Daytime Radiative Cooling: A Perspective toward Urban Heat Island Mitigation.

Traditional cooling and heating systems in residential buildings account for more than 15% of global electricity consumption and 10% of global emissions of greenhouse gases. Daytime radiative cooling (DRC) is an emerging passive cooling technology that has garnered significant interest in recent years due to its high cooling capability. It is expected to play a pivotal role in improving indoor and outdoor urban environments by mitigating surface and air temperatures while decreasing relevant energy demand. Yet, DRC is in its infancy, and thus several challenges need to be addressed to establish its efficient wide-scale application into the built environment. In this Perspective, we critically discuss the strategies and progress in materials development to achieve DRC and highlight the challenges and future paths to pave the way for real-life applications. Advances in nanofabrication in combination with the establishment of uniform experimental protocols, both in the laboratory/field and through simulations, are expected to drive economic increases in DRC.

Effect of time-of-day on human dynamic thermal perception.

Implementing heating and cooling set-point temperature modulations in buildings can promote energy savings and boost energy flexibility. However, time and time-of-day requirements in current indoor climate regulations are either overly simplified or ignored completely. A better understanding of how human thermal responses vary throughout the day is useful to effectively design and operate energy-flexible buildings. To date, only a handful of studies have looked at diurnal changes in thermal perception and mostly near steady-state neutrality without controlling for light exposure. This is the first experimental investigation aimed at understanding how the time of the day influences physiological and subjective human sensory responses to a localized dynamic thermal stimulus under constant light rich in long wavelengths (red). Results indicated that humans responded physiologically differently depending on the time of the day with a higher rate of change in the skin temperature in the evening compared with the afternoon. Furthermore, the increase of thermal sensation during the warming skin temperature transients was found to be greater in the evening. No differences were observed under steady-state thermal conditions. This evidence suggests that accounting for the time of the day is important when dynamically operating buildings, such as during demand-response programs.

Long-Term Thermal Comfort Monitoring via Wearable Sensing Techniques: Correlation between Environmental Metrics and Subjective Perception.

The improvement of comfort monitoring resources is pivotal for a better understanding of personal perception in indoor and outdoor environments and thus developing personalized comfort models maximizing occupants' well-being while minimizing energy consumption. Different daily routines and their relation to the thermal sensation remain a challenge in long-term monitoring campaigns. This paper presents a new methodology to investigate the correlation between individuals' daily Thermal Sensation Vote (TSV) and environmental exposure. Participants engaged in the long-term campaign were instructed to answer a daily survey about thermal comfort perception and wore a device continuously monitoring temperature and relative humidity in their surroundings. Normalized daily profiles of monitored variables and calculated heat index were clustered to identify common exposure profiles for each participant. The correlation between each cluster and expressed TSV was evaluated through the Kendall tau-b test. Most of the significant correlations were related to the heat index profiles, i.e., 49% of cases, suggesting that a more detailed description of physical boundaries better approximates expressed comfort. This research represents the first step towards personalized comfort models accounting for individual long-term environmental exposure. A longer campaign involving more participants should be organized in future studies, involving also physiological variables for energy-saving purposes.

Tailoring High-Entropy Oxides as Emerging Radiative Materials for Daytime Passive Cooling.

In the framework of intense research about high-entropy materials and their applications in energy-oriented technologies, in the present work, we discuss the potential applicability of selected oxides and of the alloys they form at different concentrations for daytime radiative cooling implementation. In particular, by combining density functional theory and the finite difference method, we provide an unbiased, scattering-free description of structural, electronic, and dynamic features of the best candidates, showing the required strong radiative properties for passive cooling while offering the benefits of affordability and compatibility with commercial coating fabrication processes.

Management of disposable surgical masks for tackling pandemic-generated pollution: Thermo-acoustic investigations and life cycle assessment of novel recycled building panels.

The COVID-19 pandemic has changed people's habits, causing them to use large amounts of disposable items and exacerbating the already existing issue of pollution. One way to reduce the environmental impact of this shift in daily habits is to recycle these items, e.g. surgical masks that are the most common personal protective equipment against the virus, to produce panels for building applications. In this work, both the thermal and acoustical performance of such panels are evaluated using a small and a large scale investigation under real-world conditions. Small scale thermal tests are performed by means of the Hot Disk instrument while the acoustic investigations are performed by means of the impedance tube. Large scale tests are carried out in a reverberation chamber assessing both the heat flow passing through the wall and the acoustic absorption coefficient of the panels. Finally, the environmental impact of the innovative recycled panel is also investigated in a life cycle perspective. Overall, the material behavior scored well on these tests, suggesting that the proposed approach may be a good recycling method.

Multi-domain human-oriented approach to evaluate human comfort in outdoor environments.

