Search

Green building studies generally focus on singular performance aspects (e.g., energy, waste, water, indoor environment) with few tackling the relationships between each other, particularly the relationship between indoor environmental quality (IEQ) and building energy consumption. This study aims to explore the relationship between IEQ performance and energy consumption in National Australian Built Environment Rating System (NABERS) certified buildings. A verified climate normalization factor was localized to standardize energy use intensity in buildings from different climate zones of Australia. The normalized energy use intensity (NEUI) was calculated for all office buildings and correlated with their NABERS Energy and IE rating scores. Multivariate linear regression results reveal that one unit increase in NABERS Energy rating score and IE score can reduce NEUI by 21.98 kWh/m2 and 9.88 kWh/m2 per annum, respectively. Also, this study develops an Energy and Indoor Environment Index to benchmark the energy and IEQ performance of Australian office building. Buildings with excellent NABERS Energy and IE ratings (scores equal to/higher than 5) have been classified as high-performance NABERS buildings (HNBs) and the rest as low-performance NABERS buildings (LNBs). A comparison between 49 HNBs and 48 LNBs demonstrates that, on average, HNBs can deliver 12.6% better indoor environment quality with 35.9% less energy consumption than LNBs. In contrast, many LNBs either use excessive energy to provide a sufficient IEQ, or sacrifice IEQ to reduce energy costs and/or achieve a high NABERS Energy rating.

The cities of desert climates are anticipated to recognize a synergy of urban heat island (UHI) and severe heat waves during summertime. To improve the urban thermal environment, the present study aims quantitatively explore a strategically designed network of vegetation patches called green infrastructure (GI) in subtropical desert cities such as Dubai. To achieve a more comfortable temperature environment, we built and simulated four GI situations with higher GI fractions, GI25, GI50, GI75, and GI100. Using a mesoscale urban model, the mosaic approach is utilized to test potential thermal improvement and urban climate impact, and a portion of each urban grid cell in the model domain is altered with various species of urban vegetation patches by 25%, 50%, 75%, and 100%. The daily peak reduction in ambient temperature at 17:00LT is similar to 0.0168 °C per unit of GI increase when compared to the untreated scenario; however, the maximum anticipated daytime summer temperature decline for GI25, GI50, GI75, and GI100 is 0.6 °C, 1.1 °C, 1.4 °C, and 1.7 °C, respectively. The associated reduction in nighttime ambient temperature per unit increase in the GI is 0.0432 °C, with a maximum temperature drop of around 2.4 °C for the GI100 scenario. Increased GI reduces the height of the planetary boundary layer (PBL) by up to 468 m, which might lead to greater pollution concentrations. While GI-based cooling has a significant influence on delayed sea breeze and humidity, it may raise the risk of heat discomfort in the indoor building environment. This study adds to our understanding of the potential for GI mitigation as well as the seasonal impact of developing GIs on the desert urban boundary layer.

“Net-zero energy”, a burning concept of the current world, has been being considered and applied on a building scale for the last few decades, however, there are significant advantages to moving to the community level. This study identifies the technological advancements of net-zero energy communities through in-depth literature review study. 23 case study settlements have been identified and analyzed based on their design methodology along with some practical applications around the globe. The focus of this work is on technologies and measures utilized for the reduction of energy consumption, minimization of greenhouse gas (GHG) emissions, and the generation of electrical and thermal energy by renewables. We identified different mitigation strategies adopted for outdoor heat sources, building adaptation techniques, and renewable energy technologies along with control strategies. The study reveals that all the settlements mainly focus on the onsite energy generation, while 17 settlements among them, additionally, consider various adaptation techniques that have significantly lessened the energy demand of the buildings. A few studies (4 settlements only) incorporate some mitigation strategies to mitigate the outdoor heat sources that enable to lower the ambient temperature along with diminishing the GHGs emissions as well as minimizing the energy demand of the community. In addition, the climate zones have significant impacts on selecting the building adaptation tools and measures. Alongside the energy balance, we have also epitomized the effects of various energy management and control strategies adopted for the smooth operation of energy. Finally, we shed light on the problems and challenges of existing net-zero energy settlements and make recommendations by considering the environment, energy, and economy towards achieving the net-zero energy purpose at the community level.

The ambient air urban heat island effect (at a height of 4÷4.5 m) is studied in the coastal city of Patras. For this purpose, 11 fixed temperature stations have been placed in chosen representative...

