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Abstract

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.

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... models in many aspects, such as in terms of numerical schemes (Bosselmann et al., 1995;Sousa et al., 2015), turbulence models (Si et al., 2016;Wortmann, 2017;Natanian et al., 2020), grid schemes, mesh generation methods (Marcum and Weatherill, 1995;Löhner, 1997;Nakahashi et al., 2003), making CFD simulations easy to understand and perform. In addition, most CFD plug-ins are user-friendly, providing convenient access to geometry generation, CFD simulation, and visualization within one interface of the design platform, substantially simplifying the simulation workflow. ...
... Moreover, simulations considering the effect of windthermal coupling on the velocity distribution and flow field have been conducted (Hamdan and de Oliveira, 2019;Utkucu and Sözer, 2020a;Loh and Bhiwapurkar, 2021). Several studies have coupled airflow, solar radiation, and thermal simulations to perform thermal comfort assessments (Johansson and Yahia, 2020;Sun and Rao, 2020;Lin et al., 2021) and energy consumption calculations Xu et al., 2019;Graham et al., 2020;Kastner and Dogan, 2020b;Natanian et al., 2020;Ibrahim et al., 2021b). However, pollutant dispersion simulations using CFD plug-ins during the design stages have not been widely studied (Ma et al., 2018;Jia et al., 2021). ...
... All of these studies used a similar workflow: the wind speed results obtained from Butterfly's airflow simulations on urban blocks were input into Ladybug and then combined with weather data, such as air temperature and mean radiant temperature, to quantify thermal comfort (Fig. 4). Natanian et al. (2020) developed another workflow for outdoor thermal comfort assessment based on the Grasshopper. In this workflow, the local microclimate data obtained from the weather stations by the plug-in Dragonfly, the mean radiant temperature on the building surface calculated by the plug-in Honeybee, and the wind factor calculated by Eddy3D were packaged as input into EnergyPlus for detailed outdoor UTCI calculations. ...
Article
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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.
... Nevertheless, a common attribute across the EMME region is that urban pollution renders children more vulnerable, imposing higher health risk relative to carcinogenic and non-carcinogenic effects (Al-Bassam et al., 2009;Jadoon et al., 2020;El-Fadel & Massoud, 2000;Tecer, 2009;Kara et al., 2013;Stergiopoulou et al., 2018;Bourliva et al., 2017;Aminiyan et al., 2018;Farzaneh et al., 2019;Jahandari, 2020;Grmasha et al., 2020;Davoudi et al., 2020;Kalantzi et al., 2011;Ozdemir et al., 2012;Rabee, 2015;Ghanavati et al., 2019;Al-Shidi et al., 2020). Another thematic that EMME countries across the EU divide show high interest in is UHIs, which are highly related to the thermal comfort of urban populations, as well as CC (Potchter and Itzhak Ben-Shalom, 2013;Keramitsoglou et al., 2017;Founda and Santamouris, 2017;Paravantis et al., 2017;Santamouris et al., 2015;Katavoutas and Founda, 2019;Kolokotsa et al., 2009;Pantavou et al., 2011;Natanian et al., 2020;Alizadeh-Choobari et al., 2016;Moghbel and Shamsipour, 2019). These common research interests indicate that regardless of regulatory frameworks, EMME countries are concerned with those factors most affecting public health and welfare, urban pollution and the challenges of extreme urban heat within the context that applies to each country. ...
... Relative to urban heat, a number of studies examined different aspects of health and wellbeing through a MOD lens. For instance, in the context of CC, one study has examined the relationship of mortality and ambient temperature in Beirut, while another offered a wider perspective on outdoor thermal comfort, relating it also to urban development, green spaces and historical reflection, suggesting that local vernacular architecture approaches simulated a higher level of thermal comfort (Natanian et al., 2020;El-Zein et al., 2004). Moreover, the mitigating role of UV and the susceptibility of greenery and drinking water systems in urban settings were assessed employing different techniques (Jaafari et al., 2020;Amini Parsa et al., 2019;Darabi et al., 2018;Hashempour et al., 2020), as well as vulnerability to NH such as flooding, earthquakes and heatwaves (Katavoutas and Founda, 2019;Giannakidou et al., 2020;Ertugay et al., 2016). ...
