• Energy Research

Abstract A strategy to make cities greener involves the use of green infrastructures. In this context, green facades applied to vertical envelope of buildings are one of the most promising technologies. Their contribution is particularly significant as passive cooling systems for buildings. Green facades allow to decrease air and surfaces temperatures mainly by canopy evapotranspiration and shading. Such processes are strongly influenced by environmental conditions and canopy characteristics. Aim of this research was to model and evaluate evapotranspirative and shading effects. Data recorded on an experimental prototype of building equipped with green facade were used for model development and assessment. Canopy characteristics, as leaf area index in vertical greening, were defined. Evapotranspiration was both measured with a load cell and evaluated through the green layer energy balance. The goodness-of-fit of the models was assessed by statistical indices. The models using Penman-Monteith and Deardorff formula, in summer, recorded average values of root mean square error equal to 12.48 W m−2 and to 14.61 W m−2, respectively. Plant coefficients useful for the application in vertical greening of the standardized evapotranspiration reference equation were defined. These were equal to 1.3 and 2.0 for Rhyncospermum Jasminoides in summer and spring, respectively. The daily overall cooling effect in summer, due to evapotranspiration and shading, was equal, on average, to 16.2 MJ m−2 of wall surface. Shading contributed about twice as much as the evapotranspiration. The findings of this research can be a useful contribution to writing routines of building energy models expressly developed for green facades.

The use of vegetated vertical systems is a sustainable technology for improving the energy efficiency of buildings in cities in order to reduce the energy consumption for air conditioning in summer and to increase the thermal insulation in winter. increasing urban green infrastructure (ugi) in a city can contribute to improve urban climate in summer reducing buildings surface temperature and urban air especially in southern europe. the application of vertical green systems requires the knowledge of the energy performance of the applied greenery system. the choice of the green facades depends on the local climate, water availability, building shape. the presence of green facades affects the building microclimate all day, by reducing heat waves during the warm periods and heat losses from the building in the cold period. the heat and mass transfer between the external environment, the green facades and the building surface determine the building microclimate. solar radiation, long wave infrared radiation, convective heat transfer and evapotranspiration are the main mechanisms of heat transfer in a green façade. the paper describes the main parameters concerning heat flow in green facades that can be used in simulation models for predicting temperatures in buildings using the external weather conditions as model inputs. the input parameters are: external air temperature and relative humidity, solar radiation, wind velocity and direction, plants and building characteristics. the green facade was described by a schematic representation, four layers were defined: the green layer, the external surface of the building wall, the internal surface of the building wall, the air inside the building. the energy balance was defined for each layer and all the terms involved in the energy exchange between the layers were defined as a function of the plant, the weather conditions and the constructive characteristics of the wall.

Buildings consume a significant part of the world’s resources and energy. The growing environmental awareness and urgent need to reduce energy consumption have highlighted the importance of introducing innovative solutions as nature-based systems in new buildings’ construction and retrofitting. In this regard, green façades that integrate vegetation into building envelopes are attractive. This paper presents a bibliographic analysis, based on science mapping, of the available literature on green façades from 1999–2022 with a focus on the thermal effect on the building and on the surroundings. The objective of this study is to reveal the structure and the evolution of the research activity in the field, outlining the main research topics and the future research directions. The analysis was performed on a dataset of 270 documents. The results indicate a growing interest in this topic over the last six years and the multidisciplinary dimension of the studies. The keyword cluster analysis indicates the emergence of three main search topics: thermal behavior and energy modeling; urban design and large-scale effects; sustainable buildings management. A greater future dissemination of green façades could be enabled by further research results based on the application of a multidisciplinary approach and of standardized methods.

Green façades are effective passive systems for buildings, but the research about their winter effects is still few. This study investigated the influence of a green façade during winter nights in a Mediterranean area. The effects on microclimate and heat transfer were evaluated based on experimental data. These data were used to calculate radiative and convective heat transfer by formulae available in literature. The behaviours of the covered wall and a bare wall were compared. Vegetation allowed to keep the air velocity near the wall below 0.9 m s−1. The covered wall external surface and the nearby air recorded a warming of up to 3.4°C and 3.3°C, respectively. The walls lost radiative and convective energy, but for the covered wall these losses were 60% and 38% lower, respectively. Acting as a thermal and wind barrier, the green façade reduced overall heat losses by 57% improving building envelope performance.

Energy consumption in greenhouse heating could reach up to 90% of the total energy requirement depending on the type of greenhouse, environmental control equipment and location of the greenhouse. The use of climate conditioning technologies that exploit renewable energy and the application of passive systems to improve the energy efficiency and the sustainability of the greenhouse sector are recommended. During winter 2020-2021, an experimental test was carried out at the University of Bari in a Mediterranean greenhouse heated by a polygeneration system, composed of a solar system and an air-water heat pump. Three localized heating systems were tested to transfer thermal energy close to plants of Roman lettuce. Heating pipes were placed inside the cultivation substrate in the underground pipe system and on the cultivation substrate in the laid pipe system. The third system consists of metal plates heated by steel tubes and placed in the aerial area of plants. A weather climatic station and a sensor system interfaced with a data logger for continuous data acquisition and storage were used. The plate system was the best for air temperature rising, as it allowed an increase of 3.6% compared to the set-up without any localised heating system. The underground pipe system was the best for the soil heating, as it achieved a temperature increase of 92%. Localized soil heating systems contributed significantly to an earlier harvest by almost 2 weeks.

Abstract Urban green infrastructures contribute to increase sustainability in cities. Among green infrastructures, vertical green systems applied on buildings envelope are promising solutions. Green facades, applied to building walls, allow a sustainable passive climate control in buildings. Energy modelling of green facade systems allows their effective design, simulation and application. Upstream of the modelling there is the mathematical description of the energy transfer that takes place in the system. Radiative heat exchanges in the long-wave infrared range is one of the mechanisms to be considered. This implies the knowledge of geometric configuration factors, surfaces radiometric properties and sky radiation models. This paper focuses on the infrared exchanges occurring on the external surfaces of a green facade, compared with those of a bare wall. A mathematical procedure was followed to define the configuration factor between ground and vertical surface. Nine different sky radiation models were applied to find out, through statistical indices, the best fitting one. The analytical study was supported by empirical data, gathered on an experimental green facade built at the University of Bari. Calculations of the infrared fluxes were made for a summer, an autumn and a winter period, both daytime and night-time. It resulted that the sky model of Walton provided the best agreement with the measured data. In winter, the covered wall showed a reduction of long-wave infrared radiative energy losses equal to 79% compared to the bare wall, so the green facade acted as a thermal barrier.

Abstract The building sector plays a crucial role in relation to energy and environmental issues. For this reason, today, it pays great attention to the need of a bioclimatic architecture closely related to environment, history and traditions of the various places. In this context, the guidelines for careful planning of environmental issues can be traced precisely in vernacular architecture, the result of a close link with the territories and a great sensitivity towards nature. This study focuses on an example of vernacular Mediterranean architecture, represented by the old town of Ostuni (Puglia, Italy). The objective is to analyze the peculiarities of the building and urban layout, with particular attention to the external coating with white lime base, showing in detail the influence of the staining on microclimatic conditions. The results of the carried out analysis highlight the benefits and weaknesses of studied constructive solutions. Thus, it is supported the view that it is necessary to rediscover and be inspired by the vernacular architecture, not representing them as anachronistic, but always drawing on the contributions of technical and scientific progress. The research points out the influence of exterior finishing surfaces on the energy performance of buildings as well as on the outdoor thermal and visual comfort of the inhabitants.

Green facades are passive living technologies applied to buildings. They produce many advantages for human wellbeing, building performance, and city environments. Knowledge of the energy behaviour of green facade systems is needed to inform their best design and application, and to define their energy performances. Heat and mass exchanges between the system and the surrounding environment must be determined. In this paper, the schematisation of the green facade system into layers and the energy balance approach are proposed. This study focuses on the analysis of the convective heat transfer occurring between the plant layer and the external air. It is difficult to realistically describe this mechanism and many approaches in the literature were considered. Six different formulae were evaluated. Mathematical modelling and empirical data were both used. Once it was discovered that forced convection was the prevailing convective type, selected formulae were applied to the data, which were collected from an experimental green facade at the University of Bari. Based on the energy balance of the plant layer, a comparison between the calculated and measured values was carried out. Qualitative and quantitative statistical methods were used to assess the goodness-of-fit of the considered convective models. These analyses suggest the least and the most suitable approaches for convective heat transfer evaluation. The empirical equation of Morrison and Barfield and an adaptation to green facades of Deardorff model showed the best agreement. This study could be extended in order to write codes for building energy simulation software.