Assessment of predicted versus measured thermal comfort and optimal comfort ranges in the outdoor environment in the temperate climate of Glasgow, UK

In a warming world, the risk of overheating is significant in temperate climate areas such as Glasgow, UK where adaptation to overheating is low. An easy-to-use thermal comfort evaluation is therefore a necessary first step towards developing effective coping mechanisms. In this study, we explore the effectiveness of Predicted Mean Vote, Predicted Percentage of Dissatisfied and Physiologically Equivalent Temperature, together with air temperature in mimicking actual thermal sensation votes of street users obtained in 2011 in Glasgow City Centre. The Predicted Mean Vote/Predicted Percentage of Dissatisfied indices developed for controlled indoors show a surprising similarity to actual thermal sensation votes derived from outdoor surveys, than the Physiologically Equivalent Temperature developed specifically for the outdoors. The method of calculation of mean radiant temperature is the key to improved performance of Physiologically Equivalent Temperature, with fish-eye lens photographs improving its performance. The results also show air temperature alone has nearly equal predictive power of the actual thermal sensation. A preliminary comfort range for Glasgow is also derived and its limitations are explored. Practical application: The strong relation between thermal sensation votes and air temperature (Ta) enables future thermal comfort studies to predict the thermal comfort using easy-to-access Ta only. A current thermal comfort study in Glasgow aiming at developing a link between urban morphology and Ta is already using this strong relation to predict outdoor thermal comfort in the city centre. This helps to establish a correlation between these three factors. </jats:p

The impact of urban geometry on the radiant environment in outdoor spaces

Urban geometry, namely the quantitative relationship of building volumes and open spaces (i.e. built density) and their spatial configuration (i.e. urban layout), is a major modifier of urban microclimate. This paper presents the results of an ongoing research which explores the impact of urban geometry on the radiant environment in outdoor spaces, with direct implications for urban microclimate and outdoor thermal comfort. In particular, the research investigates the relationship between a set of urban geometric indicators (such as Built Density, Site Coverage, Mean building Height and Frontal Area Density) and Mean Radiant Temperature (Tmrt) at the pedestrian level, in different areas of London. Three representative areas of London were selected to be studied; in central, west and north London which are of high, medium and low built density, respectively. Each area was divided into squares of 500m x 500m size, with a total of 84 urban squares included in the study. The methodology comprises three stages: (i) A set of simple geometric indicators have been computed for all urban squares using special algorithms written and executed in Matlab software. (ii) Radiation simulations have been performed for 10 days of a typical year in London, with the use of SOLWEIG software. SOLWEIG simulates hourly, 3-D radiation fluxes, incoming to / outgoing from the ground, spatial variations of Tmrt, Ground View Factor (GVF) as well as Sky View Factor (SVF). Sunny and cloudy days have been considered, evenly distributed in the year in order for the effect of solar angles to be examined. (iii) Statistical tests have been conducted for investigating the correlation between urban geometry, as expressed by the geometric variables, and hourly, average values of Mean Radiant Temperature in the outdoor spaces of the urban squares. The simulation results show that at night-time and in fully overcast conditions, the outdoor spaces of central London’s urban squares are warmer than those of west and north London, due to greater longwave radiation emitted and reflected by building volumes. In contrast, on sunny days, average daytime Tmrt values have been found to be higher in North London’s urban squares due to the larger insolation of their outdoor spaces. Additionally, the statistical analysis has shown that in the absence of direct solar radiation, the correlation between the geometrical variables and average values of Tmrt is very high with an almost perfect linear relationship between the geometrical variables and average SVF values (r2= 0.980). In the presence of direct solar radiation, the strength of the correlation varies with the sun altitude angle; the higher the sun altitude angle, the higher the correlation. In particular, a threshold altitude angle of 20 degrees has been identified, above which the correlation of average Tmrt values with urban geometry approximates that of night-time / cloudy hours. Finally, further statistical tests showed that site coverage (built area over site area) and frontal area density (façades’ total area over site area) are the strongest indicators among those considered in the analysis

