Article

From Energy Performative to Livable Mediterranean Cities: An Annual Outdoor Thermal Comfort and Energy Balance Cross-Climatic Typological Study

July 2020
Energy and Buildings 224(12)

DOI:10.1016/j.enbuild.2020.110283

Authors:

Jonathan Natanian

Technion - Israel Institute of Technology

Patrick Kastner

Georgia Institute of Technology

Timur Dogan

Cornell University

Thomas Auer

Technische Universität München

With the rise of awareness of health and well-being in cities, urban environmental analysis should expand from energy performance to new environmental quality-based considerations. The limited potential to annually evaluate outdoor thermal comfort, predominant among these considerations, has restricted the exploration of the interrelations between urban morphology and annual energy performance. This study aims to bridge this gap by capitalizing on the new capabilities of Eddy3D – a Grasshopper plugin which enables effective calculations of hourly microclimatic wind factors via OpenFOAM which in turn are used to generate annual outdoor thermal comfort plots. Using this method, a parametric study was conducted for different typology and density scenarios in three different hot climatic contexts in Israel. The automated analytical workflow evaluated a total of 60 design iterations for their energy balance, outdoor thermal comfort autonomy (OTCA) and self-shading levels using the shade index. The high correlation found here between the annual shade index and the OTCA, across all climatic contexts, shows the potential of the shade index to serve as an effective indicator, in these contexts, for comparative or optimization outdoor comfort studies. Further results are both the superiority of the courtyard typology in both energy and outdoor comfort studies, and the contrasting impact of higher density on the annual energy balance (lower performance) and outdoor thermal comfort (higher performance) in hot climates. The annual plots of both the energy balance and OTCA reveal various seasonal and monthly trends in the three different climatic zones which can lead to localized and seasonal urban design strategies.

Outdoor Thermal Comfort Integrated with Energy Consumption for Urban Block Design Optimization: A Study of the Hot-Summer Mediterranean City of Irbid, Jordan

Article

Full-text available

May 2023

With an increasing awareness of urban health and well-being, this study highlights the growing importance of considering environmental quality in urban design beyond mere energy performance. This study integrates outdoor and indoor quality by investigating the effect of design parameters at an urban block scale (building form restricted to width and length as rectangular and square, building orientation, block orientation, building combination, building height, facade length, built-up percentage, setbacks, and canyon aspect ratio) on outdoor thermal comfort and energy use intensity. In addition, it explains the different correlations between outdoor thermal comfort and energy use intensity in different urban block designs in a hot-summer Mediterranean climate in Jordan. The study adopts a performance-driven approach using simulation tools of Ladybug, Honeybee, Dragonfly, and Eddy3d plugins across the grasshopper interface and evaluates 59 different urban block designs with nine different orientations (0°, 1°, 45°, 85°, 87°, 90°, 355°, 358°, and 359°). The results show that there is a positive correlation between the canyon aspect ratio and the environmental performance of the urban block designs. North–south street canyons are more effective at enhancing microclimates. Negatively increasing the street aspect ratio by more than four affected outdoor thermal comfort by increasing longwave radiation. Further results suggest a positive correlation between the compactness of urban blocks and their environmental performance, with north–south street canyons found to be more effective in enhancing microclimates. The study emphasizes the need to understand the distribution of open spaces formed by buildings and to strike a balance between day and night, as well as summer and winter conditions in outdoor spaces.

Advances in Climatic Form Finding in Architecture and Urban Design

Article

Full-text available

May 2023

Francesco De Luca

Researchers, architects and planners are increasingly urged to develop and apply sustainable methods and solutions to reduce the impact of the built environment on climate, adapt cities to climate change and reduce or eliminate resource depletion and building-related carbon emissions. In recent years, taking advantage of state-of-the-art computational and environmental design tools, researchers and designers are developing new digital workflows, methods and solutions to investigate climate-optimal and performative buildings and urban forms. This perspective paper analyses state-of-the-art computational methods; form generation processes; and tools, criteria and workflows that present how these are integrated into climatic form finding, allowing the improvement of building and urban environmental performances. Additionally, current challenges and future directions are presented.

Application of CFD plug-ins integrated into urban and building design platforms for performance simulations: A literature review

Article

Full-text available

Feb 2023

The transformation of urban and building design into green development is conducive to alleviating resource and environmental problems. Building design largely determines pollutant emissions and energy consumption throughout the building life cycle. Full consideration of the impact of urban geometries on the microclimate will help construct livable and healthy cities. Computational fluid dynamics (CFD) simulations significantly improve the efficiency of assessing the microclimate and the performance of design schemes. The integration of CFD into design platforms by plug-ins marks a landmark development for the interaction of computer-aided design (CAD) and CFD, allowing architects to perform CFD simulations in their familiar design environments. This review provides a systematic overview of the classification and comprehensive comparison of CFD plug-ins in Autodesk Revit, Rhinoceros/Grasshopper, and SketchUp. The applications of CFD plug-ins in urban and building design are reviewed according to three types: single-objective, multi-objective, and coupling simulations. Two primary roles of CFD plug-ins integrated into the design process, including providing various micro-scale numerical simulations and optimizing the original design via feedback results, are analyzed. The issues of mesh generation, boundary conditions, turbulence models, and simulation accuracy during CFD plug-in applications are discussed. Finally, the limitations and future possibilities of CFD plug-ins are proposed.

Urban vulnerability in the EMME region and Sustainable Development Goals: a new conceptual framework

Article

Feb 2022

Crises have shocked the global population and forced entire nations to shift their operations and priorities. The adverse effects of these crises primarily impact cities and their inhabitants; nevertheless, inherently, they have the potential to overcome them. Urban centres are home to around half of the global population, and often they are correlated to high standards of life, mostly in the Western world. Nevertheless, cities are highly flawed and, at times, are coming up short when it comes to accommodating human needs. Thus, the motivation of this work is to investigate urban vulnerabilities linked to the broader topic of climate change, focusing on urban centres in the Eastern Mediterranean and the Middle East region. This study has a dual purpose: to introduce a content-based approach of analysis, akin to bibliometrics, using proxies and links to recreate a research landscape and investigate urban vulnerability under specific conditions and how it affects public health; ultimately, offering a tentative definition of it. The novelty of this study is the proxies and links approach, through which we have identified the major trends in urban vulnerability research, as well as possible under-explored themes, by interpreting qualitative findings into more tangible ones.

Knowledge Map of Urban Morphology and Thermal Comfort: A Bibliometric Analysis Based on CiteSpace

Article

Full-text available

Sep 2021

In the context of global climate change, urban morphology is closely related to thermal comfort and contributes to sustainable urban development. Academics started to pay attention to related topics and carried out many studies during the last decades. This paper aims to summarize the research achievements and the development track for future studies. The Web of Science database and CiteSpace were used in this paper to conduct a bibliometric analysis of 556 studies in related fields from 1993 to 2020. Using a three-level co-occurrence analysis of 446 keywords, 1187 cocited literature clusters, and 15 landmark studies, the research topics and mainstream research frameworks were identified. The results show that with the increasing participation of disciplines such as computer science, ecology, and chemistry, the purpose of future research will shift to a focus on anthropogenic heat emissions, energy consumption, air pollution, and other aspects, and new research tools will be needed. In addition to building-scale and block-scale morphology, urban-scale morphology and green infrastructure will become the focus in the future. This study provides a systematic review of research about urban morphology and thermal comfort, which can inspire other researchers and policy makers.

Thermal Comfort in Urban Open Green Spaces: A Parametric Optimization Study in China's Cold Region

Thesis

Full-text available

Sep 2023

In this study, typical open spaces were selected in the urban area of Lanzhou, China, with varying distances from the Yellow River and different plant configuration spaces. Then, the thermal perception of respondents was investigated through meteorological measurements, thermal comfort questionnaires, and parametric modeling. The findings indicate the following: (1) Wind speed decreases significantly as the distance from the Yellow River increases in the three open green spaces. (2) The cold lake effect of the Yellow River dominates the wind environment. (3) The closest site to the Yellow River exhibits the strongest correlation between wind speed and the respondents' thermal sensation. (4) There is a strong positive correlation between the model output and different spatial measurement values. (5) There is a certain discrepancy between the UTCI values and the actual measurements, but the fit is high and consistent with an R-squared value of 0.936. This study quantitatively evaluated the thermal comfort and perception in typical spaces and validated the reliability of parameterized modeling for such spaces, providing a reference basis for thermal environment planning in these spaces.

Improvements, extensions, and validation of the Urban Weather Generator (UWG) for performance-oriented neighborhood planning

Article

Jul 2022

Policymakers have to assess and optimize neighborhood-scale planning aspects to profit from climate mitigation and adaptation measures due to various thermal environmental concerns. There are many models to evaluate the local thermal environment, but their outputs or complexity limit their application in performance-oriented neighborhood planning. In this study, the Urban Weather Generator (UWG) was updated to meet the needs of neighborhood planners. The model improves the radiation, vegetation, and convective heat transfer calculation processes to better match the actual physical representation of the neighborhood. Besides, the functions of the model are extended to calculate the mean radiant temperature (MRT) and water temperature for the evaluation of outdoor human thermal comfort and blue infrastructure effects. A new graphical interface also makes it easier for planning decision-makers to start quickly. Then, the prediction results of the updated model are evaluated with the neighborhood observations of the hot and humid regions of Guangzhou and Nanning. The air temperature, relative humidity (RH), and MRT results revealed that this novel model performs quite consistently and demonstrated the reliability and computational efficiency of the UWG model. In the early stages of thermal environment evaluation, the UWG model can be used for performance-oriented neighborhood planning.

Design optimization of urban typologies: A framework for evaluating building energy performance and outdoor thermal comfort

Article

Jan 2022

In the physics-based simulation of urban geometries, the outdoor environment was usually simulated separately from buildings – until recently, when the holistic assessment of the urban environment began to attract more attention. Although analyzing design alternatives with multiple objectives is still a challenge, computational tools enable generating thousands of scenarios to rapidly assess performance corresponding to a specific goal. In this study, we developed a multi-phase optimization framework for conceptual urban design. We tested this framework for urban typologies in Syracuse. The energy performance of each alternative was compared with a baseline. The alternatives that generate wasteful energy performance were filtered out first, then remaining scenarios that performed better than the baseline were analyzed using outdoor thermal comfort autonomy (OTCA). Mid-rise multifamily buildings showed the best performance (55.8% energy improvement compared to the baseline). Although hot week outdoor comfort satisfaction among selected mid-rise typologies was high (92.9–98.5%), the satisfaction in cold week was very low (between 8.4–11.6%) among them. This framework contributes to identifying an acceptable range of design solutions by broadening the perspective of the field toward using a more customized optimization framework in early design that will further guarantee the requirements of energy efficient and sustainable cities.

