Search

The incident solar radiation on building facades is strongly affected by the urban characteristics, however frequently overlooked in the assessment of indoor environments due to limited data availability. Here, we show that a simplified representation of the urban environment can drastically affect the estimation of the incident solar radiation within urban canyons. We associate uncertainties with the canyon’s geometry, built surfaces, optical properties, as well as vegetation, and resort to a hybrid probabilistic-possibilistic approach to quantify the effects on thermo-visual comfort. Contrasting complex against simplified urban canyons shows that the pattern of incident solar radiation is uneven along the building facade and strongly correlated to the canyon’s characteristics. We also demonstrate that simplified models of urban canyons could underestimate the number of thermally comfortable instances by even 365 h a year (i.e., ~ 4% of the time). Similarly, a simplified canyon underestimates the visually comfortable occurrences, especially during the intermediate seasons. While a simplified canyon estimates a glare probability of 1.0, uncertainties within a complex canyon can lower the glare probability to 0.28 throughout the day. We show that for visual comfort, geometric characteristics alone, such as the canyon’s skyline, can outweigh optical properties such as the transmissivity of trees. This uncertainty, especially in the estimate of glare probability, may lead to different decisions about building envelope design, including the need for a more or less adaptable facade.

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.

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.

Cities are warmer than surrounding non-urban areas. Climate models predict that metropolitan centres will become even warmer due to the dual impacts of global warming and densification. However, the outer fringe zones of metropolitan centres will also become warmer as a consequence of urban expansion that requires replacing green and open spaces like pastures or bushland with grey infrastructure such as roads and buildings. Limiting the warming effect of urban expansion is possible. It requires dedicated heat-responsive planning and design strategies being applied systematically and at scale. But where should planners and developers start to effectively reduce urban heat? At-grade car parks are an ideal starting point. They represent the ���low-hanging fruit��� for urban cooling efforts. While unavoidable today and in the near future, at-grade car parks are predominately unshaded; made from black, heat-retaining asphalt; widespread and fairly uniform; and often large in size. Changes to current designs of at-grade car parks can therefore have a big impact. A number of strategies to effectively reduce surface heat of car parks are commercially available. Cooling car parks not only addresses their status as local heat islands, but it also leads to lower ambient air temperatures in downwind environments. This report documents: ��� Microclimates across eight car parks and reference sites covered by vegetation. Measurements of surface and air temperatures related to a range of car park surface materials. The cooling effect of shade in car parks. Current design guidelines and policies in Australia related to car parks. Alternative design solutions for cooler car parks. The empirical data and policy analysis are used to develop a set of recommendations for urban heat mitigation that can be applied to new and existing car parks. Because of the common nature of at-grade car parks around the world, the proposed cooling techniques can be applied globally, irrespective of the fact that the underlying case studies and data originated from Sydney.

Urban overheating, driven by global climate change and urban development, is a major contemporary challenge which substantially impacts urban livability and sustainability. Overheating represents a...

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...

Urban climates are highly influenced by the ability of built surfaces to reflect solar radiation, and the use of high-albedo materials has been widely investigated as an effective option to mitigate urban overheating. While diffusely solar reflective walls have attracted concerns in the architectural and thermal comfort community, the potential of concave and polished surfaces, such as glass and metal panels, to cause extreme glare and localized thermal stress has been underinvestigated. Furthermore, there is the need for a systematic comparison of the solar concentration at the pedestrian level in front of tall buildings. Herein, we show the findings of an experimental campaign measuring the magnitude of the sunlight reflected by scale models reproducing archetypical tall buildings. Three 1:100 scaled prototypes with different shapes (classic vertical façade, 10% tilted façade, curved concave façade) and different finishing materials (representative of extremes in reflectance properties of building materials) were assessed. A specular surface was assumed as representative of a glazed façade under high-incidence solar angles, while selected light-diffusing materials were considered sufficient proxies for plaster finishing. With a diffusely reflective façade, the incident radiation at the pedestrian level in front of the building did not increase by more than 30% for any geometry. However, with a specular reflective (i.e., mirror-like) flat façade, the incident radiation at the pedestrian level increased by more than 100% and even by more than 300% with curved solar-concentrating geometries. In addition, a tool for the preliminary evaluation of the solar reflectance risk potential of a generic complex building shape is developed and presented. Our findings demonstrate that the solar concentration risk due to mirror-like surfaces in the built environment should be a primary concern in design and urban microclimatology.

