The evapotranspiration process in green roofs: a review

Previous research has shown that most of the green roof benefits are related to the cooling effect. In the literature available, however, it is still not clear how and how much the evapotranspiration affects the performance of a green roof. In order to fill the gap in this research topic, this study carries out a review on the cooling effect due to the evapotranspiration process of green roofs. First of all, an overview of the evapotranspiration phenomenon in green roofs, as well as the equipment and methods used for its measurement are presented. Then, the main experimental results available in literature, the physical-mathematical models and the dynamic simulation software used for the evaluation of the latent heat flux are also analysed and discussed among the available literature. Moreover, this review proposes a classification of the results carried out by previous studies as function of the main parameters affecting the evapotranspiration process (e.g. volumetric water content, stomatal resistance, Leaf Area Index, solar radiation, wind velocity, relative humidity, soil thickness, and substrate composition). Additionally, a sensitivity analysis of the results obtained from the literature allowed underlining the correlation among the main factors affecting the evapotranspiration. Finally, a vision of the world area where green roof studies were performed is provided. From the results, it is possible to emphasize that most of the studies that evaluated the evapotranspiration used high precision load cells. Furthermore, all the heat transfer models of green roofs considered in this review took into account the latent heat flux due to evaporation of water from the substrate and plants transpiration, however, only few of them were experimentally validated.This work is partially funded by the Spanish governmentENE2015-64117-C5-1-R (MINECO/FEDER). The authors would like to thank the Catalan Government for the quality accreditation given to their research group (2017 SGR 1537). GREiA is certified agent TECNIO in the category of technology developers by the Government of Catalonia. Julià Coma would like to thank Ministerio de Economia y Competitividad de España for the Grant Juan de la Cierva, FJCI-2016-30345. This research is also funded by “the Notice 5/2016 for financing the Ph.D. regional grant in Sicily” as part of the Operational Programme of European Social Funding 2014–2020 (PO FSE 2014–2020)

Experimental validation of the exact analytical solution to the steady periodic heat transfer problem in a PCM layer

Phase change materials (PCM) are used in many industrial and residential applications for their advantageous characteristic of high capacity of latent thermal storage by means of an isothermal process. In this context, it is very useful to have predictive mathematical models for the analysis of the thermal performance and for the thermal design of these layers. In this work, an experimental validation of an analytical model that resolves the steady periodic heat transfer problem in a finite layer of PCM is presented. The experimental investigation was conducted employing a PCM with thermophysical and thermochemical behavior very close to those hypothesized in the formulation of the analytical model. For the evaluation of the thermophysical properties of the PCM sample used, an experimental procedure created by the authors was employed. In all tests realized in a sinusoidal and non-sinusoidal periodic regime, the comparison between the measured and calculated trends of the temperature at different sample heights and of the surface heat fluxes show an excellent agreement. Moreover, also having verified the analytical total stored energy, the analytical model constitutes a valid instrument for the evaluation of the latent and sensible contribution and the trend in time of the position of the bi-phase interface.The work was partially funded by the Spanish government (ENE2015-64117-C5-1-R (MINECO/FEDER), ENE2015-64117-C5-3-R (MINECO/FEDER), and ULLE10-4E-1305). GREA is certified agent TECNIO in the category of technology developers from the Government of Catalonia. The authors would like to thank the Catalan Government for the quality accreditation given to their research group (2014 SGR 123). This project has received funding from the European Commission Seventh Framework Programme (FP/2007-2013) under Grant agreement Nº PIRSES-GA-2013-610692 (INNOSTORAGE) and from European Union's Horizon 2020 research and innovation programme under grant agreement Nº 657466 (INPATH-TES). Alvaro de Gracia would like to thank Ministerio de Economia y Competitividad de España for Grant Juan de la Cierva, FJCI-2014-19940. Julià Coma would like to thank the Departament d'Universitats, Recerca i Societat de la Informació de la Generalitat de Catalunya for his research fellowship (2016FI_B2 00147). Aran Solé would like to thank Ministerio de Economía y Competitividad de España for Grant Juan de la Cierva, FJCI-2015-25741

Vertical Greenery Systems (VGS) for energy saving in buildings: A review

This review paper organizes and summarizes the literature on Vertical Greenery Systems (VGS) when used as passive tool for energy savings in buildings. First, with the information obtained in the reviewed literature some key aspects to consider when working with VGS are clarified, such as the classification systems, the climate influence, the plant species used and the different operating mechanisms. Then, the main conclusions of this literature, sorted by construction system (Green Walls or Green Façades) and climatic situation, are summarized. In general, it can be concluded that VGS provide great potential in reducing energy consumption in buildings, especially in the cooling periods. However, a lack of data on operation during the heating period as well as during the whole year has been found. On the other hand, results show that the investigations of VGS are not equally distributed around the world, being basically concentrated in Europe and Asia. Moreover, the review concludes that some aspects must be studied in depth, such as which species are the most suitable for each climate, influence on energy savings of the façade orientation, foliage thickness, presence of air layers, and finally, substrate layer composition and thickness in the case of green walls.The work was partially funded by the Spanish Government (ENE2011-28269-C03-01 and ENE2011-28269-C03-02) and from the European Union's Seventh Framework Programme(FP7/2007– 2013) under Grant agreement no.PIRSES-GA-2013–610692 (INNOSTORAGE)

