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The evaluation of wind environment has been receiving increasing attention as it has been associated with issues related to the quality of the urban climate, such as heat island intensity and air pollution, affecting health and wellbeing in large metropolitan areas. Focusing on the context of London, this study aims to associate pedestrian level wind comfort with the characteristics of urban morphology that incorporate information about the height variability and the vertical dimensions of buildings. More than 20 case studies of different configurations and dimensions 500 × 500 m were examined through CFD simulations. For each case study, eight wind directions were tested and the BRE wind comfort criteria were implemented for the different outdoor human activities. The results reveal a strong connection between the ground level mean wind speed ratio and the development of acceptable or tolerable wind conditions for pedestrians. From the morphological indicators examined, façade area ratio was the most dominant on mean wind speed ratio and on the percentage of outdoor space which is comfortable for certain activities, especially for increasing values of plan area ratio. The results of the study indicate that façade area ratio should be taken into consideration for assessing pedestrian level wind environment. • CFD studies in real urban areas with different building typologies and configurations. • Urban morphological analysis of the metropolitan area of London. • Wind comfort assessment according to BRE wind criteria. • Influence of building heights on ground level wind conditions. • Mean wind speed ratio and comfortable wind conditions for pedestrian activities. [ABSTRACT FROM AUTHOR]

• Ladybug-Tools can be used to assess outdoor shading requirements over the year. • Outdoor Mean Radiant Temperature is potentially overestimated by Ladybug-Tools (1.6). • Cairo North-South urban canyon require shading for more days than East-West. • Cairo East-West canyon Height-to-Width 1.3 require shading (10+ hours) for 103 days. • Cairo N-S canyon, H/W ratio 0.9, require 5+ hours of shading for 159 days. This study proposes a novel way of using and presenting calculations of outdoor thermal comfort, to analyze the requirements of outdoor shading; by showing whether shading would be beneficial, harmful or ineffective – in a specified urban context – for every hour of the year. The simplified Outdoor Shading Assessment Method (OSAM) aims to assist in the early stages of outdoor shading analysis, acting as a decision-support tool regarding the type, application period, design and efficiency aspects of the shade required. The study uses the Universal Thermal Climate Index (UTCI) for thermal comfort evaluation, calculated through the Ladybug-tools (LBT 1.6). The method has been tested for the climate of Cairo against field measurements, revealing a strong correlation (R2 = 0.9267) for the UTCI. It also revealed potential overestimation in the Mean Radiant Temperature (MRT) simulation by newer versions of the LBT. Two climate examples, hot and temperate, are explored through two orientations and urban geometries, demonstrating varying outdoor shading requirements. For the E-W and N-S canyons (H/W = 1.3), Cairo's hot climate shows high shade benefit for at least 2 h per day for 171 and 250 days respectively, compared to 26 and 45 days for London's temperate climate. [ABSTRACT FROM AUTHOR]

The urban canyon albedo (UCA) quantifies the ability of street canyons to reflect solar radiation back to the sky. The UCA is controlled by the solar reflectance of road and façades and the street geometry. This study investigates the variability of UCA in a typical residential area of London and its impact on outdoor and indoor microclimates. The results are based on radiation measurements in real urban canyons and on a 1:10 physical model and simulations using ENVImet v 4.4.6 and EnergyPlus. Different scenarios with increased solar reflectance of roads and façades were simulated to investigate the impact on UCA and street level microclimate. The results showed that increasing the road reflectance has high absolute and relative impact on UCA in wide canyons. In deeper canyons, the absolute impact of the road reflectance is reduced while the relative impact of the walls' reflectance is increased. Results also showed that increasing surface reflectance in urban canyons has a detrimental impact on outdoor thermal comfort, due to increased interreflections between surfaces leading to higher mean radiant temperatures. Increasing the road reflectance also increases the incident diffuse radiation on adjacent buildings, producing a small increase in indoor operative temperatures. The findings were used to discuss the best design strategies to improve the urban thermal environment by using reflective materials in urban canyons without compromising outdoor thermal comfort or indoor thermal environments. [Display omitted] • High reflectance roads are effective in increasing urban albedo in wide canyons. • Façade reflectivity has more potential to increase urban albedo in deep canyons. • High reflectance materials worsen outdoor thermal comfort in urban canyons. • Reducing the façades reflectivity has a positive impact on outdoor thermal comfort. • High reflectance on roads has a negative impact on indoor operative temperatures. [ABSTRACT FROM AUTHOR]

• The impact of urban fabric on street canyon albedo was experimentally investigated. • A detailed 1:10 scaled physical model of a residential area in London was developed. • Canyon albedo varies diurnally, seasonally, with cloud coverage and rainfall. • Glazed façades lead to lower canyon albedo than brickwork and aluminium cladding. • Brickwork façades contribute to higher canyon albedo in the infrared. This paper presents findings from a large-scale experiment on the impact of urban fabric on canyon albedo, aimed at informing the development of an urban albedo calculator for London, an empirical model to predict changes in urban albedo in relation to changes in urban fabric and solar altitude. Through different material applications on a 1:10 scaled physical model of an actual residential area, the study assessed the effect of street-level materials and three common façade types on canyon albedo alongside the canyon's reflective power in the infrared, and the impact of rain. The results showed that the addition of concrete paving at street level increased canyon albedo by 9%, while the substitution of tarmac with grass by 70%. Brickwork and aluminium cladding façades were seen to contribute to significantly higher canyon albedo than curtain wall across the measured irradiance spectrum. The results also revealed the highly dynamic nature of canyon albedo and a consistent rainfall-induced reduction of albedo in the range 22–36% throughout the experimental phases. The findings from this study can inform urban planning and policy making directed at tackling the urban heat island effect. [ABSTRACT FROM AUTHOR]

Thermal diversity in open spaces is deemed highly desirable as it can enhance humans' thermal experience and thus, the use of the urban space. This study explores the occurrence of spatial thermal diversity in open spaces in London and Paris, focusing on two parameters affecting the thermal environment. The method employed is based on the mapping of combined availability of sun and wind using DEMs and image processing techniques. The aim is to contribute to establishing a methodology for the assessment of thermal diversity, and to examine the relationship between this and the urban density and coverage variables. A mathematical formula for quantifying thermal diversity is proposed, and used for computing average and instantaneous values for 132 urban forms. The relationship of thermal diversity with the two variables is found to be statistically significant (R2 > 0.5), and best fit is achieved by polynomial curves. Solving the equations, the density and coverage values that maximize thermal diversity are identified for the two cities. To interpret the findings, the effect of built obstruction on the occurrence of the four microclimatic combinations considered (i.e. sunny-windy, sunny-lee, shaded-lee, shaded-windy) is examined. Lastly, examples of urban forms are discussed in relation to their geometry and performance. • Thermal diversity maps are produced based on sun and wind shadow maps. • A mathematical formula is proposed for quantifying thermal diversity in open spaces. • The relationship of diversity with density and coverage is strong, but not linear. • Reference density and coverage values for maximizing diversity were identified. [ABSTRACT FROM AUTHOR]