). Alvaro de Gracia would like to thank Ministerio de Economia y Competitividad de España for Grant Juan de la Cierva, FJCI-2014-19940. Finally, Julià Coma wants to thank the Departament d'Universitats, Recerca i Societat de la Informació de la Generalitat de;1; Catalunya for his research fellowship