A parametric optimisation study of urban geometry design to assess outdoor thermal comfort

Article

Sep 2021

Over the last two decades, urban geometry has been shown to be a key determinant of the microclimatic conditions in urban areas. This study uses the Ladybug-tools, the plugins of Grasshopper3D to optimise building heights, street widths and orientation to maximise outdoor thermal comfort, represented by the diurnal average Universal Thermal Climate Index (UTCI). In the hot-arid climate of Cairo, Egypt, the optimised parameters of symmetrical and asymmetrical urban canyons are compared with the Egyptian Construction Act's design regulations. The results show a strong negative correlation between the height-to-width (H/W) ratios and the output UTCI, with R² = 0.71, and much stronger (R² = 0.91) if east-west orientations are excluded from the results, exceeding correlations previously reported for Cairo. Maximum UTCI reductions due to changing H/W and orientation approach ∼6°C. Considerable variation is shown in the strength of the correlation between UTCI and the asymmetrical H/W ratio of each flank, with R² = 0.81 for Southeast side compared to R² = 0.4 for Northwest side. Design recommendations are given urban planners based on using the optimised parameters that at least achieve a UTCI reduction benchmark that exceeds those resulting from using the regulations’ thresholds.

Summer Thermal Conditions in Outdoor Public Spaces A Case Study in a Mediterranean Climate

Article

Full-text available

May 2021

Comfort in public spaces is essential to their attractiveness and continued role in improving human quality of life. Acceptable thermal conditions are determinant to ensuring users’ comfort. This study undertakes an assessment of three urban sites in Arouca, in the north of Portugal, using ENVI-met software. Simulations test the influence of pavement and façade covering material, vegetation, and site morphology. The climate of the region is classified as Mediterranean Csb, with rainy winters and dry and mildly warm summers. A typical summer day is considered. The results reveal that a combination of factors might lead to thermal discomfort even in this mild climate on an average day, mainly due to heat exchange by radiation. In addition, the impact of alterations to surface properties depends on the morphological characteristics of the site, e.g., high albedo of the pavement may lead to a decrease or an increase in mean radiant temperature, depending on the space. This variability is present in the effects observed at the studied sites. A high façade albedo always contributes, in these cases, to thermal discomfort. The conclusions of the present study highlight the importance of performing a specific study for each urban site whenever an intervention is to be planned.

sustainability-13-05348 Published

Article

Full-text available

May 2021

Assessing residential energy performance and outdoor thermal comfort within four urban typologies in Syracuse

Conference Paper

Apr 2021

In the context of climate change, the architectural sector slowly turns its interest toward holistically assessing effects of design on the neighborhood scale. In addition to the importance of residential energy performance, improving well-being in outdoor spaces should be considered in the design stage that can potentially decrease the cost and environmental impacts of buildings. Consequently, this work implements energy and comfort simulation tools to search for the best performing results of the existing condition of the built environment in Syracuse, New York, United States. This work explores the design features and characteristics of interconnected aspects of Low-rise, Mid-rise, and High-rise urban typologies, including energy performance and outdoor thermal comfort. Mid-rise multifamily buildings have shown the best performing results. The findings of this study contribute to identifying better design solutions that further will guarantee the predefined requirements of more energy efficient and responsive buildings in this climatic context.

Study on multi-objective and parametric optimization of the urban thermal environment at the regulatory planning level for hot and humid regions | 基于多目标和参数化的湿热地区控规层面城市热环境研究

Thesis

Full-text available

Apr 2023

Genyu Xu

Rapid population growth accelerates urbanization, and human activities exacerbate climate change, leading to a series of urban thermal environment problems, especially in hot and humid regions. In China, regulatory planning is a crucial aspect of urban planning significantly impacting the emergence and development of urban thermal environment problems. However, the current methods for evaluating and optimizing the urban thermal environment at the regulatory planning level are relatively insufficient. In-depth study on the urban thermal environment at the regulatory planning level in hot and humid regions, assessment of the impact and risk of meteorological background on the environment and residents, and then regulation of the thermal environment through parameterization of planning control elements, can consider the urban heat island effect, thermal safety and thermal comfort, building energy consumption and other multi-objectives to effectively mitigate urban thermal environment problems. Numerical simulation is an important way to study the urban thermal environment, and at the regulatory planning level, new models that combine multi-parameter and multi-objective evaluation are needed. In order to do this, this study shows how the algorithms and functions of the Urban Weather Generator (UWG) model can be made better and how they can be added to. In terms of algorithms, the radiant energy allocation algorithm for uniform three-dimensional rectangular building arrays, the roughness algorithm that takes into account vegetation, the vegetation energy allocation algorithm that takes into account weather, and the convective heat transfer calculation algorithm that improves the wind speed reference height are introduced. In terms of functions, the mean radiant temperature and the water temperature are extended. Following that, simulations are carried out using the improved and extended new UWG model in Guangzhou and Nanning, typical cities in hot and humid regions, and the air temperature, relative humidity, and mean radiant temperature at the regulatory planning level are evaluated using the measured data. The results show that the new UWG model performs well in predicting the trends and numerical results of the evaluated parameters (taking Guangzhou as an example, the coefficients of determination of the predicted air temperature, relative humidity, and mean radiant temperature are 0.966, 0.720, and 0.828, respectively, and the root mean square errors are 0.93 ℃, 6.59 %, and 2.34 ℃, respectively, and the mean bias errors are 0.10 ℃, 1.41 %, and −0.69 ℃, respectively), and the model has sufficient stability to simulate the changes in the thermal environment over long time periods. To carry out urban thermal environment assessment at the regulatory planning level, it is necessary to parameterize various types of thermal environment information and conduct a comprehensive evaluation from multiple dimensions. In order to do this, this study proposes a multi-dimensional urban thermal environment information extraction and evaluation method and analyzes the central city of Guangzhou as an example. First, the thermal environment information is extracted from multiple data sources such as remote sensing inversion, visual interpretation, field research, and social perception by combining the Local Climate Zone (LCZ) system and building classification, and a thermal environment database is established for the central urban area of Guangzhou. Then, relevant thermal environment parameters were input into the new UWG model to analyze the thermal environment differences in the central area of Guangzhou from three objectives: urban heat island intensity, universal thermal climate index (UTCI), and building cooling energy demand. The research results reveal that there is some variation in the degree of superiority and inferiority of the thermal environment in each LCZ area under different thermal evaluation objectives, and the thermal environment of the area represented by LCZ 3 (compact low-rise building areas) is the most unsatisfactory. The global PAWN sensitivity analysis further shows that building height, building density, and wall-to-ground area ratio are the three factors with the greatest influence on the thermal environment, with their PAWN indices all greater than 0.2. Planning-related factors like urban morphology, blue-green infrastructure, anthropogenic heat from transportation, albedo, and building function type distribution have different effects on the thermal environment over time and space. By quantitatively analyzing each factor, the degree of influence and stability of the spatial and temporal variation of each factor can be developed into a targeted planning strategy to achieve the best thermal mitigation effect. Uncertainty in the planning and design process could affect the thermal environment, which makes it harder to get the planning results that were wanted. To address this issue, this study constructs a multi-objective parametric thermal environment optimization design platform based on the new UWG model within the parametric plug-in Grasshopper in the planning scheme modeling software Rhinoceros 3D. The platform can evaluate the thermal environment at the regulatory planning level, provide suggestions on the values of planning control elements with full consideration of robustness, generate Pareto-optimal solution sets, and realize multifaceted evaluation and optimization of the thermal environment in the planning and design processes. Further, a climate adaptation planning process with the thermal environment as the core is proposed to incorporate the impact of the thermal environment into the decision-making process at the regulatory planning level. The multi-objective evaluation of thermal environment and parametric optimization applications is carried out with two regulatory planning cases as examples. The former compares the changes in urban heat island intensity, outdoor human thermal safety and comfort, and cooling energy demand for 8,760 hours of a typical meteorological year before and after the program modification and provides a quantitative method for comparing and selecting different control schemes from the thermal environment perspective. The latter provides an effective multi-objective parameterization method for optimizing the thermal environment by filtering out the thermal environment control units that need to be optimized based on the rapid calculation of multiple thermal environment control unit-related parameters, conducting a parametric search to obtain the Pareto-optimal solution set, and then outputting the corresponding proposed values of the planning control elements for the decision of the planner. In summary, this study suggests a method for evaluating and improving the urban thermal environment at the level of regulatory planning. The method uses the new UWG model to extract multivariate urban thermal environment parameters based on the LCZ system and building classification perspective, constructs a multi-objective parametric thermal environment optimization design platform, evaluates the multidimensional impact of planning control elements on the urban thermal environment, realizes rapid, quantitative, and multi-objective regulation of the thermal environment at the regulatory planning level, and provides a theoretical basis and technical support for evaluating and optimizing the thermal environment at the regulatory planning level.

From repetition to diversity: A workflow for energy-driven optimization of heterogeneous urban blocks in hot climates

Conference Paper

Full-text available

Nov 2022

Despite the global trend toward mixed-use developments as a key strategy toward urban sustainability and compactness, quantitative research on the energy performance impacts of heterogeneous urban environments of different building typologies and uses is currently lacking. This study bridges this gap by offering an analytical method to explore and optimize the energy load and generation performance of an urban block in a diverse building-use and layout configuration. The methodology includes a two-phase analytical approach in Grasshopper-first, a multi-objective optimization (MOO) study using the block's energy load cover factor and the context solar exposure as its objectives; and second-a visual selection of the non-dominated results from the optimization based on several environmental performance indicators. The combination of these two analytical modules offers a novel analytical framework for designers and policymakers, through which they can reach an optimized starting point of building-use and mass distribution on the site, based on several quantitative environmental performance indicators.

Estimating the outdoor environment of workers’ villages in East China using machine learning

Article

Dec 2022
BUILD ENVIRON

Workers' villages in East China represent a typical form of residential government-built settlements constructed between the 1950s and the 1980s to address the housing shortage. Recent emphasis has been paid to optimizing wind and thermal comfort in older neighborhoods, following the urban renewal trend. This paper collected the geometries of 150 workers' villages. Pedestrian-level wind and Universal Thermal Climate Index (UTCI) were calculated for workers' villages using validated simulation software. Seven machine learning (ML) algorithms were compared for modeling the nonlinear relationship between the building morphology and the outdoor environment of the workers' villages. The ensemble model, especially the Adaboost model, performs best when predicting static wind ratio and UTCI with R² values of 0.89 and 0.99. The trained models were applied to estimate the outdoor environment of 1118 workers' villages in East China. The result shows most workers' villages have static wind ratios over 0.7. Workers' villages in Jiangsu endure more extreme summer heat, whereas workers' villages in Zhejiang have a higher static wind ratio in winter and summer. The use of ML offers a quicker estimation of outdoor wind and thermal comfort in large-scale workers’ villages than numerical simulations, therefore shedding light on the targeting of urban renewal.

