Green walls are vertical greening structures where varied plant species grow. They are conceived as a form of urban landscape and have numerous environmental, social and economic benefits. In fact, these structures have positive effects on air quality, thermal and acoustic insulation, microclimate, psychophysical well-being and urban design. In the framework of thermal comfort, several studies demonstrated the potential of green walls to improve indoor thermal comfort and reduce heat flows through the wall of buildings. This research evaluates the thermal efficiency of two modular green walls that present an alternative substrate as growing medium. This substrate is composed of loam soil and rice husk, an agricultural organic waste derived from the rice milling process. The choice of rice husk is inspired by principles of circular economy in order to reduce the environmental impact and costs of the substrate used in greening applications. The alternative substrate was compared with expanded clay aggregate, used for plant cultivation in living walls, and the analysis was divided into two phases. Firstly, field experiments were carried out on three plant species (Chlorophytum, Dieffenbachia and Spathiphyllum) to evaluate the efficacy of these substrates to grow plants. The efficacy of the substrate was evaluated through the measurement of the concentration of chlorophyll, the determination of the growth index of plants and a qualitative observation of the root development. Secondly, two modular green walls with varied substrates and plants were designed and tested from the point of view of the thermal comfort, using the open source software TerMus-G. After the transmittance value was obtained as output for each green wall module, the heat flow and the relative variation were calculated and compared to the indoor supporting walls. This article presents a valid methodology approach to evaluate the efficiency of green walls substrate and its thermal performance. This methodology differs from those found in scientific literature and represents a valid alternative. The present research demonstrates the ability of designed modules and, more generally, of indoor green walls to increase thermal insulation without causing condensation. Furthermore, the investigation shows a positive contribution both in winter and in summer. Finally, the use of this undervalue by-product rice husk mixed with loam soil shows to be appropriate for green wall application, providing better performance than the expanded clay in terms of thermal comfort and plant growth rate. Moreover, its use as substrates should further improve the ecological footprint of green vertical structures and reduce costs.

Rice husk and thermal comfort: Design and evaluation of indoor modular green walls / De Lucia, Matteo; Treves, Anna; Comino, Elena. - In: DEVELOPMENTS IN THE BUILT ENVIRONMENT. - ISSN 2666-1659. - ELETTRONICO. - 6:100043(2021), pp. 1-7. [10.1016/j.dibe.2021.100043]

Rice husk and thermal comfort: Design and evaluation of indoor modular green walls

Anna Treves;Elena Comino
2021

Abstract

Green walls are vertical greening structures where varied plant species grow. They are conceived as a form of urban landscape and have numerous environmental, social and economic benefits. In fact, these structures have positive effects on air quality, thermal and acoustic insulation, microclimate, psychophysical well-being and urban design. In the framework of thermal comfort, several studies demonstrated the potential of green walls to improve indoor thermal comfort and reduce heat flows through the wall of buildings. This research evaluates the thermal efficiency of two modular green walls that present an alternative substrate as growing medium. This substrate is composed of loam soil and rice husk, an agricultural organic waste derived from the rice milling process. The choice of rice husk is inspired by principles of circular economy in order to reduce the environmental impact and costs of the substrate used in greening applications. The alternative substrate was compared with expanded clay aggregate, used for plant cultivation in living walls, and the analysis was divided into two phases. Firstly, field experiments were carried out on three plant species (Chlorophytum, Dieffenbachia and Spathiphyllum) to evaluate the efficacy of these substrates to grow plants. The efficacy of the substrate was evaluated through the measurement of the concentration of chlorophyll, the determination of the growth index of plants and a qualitative observation of the root development. Secondly, two modular green walls with varied substrates and plants were designed and tested from the point of view of the thermal comfort, using the open source software TerMus-G. After the transmittance value was obtained as output for each green wall module, the heat flow and the relative variation were calculated and compared to the indoor supporting walls. This article presents a valid methodology approach to evaluate the efficiency of green walls substrate and its thermal performance. This methodology differs from those found in scientific literature and represents a valid alternative. The present research demonstrates the ability of designed modules and, more generally, of indoor green walls to increase thermal insulation without causing condensation. Furthermore, the investigation shows a positive contribution both in winter and in summer. Finally, the use of this undervalue by-product rice husk mixed with loam soil shows to be appropriate for green wall application, providing better performance than the expanded clay in terms of thermal comfort and plant growth rate. Moreover, its use as substrates should further improve the ecological footprint of green vertical structures and reduce costs.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11583/2898301