The built environment research expands rapidly making it challenging to synthesize the evidence for informing environmental policies within narrow timeframes. Rapid systematic reviews (rapid reviews) are a practical and viable alternative to comprehensive (full) systematic reviews of research evidence across disciplines. While systematic reviews are now widespread in published academic literature, rapid reviews are still rare. Accordingly, there is an urgent need to familiarise environmental researchers with rapid reviews, clarify misunderstandings, and to improve the use and visibility of rapid reviews in this field. This work outlines the main principles of performing robust and transparent rapid reviews, along with examples of eight such reviews on different topics related to sustainable built environment research. It also provides practical and tested recommendations on the ways to expedite systematic review process while minimising bias and maximising transparency. When conducted according to the best practice, rapid reviews can be of similar quality as many published systematic reviews.

Urban overheating affects the health and wellbeing of communities, the environmental quality, and the economic performance of cities. This study demonstrates that outdoor thermal comfort can be improved in a single street by decreasing ambient (Ta) and surface (Ts) temperatures by implementing innovative and traditional heat mitigation strategies. Ten scenarios were modelled in ENVI-met and evaluated based on detailed in-situ and airborne-based meteorological data collected along Phillip Street (Parramatta) in Sydney, Australia. The best-performing scenario combining reflective materials, increased greenery, spray systems, and traditional shading provides a very significant reduction of Ta and Ts of up to 3.3 °C and 30.9 °C, respectively. On its own, radiative cooling materials applied on shading devices offer a comparable incanyon cooling capacity with maximum Ta and Ts decrease of up to 1.6 °C and 24.2 °C. Similar results are obtained by applying traditional solar control devices, which reduce peak Ta by 1.3 °C and Ts by 21.8 °C. When reflective pavements are accompanied by an increment in greenery, peak Ta and Ts are additionally reduced by 0.2 °C and 3.6 °C, respectively. When applied individually, an increase in evaporative cooling and greenery shows a strong local effect with a maximum in-canyon Ta decrease of 2.7 °C and 0.5 °C, respectively. Results show increased wind speeds have a positive impact on greenery, shading, radiative and reflective technologies and an unfavourable effect on spray systems. Future research should concentrate on examining the cooling potential of radiative coolers in different proportions and arrangements and quantifying the contributions and interactions between different strategies when applied simultaneously.

The Leaf Community is a unique blend of inspired qualified personnel where the preservation of the natural environment, renewable energy sources and worldwide R&D meets education, local culture and society. The Leaf Lab is an industrial building of a rectangular shape and a floor area of approximately 6,000 m 2 located in the Leaf Community, one of the very well‐established smart microgrids in Europe. The Leaf Lab is a near‐zero energy building, combining passive systems, energy‐efficient technologies, integrated monitoring and control, as well as renewable energy production. The number of residents in the Leaf House varies, as it accommodates both employees of the Loccioni Group and short‐term visitors of the Leaf Community. The apartments in the Leaf House are equipped with a touch display providing access to an energy management interface for observing indoor conditions and energy‐related data as well as managing the heating, ventilation and air conditioning; lights; and window shutters.

This chapter presents a comprehensive approach for evaluating the performance of one industrial and one residential smart/near‐zero energy building. The research activities performed and presented in this chapter target the estimation and evaluation of the performance gap between the design and operational phase of zero energy buildings. The steps are as follows: selection of the case study buildings; analysis of the buildings and their systems' design and an assessment of power and energy requirements through dynamic thermal simulation models; data collection while the buildings are in operation; and a comparison of the results of the buildings and the extraction of useful remarks and conclusions. The chapter analyzes the Leaf Lab's energy performance and compares modeling results with real‐time data. There is a systematic and continuous approach in establishing near‐zero energy targets, through research and innovation activities.

Passive daytime radiative cooling represents one of the boldest answers to tackle the future cooling needs of the built environment and to mitigate urban heat island effects. Recent developments in the field targeted sub-ambience with several successful examples. On the other side, heating demands may get exacerbated unless effective countermeasures against overcooling are identified, especially in wintertime or heating-dominated climates. This review aims at collecting state-of-the-art technologies and techniques to dynamically control the heat transfer to and from the radiative emitter and ultimately modulate its cooling capacity. Potential solutions are selected from different applicative fields, including spacecraft thermal control, thermal camouflage and electronics. Environmentally-responsive solutions are analyzed in depth given their perfect match with radiative cooling design requirements. Among them, VO2-tuned Fabry-Perot resonators are given particular emphasis, owing to their proven applicability. Active solutions are presented for completeness, but in less detail. Underlying principles, structural composition and experimental/simulated results are detailed and discussed to identify prominent pathways towards technically and economically effective integration in the built environment.