Thermal Performance of Horizontal Fixed Sun Shading Device

Earlier investigations on passive cooling methods applied software modelling, and the findings were not confirmed through field measurement. Hence, this study applied a stationary experiment on a real structure and weather conditions employing horizontal sun shading (SDH). The purpose of this study was to compare the performance of fixed passive sun-shading devices put on to the bare façade of three-story terrace shophouses in Malaysia. The experiment findings revealed that SDH significantly improved the internal thermal environment by lowering the average monthly indoor air temperature (Ta) by 0.98 K and the peak temperature by 2.11 K. SDH is also effective during the warmest sunny days, lowering 1.23 K on average for the day. Meanwhile, SDH reduced the temperature in the control room by 5.40 K during the warmest peak time. When it came to indoor mean radiant temperature (Tmrt), SDH performed better than the control room in the very hot peak over a month (2.38 K) and on the highest temperature of the day (7.70 K). Finally, it can be inferred that SDH worked better from late at night until early in the morning, cooling the room temperature faster. This quiescent choice is one of the best for enhancing a building's internal thermal performance while also possibly contributing to a decrease in operational energy consumption

Assessment and mitigation strategies to counteract overheating in urban historical areas in Rome

As urban overheating is increasing, there is a strong public interest towards mitigation strategies to enhance comfortable urban spaces, for their role in supporting urban metabolism and social life. The study presents an assessment of the existing thermal comfort and usage of San Silvestro Square in Rome during the summer, and performs the simulation of cooling strategies scenarios, to understand their mitigation potential for renovation projects. The first stage concerns a field analysis of the thermal and radiative environment on the 1st and 2nd of August 2014, including meteorological measurements and unobtrusive observations, to understand how people experience and respond to extreme microclimate conditions. In the second stage, the research proposes scenario simulations on the same day to examine the influence of cool colored materials, trees and vegetative surfaces on thermal comfort. The thermal comfort assessment was based on Physiologically Equivalent Temperature (PET), whereas microclimatic simulations were conducted with CFD calculations (ENVImet v.4.3.1). The first stage shows a strong relationship between lower PET values and attendance rate, depending on daily shading patterns. The second stage shows a relevant improvement of thermal comfort, with PET values of 12 °C comparing to the no-intervention scenario, associated with a combination of cool materials and trees

Solar Radiation and Urban Wind Effect on Urban Canyon in Hot, Humid Regions

Urban configuration modification is an efficient approach to mitigating Urban Heat Island effect. This study investigates the significant impact of solar radiation and urban wind on microclimate and thermal comfort in the different setting of urban canyon configuration. The Envi-met (V3.1 beta) simulation presents that East-West canyon direction received the worst level of air temperature and meant radiant temperature compared to when the canyon was directed perpendiculars to the wind direction (South East – North West). The finding scientifically demonstrates that in Kuala Lumpur context, with the slow urban wind speed influences, solar radiation plays the significant impact on the microclimate.© 2016. The Authors. Published for AMER ABRA by e-International Publishing House, Ltd., UK. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).Peer–review under responsibility of AMER (Association of Malaysian Environment-Behaviour Researchers), ABRA (Association of Behavioural Researchers on Asians) and cE-Bs (Centre for Environment-Behaviour Studies), Faculty of Architecture, Planning &amp; Surveying, Universiti Teknologi MARA, Malaysia.Keywords: Solar radiation; urban wind; urban microclimate, urban simulation

Influence of ground surface characteristics on the mean radiant temperature in urban areas

The effect of variations in land cover on mean radiant surface temperature (Tmrt) is explored through a simple scheme developed within the radiation model SOLWEIG. Outgoing longwave radiation is parameterised using surface temperature observations on a grass and an asphalt surface, whereas outgoing shortwave radiation is modelled through variations in albedo for the different surfaces. The influence of surface materials on Tmrt is small compared to the effects of shadowing. Nevertheless, altering ground surface materials could contribute to a reduction on Tmrt to reduce the radiant load during heat-wave episodes in locations where shadowing is not an option. Evaluation of the new scheme suggests that despite its simplicity it can simulate the outgoing fluxes well, especially during sunny conditions. However, it underestimates at night and in shadowed locations. One grass surface used to develop the parameterisation, with very different characteristics compared to an evaluation grass site, caused Tmrt to be underestimated. The implications of using high resolution (e.g. 15 minutes) temporal forcing data under partly cloudy conditions are demonstrated even for fairly proximal sites

A GIS-based assessment method for mean radiant temperature in dense urban areas

The mean radiant temperature (Tmrt) is among the most important factors affecting thermal comfort. Its assessment in dense cities has been complicated due to the presence of buildings, pavings, and infrastructure. This paper introduced the RAMUM model, a GIS based software method developed to simulate outdoor mean radiant temperature at microscale. The advantages of this method lie in its efficiency and resolution that supports the design of buildings, streets, and public open spaces. The model is evaluated using field measurements under cold and warm weather in Boston. This study is sponsored by the EFRI-1038264 award from the National Science Foundation (NSF), Division of Emerging Frontiers in Research and Innovation (EFRI).postprin

The influence of bioclimatic urban redevelopment on outdoor thermal comfort.