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.

Summarization: Urban greenery is a natural solution to cool cities and provide comfort, clean air and significant social, health and economic benefits. This paper aims to present the latest progress on the field of greenery urban mitigation techniques including aspects related to the theoretical and experimental assessment of the greenery cooling potential, the impact on urban vegetation on energy, health and comfort and the acquired knowledge on the best integration of the various types of greenery in the urban frame. Also to present the recent knowledge on the impact of climate change on the cooling performance of urban vegetation and investigate and analyse possible technological solutions to face the impact of high ambient temperatures. Presented on

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.

Wall finishes with high solar reflectance and thermal emittance, commonly known as cool walls, can reduce the exterior surface temperatures of façades, and consequently the building cooling energy needs and power demand, and lower the sensitivity to degradation. Aging, though, may affect their performance. To investigate this risk, we exposed for four years in Milan, Italy, two series of façade finish coats, white and beige, facing north and south, in vertical and vertical-sheltered position, and we measured their solar spectral reflectance and thermal emittance before and after aging. The solar reflectance of the white finish coats drops from 0.75 to 0.55 in four years, and from 0.46 to 0.38 for the beige coats, while the thermal emittance is unchanged. Then, for a typical residential building with white walls, we computed that the cooling energy needs increase with walls aging by 5% and 11%, respectively, with or without exterior wall insulation. The exterior surface temperature is increased even by 6 °C, and the number of sudden surface temperature variations in one hour is boosted. Finally, the moisture content in the external layers is reduced, showing the impact on the heat and mass balance because of the uncertainty in solar absorption due to aging. © 2017 Elsevier B.V.

The Perez sky diffuse model has been validated in many locations, however, studies have shown that the precision of estimation can be improved through localization of the model coefficients. This paper studies the effect of tuning Perez irradiance coefficients based on local information for estimating the incident solar radiation on tilted surfaces. The added value of a calibrated Perez model is highlighted by evaluating the heating and cooling energy needs of an office building. Calibration is performed by using Subset Simulation, i.e. a sampling technique based on Markov Chain Monte Carlo. The versatility of the Subset Simulation technique allows for handling multivariant calibration problems and is therefore suitable for finetuning Perez irradiance coefficients. Measurements of global horizontal, direct normal and diffuse horizontal solar irradiation, as well as the global solar irradiation on 90°, 30° and 15° tilted surfaces form the basis of the calibration. It is found that in the studied location, the default Perez model overestimates the incident solar radiation on vertical surfaces facing south. The calibrated coefficients are then embedded in the source code of EnergyPlus. Simulations with a reference office show that the effect of calibrating Perez coefficients can be significant, because it leads to approximately 12% difference in predicted annual cooling energy use and 9% difference in peak cooling loads, respectively.

Indoor thermal comfort and air quality in school classrooms are of interest worldwide, primarily because of their potential impacts on students’ health, learning performance and productivity. Further, increasing concerns with changing climate and building energy efficiency highlight the importance of ventilation and comfort in educational settings. The existing literature on indoor air quality (IAQ), ventilation, and thermal comfort in classrooms in subtropical regions of Australia is sparse. Here, we present the results of a field study conducted in secondary school classrooms in Sydney during the school year in 2018 and 2019. We collected data with subjective surveys through questionnaires and with field measurements related to IAQ the thermal comfort in two adjacent similar classrooms. The infiltration and ventilation rates were measured during the non-occupied period using the concentration decay method. We analysed the performance of a cloud-connected demand-controlled mechanical extract ventilation system (DCV), which was installed in one of the two surveyed classrooms during mid-season. Before application of the DCV, CO2 levels were similar in both classrooms with a maximum concentration of approximately 2418 ppm during cold season. The DCV reduced the peak CO2 concentration to 1335 ppm, while CO2 raised to 2981 ppm in the classrooms without DCV during mid-season. Further, Volatile Organic Compounds (VOCs) analysed from air samples show improved air quality in the classroom with DCV. Our results highlight the impact of both indoor temperature and CO2 concentration on students’ feeling of fatigue. Students showed adaptability to indoor temperature change. A period of one week is needed for students’ adaptation to a step change in the mean outdoor temperature. Understanding classroom indoor air quality and thermal environment, as well as students’ perceived comfort, is vital to develop child-based design guidelines for schools.

Urban overheating coincides with Heatwaves (HWs) and the thermal stress might get amplified in cities. To predict the interactions between urban overheating and HWs, the surface energy balance response to HWs is crucial. HW is a regional phenomenon and the climatic conditions may influence the local conditions to alter the energy budget contrast between a city and its adjacent peripheral areas. The interactions between the urban overheating and HWs are explored in a coastal city (Sydney Australia), also in the proximity of dry landmass, while considering the site characteristics, distance from the coast, and the population density. A positive response between urban overheating and HWs is reported. Advective heat flux in the form of a dualistic circulation system is found responsible for exacerbating the urban overheating magnitude (ΔT) during the HWs and altering the available energy balance. Land-coastal distance is also found as an important contributor in magnifying the urban-suburban temperature contrast. Considering the future urbanization in western Sydney, surfaces capable of retaining higher moisture content are prescribed to reduce the occurrence of extreme HW events. Activation of the ventilation corridor for the coastal wind penetration in western Sydney is another recommendation of this study.

Climate change is one of the most significant environmental issues facing communities, while poor construction and absence of effective air-conditioning (AC) predominantly cause indoor overheating. Although AC may help meeting indoor comfort, it increases the vulnerability of low-income residents, triggers large energy consumption, and generates anthropogenic heat, which worsens heat stress outdoor. The capacity of buildings to maintain comfortable thermal conditions without mechanical cooling is the key factor protecting occupants against the rising temperature. Residents of Darwin, Australia, will be largely affected by increasing temperature where the annual peak ambient temperature may increase by 7.4 °C in 2060, while the number of hours above 30 °C will rise by 70%. Based on regional climate modelling for the Australian area and using a building energy simulation platform, we computed that by 2060 the indoor air temperature in a typical residential building may exceed 30 °C for over 4000 h under free-floating condition, with a peak daytime and night-time temperatures of 39 °C and 36.5 °C, respectively. The sensible thermal energy need for cooling per unit area under thermostatically controlled condition will increase from the current level of 110.7 kWh/m2 to 196.8 kWh/m2 in 2060. Different adaptation techniques when applied to the typical residential building yield to the peak indoor air temperature drop by 3.3–12 °C, and cooling energy needs reductions by 23.5–195.3 kWh/m2 (12–99.7%) for low, medium, and high retrofit buildings compared to the typical residential building in 2060. Our study indicates that improved building quality is necessary to enhance survivability and energy efficiency in Darwin considering the role of building adaptation measures to counterbalance the impacts of global warming.