The objective of this paper is to present the potential of daytime radiative cooling materials as a strategy to mitigate the Urban Heat Island effect. To evaluate the cooling potential of daytime radiative cooling materials, 15 theoretical materials and seven existing materials were simulated: two radiative cooling materials, a coolmaterial, two white paints, a thermochromic paint and a construction material. The novelty of this study is that it shows that the optimal spectral characteristics of radiative cooling materials depending on the climate conditions and the type of application. A sensitivity analysis was performed to evaluate the impact of each wavelength emissivity on the ability to achieve sub-ambient radiative cooling. The sensitivity analysis comprised a total of 90 theoretical materials with 15 different wavelength combinations and 6 emissivity values. The heat transfer model, which includes conduction, convection, and radiation, was developed using a spectrally-selective sky model. Two conditions were considered: a very conductive surface and a highly insulated one. All the materials were simulated in two cities that suffer from the Urban Heat Island effect—Phoenix and Sydney. The mean surface temperature reduction achieved was 5.30 °C in Phoenix and 4.21 °C in Sydney. The results presented suggest that the type of application (active or passive) is a determinant factor in the design of radiative cooling materials. Modifying the spectra of the materials led to a substantial change in the cooling potential. A material that performs well in a dry climate as a passive solution could perform poorly as an active solution.

In several areas of the world, the population concentrates along the coastal regions, benefitting from the sea breeze, with warmer inland areas. However, increasing population is driving urban sprawl in traditionally low-density areas, enhancing the synergies between global and local climate change. Here we show that local climate mitigation can reduce the impacts of climate change, with the analysis of a new development area in Sydney, 50 km from the coast. With meso-scale climate modelling, we computed that by 2050 the peak summer temperature will increase by 0.8 °C and the daily average summer temperature by 1.6 °C. Mitigation with cool materials, greenery, and irrigation will lower the peak and average daily temperatures respectively by 2.2 °C and 1.6 °C with respect to the unmitigated future climate scenario. Mitigation techniques when applied in the whole Sydney area yield to cooling energy needs reductions by 6.7–8.6 kWh/m2 (13.4–19.3%) for typical residential, office, and school buildings, with a negligible heating penalty, compared to an unmitigated future scenario. Combined adaptation and mitigation can reduce the future cooling energy needs by 31.3 kWh/m2 (70%), 29.3 kWh/m2 (57.3%), and 20.9 kWh/m2 (59.4%) for typical residential, office, and school building, respectively. Our study indicates that the consolidated and widely available mitigation technologies alone cannot counteract the energy impact of both global and local climate change. A structured system of interventions at building and urban scale is necessary while developing novel and higher efficiency mitigation technologies.

The gap between the actual and intended energy use for a building is often attributed to stochastic behaviour of occupants. This study systematically investigates the relationship of occupancy with plug and lighting loads energy consumption for several spaces of an institutional building floor. A new parameter ‘Energy-use per person (K)’ is introduced to explain the stochastic relationship between Energy and Occupancy. A model for K is developed as a function of occupancy using ‘Multiple non-linear regression (MNLR)’ and ‘Deep neural network (DNN)’ based algorithms. DNN algorithm shows a better prediction of K with less Mean absolute percentage error (MAPE) of 9.67% and 2.37% compared to 10.34% and 3.15% of MNLR for plug and lighting loads respectively. The model developed is used to estimate possible energy savings during occupied hours with a rule-based energy-use behaviour. Possible plug load energy savings are 8.9%, 3.1% and 1.3% for the classroom, open office, and computer room respectively. Similarly, possible lighting load energy savings are 65.1%, 43.6% and 38.4% for the classroom, open office, and computer room respectively. The study outcome, a robust and iterative ‘K model’ development process can be used as a support tool in decision making for facility management.

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.

Urban overheating has become a growing concern in the Northern Territory of Australia, where residents are suffering from excessive heat and frequent heatwaves. The characteristics of the local cli...

