Coconut fibre insulators: The hygrothermal behaviour in the case of green roofs Kristian Fabbri, Lamberto Tronchin ⇑ , Fabrizio Barbieri Department of Architecture, University of Bologna, Via dell’Università 50, I-47521 Cesena, FC, Italy highlights  Natural materials as coconut fibres are considered better that synthetic ones (like EPS) for environmental impact.  Coconut fibres could be used for green roofs in building constructions sector.  Coconut fibres have almost the same thermophysical characteristics of EPS.  Coconuts fibres have been found even better than EPS for their global functioning. article info Article history: Received 6 April 2020 Received in revised form 14 September 2020 Accepted 16 September 2020 Keywords: Green roofs CLT Insulating material Coconut fibreboards Hygrothermal behaviour abstract Coconut fibre insulators represent an insulating material considered as ‘‘exotic”, which clashes with the scepticism of his thermo-hygrometric behaviour, particularly in the case of covering technology such as green roofs, which is a technological solution often adopted in the case of sustainable buildings or nearly zero energy building. Green roofs represent a valid constructive solution with high thermal perfor- mances, adopted both in existing and new buildings. The purpose of the research regards the study of the thermo-hygrometric behaviour of the concrete (CLS) and Cross-Laminated Timber (CLT) slabs, insu- lated with coconut fibreboards (CF) such as an alternative of synthetic insulator, referred to 10 different green roofs scenarios. The results show that coconut fibre insulations are equally comparable to natural and synthetic materials, and the doubts for their applications, including the green roofs, are related to technological solutions for the implementation in the market and their diffusion between the buildings materials, rather than their hygrothermal features. Ó 2020 Elsevier Ltd. All rights reserved. 1. Introduction The Green roof is a recent technology for the building’s roofing that ensures high insulation and good thermal phase displacement. In most of the applications, the origin of the insulation materials adopted in the stratigraphy, are synthetic (e.g. EPS, etc.) or natural (e.g. wood fibre, wool glass, mineral wool, etc.). Between the natu- ral fibres, several products use ‘‘exotic” natural materials such as corn cobs, sheep wool, etc.. The coconut fibres, object of this research, are natural fibres with exotic material. In recent years, several Authors reported studies on green roofs, analysing the thermophysical properties and thermal behaviour of such insulators in different applications, considering buildings located in Europe, South America and in the Asian Countries, i.e. where the use of ‘‘exotic” materials is higher. In the following, an overview of some papers related to green roofs, the use of the exo- tic materials and the coconut fibres are reported. Tables 1 and 2 summarize the results of the studies. 1.1. Green roof Several papers have dealt with application and evaluation of green roofs and its thermal performance in: a) summer regime, b) winter regime, c) during the year. Tang and Zheng [1] in their research showed the dynamic properties of the roofs during the summer period, obtaining significative results about their effi- ciency for mitigating the indoor climate, while He et al. [2] in their paper showed the temperature differences between the green building envelope and the same roof but in absence of the vegeta- tion, underlying the importance of the vegetation. Cao et al. [3] also analysed the temperature difference of green roofs between inter- https://doi.org/10.1016/j.conbuildmat.2020.121026 0950-0618/Ó 2020 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. E-mail address: lamberto.tronchin@unibo.it (L. Tronchin). Construction and Building Materials 266 (2021) 121026 Contents lists available at ScienceDirect Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat