Urban Overheating Impact: A Case Study on Building Energy Performance (original) (raw)
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Tecnica Italiana-Italian Journal of Engineering Science, 2021
It is well known that the building sector is one of the main responsible for energy consumption in the current global energy scenario. In this context, the concept of efficient buildings passes through newly built and retrofitted constructions. Thus, buildings energy software become essential tools for achieving energy savings, designing the so-called green buildings, and evaluating different energy retrofit solutions for the building stock. However, climate change and its effects on buildings energy performance represent a critical issue. Therefore, the aim of this study is to evaluate the climatic conditions in Rome and its surroundings, estimating the occurrence of the Urban Heat Island (UHI) phenomenon. Consequently, meteorological data obtained from two airports near the city and those recorded for two years in a densely built neighborhood of Rome were examined and compared. In addition, the differences among weather data, also taking into consideration UNI 10349, were highlighted. Then, TRNSYS software was used for creating a simple building, in order to evaluate the effects of different climatic boundary conditions on building energy performance, in terms of heating and cooling energy demands.
Energy & Buildings, 2017
A wide variety of weather-data are readily available for simulating buildings energy performance by using dynamic software. However, climate change and its effects on buildings energy performance represent a critical issue, also considering the implications of climate change on human comfort. Starting from this, the present study aims at analyzing the climatic conditions in Rome and its surroundings, evaluating the occurrence of the Urban Heat Island (UHI) phenomenon. Therefore, meteorological data derived from two airports near the city and climatic data registered for two years in a central, densely-built zone of Rome were analyzed and compared. Furthermore, the differences among weather data were tested by means of a commonly used dynamic software in order to evaluate the effects of different climatic boundary conditions on building energy performance, in terms of heating and cooling energy demands. The results highlight significant differences with regard to temperature, wind velocity and relative humidity, as a result of a prevailing UHI phenomenon in central Rome throughout the year. The simulations show an average increase of cooling energy demand of about 30% and an average reduction of heating energy demand of about 11%. Such differences give the rise for the investigation of the reliability of weather-data files commonly used in building simulations, in order to properly estimate the buildings energy demand under a sustainable city perspective.
International Journal of Sustainable Development and Planning, 2023
Urban areas can be characterized by higher outdoor air temperatures than rural ones due to the well-known Urban Heat Island (UHI) phenomenon. This significantly affects buildings energy performance, thus influencing energy needs in terms of cooling and heating. Starting from this, the UHI in Rome was here investigated, providing an updated estimation through 2022 climate data. The influence of the UHI on energy efficiency in buildings has been highlighted by applying climatic data logged by different weather stations within a dynamic simulation tool. Thus, actual climate data have been used as thermal boundary conditions to simulate typical building energy needs, for cooling and heating. The findings of this study demonstrate a notable disparity in climatic conditions between the areas outside the city and the urban context. The maximum values of UHI intensities for daytime and night-time were identified as 3.1℃ and 3.5℃, respectively. Moreover, the accurate selection of reference data is a crucial factor for obtaining reliable information regarding the energy demands of buildings within the city. The findings emphasized that utilizing data from airport stations instead of weather stations within urban areas can result in disparities up to approximately-17% for heating and more than 50% for cooling requirements.
Renewable Energy and Sustainable Development, 2016
The heat island effect in urban environments, (whatever the size and the latitude determining the effect intensity) is dramatically increasing due to climate changes and urban sprawl. The urban heat island is a phenomenon observed since the last decades of the XIX century, but diffused to a large scale only one century later. It is characterised by the increase of air temperature in densely built urban environments with respect to nearby natural landscape areas. Many available studies show urban heat island intensities up to 12°C. This thermal stress causes social, health and environmental hazards, with major impacts on weak social classes, such as elderly and low income people. This study presents first results of air temperature monitoring campaigns in different neighbourhoods of Rome, a metropolitan area characterised by a typical Mediterranean climate and by a complex urban texture, in which densely built areas and green or not-built zones border one another. Six spots were monitored since June 2014; they include: historical city centre, semi-central zones with different construction typologies, and surrounding areas with various urban and building contexts. This paper explores the summer temperature profiles within the city and their increase respect to suburban areas' values. UHI intensities up to 10°C were monitored as well as monthly UHI up to 3.4°C in the hottest area of the city. The impact on the cooling performance and the thermal response of reference buildings were also assessed. Temperature datasets and the reference building model were inputted into adynamic calibrated calculation software. In addition, cooling net energy demand of the reference building as well as operative temperature fluctuation in the not cooled building configuration were calculated. The results of calculation allow to compare the energy and thermal performances in the urban environment with respect to the reference conditions, being the latter typically adopted by national building codes. 50 and 100% relative increasing of cooling demand were calculated, respectively, for insulated and not insulated buildings.