... HI is the strongest proxy; however, in relation to all the rest, this proxy is intermediate in strength and linkage. Notably, almost all studies invoking historical aspects are dealing with WE and UD as well (Natanian et al., 2020;De Siqueira and Al Balushi, 2020;Rostami et al., 2014;Peterson and Al Kassim, 2020;Farooq, 2020;Skayannis et al., 2017), indicating that past experiences are mostly recalled as a remedy for some type of affliction caused by the improper design of the urban environment. Another frequent interaction of history exists with WM techniques and NH, including past techniques that could be adapted to modern urban environments, the recycling of water resources in arid regions and combatting urban heat against desertification and heatwaves (Shahmohamadi et al., 2011;Alizadeh-Choobari et al., 2016;Shomar and Dare, 2015;Batisha, 2020;Koutsoyiannis et al., 2008;Angelakis et al., 2020). ...
Article
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.
... The representative article simulated the climate of the Black Forest in southern Germany and made suggestions for tourism, but it lacked an analysis of the impact of the forest on the surrounding built-up urban areas [57]. In the last five years, relevant studies have been conducted in areas mainly in the Mediterranean [58] and tropical coastal cities [29]. In addition, there are studies on the influence of the unique street isthmus morphology of historic urban neighborhoods on thermal comfort [59]. ...
... In recent years, research on building energy consumption combined with the effects of urban morphology is attracting more and more attention from scholars. Existing studies have confirmed that the courtyard form area shows better outdoor thermal comfort and annual energy consumption than the other areas [58,81]. ...
... In terms of research perspectives, environmental studies is a core discipline that has started to focus more on energy consumption [58], air quality [99], and ecology in recent years. An increasing number of interdisciplinary areas have begun to become involved in this research field, including instrument science, physics, chemistry, and computer science, all of which have contributed to further development in terms of equipment for field measurements, air quality analysis, respiratory health, and numerical simulation, together with research objectives. ...
Article
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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.
... Building typologies take into account the morphology of each design scenario. Although a wide body of literature has investigated simple theoretical urban models such as scatter, courtyard, and high-rise scenarios (Natanian, Kastner, Dogan, & Auer, 2020;Taleghani et al., 2014) as well as more complicated urban models such as galley and asymmetrical scenarios (Sözen & Oral, 2019) in hot climatesonly a limited number of these scenarios are applicable in cold climates. Consequently, design scenarios for this project include six different urban typologies, including low-rises, mid-rises, and high-rise scenarios, that are applicable to new construction and retrofitting solutions (close to existing building stock characteristics) in Syracuse. ...
... A validated Grasshopper's plug-in, Eddy3D, which uses OpenFOAM engine, serves as an annual wind calculation platform for Computational Fluid Dynamics (CFD) . Following the annual wind speed interpolation method of wind factors for multiple wind directions (0,45,90,135,180,225,270,315) (Natanian, Kastner, Dogan, & Auer, 2020), we conducted a cylindrical simulation domain approach to reuse the same mesh for every wind direction. Table 5 shows simulation parameters of annual hourly microclimatic wind factors to generate outdoor thermal comfort results. ...
Article
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.
... Another work used a similar approach for cluster of office buildings for optimization considering overheating risks, cooling loads, and outdoor comfort in Tallinn, Estonia [17]. To bridge the gap of detailed annual evaluations of outdoor thermal comfort considering hourly wind calculations, Natanian et al. implemented Eddy3D Grasshopper plug-in using OpenFoam [18]. Furthermore, many researchers have conducted their analysis in hot climates to quantify the effects of urban geometry on outdoor thermal comfort. ...
... There is a wide body of knowledge on evaluating different theoretical urban models in hot climates. Although simple theoretical models are including scatter single block, linear slab block, courtyard, and high-rise scenarios [18,22], there are more complicated theoretical models, including, but not limited to, use of galleries and asymmetrical considerations [23]. However, some of these models (e.g., courtyard) are not applicable for cold or very cold climates, and they do not reflect the real condition of built environment in such contexts (e.g., Syracuse). ...