Shade and Thermal Comfort in Courtyards: Experimental Versus Simulation Results

Article

Full-text available

Nov 2022

Outdoor comfort is gaining attention in the design of our cities to face the current context of rising temperatures. Although simulation is required to inform the early design stage of projects considering outdoor space and strategies to improve their thermal performance, different tool options must be compared through monitoring to determine the accuracy of their modeling. This study analyses the thermal comfort benefits of the installation of a shading device in a courtyard in the Mediterranean climate. In the study, two simulation workflows were analyzed, one using ENVI-met software and the other using the Ladybug Tools, to evaluate their performance. Air temperature monitoring data were used to validate and calibrate the simulations. Then, both were used to compute the Universal Thermal Climate Index (UTCI) to evaluate comfort. The results show that the simulation reproduced an air temperature reduction when the shading was installed, but this was not as high as the monitoring results (up to 13.7 °C). In the UTCI, in contrast, the two simulation workflows provided contradictory results. These differences were explained by analyzing the different parameters affecting comfort and the mean radiant temperature, and the air temperature was found to be the parameter most affecting the UTCI in this context. Thus, future research should focus on improving the accuracy of the simulations of these two parameters.

A Comparative Study of the Simulation Accuracy and Efficiency for the Urban Wind Environment Based on CFD Plug-Ins Integrated into Architectural Design Platforms

Article

Full-text available

Sep 2022

The deterioration of the urban environment is a problem which has captured the attention of governmental departments and researchers, who are committed to improving the urban environment from the perspective of optimizing urban morphology. Although many researchers have applied computational fluid dynamics (CFD) plug-ins to study the problems of urban ventilation and pollutant accumulation, studies on the reliability and simulation accuracy verification of CFD plug-ins are currently scarce. Therefore, we used three CFD plug-ins based on different architectural design platforms to evaluate and compare their operation difficulty, simulation accuracy, and efficiency through the analysis of the simulation results of urban ventilation. This study complements the reliability validation of CFD plug-in simulations and guides urban planners and architects in the selection and application of CFD plug-ins. The results show that the CFD plug-in generally underestimates the wind speed at the pedestrian level and the prediction accuracy is poor in the wake area of obstacles, especially with the GH_Wind plug-in. Under the 0° inflow direction, the simulation results of the Butterfly plug-in were the most consistent with the experimental values. When the inflow direction increased to 22.5° and 45°, the Autodesk CFD showed the best simulation accuracy. Overall, Autodesk CFD achieves a balance between simulation accuracy and speed in urban airflow simulation.

THE EFFECTS OF CLIMATE CHANGE ON URBAN THERMAL COMFORT CONDITIONS

Article

Full-text available

Jun 2022

Climate change is a global reality, leading to consequences for both the natural and urban environment. These changes and their implications can be perceived in features such as ecological cycles, in the economic status of a country, or on the well-being and physical integrity of a population. Hence, this study aimed to analyse the effects of climate change on urban thermal comfort and the physiological limits of a population in a tropical city, applying the Physiological Equivalent Temperature (PET) index and correlating it to the local wet-bulb temperature. The method adopted consists of four stages: (1) assembling weather files for future scenarios; (2) setting up scenarios for computational simulations; (3) choosing the most adequate urban thermal comfort index; and (4) selecting a risk parameter to evaluate human health risk. The results show that the presumed urban temperatures, considering 2050 and 2080 scenarios as parameters, can cause serious damage to inhabitants' health, given the frequency of high temperatures recorded in some months of the year. Accordingly, it is clear that there is a need for balance between the temperature variables and relative air humidity is required, striving for better comfort conditions, as well as improving users' permanence in external environments.

Urban Ventilation in the Compact City: A Critical Review and a Multidisciplinary Methodology for Improving Sustainability and Resilience in Urban Areas

Article

Full-text available

Mar 2022

In the last decades, a tendency towards urban tissue densification has been observed to counteract the urban sprawl. Densification may be achieved through more compact built areas, preferring the vertical to the horizontal development of buildings but avoiding bulky high-rise building blocks. This strategy significantly affects several aspects of the microclimate and produces direct and indirect effects on human health and well-being. In this regard, air pollution and heat stress constitute two increasing threats to human health and well-being that need to be faced immediately. The involved phenomena are various, intertwined, and may lead to conflicting results. Hence, regenerating existing, well-structured, and stratified urban areas by densification is not an easy challenge. Urban ventilation may favor the mitigation of detrimental effects of air pollution and heat stress on human life. Therefore, a multidisciplinary methodology is presented for embedding urban ventilation performance evaluation into urban management and planning processes. The scope is to propose a framework for urban renewal plans that is citizens-centered and aims at improving their health and well-being in existing urban areas. The methodology builds upon the performance-based approach and is supported by the conceptual framework and the literature reviews provided through the paper.

Analysis of energy and entropy balance in a residential building

Article

Full-text available

Dec 2021
J CLEAN PROD

The energy performance of a building located in La Roca del Vallès, close to Barcelona in Spain designed under the near Zero Energy Building (nZEB) and Net Zero Energy Building (NZEB) criteria was investigated. The aim was to introduce entropy generation rate as a magnitude to describe energy efficiency in buildings. This was achieved by studying the energy and entropy balances using a commercial energy performance simulation software for different scenarios proposing different efficiency conditions. The annual energy and entropy flow balances cancel. Entropy generation was due to heat losses through the envelope, sun irradiance, appliances, lighting and occupation of the building. The building designed following nZEB criteria was compared with the same building with poorer energy performance. The first one generated 45,834 kJ K⁻¹ while the second one generated 79,985 kJ K⁻¹. This is an important result because with a single magnitude, entropy generation, we combine the impact of all energy transformations taking place in the building. Sun irradiance is found to be the most important entropy generation source: a building with sun irradiance can generate nearly 3.4 times more entropy than a shadowed building. Finally, we evaluated the generated entropy ratio between the transferred entropy to the environment in terms of Gouy-Stodola theorem and the cumulated entropy that contributes to building degradation. Although cumulated degradation entropy is well below the threshold of building collapse, practical degradation effects in the building were shown.

The Solar Block Generator: an additive parametric method for solar driven urban block design

Article

Full-text available

Nov 2021

This paper addresses the limitations of existing Solar Envelope (SE) methods to explore the trade-offs of solar radiation and urban shading, and to simultaneously account for several different Key Performance Indicators (KPIs). It offers an alternative parametric workflow-the Solar Block Generator (SBG)-which is based on an additive voxelization method by which multiple solar-driven massing alternatives are generated and evaluated for a given site, corresponding to a set of user-defined environmental KPIs. This method is tested here on an urban redevelopment case study in the Mediterranean (Tel Aviv). The results help achieve a more holistic approach for solar driven urban design.

A Benchmark Model for Predicting Building Energy and Daylight Performance in The Early Phase of Design Utilizing Parametric Design Exploration

Article

Full-text available

Sep 2021

Along with the enormous impact on computational development in architecture and urban design, the way in approaching the built environment is shifting and intended to look closer to performance and evidence-based design. This development holds promise in handling complex computation to approach desired targeted design goals. However, the implementation of form-finding and design performance optimization still lacks, particularly in Japan’s sub-tropical climate. This paper describes the parametric design and design exploration process’s implementation through the generative algorithm platform to develop a benchmark model to predict building energy and daylight performance and find possible design solutions from the iteration process during the early phase of the design process. The variables incorporated related to the glazing ratio, the length of the overhang, and building orientation. Grasshopper, a parametric-based plugin that works in Rhinoceros, is used to arrange a parametric definition for the overall experiment. The tools used to investigate the environmental analysis and energy consumption are Ladybug and Honeybee, and the exploration process will be conducted using Design Explorer. The context will be situated in Orio district and uses the EPW file of Kitakyushu city, Fukuoka, Japan. The results of this research furthermore can potentially be a comparison for more dynamic factors.

On the Optimisation of Urban form Design, Energy Consumption and Outdoor Thermal Comfort Using a Parametric Workflow in a Hot Arid Zone

Article

Full-text available

Jul 2021

The recent reports from the Intergovernmental Panel on Climate Change (IPCC) urge for the reconceptualization of our design of the urban built environments. However, current efforts to integrate urban environmental assessment into practice in Egypt are proving insufficient. This paper utilises the Ladybug tools simulation plugins to investigate the impact of changing the morphological characteristics of three-block typologies (scattered, linear and courtyard) and their associated parameters to understand their multidimensional relationship with environmental conditions, outdoor thermal comfort and energy use intensity. This study based in Cairo, Egypt, considers 3430 hypothetical geometrical configurations comprising of a variety of design parameters and indicators. The results show a strong correlation between the design parameters and the combined performance of thermal comfort and energy consumption (R2 = 0.84), with urban density having the strongest impact on both thermal comfort and energy use (R2 = 0.7 and 0.95, respectively). The design parameters exhibited a consistent impact on the different typologies, albeit with varying magnitude. Compact and medium-density urban forms are shown to elicit the best overall performance, especially for ordinal orientations (e.g., ~45°) across all typologies. Compact high-density scattered forms are favoured when considering thermal comfort, while courtyards outperform other typologies when considering energy efficiency and overall performance.

NEAR ZERO ENERGY BUILDINGS ENTROPY PERFORMANCE

Conference Paper

Full-text available

May 2021

Tall Buildings Cluster Form Rationalization in a Nordic Climate by Factoring in Indoor-outdoor Comfort and Energy

Article

Full-text available

Feb 2021
ENERG BUILDINGS

Considering climate change, controlling outdoor microclimates is an increasingly pressing concern. Microclimates have a significant effect on both outdoor and indoor comfort, and on the energy efficiency of buildings. This concern is particularly important as current climate conditions reveal that warmer summers are threatening the comfort of pedestrians and causing overheating in office environments, which is consequently increasing cooling energy consumption. A further concern is that this trend now extends to Nordic latitudes. Existing literature demonstrates how a local microclimate depends on many factors such as urban density, shape and orientation of buildings, the types of materials present, the number of green areas and anthropogenic activities. However, there is little research focusing on how reciprocal distances among tall buildings, and their relative position, affect outdoor and indoor comfort, and the associated energy consumption of buildings. This paper presents a unique and comprehensive insight into the interconnected nature of indoor and outdoor comfort via coupled simulations. It presents a study of clusters of tall commercial buildings located in the Nordic climate of Tallinn (Estonia) with different microclimates, and shows that the differences are due to variable shadowing and reflections and different wind patterns. The results, which focus on summer conditions, show that small variations of cluster layout strongly affect the local indoor and outdoor comfort, thus highlighting the need to conduct both studies simultaneously in research aiming to increase pedestrian and indoor comfort and resource efficiency.

