URBAN MORPHOLOGY AND ENERGY PERFORMANCE: THE DIRECT AND INDIRECT CONTRIBUTION IN MEDITERRANEAN CLIMATE (original) (raw)
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The relationship between morphology, climate and energy has always influenced deeply the development of urban settlements. In the Mediterranean context, this process led to compact and dense urban textures, made of highly inertial materials and cladded with bright colors in order to prevent overheating and thermal discomfort. Nowadays, cooling and heating systems relieves the architectural design from climatic constraints. However this has resulted in increased energy consumption, especially in the summer season because of the widespread use of air conditioning systems. The problem is worsened by the Urban Heat Island (UHI) effect. Shape and geometry of a city affect its climate, and so the energy demand at the urban scale (Ratti 2003, Morganti 2012). The proportions of the urban canyon (height/width ratio) can produce multiple reflections of solar radiation. In addition, the cooling process is decreased during the night due to the low values of the sky view factor (Oke, 2012). Therefore, in a dense and compact urban texture, higher temperatures can occur especially during the night. The present study seeks to highlight the effect of urban morphology on the UHI intensity in the Mediterra-nean context. Several morphologically homogeneous textures of Rome and Barcelona are parametrically modelled and compared, by means of the Urban Weather generator tool (Bueno, 2012). The results show that air temperature substantially varies according to different urban morphologies. Understanding the microclimatic behavior of most recurrent urban textures can steer energy and retrofitting policies at urban scale and help to achieve the energy goals set by E.U.
Cities and energy: urban morphology and residential heat-energy demand
Environment and Planning B: Planning and Design, 2014
Our aim is better understanding of the theoretical heat-energy demand of different types of urban form at a scale of 500 m × 500 m. The empirical basis of this study includes samples of dominant residential building typologies identified for Paris, London, Berlin, and Istanbul. In addition, archetypal idealised samples were created for each type through an analysis of their built form parameters and the removal of unwanted 'invasive' morphologies. The digital elevation models of these real and idealised samples were run through a simulation that modelled solar gains and building surface energy losses to estimate heat-energy demand. In addition to investigating the effect of macroscale morphological parameters, microscale design parameters, such as U-values and glazing ratios, as well as climatic effects were analysed. The theoretical results of this study suggest that urban-morphology-induced heat-energy efficiency is significant and can lead to a difference in heat-energy demand of up to a factor of six. Compact and tall building types were found to have the greatest heat-energy efficiency at the neighbourhood scale while detached housing was found to have the lowest.
Energy aspects of urban planning. The urban heat island effect
Cse City Safety Energy, 2014
The research aims to analyze the tight relationship between the conformation of the city and the urban climate. The "heat island" phenomenon, typical of big urban centers, has a great impact on external temperatures, causing their increase compared to the surrounding rural areas. The study points out that the main factors responsible for such phenomenon are: the high percentage of built-up areas, the considerable presence of impermeable areas at the expense of the permeable ones, particularly green areas, the introduction of artificial heat in the atmosphere, generated by the combustion of hydrocarbon for transportations and domestic uses. Moreover a pivotal role is played by the urban canyons (which are generated by the geometrical configuration of the spaces among the buildings), the morphology of the urban tissue and the radiation properties (such as albedo and emissivity) of the surfaces. These considerations are confirmed by the results obtained in the experimentation conducted, in the city of Bari. Actually the results demonstrate that light color surfaces, with a higher level of albedo and wider green areas in some neighborhoods of Bari leads to a drop in temperatures of the external air, even of some degree days in the summertime. The experimentation conducted outlines a guideline which considers the energy aspects of urban planning, thanks also to the possibility of realizing simulations by means of some particular software (suitable for the study of surfaces-vegetation-air interactions in the urban context) and to define different scenarios of project planning.
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.
MITIGATING URBAN HEAT ISLAND EFFECT BY URBAN DESIGN: FORMS AND MATERIALS
This paper provides a synthesis of three complementary research works that contribute to the same objective: proposing solutions to reduce building energy consumption by modifying local climate. The first work explores urban forms: it proposes methods to describe them and analyze the climatic performances of classified urban forms. The second one focuses on one parameter of direct relevance to urban heat island phenomenon: the surface albedo. The albedo of a city or a district depends on surfaces' arrangement, materials used for roofs, paving, coatings, etc., and solar position. The third one proposes a simulation tool that permits to evaluate the impact outdoor urban environment on buildings' energy consumption. This analysis permits us to propose morphology indicators to compare the relative efficiencies of different typologies. The conclusion discusses the relevance of using indicators (based on physics or morphology, related to site or to built form) in urban design process and proposes a methodology to produce indicators.
The Sensitivity of Predicted Energy Use to Urban Geometrical Factors in Various Climates
Urban morphology, including building typology and layout, has a significant influence on the built environment's access to the sun, which impacts its energy exchange with the environment. This energy exchange is a strong factor in determining the comfort levels of occupants in buildings and the energy consumed to reach comfort. The influence of urban form has been quantified in previous studies for certain building typologies and programs for specific climates (i.e. location-specific case studies). We are interested in taking this further to assess the variation, due to climate, of the influence of different urban forms on the urban energy balance. This is part of a larger project to study the interaction between form and climate vis-à-vis energy and comfort in buildings. In this paper, we explore this issue through simulation, in various climates, of 3D neighbourhood models. These models consist of a series of parametrically generated variations on building typologies like bloc...
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.
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.
Urban Morphology and Energy Consumption
Advances in civil and industrial engineering book series, 2014
Urban form matters in assessing the energy consumption of buildings. This chapter introduces three useful tools to assess the environmental impact of the urban form and to define possible energy scenarios. These outcomes can be used to inform the redevelopment or the new design of urban districts, or simply to evaluate the overall energy performance of different urban fabrics. The tools presented comprise: (a) simplified indicators of energy-dependent variables based on morphological information of the urban form; (b) algorithms for the estimation of the heating energy needs of the urban fabric, based on the implementation of European Standards; (c) algorithms for the assessment of the solar potential of the urban form, computing the solar irradiance impacting on different sloped urban surfaces. The techniques introduced are based on an innovative approach that makes use of Digital Urban Surface Models (DUSMs) and Digital Image Processing (DIP) techniques.
Recent studies demonstrated how the energy consumption of buildings is composed by two main components: one related to the building's envelope, systems' efficiencies, and climate; the other related to the surrounding environment, the urban context and the locally variations of microclimate. In this work the component of energy consumption for space heating related to the urban context is analysed for the city of Turin, in the Northern part of Italy. Turin is one of the most populous Italian cities with more public green but its climate is influenced by the Urban Heat Island effect. The aim of this study is to understand how the urban form of the city can influence the buildings' energy consumptions for space heating. A central zone in Turin was selected with typical blocks of buildings and their energy consumptions were compared with the characteristics of urban morphology and solar exposure. To differentiate more the urban forms and characteristics of solar exposure other simulations have been made changing principally the: building coverage ratio (BCR), aspect ratio (H/W), and main orientation of streets (MOS). The urban characteristics of blocks of buildings were calculated with ArcGIS (ESRI) and for the energy consumptions of space heating the tool CitySim was used. The results show how the energy consumptions vary as a function of the urban morphology and the solar exposure of outdoor spaces with lower values for medium urban buildings densities; moreover, especially for high buildings' densities, the solar exposure strongly influence energy consumptions. The results of this work could be used in the urban planning to improve the sustainability of the new districts.