Energy and Buildings, 2017
Average air temperatures in the Mediterranean region are in the thermal comfort zone for human beings in summer. However, irradiation conditions, construction technologies and subjective comfort expectations are dramatically increasing the cooling demand in buildings, exacerbated by the ambient temperature increase due to the climate change and the urban heat island phenomenon. This paper investigates the impact of the urban environment on the energy and thermal response of residential buildings, considering the case of the city of Rome, Italy. Ambient air temperature and relative humidity were continuously measured in four neighborhoods in 2015 and 2016. The monitored neighborhoods are characterized by: location in the urban area; construction materials for buildings and pavements; geometry of the urban texture. Data were also measured by a non-urban station, used as undisturbed reference. The climatic data were then used to calculate the thermal response of a typical Italian residential building, ideally located in the monitored areas of the city. Two envelope configurations were taken into account: with and without thermal insulation. Heat island intensities up to 8 °C was detected, with maximum monthly averages equal to 2 °C. The urban heat island increases the building cooling energy needs by 12% in the peripheral neighborhood and by up to 46% in the city center, respect to the undisturbed zone. For not cooled buildings, it was found out that the number of hours of thermal discomfort remains significant in urban buildings, despite the application of night ventilation strategies, while comfort conditions are mostly reached for buildings in the countryside.
buildings, 2023
This study examined the atmospheric urban heat island (UHI) phenomenon within the city of Rome (Italy) and its effects on building energy demand. Weather data from 2020 and 2022 collected from six meteorological stations were considered. A Geographic Information System (GIS) was used to analyze the landscape, correlating the percentage of impermeable surfaces with UHI intensity values in each area. Dynamic simulations were conducted using different climatic data to estimate the heating and cooling energy demands for two representative residential buildings. The findings revealed significant differences in the climatic conditions between urban and rural areas, primarily due to temperature increases. The UHI intensities reached maximum values of 4.67◦C and 3.54 ◦C in 2020 and 2022. In urban areas, the UHI has positive effects on the heating energy demand but results in a significant increase in energy demand for cooling. Considering a building type constructed between 1900 and 1950, a variation of up to 33.03% in the heating energy demand in urban areas compared to rural areas was calculated, along with a variation of up to 81% for cooling. In contrast, considering a more recent building type constructed between 1991 and 2005, the corresponding values reached up to 36.47% and 75.7%.
Urban Heat Island Effect on the Energy Consumption of Institutional Buildings in Rome
IOP Conference Series: Materials Science and Engineering, 2011
The urban heat island (UHI) effect is constantly increasing the energy consumption of buildings, especially in summer periods. The energy gap between the estimated energy performance-often simulated without considering UHI-and the real operational consumption is especially relevant for institutional buildings, where the cooling needs are in general higher than in other kind of buildings, due to more internal gains (people, appliances) and different architectural design (more transparent façades and light walls). This paper presents a calculation of the energy penalty due to UHI in two institutional buildings in Rome. Urban Weather Generator (UWG) is used to generate a modified weather file, taking into account the UHI phenomenon. Then, two building performance simulations are done for each case: the first simulation uses a standard weather file and the second uses the modified one. Results shows how is it necessary to redevelop mitigation strategies and a new energy retrofit approach, in order to include urbanization ad UHI effect, especially in this kind of buildings, characterized by very poor conditions of comfort during summer, taking into account users and occupant-driven demand.
Energy Consumption of Institutional Buildings Considering the Urban Climate in Rome
Proceedings of the 16th IBPSA Conference, 2020
Institutional buildings are very important considering the impact on energy consumption of a city. Due to the conditions of operation, the size and the density of occupants, institutional buildings represent a challenge to save energy in both cold and hot seasons. Urban climate influences the building performance, typically reducing thermal demand in winter and increasing in summer. The context is relevant in determining urban heat island effect, shadows, ventilation and in general the thermal environment that surrounds buildings. This paper develops a strategy to estimate the energy penalty obtained by including in building performance simulation the urban effects. Urban Weather Generator v. 4 beta and TRNSYS v. 17 tools are used to obtain base and urban energy demand through the whole year in three cases of study in Rome.
The Urban Heat Island (UHI) effect is particularly concerning in Mediterranean zone, as climate change and UHI scenarios foresee a fast growth of energy consumption for next years, due to the widespread of air conditioning systems and the increase of cooling demand. The UHI intensity is thus a key variable for the prediction of energy needs in urban areas. This study investigates the intensity of UHI in Barcelona (Spain), the densest Mediterranean coastal city, and its impact on cooling demand of residential buildings. The experimental analysis is based on temperature data from rural and urban Weather Stations and field measurements at street level. The maximum average UHI intensity is found to be 2.8 ◦C in winter and 1.7 ◦C in summer, reaching 4.3 ◦C at street level. Simulations performed with EnergyPlus indicate that the UHI intensity increases the sensible cooling load of residential buildings by around 18%–28%, depending on UHI intensity, amount of solar gains and cooling set point. In the light of the results, the UHI intensity in Mediterranean context should be properly considered in performing energy evaluations for urban contexts, since standard meteorological data from airport weather stations are not found to be accurate enoug.
The Influence of the Urban Heat Island over Building Energy Demand: the Case of Milan
2009
Dynamic energy simulation tools of building energy consumption usually require as climatic input a Test Reference Year, which reports hourly values of dry-bulb air temperature, solar radiation, relative humidity and wind velocity. For the city of Milano (Northern Italy) unfortunately this sequence is available only from old data measurements in a non-urban context (local airports). Therefore, in this paper, a new TRY based on data collected in the centre of Milan is proposed. Consequently, energy demand simulations are carried out for a building type widespread in Milan using urban and non-urban data. The aim of this paper is hence to achieve a first evaluation of the influence of the Urban Heat Island in Milan over the energy demand of buildings