Comparative Analysis of Energy Demand and CO2 Emissions on Different Typologies of Residential Buildings in Europe

The building sector accounts for one third of the global energy consumption and it is expected to grow in the next decades. This evidence leads researchers, engineers and architects to develop innovative technologies based on renewable energies and to enhance the thermal performance of building envelopes. In this context, the potential applicability and further energy performance analysis of these technologies when implemented into different building typologies and climate conditions are not easily comparable. Although massive information is available in data sources, the lack of standardized methods for data gathering and the non-public availability makes the comparative analyses more diffcult. These facts limit the benchmarking of different building energy demand parameters such as space heating, cooling, air conditioning, domestic hot water, lighting and electric appliances. Therefore, the first objective of this study consists in providing a review about the common typologies of residential buildings in Europe from the main data sources. This study contains specific details on their architecture, building envelope, floor space and insulation properties. The second objective consists in performing a cross-country comparison in terms of energy demand for the applications with higher energy requirements in the residential building sector (heating and domestic hot water), as well as their related CO2 emissions. The approach of this comparative analysis is based on the residential building typology developed in TABULA/EPISCOPE projects. This comparative study provides a reference scenario in terms of energy demand and CO2 emissions for residential buildings and allows to evaluate the potential implementation of new supply energy technologies in hot, temperate and cold climate regions. From this study it was also concluded that there is a necessity of a free access database which could gather and classify reliable energy data in buildings.This study has received funding from European Union’s Horizon 2020 research and innovation programme under grant agreement Nº723596 (Innova MicroSolar). The work is partially funded by the Spanish government (RTI2018-093849-B-C31). Julià Coma would like to thank Ministerio de Economía y Competitividad de España for Grant Juan de la Cierva, FJCI-2016-30345. José Miguel Maldonado would like to thank the Spanish Government for his research fellowship (BES-2016-076554). This work is partially supported by ICREA under the ICREA Academia programme

New green facades as passive systems for energy savings on buildings

2013 ISES Solar World CongressThe new technologies of plants integration on buildings offer new possibilities from the sustainable construction point of view, especially in energy savings. In previous studies the great capacity of double-skin green facade or green screen to intercept solar radiation was confirmed, observing differences up to 18 °C in surface temperatures between sunny and shade areas on the wall of the building. The experiment presented here consists of two identical house-like cubicles (3 x 3 x 3 m) located in Puigverd de Lleida, Spain. The only difference between the two cubicles is the double-skin green facade installed in one of them. In a first step only the South wall was covered by a provisional green facade. As the results from first experiment were positive with interesting low electrical energy consumptions when only the 50% of the South wall was covered by plants, a new stable green facade was built covering the South, East and West facades by a deciduous specie well adapted to the Mediterranean Continental climate. With this study the confirmation of the good operation of green facades made with deciduous species as passive system for energy savings in buildings is expected to be characterized.The work was partially funded by the Spanish government (project ENE2011-28269-C03-02 and ULLE10-4E-1305). The authors would like to thank the Catalan Government for the quality accreditation given to their research group (2009 SGR 534), and to City Hall of Puigverd de Lleida

Green roofs as passive system for energy savings when using rubber crumbs as drainage layer

1st International Conference on Solar Heating and Coolingfor Buildings and Industry (SHC 2012)This study is another step of a long-term work in order to study the thermal behaviour of extensive green roofs in dry Mediterranean Continental climate. In this paper there are two main goals. On one hand, the possibility of using rubber crumbs as a drainage layer in green roofs, substituting the porous stone materials used in some commercial solutions is studied. On the other hand, new data concerning the use of green roofs as passive system for energy savings in dry Mediterranean Continental climate is provided. First results correspond to summer 2011, when the roof was just planted and the irrigation system installed. The vegetation cover in those days was about 20% of the roof surface. With an internal set-point of 24 °C first results show an improvement in energy consumption with respect to the reference cubicle. New data will be recorded during 2012 when the vegetation has developed and it is expected better results than in 2011.This work was partially funded by the Spanish government (ENE2011-28269-C03-02) and the European Union (COST Action COST TU0802), in collaboration with the companies Gestión Medioambiental de Neumáticos S.L (Polígon Industrial Piverd s/n, Maials.) and Soprema. The authors would like to thank the Catalan Government for the quality accreditation given to their research group (2009 SGR 534)