A multi-objective optimization framework for designing urban block forms considering daylight, energy consumption, and photovoltaic energy potential

Article

Jul 2023
BUILD ENVIRON

A Simplified Outdoor Shading Assessment Method (OSAM) to Identify Outdoor Shading Requirements over the Year within an Urban Context

Article

Jul 2023

Phenomenon of courtyards being roofed and its significance for building energy efficiency

Article

Jun 2023
ENERG BUILDINGS

Influence of street configuration on human thermal comfort and benefits for climate-sensitive urban planning in Santiago de Chile

Article

Jan 2023

Global warming is a growing trend that challenges cities to adapt to future thermal conditions. Heat stress is one of the consequences that must be tackled through urban planning and architectural design by linking urban geometry and human biometeorology. The present research quantifies the effects of urban street configuration on human thermal comfort to formulate urban guidelines for city growth and protection of human life in the era of climate change. Meteorological data from a weather station (2010-2019) was used to assess thermal indices such as Physiologically Equivalent Temperature (PET) in open spaces and in various urban canyon configurations. A parametric study was conducted using the RayMan model in two urban development schemes: in-filling and sprawl. Simulations applied to the urban canyon addressed aspect ratio and orientation using temporal analyses. Findings reveal a similar pattern of thermal conditions in both schemes, except for sprawl with H/W = 2.5. In the summer months, the east-west axis displays the highest PET discomfort value, while the north-south axis offers the highest PET comfort value. The pattern showed that the lower the aspect ratio, the greater the heat stress in January, but performance was stable in July with aspect ratio ≥1.5.

Influence of street configuration on human thermal comfort and benefits for climate-sensitive urban planning in Santiago de Chile

Article

Jan 2023

A review of integration between BIM and CFD for building outdoor environment simulation

Article

Nov 2022
BUILD ENVIRON

Numerous studies have demonstrated that the climate of cities and human settlements can affect building performance and human comfort. Historically, ambient data were collected through on-site measurements or simulations using physical models. Nowadays, with the advancement of data-based techniques and computing resources, especially Building Information Modeling (BIM) used to address the requirement for building data and numerical simulation with Computational Fluid Dynamics (CFD) used to assess building outdoor environments have increased in popularity. This paper presents a review of publications on this topic till 2022. The reviewed publications are categorized into different sections according to the following characteristics: general BIM-CFD integration process, building design optimization, and integration process optimization. In addition, the reviewed publications are categorized by the BIM design parameters, CFD simulation equations, building locations, BIM software, and BIM-CFD integration approach under consideration. This review discusses current research trends and major research issues in detail and presents future perspectives. The results show that from the early to late stages of the BIM-CFD integrated environmental studies, the BIM parameters considered were shifted from 3D to nD (e.g., energy). Meanwhile, CFD models and new technologies were chosen more carefully to meet the needs of different building scenario simulations. Although the current dynamic data transfer and synchronization capabilities between BIM and CFD need to be improved and rely heavily on the development of efficient Application Programming Interfaces (API), both BIM and CFD still play an indispensable role in building design practice.

Effect of thermal inertia and natural ventilation on user comfort in courtyards under warm summer conditions

Article

Nov 2022
BUILD ENVIRON

Thermal inertia and natural ventilation are strategies widely used and studied in indoor building performance. However, little analysis has been done on its effect on the outdoor microclimate. Furthermore, this analysis is needed for the specific case of inner courtyards, given that these outdoor spaces are highly affected by their surrounding building surfaces. This study takes a real-scale prototype constructed for the 2019 Solar Decathlon competition in Hungary as a case study to analyze the thermal inertia and ventilation effects on the thermal performance of courtyards. Monitoring data are used to calibrate a simulation model that combines BES and CFD to predict the thermal performance for three wall configurations with different inertia and two situations: the closed courtyard and the ventilated courtyard. Results show that the thermal inertia and ventilation effects inside the courtyard are similar to what is generally observed inside the buildings. Thermal inertia for the close courtyard was able to increase the courtyard tempering effect up to 1.6 °C and comfort up to 1.4 °C UTCI. The ventilation reduced the tempering potential of the courtyard during the day, but it also reduced overheating during the night. Depending on the wind speed it can also increase thermal comfort.

The Effect of Building Orientation on Energy Efficiency

Preprint

Full-text available

Jun 2022

Shahryar Habibi

The energy demand of buildings is currently central to the generation of greenhouse gas emissions, primarily from the combustion of fossil fuels for energy. As energy demand increases, it is critical to reduce energy-related greenhouse gas emissions in the building sector. Several architectural studies have shown that building orientation is one of the first decisions that affect building performance. However, there are still many misaligned buildings where energy costs are higher than when standard methods are used. To address this discrepancy, a research study was conducted using different building profiles. Simulations were run as part of the research to link a building's orientation to performance measures such energy use intensity (EUI), cooling load, and heating load. In addition, the impacts of solar heat gain and ventilation air exchange values on building energy performance at various orientations were demonstrated. Although building orientation affects building energy performance, the study shows that not all building efficiency factors are equally affected by orientation, and the effects vary by climate zone and building size.

The disciplines of architectural design and construction technology

Chapter

Jan 2022

Shahryar Habibi

This chapter offers new innovative approaches for architectural design using digital tools.

Thermal Comfort Effects in Different Open Green Spaces: A Parametric Optimization Study of Urban Spaces Design in China's Cold Region

Article

Jan 2022

A review of studies and modelling of solar radiation on human thermal comfort in outdoor environment

Article

Feb 2022
BUILD ENVIRON

Thermal environment influences human thermal comfort significantly when people have outdoor activities. Four environmental parameters determine outdoor thermal comfort, which are air temperature, relative humidity, wind speed, and solar radiation. It is noteworthy that, different from the indoor environment, solar radiation significantly affects outdoor thermal comfort, which needs to be comprehensively understood and analyzed. In this paper, we focused on thermophysiological models and thermal comfort models with consideration of solar radiation, applications of these models, and discussed existing problems and future potential works. Here, those key points are summarized: (1) Many comprehensive thermophysiological models for simple and complex body models have been put forward. For solar load on the human body, Fanger's model showed a good fitting degree in predicting absorbed solar radiation. (2) Existing thermal indexes may not be suited to dynamic conditions of solar radiation while the DTS model may be a good example for thermal comfort evaluation under dynamic solar radiation. (3) For temporary conditions, non-Fourier models, such as the dual phase-lag model, may be applied in thermophysiological models due to the non-uniform internal structure of biological tissues. (4) A scheme of establishing dynamic thermal comfort models is put forward, considering dynamic features of environment parameters, thermophysiological parameters, and thermal adaptation.

Thermal comfort modelling and empirical validation of predicted air temperature in hot-summer Mediterranean courtyards

Article

Jan 2022

Courtyards are a passive strategy to improve the energy performance of buildings. However, the accurate simulation of courtyards’ thermodynamic performance in the early design stage is still challenging, even though there has been an emergence of new methods to assess outdoor simulation. This paper tests a novel workflow using the Ladybug Tools that uses CFD for outdoor temperature and comfort simulation of courtyards and is suitable for the early stage of building design, comparing the results with monitored data and simulated data from ENVI-met. Results show high accuracy in the prediction of temperature from Ladybug Tools with error ranges from 3.8–7.5%, which is lower than with ENVI-met. In terms of comfort, the simulated Universal Thermal Climate Index values differ by up to 10°C between ENVI-met and the Ladybug Tools. The results show a significant improvement towards the design of the courtyard in the search for net-zero energy buildings.

Fast fluid dynamics simulation of the airflow distributions in urban residential areas

Article

Nov 2021
ENERG BUILDINGS

Conventional CFD models can resolve complex physical fields around single or multiple buildings with high spatial resolution, but they are unable to meet the demand for fast simulations with meter-level spatial resolution and minute-level temporal resolution due to the huge computational domain with numerous grids for urban residential areas. In this paper, three fast fluid dynamics (FFD) models with different pressure-correction schemes (i.e., SIPC, NIPC and RIPC) for solving Navier-Stokes (N-S) equations are implemented in OpenFOAM. The computational accuracy and speed of these FFD models is validated and analyzed through three cases. For the prediction of airflow distribution in urban residential areas, the average relative error between the simulation results of the FFD models and the wind tunnel experimental data is less than 15 %. The speeds of these FFD models show SIPC>NIPC>RIPC from fast to slow under the same number of grids, turbulence model and time step size, and these speeds are about 15 times faster than the commercial CFD code Ansys Fluent. The computing time of the three FFD models approximately shows a linear increase with the number of grids, and the difference in computing time between the other two FFD schemes and the SIPC scheme becomes larger and larger as the number of grids increases from 0.3 million to 3.0 million. There is almost no difference in the number of grids required to achieve grid independence for the three FFD models. On the premise of ensuring accuracy, the SIPC scheme has the fastest computational speed, and it could be preferred to quickly evaluate the airflow distribution of different residential areas in urban planning stage.

From Simulation to Data-Driven Approach: A Framework of Integrating Urban Morphology to Low-Energy Urban Design

Article

Aug 2021
RENEW ENERG

Energy-efficient urban design is an important prerequisite to sustainable urban development and reduction of greenhouse gas emissions. This study proposes an automatic framework to optimize urban design through the use of an urban building energy model. Three optimization goals were defined: maximum solar energy utilization, solar lighting of the first floor, and minimum building energy demand. Urban morphology was integrated into the optimization process as the bridge between the urban design scenario and the actual urban block. To validate the model, this study abstracted basic urban forms from actual urban contexts to generate urban blocks with the Rhino tool and run optimization in the Wallacei X, for multi-objective optimization in Rhino. The long short-term memory (LSTM) network was applied to infer energy performance of 41 actual urban blocks in Jianhu, China. In the results, the proposed framework can be validated feasibly with optimization of 100 iterations. A set of optimal results will be achieved for three goals and five clusters defined for different concerns of urban design strategies. The LSTM can achieve the best accuracy of 1.21% and 1.37% for energy generation of photovoltaic and total building energy use intensity respectively.