Sharing of key evidence on strategies for reducing resources consumption and lowering carbon footprint is essential to alleviating risks of increasing urbanization, population growth and looming climate change impacts. However, finding scientifically robust research and distilling knowledge to draw confident conclusions in a reasonable timeframe is challenging due to the sheer volume of rapidly accumulating research evidence. Primary evidence is aggregated in secondary studies, i.e. various types of reviews, including systematic reviews and meta-analyses. However, the number of secondary studies is also growing rapidly and their quality varies. This work presents the first systematic review of secondary studies which were claimed to be systematic reviews or meta-analyses of literature relevant to reducing carbon footprint of the built environment or its co-benefits (e.g., health and well-being). The resulting searchable and updatable database contains 131 reviews published between 2001 and early 2018. Importantly, the quality of the included reviews was assessed and categorized. The database is available via a dedicated website which includes interactive visualizations and filtering tools. In its current form, the interactive map and database can help discovery and appraisal of secondary evidence for decision-making and research use, supporting transition to low carbon future. This overview aimed to reveal trends and patterns, including gaps, in the publications of research syntheses relevant to sustainable built environment. The results showed that the number of reviews claiming to by systematic reviews or meta-analyses is rapidly increasing in recent years. However, the exact methodology used and the standard of adherence to methodological and reporting guidelines varies widely among reviews. The included reviews span different disciplines, such as environmental sciences, engineering, urban planning, public health, and social sciences. The first authors from USA, UK and Australia contributed the most relevant reviews. Health and well-being, along with closely related environment and nature, are currently the best synthesized subject areas, while there are still very few included reviews related to policy, economy or information technology, indicating synthesis gaps in these areas. Our analysis reveals the lack of standardized definitions of different types of research syntheses across disciplines, as well as poor reporting quality of research syntheses. We encourage detailed descriptions of methods, providing datasets and interactive visualizations as integral components of the future systematic reviews and evidence maps.

Heat island effects raise the ambient air temperature in metropolitan areas by 4–5 degrees Celsius and can reach 10 degrees Celsius at their maximum. This phenomenon magnifies cities’ energy difficulties while reducing comfort. Mitigation strategies have been developed and recommended to deal with the issue. Methods to increase albedo and the utilisation of vegetation appear to be the most promising, with a reasonably high heat island reduction capacity. This paper examines the heat mitigation techniques and their effectiveness under Sydney’s climate conditions and compares strategies. We implement two perspectives, namely urban greening (green roofs, green pavements) and albedo (street, roof), and characterise urban surface structures, and Envi-met software is employed for our simulation method. Mitigation strategies show a cooling potential of 4.1 °C in temperature along this precinct during the heatwave period. Scenarios that increase high-albedo material on the road, pavements and rooftops and full mitigation show the maximum cooling potential. The mitigation strategies have higher predicted cooling potential on the peak ambient temperature, up to 1.18 °C, while having no or little impact on minimum ambient temperature. The outdoor thermal comfort based on PMV indices varies between a minimum of −0.33 in scenario seven in large layout areas to 3. However, the mitigation scenario presents more acceptable outdoor thermal comfort, but large layouts are predicted to have a hot condition.

Hot and humid regions consist of the tropical climate, Middle Eastern climate, and Mediterranean climate. Such regions are normally located near the equator but also include dessert regions located far from the equator, such as the Gobi Desert. These regions experience uncomfortable thermal comfort levels due to the high outdoor air temperature and, in some cases, high humidity. This situation makes it challenging to provide thermal comfort in these regions. The increased economic activities in most of the countries in hot and humid regions have changed the morphology of urban areas, cities, buildings, and houses. The increase in urbanization affects the outdoor and indoor environments of buildings and houses. The increasing urban temperature due to the increase of heat generation from people, cars, appliances, and other human activities affect the chemical and biological situations of urban areas. The increasing outdoor air temperature due to urban heat generation (aka, urban heat island) in hot and humid regions worsens the already unpleasant outdoor air conditions. It has also resulted in an increase in the use of air conditioning systems and energy consumption as the heat sink temperature (outdoor air) increases. With this, the difference between the indoor air and outdoor air temperature has increased.