The increasing frequency of extreme hot days has a considerable impact on health and energy. Heat stress related to high temperatures cause increased rates of mortality and morbidity, particularly amongst vulnerable populations such as those belonging to lower socio-economic groups. Most studies on heat related mortality and morbidity generally use temperatures from weather stations that do not consider the urban heat island (UHI) effect, leading to inaccurate predictions, particularly during heat waves. This study uses data collected by citizen scientists in predicting outdoor thermal comfort as well as indoor heat stress and peak cooling energy for low income housing in Australia. The results show that the outdoor Universal thermal climate index (UTCI) values estimated during hot afternoon ranged from 26 °C to 46 °C which equate to moderate to extreme heat stress. The indoor Discomfort index (DI) values calculated inside the living and bedrooms were below the heat stress limits (DI

Cities in Australia are experiencing unprecedented levels of urban overheating, which has caused a significant impact on the country’s socioeconomic environment. This article provides a comprehensive review on urban overheating, its impact on health, energy, economy, and the heat mitigation potential of a series of strategies in Australia. Existing studies show that the average urban heat island (UHI) intensity ranges from 1.0 °C to 13.0 °C. The magnitude of urban overheating phenomenon in Australia is determined by a combination of UHI effects and dualistic atmospheric circulation systems (cool sea breeze and hot desert winds). The strong relation between multiple characteristics contribute to dramatic fluctuations and high spatiotemporal variabilities in urban overheating. In addition, urban overheating contributes to serious impacts on human health, energy costs, thermal comfort, labour productivity, and social behaviour. Evidence suggest that cool materials, green roofs, vertical gardens, urban greenery, and water-based technologies can significantly alleviate the UHI effect, cool the ambient air, and create thermally balanced cities. Urban greenery, especially trees, has a high potential for mitigation. Trees and hedges can reduce the average maximum UHI by 1.0 °C. The average maximum mitigation performance values of green roofs and green walls are 0.2 °C and 0.1 °C, respectively. Reflective roofs and pavements can reduce the average maximum UHI by 0.3 °C. In dry areas, water has a high cooling potential. The average maximum cooling potential using only one technology is 0.4 °C. When two or more technologies are used at the same time, the average maximum UHI drop is 1.5 °C. The mitigation strategies identified in this article can help the governments and other stakeholders manage urban heating in the natural and built environment, and save health, energy, and economic costs.

In building performance simulations it is typically assumed that outdoor HVAC equipment is exposed to air at the outdoor ‘ambient’ temperature, obtained from a weather file. However, in reality, significant spatial variations in the outdoor air temperature can exist close to buildings. This simplification may lead to significant errors, especially when comparing simulations of buildings with and without cool roofs, since the colder surface of the cool roof would reduce above-roof air temperatures, thereby influencing the energy consumption of rooftop HVAC equipment. Above-roof temperature variations were measured in detail at three shopping centre buildings, and the experimental data was used to develop a model that can estimate air temperatures above hot or cold roof surfaces. The model requires only four input variables, all of which are available in typical building simulation tools. Implementation of the model in a set of case-study simulations revealed that above-roof air temperatures can have a large effect on the predicted performance of cool roofs. In cases where cooling equipment and ventilation inlet ducts were both located on the roof, the electricity savings and gas ‘penalties’ attributable to cool roofs would have been underestimated by 44–85% (61% on average) if above-roof air temperature variations had not been modelled accurately.

Urban overheating affects the energy, health, power, survivability and environmental quality of cities. We calculated the magnitude of overheating in Sydney, Australia, at close to 9 °C, which causes a cooling penalty of up to 16% and an increase in the indoor overheating levels of up to 56%. We developed and evaluated eight heat mitigation scenarios based on the use of reflective surfaces, additional greenery, an increase in the evapotranspiration rate and several combinations of these factors. We estimated that mitigation can decrease the peak ambient temperature by up to 2.9 °C, reduce the maximum annual cooling consumption by up to 1.5 TWh, decrease the CO2 emissions by as much as 1.21 MT CO2, reduce indoor overheating by up to 80%, decrease the heat-related morbidity by 1.07–1.49, and decrease the heat-related mortality anomaly by as much as 1.39 per 100,000 citizens. We estimated the associated water penalty range to be between 80 and 100 Gl/year or between 13 and 16.7% of the water consumption in Sydney.