Conference Paper
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.
... With almost 70% of the global population projected to live in cities by 2050 [1][2][3], as well as the major role cities play as both energy consumers and carbon emitters, it is not surprising that the urban scale, from the block to the entire city, is subjected to increasing scrutiny in discussions of responsive design for future built environments [3,4]. ...
... Consequences of urban warming include health threats to the physical and mental well-being of humans [11]. The management of urban energy flows (supply, demand, and the balance between them) is no longer sufficient; nowadays, it must be supplemented and measured against new criteria for urban environmental quality, health, and well-being (e.g., thermal and visual comfort, or contact with nature) [4]. ...
Article
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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.
... With almost 70% of the global population projected to live in cities by 2050 [1][2][3], as well as the major role cities play as both energy consumers and carbon emitters, it is not surprising that the urban scale, from the block to the entire city, is subjected to increasing scrutiny in discussions of responsive design for future built environments [3,4]. ...
... Consequences of urban warming include health threats to the physical and mental well-being of humans [11]. The management of urban energy flows (supply, demand, and the balance between them) is no longer sufficient; nowadays, it must be supplemented and measured against new criteria for urban environmental quality, health, and well-being (e.g., thermal and visual comfort, or contact with nature) [4]. ...
Article
Full-text available
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.
... This was recommended based on a preliminary sensitivity analysis by the authors. Natanian et al. (2020) performed a sensitivity analysis on the solar and wind parameters included in the calculation of UTCI using the same workflow in a hot desert climate, similar to our study. Their results showed that MRT had the strongest impact on UTCI, and that using the wind data from the weather file (rather than a detailed CFD analysis) had a minimal effect on the output UTCI. ...
... In this study, we chose not to include wind analyses in favour of running a remarkably increased number of geometric permutations, since the workflow has shown considerable reliability using wind speeds from the IWEC file. Other approaches available in Grasshopper include wind analyses using Butterfly (Mackey et al., 2017) or Eddy3D (Natanian et al., 2020) which produce wind factors, the ratio between the simulated wind speeds and the inlet wind speed generated from a number of directions. These approaches, however, are not as accurate as if the turbulent heat exchanges are considered within the model, which is a feature in the OpenFOAM software, but is not yet integrated (currently under development) in either of the two plug-ins. ...
Article
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.
... An energy balance evaluates the relationship between input and output energies. Energy balance analysis is a common approach to improve building's efficiency, from architecture (Schlueter and Geyer, 2018), engineering (Tornay et al., 2017), climatic (Natanian et al., 2020) or biomimetic (Imani and Vale, 2020) points of view. The design strategies to improve energy efficiency in terms of energy balance are well-established: efficient envelope to minimize heat flows, efficient appliances, sun irradiance control, efficient climate systems and optimal operational use of the building are the most important. ...
... Table 2 lists the different simulation parameters as used in this study, while the physical and thermal properties of the construction materials can be found in Appendix A. Based on a preliminary study by the authors, coupling the simulation workflow with OpenFOAM for CFD analyses using the wind factors method had minimal impact on the output UTCI. The sensitivity analysis of Natanian et al. [86] using the same workflow in a hot desert climate confirmed our inference and showed the MRT to be the most dominant factor. Consequently, weather file 10 m-high wind speeds were converted into 2 m-high wind speeds and based on the wind profile power law by using a dedicated Ladybug component. ...
Article
Full-text available
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.
... The tools used in this research are Ladybug, Honeybee, and Colibri that were using the Mediterranean district's weather data. The research's main finding was the mitigation of the different performance of each typology and the potential of the workflow to assist the designer during the decision-making phase [14]- [16]. ...
... Ladybug tools makes enable developing an integral analysis on the same interface. Several studies employed this resource to assess the external comfort, such as Ottone et al. (2019), Natanian et al. (2020) and De Luca, Naboni and Lobaccaro (2021), who coupled the urban climate changes created by the UWG in the Grasshopper process. ...
Article
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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.