One of the greatest environmental challenges for the sustainability of future cities is the mitigation of the urban heat island phenomenon and thus, improvement of outdoor comfort conditions for people. The emphasis of this work is to analyze how mitigation techniques in a dense urban environment affect microclimate parameters and outdoor thermal comfort. The quantitative differentiation of outdoor thermal comfort conditions through bioclimatic urban redevelopment for an area in the city of Serres, Greece is investigated. The main bioclimatic interventions concern the application of cool paving materials, the increase of vegetated areas and the creation of water surfaces. The analysis and comparison are performed for a hot summer day with the ENVI-met model. Software simulations regarding microclimatic and outdoor thermal comfort conditions are performed for the daytime period 06.00–20.00 (14 h) at the height of 1.8 m from the ground. The examined parameters are air temperature, surface temperature and mean radiant temperature (Tmrt). The evaluation of outdoor thermal comfort conditions is conducted using the index PMV (Predicted Mean Vote), adapted for outdoor conditions. The results of simulations are discussed regarding the assessment of bioclimatic interventions.N/

Contributions of trees for thermal bioclimate in the urban design in tropical cities : the case of Campinas, SP

Orientador: Lucila Chebel labakiTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e UrbanismoResumo: O sombreamento por arvores pode melhorar o bioclima termico em cidades tropicais como Campinas, SP. As arvores se comportam de maneiras distintas no microclima urbano porem existem poucos estudos sobre a quantificacao dos beneficios trazidos pelas diferentes especies arboreas e sua disposicao no ambiente construido. O objetivo desta pesquisa e quantificar a contribuicao de individuos arboreos e agrupamentos para a melhoria dos microclimas urbanos e do ambiente construido a partir da caracterizacao do bioclima termico local, estudos dos efeitos dos canios urbanos e avaliacao da escala de influencia da vegetacao, bem como diretrizes de projeto urbano e arquitetonico para clima tropical de altitude. Foram analisadas as especies Ipe Amarelo (Tabebuia chrysotricha (Mart. ex DC.) Stand.), Jacaranda mimoso (Jacaranda mimosaefolia D. Don.), Jambolao (Syzygium cumini L.), Mangueira (Mangifera indica L.), Pinheiro (Pinus palustris L.) e Pinheiro (Pinus coulteri L.) - isoladas, Mirindiba Bagre (Lafoensia glyptocarpa L.), Sibipiruna (Caesalpinia pluviosa F.), Espatodea (Spathodea campanulata P.Beauv.), Tipuana (Tipuana tipu F.) - isoladas e agrupadas -, Flamboyant (Delonix indica F.) e tambem, Chuva de Ouro (Senna siamea L.) - agrupadas. Foram utilizados dados meteorologicos - temperatura do ar, umidade relativa, velocidade do vento e radiacao solar - da estacao meteorologica urbana do Instituto Agronomico de Campinas (IAC) no periodo de 2003 a 2010 e dados coletados "in loco" no periodo de 2007 a 2010. Para as analises climaticas para a cidade de Campinas e simulacao da variacao de sombra, aproveitamento do vento e canions urbanos, foram calculados Temperatura Fisiologicamente Equivalente (PET) e Temperatura Media Radiante (Tmrt). Para quantificar a escala de influencia da vegetacao no microclima, analises da atenuacao da Radiacao Solar, Taxa de Cobertura Verde, Indice da Area da Planta (PAI), PET e Tmrt foram realizadas. Concluiu-se que a promocao de sombra e aproveitamento do vento bem como o manejo de arvores para o sombreamento de calcadas e edificios, sao estrategias a serem consideradas no projeto urbano e arquitetonico que visa melhorar o conforto termico das cidades. Observou-se que a especie Sibipiruna (Caesalpinia pluviosa F.) possui o melhor comportamento no microclima devido as caracteristicas relacionadas a especie, tais como Cobertura Verde e PAI e tambem aquelas relacionadas ao ambiente como disposicao no espaco. Um clima confortavel leva ao ambiente interno confortavel particularmente em edificios e, consequentemente, a eficiencia energetica. Proporcionar condicoes adequadas de conforto termico ao ar livre e um passo importante para