On the Thermal Environmental Quality of Typical Urban Settlement Configurations

Urban overheating and energy imbalances are severe environmental concerns. The role of urban sprawl patterns in the formation of Heat Island has recently absorbed the researchers’ interest. The research focuses on metropolitan areas with a range of urban typologies. However, there still is a knowledge gap in how UHI responds to different urban typologies. The interaction between urban configurations and heat island characteristics is explored in Sydney. A combination of terrestrial surveys and modelling techniques was implemented, and results were extracted based on simulation results. The Urban Taskforce Australia suggested the applied categorization methods that follow Stewart and Oke’s Local Climate Zones (LCZs) scheme. We assessed eleven urban designs on ambient air temperature, wind characteristics, heat intensity, and outdoor thermal comfort over three summer days. We correlated results to density and the built-up ratio in all configurations and found that the maximum configurational impact on the heat island reached 2.33 °C. Configurations with a built-up ratio between 0.37 to 0.5 present a sharp downward trend in the average wind speed value and indicate a minimum with a built-up ratio of 0.63. Wind maps present an increase in layouts with built-up ratios of 0.23 to 0.37, whereas they decreased with built-up ratios of higher than 0.43. The average temperature decrease in high-rise compact configurations was 1.12 °C per hour. This record is substantially higher than its open counterparts. The study showed the importance of urban configuration on thermal environmental quality. In addition, implementing appropriate urban design parameters is vital to mitigate heat islands and improve environmental thermal comfort in urban areas

Canopy urban heat island and its association with climate conditions in Dubai, UAE

The impact that climate change and urbanization are having on the thermal-energy balance of the built environment is a major environmental concern today. Urban heat island (UHI) is another phenomenon that can raise the temperature in cities. This study aims to examine the UHI magnitude and its association with the main meteorological parameters (i.e., temperature, wind speed, and wind direction) in Dubai, United Arab Emirates. Five years of hourly weather data (2014–2018) obtained from weather stations located in an urban, suburban, and rural area, were post-processed by means of a clustering technique. Six clusters characterized by different ranges of wind directions were analyzed. The analysis reveals that UHI is affected by the synoptic weather conditions (i.e., sea breeze and hot air coming from the desert) and is larger at night. In the urban area, air temperature and night-time UHI intensity, averaged on the five year period, are 1.3 °C and 3.3 °C higher with respect to the rural area, respectively, and the UHI and air temperature are independent of each other only when the wind comes from the desert. A negative and inverse correlation was found between the UHI and wind speed for all the wind directions, except for the northern wind where no correlation was observed. In the suburban area, the UHI and both temperatures and wind speed ranged between the strong and a weak negative correlation considering all the wind directions, while a strong negative correlation was observed in the rural area. This paper concludes that UHI intensity is strongly associated with local climatic parameters and to the changes in wind direction

Analysis of the indoor air quality in greek primary schools

The exposure of children to indoor air pollutants in school classrooms might cause them adverse health effects. In order to confront this issue, the in-depth study and evaluation of the indoor air quality in classrooms is necessary. The aims of this study are to characterize the environmental factors that affect indoor air quality. Several indoor air pollutants such as the concentrations of the particulate matter (PM) of several different size ranges, carbon dioxide (CO2), carbon monoxide (CO) and VOCs, were simultaneously measured in classrooms as well as the outdoor environment in nine primary schools in Athens, Greece during April 2013. Measurements were performed for more than 7 hours per day, for a period of one to five days in a classroom, per school. The first results indicate extreme PM10 concentrations in many cases with varying fluctuations throughout the day, mainly attributed to the presence of students, inadequate level of ventilation and chalk dust while the ultrafine particles (UFP) remained in rather low levels. In most of the cases the indoor concentrations exceeded the outdoor ones by more than ten times. Carbon dioxide concentrations in many cases exceeded the recommended limit value indicating inadequate levels of ventilation

Expanding the applicability of daytime radiative cooling: Technological developments and limitations

Daytime radiative cooling is regarded as the gold promise of future sustainable building energy systems and a breakthrough in the fight against local climate change. Despite the fervid research interest, most literature reports exceptional theoretical performances under ideal, desert-like conditions, but overlooks the cooling impairment that occurs under low atmospheric transparency (cloudy, humid, polluted conditions) and reduced sky access (packed urban contexts). Power recovery and stabilization call for decoupling of incoming and outgoing radiation at equal wavelengths. Enhanced directionality and high-contrast, broadband asymmetric transmission have been recently proposed to expand the applicability of radiative coolers over a wider spectrum of climates, weathers and terrains. This review offers itself as a first, timely synthesis of the current technological arena. Physical principles, materials and designs, collected from a variety of applicative fields, are detailed and discussed in terms of performance and feasibility, to inspire the transition into sustainable building cooling, worldwide. Major grey areas and serious concerns on potential violations of the 2nd law of thermodynamics reinforce the need for experimental demonstrations in future research

Energy Performance of Cool-colors and Roofing Coatings in Reducing the Free Solar Gains during the Heating Season: Results of an In-Field Investigation☆

Abstract Today, it is not well-known the impact of cool roofs during heating season in balanced climates. Proposed study tries to quantify the increase of energy demands of buildings characterized by high-reflective and high-emissive coatings of roof, by means of experiments and numerical simulations. Three coatings are investigated with different solar absorptance and thermal emittance. The experiments have been carried out at the living lab of the University of Sannio, a full-scale test-room, provided with a large flexibility in terms of variability of the thermal envelope and air-conditioning system. Moreover, numerical evaluations of heating and annual energy consumptions are presented