In this study we investigated the association between daily weather types (WTs) and the Urban Heat Island (UHI) in two Mediterranean coastal metropolises. For this purpose, we employed an existing weather type classification scheme and examined which WTs influence or drive the intensity of the UHI. We used the gridded weather typing classification (GWTC), in which meteorological conditions at a single location are categorized in daily WTs. We compared these WTs with the maximum temperature differences between urban centers and rural areas in the two major metropolises of Greece (Athens and Thessaloniki). These metropolises have dissimilar geography and spatial planning as well as their urban climate characteristics have differences. We used two groups of temperature time series on a daily basis. One with high and the other with low temperature differences (upper 5% and lower 5% of the maximum temperature differences (ΔΤ

Urban and building typologies have a serious impact on the urban climate and determine at large the magnitude of the urban overheating and urban heat island intensity. The present study aims to analyze the impact of various city typologies and urban planning characteristics on the mitigation of the urban heat island. The effect of the building height, street width, aspect ratio, built area ratio, orientation, and dimensions of open spaces on the distribution of the ambient and surface temperature in open spaces is analyzed using the Sydney Metropolitan Area as a case study for both unmitigated and mitigated scenarios. Fourteen precincts are developed and simulated using ENVI-met the simulation tool. The ambient temperature, surface temperature, and wind speed are extracted. The parameter ‘Gradient of the Temperature Decrease along the Precinct Axis’ (GTD) is introduced to study the cooling potential of the various precincts. In the mitigated precincts, the GTD ranges between 0.01 K/m to 0.004 K/m. In the non-mitigated precincts, the GTD ranges between 0.0093 K/m to 0.0024 K/m. A strong correlation is observed between the GTD of all the precincts, with and without mitigation, and their corresponding average aspect ratio, (Height of buildings to Width of streets). The higher the aspect ratio of the precinct, the lower the cooling potential. It is also observed that the higher the Built Area Ratio of the precincts, the lower the cooling contribution of the mitigation measures.

Urban Heat Island (UHI) phenomenon concerns the development of higher ambient temperatures in urban districts compared to the surrounding rural areas. Several studies investigated the influence of individual parameters in the UHI phenomenon, on the other hand, an exhaustive study that quantifies the influence of each parameter in the resulting UHI is missing in the related literature. This paper proposes a new index aimed at quantifying the hazard of the absolute maximum UHI intensity in urban districts during the Summer season by taking all the parameters influencing the phenomenon into account. In addition, for the first time, the influence of each parameter has been quantified. City albedo and the presence of greenery represent the most important characteristics with an influence of 29% and 21%. Population density, width of streets, canyon orientation and building height has a medium influence of 12%, 10%, 9% and 8% respectively. The remaining parameters have an overall influence of 11%. These results are achieved by exploiting three synergistically related techniques: the Analytic Hierarchy Processes to analyse the parameters involved in the UHI phenomenon; a state-of-the-art technique to acquire a large set of data; and an optimization procedure involving a involving a Jackknife resampling approach to calibrate the index by exploiting the effective UHI intensity measured in a total of 41 urban districts and 35 European Cities.

Overheated outdoor environments adversely impact urban sustainability and livability. Urban areas are particularly affected by heat waves and global climate change, which is a serious threat due to increasing heat stress and thermal risk for residents. The tropical city of Darwin, Australia, for example, is especially susceptible to urban overheating that can kill inhabitants. Here, using a modeling platform supported by detailed measurements of meteorological data, we report the first quantified analysis of the urban microclimate and evaluate the impacts of heat mitigation technologies to decrease the ambient temperature in the city of Darwin. We present a holistic study that quantifies the benefits of city-scale heat mitigation to human health, energy consumption, and peak electricity demand. The best-performing mitigation scenario, which combines cool materials, shading, and greenery, reduces the peak ambient temperature by 2.7 °C and consequently decreases the peak electricity demand and the total annual cooling load by 2% and 7.2%, respectively. Further, the proposed heat mitigation approach can save 9.66 excess deaths per year per 100,000 people within the Darwin urban health district. Our results confirm the technological possibilities for urban heat mitigation, which serves as a strategy for mitigating the severity of cumulative threats to urban sustainability.