Unsteady-state CFD simulations on the impacts of urban geometry on outdoor thermal comfort within idealized building arrays

Article

Jul 2021

This study investigated outdoor thermal comfort within 5 × 5 idealized building arrays on five consecutive days by conducting unsteady computational fluid dynamic (CFD) simulations. The dynamic interacting effects of building height topology, building distance and building layout on airflow patterns, spatial distributions and spatially averaged outdoor thermal environment were evaluated by UTCI (Universal Thermal Comfort Index). CitySim Pro was used to simulate the transient solar-induced temperatures on the walls of buildings and grounds inside building arrays, which were then set as thermal boundary conditions in CFD simulations. The results showed that the influence of transient wind conditions on airflow patterns and urban thermal comfort was significant so steady simulations or unsteady simulations of one typical day might not provide a complete overview of the wind-thermal environment. The results also showed that presenting the results by average UTCI or spatial distribution could lead to different conclusions on the impacts of urban geometry on urban thermal comfort, especially the impact of building distance. Increasing the building height always provided positive effects on urban thermal comfort. The spatial distributions of UTCI in three-dimensional building arrays with equal aspect ratio diverse significantly, which was not observed in the pattern of average UTCI.

Towards High-Resolution Annual Outdoor Thermal Comfort Mapping In Urban Design

Conference Paper

Full-text available

Apr 2020

Global warming and increasingly dense cities lead to poor outdoor thermal comfort that may not only be detrimental to our health and well-being but also decreases social and commercial activities. Although workflows for the analysis of thermal comfort exist, they have yet transitioned into the quotidian architectural design process. Our work-flow allows for annual outdoor comfort analyses that are seamlessly integrated into a commonly-used CAD environment. We simulated the annual outdoor thermal comfort on a university campus and discuss which simplifications seem appropriate by means of preliminary on-site measurements. The results exemplify the possibility to conduct such analyses within reasonable time and accuracy if some simplifications to the UTCI estimation are acceptable.

A Cylindrical Meshing Methodology for Annual Urban Computational Fluid Dynamics Simulations

Article

Full-text available

Dec 2019

For urban CFD simulations, it is considered a best practice to use a box-shaped simulation domain. Box-shaped domains, however, show drawbacks for airflow from several wind directions as remeshing and additional preprocessing steps become necessary. We introduce a routine to create a cylindrical mesh that expedites the simulation of arbitrary wind directions using OpenFOAM. Results computed with the cylindrical domain are validated against wind tunnel data. We report that the cylindrical method yields comparable results in terms of accuracy and convergence behaviour. Further, run time comparisons in a real-world scenario are conducted to discuss its advantages and limitations. Based on the findings, we recommend using the cylindrical approach if at least eight wind directions are analyzed for which we report 18% run time savings. The cylindrical domain along with automated best practice boundary conditions has been implemented in Eddy3D – a plugin for Rhinoceros.

Synergetic urban microclimate and energy simulation parametric workflow

Article

Full-text available

Nov 2019

Although the interrelations between urban microclimates and energy demand have been acknowledged, few workflows integrate microclimatic boundary conditions to predict energy demand in parametric morphological studies. This paper helps bridge this gap by introducing a novel workflow which brings together energy and microclimatic modelling for a synergetic assessment at the block scale. The interrelation between form, energy and urban microclimatic conditions is explored here in the climatic context of Tel Aviv by coupling Envimet and EnergyPlus. The potential of this coupling is explored in three different block typologies, each tested for four different density scenarios focusing on the cooling demand on a typical hot day. Results show the substantial increase of as high as 50% in cooling demand when the microclimatic weather data is taken into account and indicate the potential to capitalize on new computational tools which allow to quantify the interrelations between urban form, microclimate and energy performance more accurately.

Shade maps for prioritizing municipal microclimatic action in hot climates: Learning from Tel Aviv-Yafo

Article

Full-text available

Nov 2019

This article presents a methodology for evaluating microclimatic summer conditions across an entire city, focusing on the provision of outdoor shade as a primary comfort indicator. Based on high-resolution 2.5D and 3D mapping of buildings, ground, and tree canopies in Tel Aviv-Yafo, a city of hot-summer Mediterranean climate, we employed a detailed calculation of solar exposure of streets and open spaces (public and private) using commonly available GIS algorithms. The raw results of these calculations were used for calculating summer Shade Index values for every street segment and neighbourhood of the city, which were then plotted to a comprehensive 'shade maps' reflecting the city's spatial hierarchy of shade. The shade maps, combined with analysis of tree canopy cover on similar scales, enabled to relate building and tree morphologies to outdoor shade conditions. For prioritizing intervention of local planning authorities in improving poor shade conditions or conserving highly-shaded locations, we related the climatic analysis to space-syntax classification of streets according to their potential to attract pedestrian movement, and produced a city-wide map that highlighted streets that have high pedestrian movement potential while requiring high level of shade intensification or conservation.

A parametric approach to optimizing urban form, energy balance and environmental quality: The case of Mediterranean districts

Article

Full-text available

Aug 2019
APPL ENERG

Despite the global call for a paradigm shift towards new environmentally conscious urban planning, little has changed in practice, especially in hot climatic regions. This paper helps bridge this gap by introducing an automated parametric workflow for performance driven urban design. The methodology was tested here in the climatic and urban Mediterranean context consists of a parametric typological analysis, automated through Grasshopper with a total of 1920 iterations. For each iteration the performative effects of both building (i.e. typology, window to wall ratio and glazing properties) and urban design parameters (i.e. distance between buildings, floor area ratio and the orientation) were evaluated for residential and office building uses. The performance metrics - monthly/hourly energy load match and spatial daylight autonomy - were calculated using Energyplus and Radiance, respectively, and recorded for each iteration. The main results indicate substantial performative differences between typologies under different design and density scenarios; the correlation between the shape factor and the energy load match index as well as the benefits of the courtyard typology in terms of energy balance, with its challenging daylight performance, were established. These results demonstrate the potential of this workflow to highlight the design trade-offs between form and environmental performance considerations by designers and thus provide a new way to bridge the performative gap between buildings and their urban surroundings. Its application should help designers and policy makers contextualize nearly zero energy block concepts as well as define new criteria and goals.

A review of assessment methods for the urban environment and its energy sustainability to guarantee climate adaptation of future cities Contribution Highlights

Article

Full-text available

Jun 2019
RENEW SUST ENERG REV

Reviewed assessment methods for the urban environment • Critically analysed papers working on urban climate and energy demand, outdoor thermal comfort and the urban energy systems. • Demonstrated the links between the processes • An integrated workflow is proposed for assessment of the urban environment. Abstract The current climate change is calling for a drastic reduction of energy demand as well as of greenhouse gases. Besides this, cities also need to adapt to face the challenges related to climate change. Cities, with their complex urban texture and fabric, can be represented as a diverse ecosystem that does not have a clear and defined boundary. Multiple software tools that have been developed, in recent years, for assessment of urban climate, building energy demand, the outdoor thermal comfort and the energy systems. In this review, we, however, noted that these tools often address only one or two of these urban planning aspects. There is nonetheless an intricate link between them. For instance, the outdoor comfort assessment has shown that there is a strong link between biometeorology and architecture and urban climate. Additionally, to address the challenges of the energy transition, there will be a convergence of the energy needs in the future with an energy nexus regrouping the energy demand of urban areas. It is also highlighted that the uncertainty related to future climatic data makes urban adaptation and mitigation strategies complex to implement and to design given the lack of a comprehensive framework. We thus conclude by suggesting the need for a holistic interface to take into account this multi-dimensional problem. With the help of such a platform, a positive loop in urban design can be initiated leading to the development of low carbon cities and/or with the use of blue and green infrastructure to have a positive impact on the mitigation and adaptation strategies.

Climatic performance of urban textures: Analysis tools for a Mediterranean urban context

Article

Full-text available

Feb 2019
ENERG BUILDINGS

Urban heat island effect is almost always neglected in building energy simulations, due to difficulties in obtaining site-specific climate data with a district-scale resolution. This study aims at filling this gap for the Mediterranean urban context, presenting a set of tools to estimate the climatic performance of urban fabric at the local scale. The results are based on climatic analysis conducted in Rome (Italy) and Barcelona (Spain) with the Urban Weather Generator (UWG) model, validated using temperature measurements taken in urban meteorological stations. Parametric analysis of the UHI intensity was performed considering five key variables: urban morphology, vegetation cover, anthropogenic heat from buildings, anthropogenic heat from traffic and albedo. The results show that the variability of urban morphology has the major impact on urban temperature. Two robust relationships between three morphology descriptors of urban fabric and UHI intensity were established applying multiple regression analysis. Such relationships indicate that both the horizontal and the vertical density of buildings play a major role on the temperature increase in urban areas. Easy-to-use graphical tools have been provided to compare the climate performance of different urban textures and to estimate the average UHI intensity variability in Mediterranean cities.

Balancing urban density, energy performance and environmental quality in the Mediterranean: a typological evaluation based on photovoltaic potential

Article

Full-text available

Oct 2018

As research on the correlation between urban design and environmental performance is still lacking, the following long-standing question still stands – How far can we densify urban districts without sacrificing their energy balance and indoor environmental quality? This question served as the starting point for a parametric typological study conducted at the block scale in the context of Tel Aviv, with the overall aim of promoting performance driven design of Mediterranean urban environments. Dynamic input parameters included fenestration ratio, aspect ratios and floor area ratios of 5 different building typologies in both office and residential land uses. Environmental outputs included energy cooling loads, spatial daylight autonomy and the monthly average load match between energy demand and photovoltaic energy supply. The courtyard typology was found to achieve the best performance in terms of monthly Load Match, however mostly in residential uses of lower density. Although the high-rise typology offered the best daylight conditions, it recorded the worse performance in terms of energy balance and energy cooling demand. Results demonstrate the potential of a parametric typological workflow to effectively indicate the tradeoffs between single building and urban scale design considerations. This potential could be harnessed to assess the environmental feasibility of net zero energy typologies in Mediterranean climates and will be used for district energy studies as part of future work.