Providing evidence of potential changes in the climate has become increasingly important as it is the first step towards adopting mitigation and adaptation measures and planning for urban resilience. In this study a statistical analysis of the ambient air temperature time series over Sydney, Australia during 1970-2016 has been carried out with the aim to investigate potential changes towards higher temperatures. The dataset has been statistically analyzed using different techniques, concluding that the investigation should be performed on a monthly basis. A persistence analysis was conducted using different statistical approaches to investigate the dependence between consecutive monthly and daily ambient air temperature values. A trend analysis of the ambient air temperature and degree days time series has been conducted using linear regression to estimate the linear trend (slope) and its statistical significance (using a Student-t-test) and the Kendall-Mann test to identify the time at which the tendency starts to occur as well as the time after which it becomes statistically significant.

In the pursuit of ever more efficient built environments, able to resiliently respond to the many implications of climate change, near room-temperature caloric cooling could be a game changer from multiple standpoints. In this paper, perspectives and challenges of successful implementation of elastocaloric devices in the built environment are explored by contrasting the current readiness level with the envisaged potentiality. Material-level and device-level criticalities are identified and potential solutions are discussed. The roadmap towards an informed and efficient use of this environmentally friendly technology is eventually proposed aiming at an increase of building’s energy efficiency, but also at counteracting the urban heat island effect.

The urban heat island is a vastly documented climatological phenomenon, but when it comes to coastal cities, close to desert areas, its analysis becomes extremely challenging, given the high temporal variability and spatial heterogeneity. The strong dependency on the synoptic weather conditions, rather than on city-specific, constant features, hinders the identification of recurrent patterns, leading conventional predicting algorithms to fail. In this paper, an advanced artificial intelligence technique based on long short-term memory (LSTM) model is applied to gain insight and predict the highly fluctuating heat island intensity (UHII) in the city of Sydney, Australia, governed by the dualistic system of cool sea breeze from the ocean and hot western winds from the vast desert biome inlands. Hourly measurements of temperature, collected for a period of 18 years (1999–2017) from 8 different sites in a 50 km radius from the coastline, were used to train (80%) and test (20%) the model. Other inputs included date, time, and previously computed UHII, feedbacked to the model with an optimized time step of six hours. A second set of models integrated wind speed at the reference station to account for the sea breeze effect. The R2 ranged between 0.770 and 0.932 for the training dataset and between 0.841 and 0.924 for the testing dataset, with the best performance attained right in correspondence of the city hot spots. Unexpectedly, very little benefit (0.06–0.43%) was achieved by including the sea breeze among the input variables. Overall, this study is insightful of a rather rare climatological case at the watershed between maritime and desertic typicality. We proved that accurate UHII predictions can be achieved by learning from long-term air temperature records, provided that an appropriate predicting architecture is utilized.

Chemical and physical stress, weathering, organic and inorganic matter deposition, and microbial growth over time, or “aging”, affect the optical-radiative performance of building envelope materials. Natural exposure helps to quantify these effects, but it usually requires several years. Further, the contribution of the different degradation agents cannot be isolated, and results from different campaigns cannot be easily compared because of the variability in the boundary conditions producing aging. Here we present an adaptation of the protocol implemented by ASTM as D7897-18 “Standard Practice for Laboratory Soiling and Weathering of Roofing Materials to Simulate Effects of Natural Exposure on Solar Reflectance and Thermal Emittance”. The aim is to reproduce in the laboratory the changes in albedo (solar reflectance) and thermal emittance experienced by building envelope materials in European urban areas rather than in the United States. We tuned the spraying duration and weathering cycles, and we compared the UV–vis–NIR reflectances of naturally-aged specimens (48 months in Rome and Milan) of roofing and wall finish materials to those exposed to laboratory weathering and soiling. Excluding those materials that show early physical-chemical degradation, the mean absolute deviation between natural and laboratory exposure of roofing products is equal to 0.027 in albedo. This is a lower value than the differences between two natural exposure campaigns at the same site. We clearly defined the limits of application of the protocol, providing an appraisal of the repeatability of natural aging. Moreover, we identified possible improvements in the methodology to conduct both natural and laboratory exposure.