... Exposure metrics include-(1) the Context Exposure Index (CEI), the New building Exposure Index (NEI) based on the Israeli green building code's thresholds (SI 5281 [9]), and (3) the Sky Exposure (SE) metric [6]. Shading metrics include -(4) the Outdoor Shading Index (OSI) [10], and (5) the East-West Facades Shading Index (FSI) [11]. The examination of these metrics allows the user to expand the performative perspective to various environmental performance considerations as well as to explore the balance between the different impacts of solar exposure, e.g., the tradeoff in higher density between visual comfort (SE), outdoor thermal comfort (OSI) and energy efficiency (FSI). ...
Article
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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.
... An energy balance evaluates the relationship between input and output energies. Energy balance analysis is a common approach to improve building's efficiency, from architecture (Schlueter and Geyer, 2018), engineering (Tornay et al., 2017), climatic (Natanian et al., 2020) or biomimetic (Imani and Vale, 2020) points of view. The design strategies to improve energy efficiency in terms of energy balance are well-established: efficient envelope to minimize heat flows, efficient appliances, sun irradiance control, efficient climate systems and optimal operational use of the building are the most important. ...
Article
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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.
... It is worth noticing that this classification has been proposed for sorting the large number of documents that has been reviewed and identifying the documents in line with the scope of the present manuscript. The identified topics should not be interpreted as separated but intertwined, e.g., energy and microclimate [125][126][127][128][129][130][131], energy and indoor [132], energy and design [133], energy and assessment [134], and microclimate and design [135]. Specifically, the term energy has been used to characterize studies aiming at evaluating the energy performances of buildings in terms of energy consumption for cooling, energy consumption for heating, and energy production potential. ...
Article
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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.
... Although the UTCI analysis is computationally intensive, it was selected to assess outdoor thermal comfort because it is a reliable metric which guarantees a high accuracy of results for different climates and local conditions. This accuracy is much higher in comparison to other simplified methods based only on direct solar exposure that, to the best of the authors' knowledge, proved only to be reliable in hot climates [66,67]. ...
Article
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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.
Article
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.
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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.
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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.
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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.
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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.
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This chapter offers new innovative approaches for architectural design using digital tools.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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Existing procedures for the assessment of the thermal environment in the fields of public weather services, public health systems, precautionary planning, urban design, tourism and recreation and climate impact research exhibit significant shortcomings. This is most evident for simple (mostly two-parameter) indices, when comparing them to complete heat budget models developed since the 1960s. ISB Commission 6 took up the idea of developing a Universal Thermal Climate Index (UTCI) based on the most advanced multi-node model of thermoregulation representing progress in science within the last three to four decades, both in thermo-physiological and heat exchange theory. Creating the essential research synergies for the development of UTCI required pooling the resources of multidisciplinary experts in the fields of thermal physiology, mathematical modelling, occupational medicine, meteorological data handling (in particular radiation modelling) and application development in a network. It was possible to extend the expertise of ISB Commission 6 substantially by COST (a European programme promoting Cooperation in Science and Technology) Action 730 so that finally over 45 scientists from 23 countries (Australia, Canada, Israel, several Europe countries, New Zealand, and the United States) worked together. The work was performed under the umbrella of the WMO Commission on Climatology (CCl). After extensive evaluations, Fiala's multi-node human physiology and thermal comfort model (FPC) was adopted for this study. The model was validated extensively, applying as yet unused data from other research groups, and extended for the purposes of the project. This model was coupled with a state-of-the-art clothing model taking into consideration behavioural adaptation of clothing insulation by the general urban population in response to actual environmental temperature. UTCI was then derived conceptually as an equivalent temperature (ET). Thus, for any combination of air temperature, wind, radiation, and humidity (stress), UTCI is defined as the isothermal air temperature of the reference condition that would elicit the same dynamic response (strain) of the physiological model. As UTCI is based on contemporary science its use will standardise applications in the major fields of human biometeorology, thus making research results comparable and physiologically relevant.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
Article
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
Article
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
Article
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.
Article
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.
Article
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.
Article
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.
Article
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.