Periodic Urban Models for Optimization of Passive Solar Irradiation

Article

Full-text available

Mar 2018
SOL ENERGY

Urban sprawl and energy consumption issues suggest to consider how to design energy efficient dense cities. Solar radiation is a significant heat input in well insulated buildings in temperate climates. However, the solar masks generated by the surrounding buildings in dense urban areas can reduce significantly this energy gain. This paper proposes a definition of a district as a periodic urban fabric, where a given configuration of buildings, called urban cell, is repeated to represent the urban outline. It allows us to evaluate the relationship between cumulative solar potential on façades and urban shape, with solar masks that are consistent with the considered area. In this study, an evolutionary algorithm is used to explore the set of urban cells composed of a square grid of blocks of varying height. Four conditions for solar radiation are taken into account: clear sky direct radiation at the latitude of 50° North for three particular days (winter solstice, summer solstice and equinox), and annual direct and diffuse radiation based on the meteorological data of Paris, France. For each condition of solar radiation, the influence on the optimization results of the size of the area of interest and its built density is assessed. The results provide information on what are the urban shapes maximizing solar potential and give some quantitative indications on the amount of solar radiation that can be captured.

A critical review of daylighting metrics for residential architecture and a new metric for cold and temperate climates

Article

Full-text available

Feb 2018

Residential architecture constitutes one of the largest market segments in the construction sector. However, the attention that it is given in the field of daylight performance simulation is surprisingly low. This poses the question of whether existing daylighting metrics are well suited for residential design. Findings from 79 references are summarized, and a critical review of current climate-based daylighting metrics in the context of residential architecture is provided. It is found that existing workflows often overlook relevant aspects of daylight in residential spaces, such as diurnal and seasonal availability of daylight and access to direct sunlight. Hence, a concept for a new climate-based, annual evaluation framework that overcomes these shortcomings, called the residential daylight score, is introduced.

Overview and future challenges of nearly Zero Energy Buildings (nZEB) design in Southern Europe

Article

Full-text available

Sep 2017
ENERG BUILDINGS

A parametric sensitivity analysis of the influence of urban form on domestic energy consumption for heating and cooling in a Mediterranean city

Article

Full-text available

Sep 2016

Aristotelis Vartholomaios

The study presents the results of a parametric analysis of the impact of urban form on domestic energy consumption for heating and cooling. Three urban typologies, the pavilion, the slab and the perimeter urban block are examined using the dynamic building energy simulation software EnergyPlus. The simulation results are processed through a sensitivity analysis using the ‘standardised rank regression coefficients’ technique to determine the relative influence of the examined parameters on energy consumption. The study focuses on the Mediterranean city of Thessaloniki which has both heating and cooling requirements. The results support the argument that there is a synergy between the strategies of high urban compactness and passive solar design and that this synergy can be achieved at different urban densities.

Simulation-based daylighting analysis procedure for developing urban zoning rules

Article

Full-text available

May 2016
BUILD RES INF

Increasing urban density leads to a conflict between space-use efficiency and daylight access. Cities have traditionally relied on zoning guidelines that consist of section-based geometric evaluation techniques and/or hours of access to direct sunlight. However, it is now possible to quantify the performance of detailed design proposals before construction. Annual climate-based daylighting performance metrics for urban environments can be computed accurately, in high spatial resolution and in a timely manner. Given that massing design decisions at the urban planning level may make or break the long-term daylighting potential of a whole neighbourhood, the adoption of these tools by zoning boards, developers and urban planners seems particularly relevant. A simulation-based daylighting analysis procedure reveals the capabilities for both formulating more nuanced prescriptive zoning rules as well as for use by design teams. The procedure is used to evaluate the daylighting performance of 50 block typologies in New York City (NYC). The analysis demonstrates that certain urban massing approaches (e.g. pencil towers on a contextual base) outperform conventional massing strategies. A second case study application of an actual city block shows that innovative urban massings can improve access to daylight for the massing itself as well as for neighbouring buildings.

Outdoor Thermal Comfort: Impact of the Geometry of an Urban Street Canyon in a Mediterranean Subtropical Climate – Case Study Tunis, Tunisia

Article

Full-text available

Jan 2016

This paper discusses the impact of the geometry of an urban street canyon on outdoor thermal comfort. The study focuses on the Mediterranean subtropical climate of Tunis, Tunisia. The investigation was carried out by using the ENVI-met model, and run for a typical summer day in Tunis. We compared three fabrics whose streets have various H/W ratios and different orientations. The assessment of the outdoor thermal comfort was based on the UTCI. The results showed that the deepest streets are the most comfortable. This research demonstrated the importance of the prospect of the street and its orientation in the creation of a comfortable environment.

Ladybug: A parametric environmental plugin for grasshopper to help designers create an environmentally-conscious design

Article

Full-text available

Jan 2013

As high performance design is becoming more desirable in the field of architecture, the need for supporting architects with environmental analysis tools is also growing. Rhino/Grasshopper is one of the most widely used platforms that are used by designers today. There are already a number of environmental plugins developed for Rhino/Grasshopper. However, Ladybug offers several advantages that are currently not offered by existing Rhino/Grasshopper related environmental design plugins. Ladybug imports standard EnergyPlus Weather files (.EPW) in Grasshopper and provides a variety of 2D and 3D designer-friendly interactive graphics to support the decision-making process during the initial stages of design. It also simplifies the process of analysis, automates and expedites the calculations, and provides easy to understand graphical visualizations in the 3D modeling interface of Rhino/Grasshopper. It also allows users to work with validated energy and daylighting engines such as EnergyPlus, Radiance and Daysim. Integration with the parametric tools of grasshopper allows for almost instantaneous feedback on design modifications, and as it runs within the design environment, the information and analysis is interactive. The development is a free and open source; users can customize the tool based on their needs and contribute to the source code.Copyright

Urban Daylight simulation Calculating the daylit area of urban designs

Conference Paper

Full-text available

Jan 2012

This paper describes the development of a new tool that allows designers to simulate and evaluate the daylight potential of urban master plan proposals. The tool is a plug-in for the Rhinoceros3D CAD modeler and follows a two-step workflow. During the initial step, hourly solar radiation levels on all facades within an urban scene are simulated based on Radiance/Daysim. During the second step, exterior radiation levels are converted into hourly interior illuminance distributions using a generalized impulse response. Climate based daylighting metrics, such as daylight autonomy, are also computed. The results yielded by the new method are carefully compared to regular and substantially more time-consuming Daysim simulations. This comparison shows that the overall daylit area in the investigated master plan matches Daysim predictions within 10%. Given its implementation into the Rhinoceros3D environment, as well as the almost instant simulation feedback, the tool may serve as a generative method for designers.

The impact of urban design decisions on net zero energy solar buildings in Sweden

Article

Full-text available

Jan 2014

Planning for future energy-efficient and energy-producing buildings requires specific knowledge during the design process. Many design decisions taken by urban planners –form, density, roof type and orientation – have a significant effect on the conditions of such buildings, although urban planners might not always be aware of the effect of their design. This study examines the effects of important design decisions on the solar energy potential of net zero energy solar buildings. Typical Swedish building blocks with varying form, density, roof type and orientation were used to simulate the annual solar irradiation and energy production, and to calculate the load match for heating and electricity under Swedish conditions. Results of this study show that the urban density is the most influential parameter on the solar potential of building blocks. Furthermore, flat roofs often returned the highest load match value, while the effect of orientation on the solar potential turned out not to be that straightforward. With the results of this study, urban planners can make better informed decisions, while it also provides a ground for the net zero energy solar buildings discussion by exposing the boundaries of such buildings in the urban environment.

Contribution of Greening and High-Albedo Coatings to Improvements in the Thermal Environment in Complex Urban Areas

Article

Full-text available

May 2015

The aim was to identify microclimate characteristics in relation to ground cover in green areas and the reflectivity of building coating materials. Furthermore, microclimate modeling of temperatures was conducted using ENVI-met, to analyze the effects of improved thermal environments based on increased green areas and increased reflectivity of exterior coatings. The accuracy of ENVI-met was validated through comparisons with field temperature measurements. The RMSE deviation of the predicted and actual field temperature values was 3-6°C; however, the explanatory power was as high as 60%. ENVI-met was performed for commercial and single residential areas that have high densities of artificial cover materials, before and after changes related to development of green areas and to increase in the reflectivity of coating materials. The results indicated that both areas exhibited distinct temperature reductions due to the creation of green spaces. When the reflectivity of the coating material was increased, a temperature increase was observed in all land-use types. Therefore, in order to improve the thermal environment of complex urban areas, it is necessary to improve green-area development and to use high-reflectivity ground and building cover materials, while taking into account the spatial characteristics of land-use types and their surrounding areas.

Modeling the comfort effects of short-wave solar radiation indoors

Article

Full-text available

Jun 2015
BUILD ENVIRON

Umi – An Urban Simulation Environment For Building Energy Use, Daylighting And Walkability

Conference Paper

Full-text available

Aug 2013

One widely recognized opportunity to reduce global carbon emissions is to make urban neighborhoods more resource efficient. Significant effort has hence gone into developing computer-based design tools to ensure that individual buildings use less energy. While these tools are increasingly used in practice, they currently do not allow design teams to model groups of dozens or hundreds of buildings effectively, which is why a growing number of research teams are working on dedicated urban modeling tools. Many of these teams concentrate on isolated sustainable performance aspects such as operational building energy use or transportation; however, limited progress has been made on integrating multiple performance aspects into one tool and/or on penetrating urban design education and practice. In this paper a new Rhinoceros-based urban modeling design tool called umi is presented which allows users to carry out operational energy, daylighting and walkability evaluations of complete neighborhoods. The underlying simulation engines are EnergyPlus, Radiance/Daysim as well as a series of Grasshopper and Python scripts. Technical details of umi along with a case study of a mixed use development in Boston are documented.

Urban Microclimate – Designing the Spaces Between Buildings

Conference Paper

Full-text available

Jun 2011

The quality of life of millions of people living in cities can be improved if the factors that affect the urban microclimate are understood and the form of the city responds to them in a manner that is appropriate to its location. Underlying this approach is the idea that climatically responsive urban design is vital to any notion of sustainability: it enables individual buildings to make better use of 'natural' energy, it enhances the potential for pedestrian comfort and activity in outdoor spaces, and it encourages city dwellers to moderate their dependence on air-conditioned buildings and private vehicles (Erell et al, 2010). This paper suggests principles for successful integration of climatic strategies in urban planning processes, and provides case studies illustrating their implementation in practice.