The physical integrity and photocatalytic performance of titanium dioxide (TiO2) deteriorate with aging. Here we propose a pre-treatment with nitric or sulfuric acid of commercial TiO2 nanopowders used in coating, mortars, or paints. The diffuse reflectance is increased between 1500 and 2500 nm by 0.04 and 0.06, respectively, with nitric and sulfuric acid (unaffected by neutralization). Nitric acid causes a decrease in crystallinity and photocatalytic activity, which drops by almost 20%; this drawback is prevented by post-treatment neutralization, which allows to recover initial photocatalytic efficiency and even increase it. Treatment with sulfuric acid shows no significant effect on photoactivity, instead.

Over three million people live below the poverty line in Australia. Low-income households suffer from overheated or cold homes and experience problems associated with energy inefficiency and poor indoor environmental quality (IEQ), which ultimately affect residents’ quality of life, comfort, well-being, physical and mental health. These circumstances are the main drivers of a social challenge known as Energy Poverty (EP) when residents have difficulties in paying the electricity bills. EP needs to be addressed by i) implementing energy efficiency measures in social housing, ii) educating low-income families about energy saving practices and behaviours, iii) developing new energy policies. We investigated the level of EP in social housing located in New South Wales, Australia. Indoor thermal environment and air quality were monitored in 106 low-income households over the winter and summer periods 2018/2019. Questionnaire responses informed the real living conditions of participating families, including their medical history and behaviours concerning energy use. The information presented here will be used to investigate the possible evolution of IEQ and EP as a function of climate change and extreme weather events on housing and suggest countermeasures and target policies to benefit the vulnerable households and alleviating the EP level of the region.

Urban areas are characterized by a plurality of microclimates given by the diversity of morphologies, optical and radiative properties, solar access and air circulation in different street canyons. For these reasons, beyond strategies at urban scale, mitigation needs to be addressed at district or even at urban canyon scale, just like the design of buildings. Among different options, canopy shading has been proposed in several urban contexts, and to assess the impact of this mitigation technique on air temperature and outdoor thermal comfort conditions we performed numerical simulations for a north-south oriented urban canyon with high solar access (height to width ratio equal to 0.18) in the climate context of Milano (Italy).

Cities often show nighttime air temperatures higher by 3–4 °C than adjacent non-urban areas. This yields to cooling loads in average higher by 13% for urban than rural buildings. Here we assess the hygrothermal performance and the heating and cooling loads of a reference building representative of the Italian stock. We compare its performance calculated with hourly urban weather data (2002–2008) with the performance of the same building using a rural dataset instead. Milan’s Urban Heat Island reduces the heating loads by 12% and 16%, for the non-insulated and insulated building, respectively, while the cooling loads are increased by 41% and 39%. The urban building also shows dehumidification loads 74–78% lower than the rural building. Moreover, during the 2003 heat wave, the indoor air temperature is computed to be 1.5 °C–2.2 °C higher in a non-conditioned urban building than in the rural one. This increases the wakefulness, occupants’ vulnerability to overheating, and impacts the overall hygrothermal performance. Our findings highlight the need of a different design concept for urban with respect to non-urban buildings, even though they are, by law, in the same climate zone.

International audience; The development of photoactive materials with self-cleaning and depolluting qualities is a hot topic in materials science, given their impact on several technologies, in a wide range of contexts of applications. Anatase phase titanium dioxide (TiO2) is the largest used photocatalyst, with increasing applications ranging from air quality control to renewable energies, to green building materials for zero energy communities. Yet, it is partially transmissive in the near infrared (NIR), which negatively affects the solar reflectance of TiO2 containing materials. In this contribution we describe an unexpected increase in anatase near infrared (NIR) reflectance observed during environmental exposure. We unveil its complex mechanisms, based on the contact with nitric acid generated by NOx photocatalytic degradation, which causes partial reduction and decrease in crystallinity to TiO2. This may open the way for introducing multiple environmentally beneficial effects on TiO2 pollutants degradation, self-cleaning, and energy performance.

