Contents lists available at ScienceDirect Solar Energy journal homepage: www.elsevier.com/locate/solener Analysis of the energy performance of an Opaque Ventilated Façade under winter and summer weather conditions A. Gagliano ⁎ , S. Aneli Department of Electrical Electronic and Informatics Engineering, Viale Andrea Doria 6, 95125 Catania, Italy ARTICLE INFO Keywords: Ventilated facade Computational fuid dynamic Energy saving ABSTRACT Nowadays, there is continuing worrying about energy efciency and the reduction of GHG emissions in the building sector. It has been claimed that ventilated building envelopes help to reduce energy use in buildings and improve occupant comfort. This study proposes a comprehensive comparison of the thermal behaviour between an Opaque Ventilated Façade (OVF) and a conventional unventilated Façade (UF) considering two reference days for the winter and summer period. The analysis is developed investigating diferent façade orientations and two states of windiness, which are a state of calm wind and a state with wind velocity higher than zero (i.e. 5.0 m/s at 10 m of height) are taken into account. These analyses were developed utilizing fuid-dynamic calculation under dynamic conditions. Thus for the two façades were calculated: (I) the hourly surface temperatures of the most external, (II) the temperature profles for all the facade’s layers; (III) the airfow profles inside the cavity and near the façade; (IV) the hourly thermal fuxes that cross the façade. Finally, the daily energy fuxes and the energy-saving, achievable through the adoption of the OVF, is cal- culated for the diferent façade exposures and the conditions of windiness. The outcomes of this study highlight that the OVF guarantees an energy-saving ranging from 20 to 55%, with the highest rate during the summer day for the façade facing East/West. 1. Introduction Tackling climate change is a common priority, due to ethical issues related to the general concept of sustainability and a viable future. In recent years, a global warming process is underway that will surely make the evolution of the quality of life on earth alarming. Reducing GHG emissions and energy waste are two of the main objectives of international policy. The International Energy Agency estimated that in the United States energy consumption in the building sector is 45% and in Europe, it is around 40%, where for example in the United Kingdom it is around 42% whereas, in Italy, it is 40% (IEA, 2012). In Europe, the energy consumption of buildings built before 1990 played a higher impact, i.e. before adopting a common energy- saving policy (European Environment Agency, 2014). EU countries are promoting the development of more efcient cities where an important role is played by the fgure of net-zero-energy buildings. One of the main objectives of the energy design of buildings is to take advantages of the thermophysical characteristics of the ma- terial used, which should be climate-responsive (W.D. Seo et al., 2013). The efcient design reduces thermal fuxes between outdoor and indoor space, as well as the overheating efect due to solar radiation (Arce et al., 2009; Giancola et al., 2014). The energy performance of buildings directive (EU Directive, 2012) emphasized the urgency of adopting strategies that contribute to improving the thermal performance of new and existing buildings. Although the energy demand of energy-intensive buildings could be, partially or totally, balanced by the widespread use of renewable en- ergy sources, this nevertheless represents a waste of clean energy and does not meet the problem of the urban heat islands (Ascione, 2017). The most common retroft intervention on the building envelope is the laying of an external thermal insulation coating system (ETICS), which allows a signifcant reduction in the thermal transmittance of the opaque façades and the consequent reduction of energy consumptions (Kolaitis et al., 2013; Alonso et al., 2016, Gagliano et al., 2017; Mandilaras et al., 2014). On the other hand, the thermal coat can in- crease the energy requirement during the cooling period and create problems of transpiration of the façades if not properly designed (Garay et al., 2017; ENEA, 2015). https://doi.org/10.1016/j.solener.2020.05.078 Received 28 March 2020; Received in revised form 23 May 2020; Accepted 25 May 2020 ⁎ Corresponding author. E-mail address: antonio.gagliano@unict.it (A. Gagliano). Solar Energy 205 (2020) 531–544 0038-092X/ © 2020 International Solar Energy Society. Published by Elsevier Ltd. All rights reserved. T