Article
Outdoor thermal comfort in urban spaces is known as an important contributor to pedestrians’ health. The urban microclimate is also important more generally through its influence on urban air quality and the energy use of buildings. These issues are likely to become more acute as increased urbanisation and climate change exacerbate the urban heat island effect. Careful urban planning, however, may be able to provide for cooler urban environments. Different urban forms provide different microclimates with different comfort situations for pedestrians. In this paper, singular East-West and North-South, linear East-West and North-South, and a courtyard form were analysed for the hottest day so far in the temperate climate of the Netherlands (19th June 2000 with the maximum 33°C air temperature). ENVI-met was used for simulating outdoor air temperature, mean radiant temperature, wind speed and relative humidity whereas RayMan was used for converting these data into Physiological Equivalent Temperature (PET). The models with different compactness provided different thermal environments. The results demonstrate that duration of direct sun and mean radiant temperature, which are influenced by urban form, play the most important role in thermal comfort. This paper also shows that the courtyard provides the most comfortable microclimate in the Netherlands in June compared to the other studied urban forms. The results are validated through a field measurement and calibration.
Article
An important part of the world's energy is used for space cooling and heating of buildings. Its minimization has great energy saving potential. An important part of the heat exchange between buildings and the ambient surrounding is due to convective and radiative heat flows. In this study detailed building energy simulation (BES) is used to analyse the effect of neighbouring buildings on these heat flows and their influence on the space cooling and heating demand of buildings. BESs were conducted for stand-alone buildings and buildings in street canyon. This study demonstrates the importance of accounting for the urban microclimate for the prediction of the energy demand of buildings. With the proposed model most of the thermal effects of the urban microclimate can be captured and quantified on street canyon scale. Due to multiple reflections more solar and thermal radiation is absorbed at the façades of buildings in street canyons than at façades of stand-alone buildings. These effects cause higher surface temperatures in street canyons leading to higher space cooling and lower space heating demands. Other reasons are the lower convective heat transfer coefficients in street canyons, the reduced removal of heat from street canyons and the urban heat island effect.
Article
The term Net ZEB, Net Zero Energy Building, indicates a building connected to the energy grids. It is recognized that the sole satisfaction of an annual balance is not sufficient to fully characterize Net ZEBs and the interaction between buildings and energy grids need to be addressed. It is also recognized that different definitions are possible, in accordance with a country's political targets and specific conditions. This paper presents a consistent framework for setting Net ZEB definitions. Evaluation of the criteria in the definition framework and selection of the related options becomes a methodology to set Net ZEB definitions in a systematic way. The balance concept is central in the definition framework and two major types of balance are identified, namely the import/export balance and the load/generation balance. As compromise between the two a simplified monthly net balance is also described. Concerning the temporal energy match, two major characteristics are described to reflect a Net ZEB's ability to match its own load by on-site generation and to work beneficially with respect to the needs of the local grids. Possible indicators are presented and the concept of grid interaction flexibility is introduced as a desirable target in the building energy design.
Article
The increase in air temperature produced by urbanization, a phenomenon known as the urban heat island (UHI) effect, is often neglected in current building energy simulation practices. The UHI effect can have an impact on the energy consumption of buildings, especially those with low internal heat gains or with an inherent close interaction with the outdoor environment (e.g. naturally-ventilated buildings). This paper presents an urban weather generator (UWG) to calculate air temperatures inside urban canyons from measurements at an operational weather station located in an open area outside a city. The model can be used alone or integrated into existing programmes in order to account for the UHI effect in building energy simulations. The UWG is evaluated against field data from Basel (Switzerland) and Toulouse (France). The error of UWG predictions stays within the range of air temperature variability observed in different locations of the same urban area.