CALCULATING UTCI EQUIVALENT TEMPERATURE

Article

Full-text available

Jan 2009

The growing need for valid assessment procedures of the outdoor thermal environment in the fields of public weather services, public health systems, urban planning, tourism & recreation and climate impact research raised the idea to develop the Universal Thermal Climate Index UTCI based on the most recent scientific progress both in thermo-physiology and in heat exchange theory. Following extensive validation of accessible models of human thermoregulation, the advanced multi-node 'Fiala' model was selected to form the basis of UTCI. This model was coupled with an adaptive clothing model which considers clothing habits by the general urban population and behavioral changes in clothing insulation related to actual environmental temperature. UTCI was developed conceptually as an equivalent temperature. Thus, for any combination of air temperature , wind, radiation, and humidity, UTCI is defined as the air temperature in the reference condition which would elicit the same dynamic response of the physiological model. This review analyses the sensitivity of UTCI to humidity and radiation in the heat and to wind in the cold and compares the results with observational studies and internationally standardized assessment procedures. The capabilities, restrictions and potential future extensions of UTCI are discussed.

Simulating air temperature in an urban street canyon in all weather conditions using measured data at a reference meteorological station

Article

Full-text available

Oct 2006
INT J CLIMATOL

A model is proposed that adapts data from a standard meteorological station to provide realistic site-specific air temperature in a city street exposed to the same meso-scale environment. In addition to a rudimentary description of the two sites, the canyon air temperature (CAT) model requires only inputs measured at standard weather stations; yet it is capable of accurately predicting the evolution of air temperature in all weather conditions for extended periods. It simulates the effect of urban geometry on radiant exchange; the effect of moisture availability on latent heat flux; energy stored in the ground and in building surfaces; air flow in the street based on wind above roof height; and the sensible heat flux from individual surfaces and from the street canyon as a whole. The CAT model has been tested on field data measured in a monitoring program carried out in Adelaide, Australia, in 2000–2001. After calibrating the model, predicted air temperature correlated well with measured data in all weather conditions over extended periods. The experimental validation provides additional evidence in support of a number of parameterisation schemes incorporated in the model to account for sensible heat and storage flux. Copyright © 2006 Royal Meteorological Society

Wind, Sun, Surface Temperature, and Heat Island: Critical Variables for High-Resolution Outdoor Thermal Comfort

Conference Paper

Aug 2017

A Framework for Outdoor Mean Radiant Temperature Simulation: Towards Spatially Resolved Thermal Comfort Mapping in Urban Spaces

Conference Paper

Aug 2017

A novel comprehensive workflow for modelling outdoor thermal comfort and energy demand in urban canyons: Results and critical issues

Article

Mar 2020
ENERG BUILDINGS

In the energy simulation of buildings there has been little focus on their impact on the microclimate; simulation tools have usually dealt either with building or with outdoor simulation, and only recently these aspects are being interconnected. Within this framework, the paper describes a novel simulation workflow developed in the Grasshopper environment, where the Ladybug Tools are used to model the mutual relations amongst urban microclimate, building energy performance and outdoor thermal comfort. With reference to an urban canyon located in Catania, Southern Italy, the workflow – by coupling the indoor and the outdoor thermal field – provides both the dynamic thermal load of the buildings overlooking the canyon and the parameters needed to measure the outdoor comfort perceived by pedestrians. In comparison to other existing approaches, this workflow offers significant flexibility and makes it possible to perform a parametric investigation of the effects of different design solutions on both the indoor and the outdoor environment. The outdoor Mean Radiant Temperature calculated through the model is compared to on-site measurements performed with a black globe thermometer during two different days in the summer. The comparison suggests good agreement in the shaded areas of the canyon, but a non-negligible overestimation in sunlit areas. These results have driven the authors to a critical insight into the algorithms implanted in the Ladybug Tools, and have helped to highlight some critical issues that will be further investigated in upcoming research.

Beyond Nearly Zero Energy Urban Design: A Holistic Microclimatic Energy and Environmental Quality Evaluation Workflow

Article

Feb 2020

Despite the urgent global call for an energy transition and the promotion of health and well-being in cities, a holistic approach to evaluating the trade-offs between an urban energy balance and environmental quality considerations is lacking. This paper bridges this gap by introducing a Grasshopper digital workflow through which the impacts of a wide range of building and urban design parameters on both energy performance and environmental quality can be effectively evaluated. This workflow is tested here for both theoretical and site-specific urban test cases in the context of Tel Aviv. For these test cases, the performance metrics - energy load match, spatial daylight autonomy and universal thermal climate index - were calculated using EnergyPlus, Radiance and ENVI-met simulation engines for different block typologies and were then analyzed. The results showed that among the block typologies, the courtyard achieved the optimal combination across the tested environmental criteria, despite the daylight and energy generation penalty associated with self-shading in compact block typologies. This workflow highlights the performative tradeoffs between energy and environmental quality considerations and can thus help urban designers achieve not only a lower environmental impact but also regenerative and healthier design outcomes.

Influence of mean radiant temperature on thermal comfort of humans in idealized urban environments

Book

Jan 2010

A digital workflow to quantify regenerative urban design in the context of a changing climate

Article

Jul 2019
RENEW SUST ENERG REV

The regenerative approach to design goes beyond limiting the environmental impact of the built environment and towards the enrichment of the ecosystem, adaptation to climate change, and the improvement of human health. This concept is being applied to buildings through new standards such as the Living Building Challenge, yet examples of implementation of regenerative design at the urban scale are rare. While this is a promising direction for sustainable design, in theory new metrics, design tools and workflows need to be developed to translate regenerative design concepts into practice effectively. Among other factors, barriers to implementation remain rooted in the shortcomings of existing urban simulation tools to evaluate a wide range of performance metrics simultaneously. This paper thus proposes a prototype workflow to evaluate regenerative performance using existing evaluation tools in a single digital workflow. A series of existing and customised plugins, most of which are already in use and open source, were integrated into a multi-parametric workflow based on the Grasshopper visual programming tool. The workflow was tested on Malaga as a case study and incorporated key performance indicators related to outdoor human thermal comfort, biophilia, daylight performance, and energy use and production, based on data exchange and synergies across the different tools. These indicators were evaluated for present and future climate scenarios obtained from a weather generator. This paper demonstrates the potential of this workflow to receive visual feedback on various aspects of regenerative urban design, thus enabling designers to more effectively pursue an evidence-based urban design process.

Outdoor thermal comfort autonomy: Performance metrics for climate-conscious urban design

Article

May 2019
BUILD ENVIRON

Thermal comfort in the built environment is a crucial factor impacting health, well-being, and productivity of urban dwellers. Accordingly, comprehensive analyses are needed to ensure that acceptable criteria of thermal comfort are defined and met in urban environments. The main objective of this study is to define such performance metrics and quality measures of outdoor thermal comfort (OTC), aiming to inform climate-conscious urban design. This article first discusses the motivations for introducing comprehensive thermal comfort metrics, addressing the shortcomings of conventional OTC evaluations that neglect the temporal or spatial variability of OTC. It then introduces four performance metrics, which collectively inform urban planners and designers on the performance of outdoor space with regards to thermal comfort. These metrics build upon the concept of “autonomy” previously introduced for indoor spaces and are extended to include the unique characteristics of outdoor thermal comfort. Second, we discuss the capability of these metrics given the limitations of modeling tools available for urban microclimate analysis, and evaluate the critical factors for an accurate evaluation of Outdoor Thermal Comfort Autonomy (OTCA). We observe that the spatial distribution of airflow at the pedestrian height is critical for OTCA calculation, while the consideration of realistic surface heating depends on the urban density. Lastly, we present an example of employing weather clustering methods such that OTC performance metrics are achieved on an annual basis in a comprehensive yet efficient way. By discussing the capability and the limitations of these metrics we aim to promote climate-conscious design using metrics that are tangible and accessible to non-simulationexperts.

Impact of urban block typology on building solar potential and energy use efficiency in tropical high-density city

Article

Feb 2019
APPL ENERG

This paper presents the results of an investigation on the relationship between urban block typology, solar energy harvesting potential and building energy use efficiency in the context of the tropical high-density city Singapore. Thirty generic urban block cases in six typologies that represent a diverse range of urban forms were examined through simulation-based studies under the same planning conditions and simulation assumptions so as to rule out the impact of non-design related factors. Several key planning and geometric parameters which capture the formal characteristics of the urban blocks were examined as independent variables, and the dependent variables include the performance indicators on solar energy harvesting potential and building net energy use intensity that capture the dual benefits of photovoltaic (PV) systems in reducing building cooling loads and offsetting local plug loads with electricity generated on site. The results indicate that, under the same planning conditions and design premises, differences in urban block typology could lead to up to 200% increase in solar energy harvesting potential and electricity generated from rooftop PV, twelve times higher rate of reduction in building cooling loads, tow times higher rate of reduction in net purchased electricity, and 25% lower building net energy use intensity. The courtyard and hybrid urban block typologies consistently outperform the other typologies, especially the commonly implemented tower and slab blocks, and they benefit the most from PV deployment in the tropics. The comparison between an existing residential precinct and a hypothetical alternative hybrid urban block further demonstrated the significant impact of urban design on efficiency of PV electricity generation and building energy use efficiency. In addition to the significant economic benefit in reduction in utility cost and environmental implication in terms of equivalent reduction in CO2 emissions on urban scale, this study highlights the crucial role that urban design plays in terms of maximising on-site renewable energy production such as solar energy. The significant planning and geometric parameters in relation to the performance indicators provide insight as reference for establishing solar energy friendly urban planning and architectural design guidelines. The methodology and technical workflow as developed can support reliable and efficient feasibility studies, especially in the early stage of urban planning and architectural design. Integrated with other performance evaluations, they can facilitate decision-making on implementation of renewable energy integrated green building technologies and passive design strategies.

Influence of context-sensitive urban and architectural design factors on the energy demand of buildings in Toulouse, France

Article

Feb 2019
ENERG BUILDINGS

Thermal Comfort Maps to estimate the impact of urban greening on the outdoor human comfort

Article

Aug 2018

Outdoor human comfort is an important factor in the evaluation of the liveability of a city as well as for promoting people's health and well-being. In hot arid climates in particular, urban planning and design can considerably impact the day-to-day thermal comfort of the pedestrians, for better or for worse. Strategies to reduce thermal discomfort include shading structures, water bodies, and the promotion of natural ventilation – and most significantly, green areas. Trees have a major impact on the pedestrians in the built environment as they not only provide shading but also improve the microclimate in urban areas, thereby reducing the time during which discomfort is felt. The objective of this paper is to present a new methodology for dynamically quantifying the impact of different plants in urban areas on outdoor human comfort, through 3D urban energy modelling. The proposed methodology makes use of an urban energy modelling tool, providing a comprehensive view of the city energy fluxes, with a focus on the impact of trees on the human thermal comfort. Outdoor human comfort is assessed using the Index of Thermal Stress for the campus of the Swiss International Scientific School of Dubai (UAE), where “Thermal Comfort Maps” are designed to quantify the pedestrian thermal sensation and its variation in time and space. Additionally, the energy fluxes impinging on the urban pedestrians are quantified, dynamically, in hourly time step, providing an important instrument to understand their thermal stress, and the environmental factors affecting it. Based on the simulations, thanks to native greening, a significant improvement in outdoor comfort conditions was achieved in the campus, reducing the “warm/hot” and “very hot” thermal sensations from 1,291 h (on average over the entire campus) to less than 300 h by planting Ghaf and Acacia trees.