Substantial knowledge is available on the association of the indoor school environment and its effect among schoolchildren. In the same context, the SINPHONIE (School indoor pollution and health: Observatory network in Europe) conducted a study to collect data and determine the distribution of several indoor air pollutants (IAPs), physical and thermal parameters and their association with eye, skin, upper-, lower respiratory and systemic disorder symptoms during the previous three months. Finally, data from 115 schools in 54 European cities from 23 countries were collected and included 5175 schoolchildren using a harmonized and standardized protocol. The association between exposures and the health outcomes were examined using logistic regression models on the environmental stressors assessed in classroom while adjusting for several confounding factors; a VOC (volatile organic compound) score defined as the sum of the number of pollutants to which the children were highly exposed (concentration > median of the distribution) in classroom was also introduced to evaluate the mul tiexposu re - outcome association. Schoolchildren while adjusting for several confounding factors. Schoolchildren exposed to above or equal median concentration of PM2.5, benzene, limonene, ozone and radon were at significantly higher odds of suffering from upper, lower airways, eye and systemic disorders. Increased odds were also observed for any symptom (sick school syndrome) among schoolchildren exposed to concentrations of limonene and ozone above median values. Furthermore, the risks for upper and lower airways and systemic disorders significantly increased with the VOCs score. Results also showed that increased ventilation rate was significantly associated with decreased odds of suffering from eye and skin disorders whereas similar association was observed between temperature and upper airways symptoms. The present study provides evidence that exposure to IAPs in schools is associated with various health problems in children. Further investigations are needed to confirm our findings. (C) 2020 Elsevier B.V. All rights reserved.

Green infrastructure has the potential to cool urban environments and reduce the health burden due to heatwaves. This study develops a new method to quantify the benefits of urban heat mitigation technologies on human heat balance and population mortality. The Heat Health Impact (HHI) method is based on the state-of-the-art, multi-parameter model, Universal Thermal Climate Index (UTCI). A proof-of-concept exercise applied the HHI method to Sydney, Australia (population = 5.7 million). All available weather stations (10) were selected for full spatial coverage of the Sydney region (12,367 km2), and average hourly UTCI was calculated from meteorological observations spanning the entire year 2017. In the baseline analysis, average daily UTCI values were calculated for each of the 10 observation sites, and then spatially interpolated across the entire Sydney region for Feb 9, 2017, a representative heatwave day for Sydney. Three different greening intervention scenarios were investigated, and daily average change in UTCI (ΔUTCI) was calculated under each by comparison with the baseline scenario; this ΔUTCI was named Urban Cooling Effect (UCE). We implemented a health impact assessment methodology to estimate the change in attributable mortality due to each greening scenario for the Sydney GMR population for the representative heatwave day. Urban greening infrastructure scenarios reduced daily average UTCI between −0.2 and −1.7 °C on the heatwave day, with the health impact assessment indicating heat attributable deaths reducing up to 11.7 per day across the Sydney GMR compared to the baseline scenario. Our results highlight the health benefits of greening infrastructure to cool urban environments.

In the context of global warming, radiative coolers with high solar reflectance and strong emissivity in the atmospheric window can cool the substrate as well as the ambient air. Silica at its nano or micro-scale being randomly dispersed into a uniform transparent polymer can form scalable radiative coolers for large-scale application. Promising cooling performance has been reported for silica-polymers compared with conventional cooling materials, but their performance can be largely influenced by various fabrication parameters. So far, how fabrication parameters influence the emissivity and the cooling performance has not been experimentally demonstrated and the cooling capacity of silica-polymers reported was not substantial compared to other superior radiative coolers. In this work, random silica-polymer has been optimized experimentally. Lab measurement and experimental testing of six fabricated silica-polymers under subtropical and desert climates indicated that due to the complexity of the thermo-radiative balance, high emissivity and strong selectivity are both indispensable in the production of high cooling power. If combined with superior reflectors with higher solar reflectance and especially the emissivity in 8–13 μm enhancing the heat dissipation ability, substantial cooling capacity can be achieved: under the harsh desert climate with average peak solar radiation over 1100 Wm-2, the combination presented sub-ambient temperature of maximum 4.7 °C when air temperature reached its peak and the maximum daytime and night-time sub-ambient temperatures were 12.5 °C and 15.9 °C respectively.

UHI is the most studied phenomenon of climate change and refers to the increased ambient temperature of cities compared to rural settings. Implementation of reflective materials to urban structures, such as roads and pavements, reduces the surface and ambient temperature and contributes to counterbalance the impact of the phenomenon. The present paper describes the design and the experimental evaluation of a large scale implementation of cool asphaltic and concrete pavements in a major traffic axis of Western Athens covering a total zone of 37,000 m2. To our knowledge, this project is one of the largest urban mitigation projects in the world. Extended monitoring was performed in the area during the entirety of the summer period, while Computational Fluid Dynamics (CFD) simulation was used to evaluate the thermal impact of the application. It was concluded that the use of cool non-aged asphalt can reduce the ambient temperature by up to 1.5 °C and the maximum surface temperature reduction could reach 11.5 °C, while the thermal comfort conditions can improve considerably. Ageing phenomena may reduce substantially and up to 50% the mitigation potential of cool asphaltic materials.