Cool materials represent an interesting and acknowledged solution able to produce a threefold benefit: the reduction of cooling energy needs in buildings, the mitigation of the urban heat island phenomenon, the counterbalance of global warming trend at larger scale. In fact, they are environmentally friendly and relatively cost-effective materials characterized by high solar reflectance and infrared thermal emittance properties. Therefore, they are helpful to mitigate the urban microclimate by decreasing air and surface temperature when applied over building envelopes, i.e., roofs and walls, and urban paving surfaces. This chapter will discuss about the key research contributions to the development and testing of such cool materials’ effectiveness with a specific focus on the material engineering and characterization. More in details, the recent nanoscale developments will be addressed and the main applications of cool materials will be discussed in order to provide quantitative and quantitative assessment of the effectiveness of such technology for building energy efficiency.

Building envelope materials containing titanium dioxide have been proposed to exploit their photoactivated depolluting and self-cleaning potential, but a full appraisal of their durability and long-term performance is still missing. This study reports a two-year campaign of natural exposure in Milano, Italy, of photoactive and non-photoactive fiber-reinforced mortars, analyzing the evolution of lightness, solar reflectance, porosity and photoactivity. After aging, photoactive samples showed limited color variation. The photocatalytic activity of TiO2 containing samples, characterized with dye degradation tests, was minimal after aging. Then, after alternated cycles of UV-Vis irradiation and rinsing, almost 70% of the initial photocatalytic efficiency was recovered. © 2015 Published by Elsevier Ltd.

International audience; A laboratory method to simulate natural exposure of roofing materials has been reported in a companion article. In the current article, we describe the results of an international, nine-participant interlaboratory study (ILS) conducted in accordance with ASTM Standard E691-09 to establish the precision and reproducibility of this protocol. The accelerated soiling and weathering method was applied four times by each laboratory to replicate coupons of 12 products representing a wide variety of roofing categories (single-ply membrane, factory-applied coating (on metal), bare metal, field-applied coating, asphalt shingle, modified-bitumen cap sheet, clay tile, and concrete tile). Participants reported initial and laboratory-aged values of solar reflectance and thermal emittance. Measured solar reflectances were consistent within and across eight of the nine participating laboratories. Measured thermal emittances reported by six participants exhibited comparable consistency. For solar reflectance, the accelerated aging method is both repeatable and reproducible within an acceptable range of standard deviations: the repeatability standard deviation sr ranged from 0.008 to 0.015 (relative standard deviation of 1.2–2.1%) and the reproducibility standard deviation sR ranged from 0.022 to 0.036 (relative standard deviation of 3.2–5.8%). The ILS confirmed that the accelerated aging method can be reproduced by multiple independent laboratories with acceptable precision. This study supports the adoption of the accelerated aging practice to speed the evaluation and performance rating of new cool roofing materials.

Measurement uncertainty in meteorology has been addressed in a number of recent projects. In urban environments, uncertainty is also affected by local effects which are more difficult to deal with than for synoptic stations. In Italy, beginning in 2010, an urban meteorological network (Climate Network®) was designed, set up and managed at national level according to high metrological standards and homogeneity criteria to support energy applications. The availability of such a high-quality operative automatic weather station network represents an opportunity to investigate the effects of station siting and sensor exposure and to estimate the related measurement uncertainty. An extended metadata set was established for the stations in Milan, including siting and exposure details. Statistical analysis on an almost 3-year-long operational period assessed network homogeneity, quality and reliability. Deviations from reference mean values were then evaluated in selected low-gradient local weather situations in order to investigate siting and exposure effects. In this paper the methodology is depicted and preliminary results of its application to air temperature discussed; this allowed the setting of an upper limit of 1 °C for the added measurement uncertainty at the top of the urban canopy layer.