alcancar a sustentabilidade em espacos urbanos. A consciencia destas questoes e importante para arquitetos, planejadores e urbanistas, nao apenas por orientar as possiveis solucoes, mas tambem para enriquecer as possibilidades de projetoAbstract: Shade trees can improve the thermal bioclimate in tropical cities such as Campinas, SP. Trees behave in different ways in urban microclimate, but there is a lack of research in terms of benefits brought by different species and disposition in building environment. The aim of this research is quantify the contribution by different species and their disposition to improve urban microclimate and urban environment, based on characterization of thermal bioclimate of Campinas, quantification of the urban climate changes causes by street canyons and evaluation of influence scale of vegetation on microclimate, as well as definition of urban guidelines for urban and architectural planning focused in Tropical climates. Twelve species and clusters were analyzed: Ipe Amarelo (Tabebuia chrysotricha (Mart. ex DC.) Stand.), Jacaranda (Jacaranda mimosaefolia D. Don.), Jambolao (Syzygium cumini L.), Mangueira (Mangifera indica L.), Pinheiro(Pinus palustris L.) and Pinheiro (Pinus coulteri L.) - isolated; Mirindiba bagre (Lafoensia glyptocarpa L.), Sibipiruna (Caesalpinia pluviosa F.) , Espatodea (Spathodea campanulata P.Beauv.), Tipuana (Tipuana tipu F.) - isolated and clusters -, Flamboyant (Delonix indica F.) and Chuva de Ouro (Senna siamea L.) - clusters. The meteorological data: air temperature, relative humidity, wind speed and solar radiation for the period 2003 to 2010 and environmental parameters collected "in loco": solar radiation, air and globe temperatures, relative humidity and wind speed, at different distances from the tree trunk (2.5 m, 10m, 25m, 50m) were required. To describe the background climate of Campinas and simulations climate modifications and street canyons, Physiologically Equivalent Temperature (PET) and Mean Radiant Temperature (Tmrt) was done by using Rayman Pro model. To quantify the scale of vegetation influence on urban microclimate, the indexes as Green Coverage Ratio (GCR), Plant Area Index (PAI) and Solar Radiation Attenuated Index (SRAI) was calculated, as well as PET and Tmrt. The results show not only that solar radiation and wind speed can influence air temperature, but also thermal comfort and heat stress as well. The street orientation east-west can improve the thermal climate, and for the others cases it is recommend urban forestry for shading sidewalk and buildings. The species Sibipiruna (Caesalpinia pluviosa F.) presents the best behavior in both seasons, winter and summer, in terms of thermal comfort due to tree features and disposition. The improvement of outdoor thermal comfort is an important step in order to achieve sustainability of urban spaces and configurations. The results can be valuable for architects, planners and urban designers, not only by indicating possible solutions, but mainly by enriching the design possibilitiesDoutoradoArquitetura, Tecnologia e CidadeDoutor em Arquitetura, Tecnologia e Cidad

The most problematic variable in the course of human-biometeorological comfort assessment - The mean radiant temperature

This paper gives a review on the topic of the mean radiant temperature T mrt, the most important parameter influencing outdoor thermal comfort during sunny conditions. T mrt summarizes all short wave and long wave radiation fluxes reaching the human body, which can be very complex (variable in spatial and also in temporal manner) in urban settings. Thermal comfort researchers and urban planners need easy and sound methodological approaches to assess T mrt . After the basics of the T mrt calculation some of the methods suitable for obtaining T mrt also in urban environments will be presented.. Two of the discussed methods are based on instruments which measure the radiation fluxes integral (globe thermometer, pyranometer-pyrgeometer combination), and three of the methods are based on modelling the radiation environment with PC software (RayMan, ENVI-met and SOLWEIG). © 2011 Versita Warsaw and Springer-Verlag Wien