This study aims to develop prediction models for HVAC related energy saving in office buildings. The data-driven modelling makes use of data gathered from several energy audit reports. These reports entail building and energy consumption data for 56 office buildings in Singapore. The two models are developed using Multiple Linear Regression (MLR) and Artificial Neural Network (ANN). The methodology to select the most appropriate input variables forms the essence of this study. This variable selection procedure involves 819,150 iterations, taking all possible combinations of the 14 input variables to determine the most accurate model. The dependent variable is taken as the change in energy use intensity (EUI, measured in kWh/m2.year) between pre- and post-retrofit conditions. The results show that the ANN model is more accurate with a mean absolute percentage error (MAPE) of 14.8%. The best combination of variables to achieve this comprises of gross floor area (GFA), air-conditioning energy consumption, operational hours and chiller plant efficiency. The information on these four variables, along with the prediction model can be used to predict HVAC related energy savings in office buildings to be retrofitted.

Cities face important overheating problems caused by the local and global climate change. Detailed mitigation and adaptation plans and strategies, are designed and applied to counterbalance the impact of the overheating challenges. Albedo management seems to be among the more considered mitigation strategies. A barrier to the wider use of reflecting technologies is the lack of quantitative experimental data and concrete knowledge about their mitigation contribution. Up to now, the performance of the reflective mitigation technologies is assessed based on simulation results considering the initial optical properties of the materials and neglecting ageing and weatherization phenomena. The article present information on the global performance of reflecting mitigation technologies, as measured in a large scale urban mitigation project employing several types of reflecting technologies. It is shown, that because of the weatherization effects, the mitigation potential of the materials is reduced, during the first year after their installation, by at least, 25%. Despite the ageing effects, reflective pavements have found to contribute in reducing the peak summer ambient temperature up to 1,7 K, while their surface temperature was up to 12,3 K lower than that of conventional pavement reducing considerably the sensible heat released to the atmosphere.

Extreme urban heat alongside higher ambient temperatures in urban areas causes serious energy, comfort, health and environmental problems. The implementation of urban heat mitigation techniques can significantly reduce urban temperatures and counterbalance the impact of extreme urban heat. This study assesses the potential cooling ability of modified urban albedo strategies through the implementation of reflective and super reflective materials, as well as the global climatic impacts on a subtropical desert urban environment in Dubai, UAE. Three scenarios using low, average and high albedo modifications are designed and evaluated in parallel to a reference scenario. A physically-based mesoscale urban modeling system is used to assess the thermal and meteorological impacts of the albedo modifications during both the summer and winter seasons at a city scale. The reduction of ambient temperature during the peak of a summer day (14:00 LT) is shown to be 0.6 °C, 1.4 °C and 2.6 °C when urban albedo is increased by 0.20, 0.45 and 0.60 respectively. The winter cooling penalty ranges between 0.6 °C and 1.1 °C for the different albedo scenarios. The increase of the urban albedo also significantly reduces the planetary boundary layer (PBL) depth due to the loss of sensible heat and decreases the intensity of the convective mixing and advection flows from the desert to the city, improving the mitigation potential of the reflective materials; however this increases the risk of a higher pollutants concentration. A much higher mitigation potential is observed for the high-density parts of the city when compared to that of the low-density parts of the city. Irrespective of linear function in the drop of ambient temperature and changing fraction of global albedo, our results reported that the cooling potential of reflective materials is highly influenced by the climate, landscape, and urban characteristics of the cities.

The present article aims to present and discuss the energy and environmental reality in the building sector and critically investigate the future pathways towards its decarbonisation. The current economic and employment characteristics as well as the energy, environmental, climate and social impact of the building sector are analysed. The main current and future challenges related to overpopulation, climate change, urbanisation, energy consumption, material use and poverty are explored and evaluated. The recent building energy technological developments are explored and their current and future energy, environmental and economic potential is assessed. The main drivers determining the future energy consumption of the building sector are examined and their expected evolution is analysed. Representative scenarios on the future energy consumption are selectively presented. The proposed pathways towards the decarbonisation of the building sector are critically presented and the main advantages and potential problems are depicted.