A New Approach for the Applicaton of Nearly Zero Energy Concept at District Level to Reach EPBD Recast Requirements Through a Case Study in Turkey

Article

Jul 2017
ENERG BUILDINGS

European Union Directive 2010/31/EU (EPBD Recast) has constituted the cost considerations into the energy performance calculations and put the Member States (MS) under the obligation that by the end of 2020, all new buildings should be designed and constructed as nearly zero energy buildings. On the other hand, reaching nearly zero energy level buildings and ensuring the decrease in carbon emissions may require high-cost measures, such as renewable energy systems. Even though the energy efficiency calculation method proposed by European Commission uses the ‘global cost’, high investment costs may cause a conflict in building construction phases. This paper focuses on the highest possible energy saving for building sector while considering the global costs and market barriers caused by high investment costs and long payback periods. For this purpose, nearly zero energy level definition is suggested to be carried to the district level. It is proposed to analyze nearly zero energy levels firstly in buildings in the settlement and next in the district scale by implementing the further energy efficiency measures, such as the use of district heating/cooling systems and installation of renewable energy technologies in addition to the ones installed on-site. Financial benefits were also analyzed and compared, in terms of investment and global costs of nearly zero energy levels of buildings and districts.

Modeling and simulating urban outdoor comfort: Coupling ENVI-Met and TRNSYS by grasshopper

Article

Jul 2017
ENERG BUILDINGS

In urban areas the impact of built environment on wellbeing and human health should be considered due to urban heat island phenomenon. The present research aims at identifying a method for an accurate estimation of thermal outdoor comfort and mean radiant temperature, modeling and simulating the effects of urban form and vegetation on microclimate of cities. In order to reach this main objective, this research incorporates CFD based simulation tool ENVI-met and TRNSYS (Transient Systems Simulation) by means of Grasshopper. The results of the study demonstrate the reliability of the proposed method, i.e. that a combination of ENVI-met and TRNSYS increases the simulation accuracy in terms of outdoor thermal comfort, especially during night. This method allows exploiting the potentialities of both ENVI-met and TRNSYS for the calculation of urban features (urban form, vegetation, canyon proportion, etc.) affecting urban microclimate.

Assessing the urban heat island and its energy impact on residential buildings in Mediterranean climate: Barcelona case study

Article

Jul 2017
ENERG BUILDINGS

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 coastalcity, and its impact on cooling demand of residential buildings.The experimental analysis is based on temperature data from rural and urban Weather Stations andfield measurements at street level. The maximum average UHI intensity is found to be 2.8◦C in winterand 1.7◦C in summer, reaching 4.3◦C at street level. Simulations performed with EnergyPlus indicatethat 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 consideredin performing energy evaluations for urban contexts, since standard meteorological data from airportweather stations are not found to be accurate enough. Link to publication: http://www.sciencedirect.com/science/article/pii/S0378778817312914

From urban climate to energy consumption. Enhancing building performance simulation by including the urban heat island effect

Article

Apr 2017
ENERG BUILDINGS

Cities are dissipative structures. As such, cities generate heat, a phenomenon known as urban heat island (UHI). Even though the UHI is one of the most relevant effects of urbanization on urban climate, up-to-date methodologies to include it in the estimation of buildings’ energy consumption are still scarce. During the last 30 years, different methods and software have been developed to measure a thermal building's demand. Building performance simulation is commonly used to calculate heating and cooling demand. However, such techniques do not adequately include the urban heat island effect, which could have an extreme impact on a building's energy consumption. In fact, building operation is doubly connected with the urban environment: on the one hand, buildings generate heat that warms up the environment, and on the other hand, the urban environment alters building performance by the influence of UHI. In this paper, a methodology to incorporate the UHI effect in building performance simulation is proposed. Urban weather data were downscaled at the urban morphology building level to estimate the cooling demand of different types of residential buildings. The global energy penalty for the whole residential building stock was estimated in four South American Pacific coastal cities. The results indicate that when UHI is incorporated, an increase in energy demand between 15% and 200% can be expected. These results challenge the validity of current assessments performed in absence of the UHI effect. At the same time, these results open up the discussion for the inclusion of urban planning measures aiming at reducing the UHI effect on a building's energy demand. Link: https://authors.elsevier.com/a/1UtXE1M7zGsh4p

Sensitivity analysis of urban morphology factors regarding solar energy potential of buildings in a Brazilian tropical context

Article

Nov 2016
SOL ENERGY

Today, 75% of global energy consumption occurs in cities. On the topic of climate change, adapting urban settlements to face this growing demand is a priority issue, especially for fast-growing cities in developing countries such as Brazil. Planning the urban morphology of the built environment is a key issue in shifting to a climate adapted urban environment. This paper addresses an important threefold energy challenge of tropical cities: the major potential of harnessing solar energy as renewable resource for local electricity production and the energy-saving paradox of reducing the undesirable solar heat gains in buildings while providing satisfactory levels of daylight. It aims at measuring the effect size of urban form factors regarding these energy goals. This study applies the Design Of Experiments (DOE) approach. A DOE analysis is a statistical technique that provides a set measure of how design parameters are correlated and the effective contribution of each one to a given response of interest. This study proposes a fractional factorial DOE method coupled to a Simplified Radiosity Algorithm (SRA) aiming to evaluate the irradiation availability on building envelopes while taking a large representative sample of contrasted urban block geometries into account. The buildings' envelope solar irradiation availability assesses a set of energy-related morphological parameters. Results indicate a significant impact of the aspect ratio, the distance between buildings and the surface equivalent albedo. Establishing high values of street aspect ratio may cut solar irradiation on roofs by 130 kW h/m 2 year, while increasing the plot ratio may only yield 26 kW h/m 2 year. The results also point out important first order interaction effects between certain variables.

Urban Energy Index for Buildings (UEIB): A new method to evaluate the effect of urban form on buildings’ energy demand

Article

Apr 2016
LANDSCAPE URBAN PLAN

Jorge Rodríguez-Alvarez

In the last two decades, preliminary energy assessments have gradually become mandatory for new constructions in most of Europe, Australia and North America. Sound tools have been developed to support the energy performance analysis of building designs. However, their scale of analysis is limited by definition. The complexity that results from the minute consideration of multiple parameters grows exponentially when further buildings are added to the model. It is, therefore, highly inefficient to base the assessment of large urban areas on models that are intended for individual buildings. Yet the need for instruments that facilitate evaluations at the urban scale is unquestionable. A great extent of the current urban fabric has never been analyzed and hence measures to reduce consumption and carbon emissions from existing buildings are grounded on assumptions and generalizations. This paper presents the Urban Energy Index for Buildings (UEIB), a tool that has been specifically designed to assess the energy performance of buildings in large urban areas. It is based on the reduction of the urban geometry into a simpler notional grid that retains critical information to perform meaningful estimates. It aims for simplicity and ease of use so that energy aspects can be incorporated at the preliminary stages of urban plans and policies.

Simulation tools to assess microclimate and building energy – A case study on the design of a new district

Article

Feb 2016
ENERG BUILDINGS

Abstract Since some years, dense cities and compact buildings are promoted as sustainable and energy efficient designs. Nevertheless, urban planning strategies should take into account the interactions between buildings and the microclimate because the Urban Heat Island (UHI) phenomenon can increase the cooling load of buildings and is strongly influenced by urban morphology, urban landscaping and the thermal properties of buildings and soil. The modification of these parameters, such as building density, can mitigate UHI, with direct and indirect improvement of building energy performances. The case study presented in this paper concerns a new district in La Rochelle (France) named Atlantech. Currently at the design stage, the goal is to transform this old military camp into a zero carbon district. This study was performed in parallel with urban planning using EnviBatE and SOLENE-Microclimate simulation. Two building densities are compared through the impacts on solar irradiance, wind airflows, building indoor temperatures and energy demand. Analysis of reference and densified district highlights various impacts such as the wind velocity decrease, up to 80%, and the effect on an existing nearby building solar irradiation, reduced by 7%. These results underline the potential usefulness of these simulation tools for urban planners at the design stage.

Review and critical analysis of early-design phase evaluation metrics for the solar potential of neighborhood designs

Article

May 2015
BUILD ENVIRON

The energy performance of a building is strongly influenced by its level of solar exposure, in turn affected by the climate, built context, and building morphological characteristics. Since these are typically fixed at the early-design phase, performance assessment methods based on solar considerations at the urban scale are essential to support early decision-making. As the adaptation of the well-developed building performance simulation methods to the urban scale lead to complexity issues, it is of interest to verify whether simpler metrics can act as performance indicators, as is often done at the building level with quantities such as form factor.

Numerical studies of the outdoor wind environment and thermal comfort at pedestrian level in housing blocks with different building layout patterns and trees arrangement

Article

Jan 2015
RENEW ENERG

Computationally efficient prediction of canopy level urban air temperature at the neighbourhood scale

Article

Sep 2014

The Urban Weather Generator (UWG) is a simple and computationally efficient model that predicts canopy level urban air temperature using meteorological information measured at a reference weather station. An evaluation of an improved version of the model, which accounts for different urban morphologies and building usage distributions within a city, is presented in this paper. Calculated urban air temperatures are compared with measurements from a network of weather stations in Singapore, representing a range of land uses, morphological parameters and building usages. The comparison shows a satisfactorily performance of the model for all weather conditions and for different reference weather stations. Singapore is located in a hot and humid climate where vegetation plays a critical role in climate regulation, the urban morphology is very heterogeneous and air-conditioning systems are generally used throughout the year. This makes Singapore an interesting case study in order to analyse the potential and limitations of the model. The study shows that the model can be applied to different climates and urban configurations to obtain an estimation of the Urban Heat Island (UHI) effect. However, the simplifications and assumptions of the model prevent it from capturing very site-specific microclimate effects.

From Energy Performative to Livable Mediterranean Cities: An Annual Outdoor Thermal Comfort and Energy Balance Cross-Climatic Typological Study

Abstract

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