Article
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
Article
Shading affects outdoor thermal environments and, therefore, influences the thermal perceptions of people in outdoor spaces. Since most field studies examining outdoor thermal comfort merely elucidated characteristics measured on a particular day, these studies may not represent annual thermal conditions accurately. Therefore, this study conducted 12 field experiments to analyze outdoor thermal conditions on a university campus in central Taiwan, and utilized RayMan model for predicting long-term thermal comfort applying meteorological data for a 10-year period. The physiologically equivalent temperature (PET) is employed as a thermal index. The thermal comfort range of Taiwanese residents obtained in a previous survey was applied as the criterion for determining whether a thermal environment is comfortable or uncomfortable. Analytical results indicate that the sky view factor (SVF), which represents the percentage of free sky at specific locations, significantly affects outdoor thermal environments. Analytical results indicate that a high SVF (barely shaded) causes discomfort in summer and a low SVF (highly shaded) causes discomfort in winter. As Taiwan has hot summers and mild winters, sufficient shading should be provided by trees and buildings to improve thermal comfort in summer. However, since the Taiwanese have poor tolerance of cold temperature, outdoor space planning should avoid creating areas with excessive shading. Therefore, the thermal requirements of residents and characteristics of the local climate and environment must be considered when creating shaded outdoor areas.
Article
Significant improvements of computer facilities and computational fluid dynamics (CFD) software in recent years have enabled prediction and assessment of the pedestrian wind environment around buildings in the design stage. Therefore, guidelines are required that summarize important points in using the CFD technique for this purpose. This paper describes guidelines proposed by the Working Group of the Architectural Institute of Japan (AIJ). The feature of these guidelines is that they are based on cross-comparison between CFD predictions, wind tunnel test results and field measurements for seven test cases used to investigate the influence of many kinds of computational conditions for various flow fields.
Article
An experimental investigation was carried out to study the structure of the flow field around three-dimensional obstacles of different aspect ratios, in two different types of boundary layers. The dimensions of the rectangular block obstacles were chosen to represent generic shapes of buildings. In order to study the flow field around a building structure in a wind tunnel test, the simulation of a boundary layer similar to the atmospheric boundary layer was a crucial issue. For the oncoming flow, a boundary-layer profile representing a suburban site was adopted in the present investigation. The studies were performed using different kinds of flow visualisation techniques and a laser Doppler anemometry (LDA) system, specially developed for wind tunnel applications and designed to provide a high spatial resolution. The results of the experiments showed the dependence of the flow structure around the obstacle on its aspect ratio, the angle of attack, the Reynolds number, and the type of boundary layer. Detailed quantitative information of turbulence parameters in the vicinity of the obstacle was attained. In addition, all data were compiled to schematic sketches of the flow topology around three-dimensional obstacles.
Article
This is a conference paper. It was presented at the 6th Windsor Conference on Thermal Comfort: http://nceub.commoncense.info/index.php?n=OpenAccess.WindsorConference2010 The Universal Thermal Climate Index UTCI provides an assessment of the outdoor thermal environment in bio-meteorological applications based on the equivalence of the dynamic physiological response predicted by a model of human thermoregulation, which was coupled with a state-of-the-art clothing model. The operational procedure, which is available as software from the UTCI website (www.utci.org), showed plausible responses to the influence of humidity and heat radiation in the heat, as well as to wind speed in the cold and was in good agreement with the assessment of ergonomics standards concerned with the thermal environment. This suggests that in this regard UTCI may be universally useable in the research and in the major areas of application of human biometeorology. Published
Article
With considerably increased coverage of weather information in the news media in recent years in many countries, there is also more demand for data that are applicable and useful for everyday life. Both the perception of the thermal component of weather as well as the appropriate clothing for thermal comfort result from the integral effects of all meteorological parameters relevant for heat exchange between the body and its environment. Regulatory physiological processes can affect the relative importance of meteorological parameters, e.g. wind velocity becomes more important when the body is sweating. In order to take into account all these factors, it is necessary to use a heat-balance model of the human body. The physiological equivalent temperature (PET) is based on the Munich Energy-balance Model for Individuals (MEMI), which models the thermal conditions of the human body in a physiologically relevant way. PET is defined as the air temperature at which, in a typical indoor setting (without wind and solar radiation), the heat budget of the human body is balanced with the same core and skin temperature as under the complex outdoor conditions to be assessed. This way PET enables a layperson to compare the integral effects of complex thermal conditions outside with his or her own experience indoors. On hot summer days, for example, with direct solar irradiation the PET value may be more than 20 K higher than the air temperature, on a windy day in winter up to 15 K lower.