Scientific research on Urban heat islands (UHI) and urban. overheating has set new challenges for societies regarding risk and vulnerabilities, energy demands and mitigation strategies to favor urban environmental quality conditions against urban pollution. This review manuscript addresses systematically 171 relevant studies to identify and characterize gaps in the field of knowledge, through a robust evidence-based analysis focused on identifying taxonomic recurrences, trends in the study of urban fields of impact, global leaderships, mitigation strategies, methodological divergences, remote sensing indexes, data sources, legal frame, among other significant aspects on the context of environmental degradation and energy. The results showed that studies were carried out in 37 countries and 92 cities, mainly in North America (33%), Europe (31%), and Asia (27%) although mainly concentrated in five countries (59%) with an endogenous bias towards domestic microscale purposes. Prevailing topics, multidisciplinary interactions and regulations are focused on the study of Urban Environmental Quality degradation (95%) and on issues related to Energy (25%) demand and efficiency with applications on land cover with high interest on material science, and urban design and planning. The need to implement multiscale studies, motivate policies oriented to prevent health vulnerability and promote energy safety for urban resilience is imperative.

An innovative bioclimatic metric based on the Universal Thermal Climate Index (UTCI) is developed to quantify human thermal physiological heat stress. The Heat Stress Exposure (HSE) metric includes both duration and intensity dimensions of heat exposure, and in this paper it is applied to the Sydney Australia climatology. Geographic Information Systems (GIS) were used to spatially represent and visualize Sydney's HSE. The first stage of the analysis collated observed meteorological data from 10 weather stations across the Sydney metropolitan region, extending from coastal Sydney to approximately 50 km inland in 2017. The second stage of the analysis integrated the radiative meteorological data into estimates of hourly Mean Radiant Temperature which were then applied to UTCI. In the final stage, a threshold UTCI value of 26 °C was selected for the calculation of HSE, which was then cumulated to represent the duration of heat exposure throughout the year. The difference between each UTCI hourly reading and the 26 °C threshold defined a UTCI exceedance (ΔUTCI; °C). The cumulative total of all ΔUTCI throughout the year defined ∑ΔUTCI in units of degree hours (°C.hr), thereby capturing both intensity and duration of exposure to heat stress. Weather systems driving westerly winds from the Australian continent's central deserts brought the highest HSE to Sydney's inland western suburbs, with values ranging between 4,000–6,000 ∑ΔUTCI (°C.hr). Coastal eastern Sydney experienced considerably lower HSE values ranging from 1,600–3,000 ∑ΔUTCI (°C.hr), reflecting the moderating influences of sea breezes and evaporative cooling.

We assess the impact of advanced heat-mitigation technologies in a coastal temperate city under heatwave conditions. For the first time urban-heating mitigation scenarios that refer to ‘cool/reflective’ roofs and roads, ‘green/living’ roofs and shading by replacing low urban vegetation with deciduous broadleaf trees are considered at the highly dense-populated city of Athens (Greece). Numerical simulations are performed for a typical see-breeze and a heatwave day with the Weather Research and Forecasting (WRF) model coupled to an urban-canopy model. Highresolution data on vegetation and urban land use, derived from satellite image analysis, are considered. All scenarios show a cooling effect, with the maximum mean daytime temperature reduction in the case of ‘cool/reflective’ roofs and roads. During daytime, the mean ambient-temperature reduction reaches up to 1 °C while for the surface-temperature up to 9.5 °C and 11.5 °C, on the see-breeze and heatwave day respectively. In the case of ‘green/living’ roofs, the mean daytime latent-heat flux is increased (e.g. up to 140 W/m2 on the heatwave day) due to increased evapotranspiration while the surface temperature is more affected during nighttime. Both scenarios result in a sea-breeze attenuation of 0.5–1 m/s. The presence of deciduous broadleaf street trees has a minor impact on mean ambient temperature but an evident reduction in surface temperature. The mean urban-heating reduction ranges from 0.1 °C to 0.8 °C and from 0.3 °C to 1.7 °C during the sea breeze and heatwave day respectively, with the maximum reduction shown in ‘cool/reflective’ roofs and roads and the minimum in ‘shading trees’ scenarios.