Human comfort outdoors is widely investigated, but most studies explore the comfort domains singularly. This paper aimed to evaluate human comfort in parks, verifying the importance of using a multi-domain (simultaneously evaluating thermal, visual, acoustic, and air quality) and multi-disciplinary (combining environmental and social fields) approach. A walk through a pre-defined path from one park to another was repeated twice per day on four consecutive days in June, with three participants per walk. The two investigated parks are in central Italy and were chosen because they differ in their design and spatial characteristics. Environmental data were recorded with an innovative wearable device during the whole walk, and surveys were used to assess people's perceptions of the parks. Despite observed differences in collected physical parameters, the survey's responses were similar, and different comfort domains showed dependence on each other in the two parks. Logistic regression models were developed for each park, and they revealed that the qualitative information predicted the overall comfort level more accurately than the environmental data. In detail, the models based on environmental data resulted in R2 equal to 0.126 and 0.111 in Parks 1 and 2, respectively, whereas using the survey answers increased it up to 0.820 (Park 1) and 0.806 (Park 2). This study contributes to addressing the gap in multi-domain comfort studies outdoors and confirms the importance of using multi-disciplinary and multi-domain approaches for a complete comfort analysis, supporting holistic human-biometeorology-oriented models and forecasting opportunities that can promote improvements in urban environmental quality and liveability.

A Global Building Occupant Behavior Database.

This paper introduces a database of 34 field-measured building occupant behavior datasets collected from 15 countries and 39 institutions across 10 climatic zones covering various building types in both commercial and residential sectors. This is a comprehensive global database about building occupant behavior. The database includes occupancy patterns (i.e., presence and people count) and occupant behaviors (i.e., interactions with devices, equipment, and technical systems in buildings). Brick schema models were developed to represent sensor and room metadata information. The database is publicly available, and a website was created for the public to access, query, and download specific datasets or the whole database interactively. The database can help to advance the knowledge and understanding of realistic occupancy patterns and human-building interactions with building systems (e.g., light switching, set-point changes on thermostats, fans on/off, etc.) and envelopes (e.g., window opening/closing). With these more realistic inputs of occupants' schedules and their interactions with buildings and systems, building designers, energy modelers, and consultants can improve the accuracy of building energy simulation and building load forecasting.

A New Wearable System for Sensing Outdoor Environmental Conditions for Monitoring Hyper-Microclimate.

The rapid urbanization process brings consequences to urban environments, such poor air quality and the urban heat island issues. Due to these effects, environmental monitoring is gaining attention with the aim of identifying local risks and improving cities' liveability and resilience. However, these environments are very heterogeneous, and high-spatial-resolution data are needed to identify the intra-urban variations of physical parameters. Recently, wearable sensing techniques have been used to perform microscale monitoring, but they usually focus on one environmental physics domain. This paper presents a new wearable system developed to monitor key multidomain parameters related to the air quality, thermal, and visual domains, on a hyperlocal scale from a pedestrian's perspective. The system consisted of a set of sensors connected to a control unit settled on a backpack and could be connected via Wi-Fi to any portable equipment. The device was prototyped to guarantee the easy sensors maintenance, and a user-friendly dashboard facilitated a real-time monitoring overview. Several tests were conducted to confirm the reliability of the sensors. The new device will allow comprehensive environmental monitoring and multidomain comfort investigations to be carried out, which can support urban planners to face the negative effects of urbanization and to crowd data sourcing in smart cities.

Environmental assessment of four waste cooking oil valorization pathways.

Global waste is expected to grow substantially by 2050, therefore, defining an effective waste management strategy is a crucial topic for both industry and academia. Nowadays, food and green waste, in particular, represent a large share of the total waste production. All this considered, effectively processing and eventually reusing materials such as waste cooking oil is of paramount importance. This study investigates the potential environmental impact and the primary energy consumption for three waste cooking oil valorization pathways i.e. biodiesel, direct burning fuel, additive for recycling aged-asphalt, as well as a new application, i.e. phase change material, compared to their specific more common alternative based on a cradle-to-gate approach. The aim is to identify and recommend the most advantageous alternative in terms of environmental impact. Results showed that the waste cooking oil has a lower impact in all comparisons made, except as phase change material. The less effective performance in some cases was compensated by the waste oil entry as a burden-free resource under an attributional model. The best profile of the waste cooking oil is as direct burning fuel. However, the binder asphalt substitution is highly recommended due to the nature of the application. The major obstacles to the waste cooking oil usage are the limited stock, composition and quality variability, and the difficulty of proper collection.

A Mobile Vehicle-Based Methodology for Dynamic Microclimate Analysis.

Accurate monitoring is critical for better understanding cities' microclimate conditions and safeguard citizens' health. Previous studies have performed microclimate analyses of urbanized areas by implementing data from either stable meteorological stations or satellites, or by developing mobile stations. Here, we present a vehicle-based monitoring campaign capable of monitoring both the scalar and directionally dependent variables that regulate the canopy layer environment. Under this framework, we performed a monitoring campaign within an Italian city, and measured simultaneously air temperature (±  0.3 ∘ C @ 20 ∘ C ), relative humidity (±  2% @ 20 ∘ C ), directional shortwave radiation (calibration uncertainty: < 1.8%), CO 2 (±  50 ppm +2%) and PM10 (< 1%) concentration, wind speed (±  3% @ 40 m/s) and direction (±  3 ∘ @ 40 m/s), and specific location (latitude, longitude and elevation). The presented assessment can be carried out within almost any area that motorized vehicles are allowed to access (e.g. through public transportation vehicles). Its application together with other mobile stations that can specifically assess also pedestrian areas, such as footpaths, urban parks, sidewalks and bike paths, as well as fixed meteorological stations and remote sensing techniques can contribute to a better understanding of microclimate patterns and hence to more efficient urban planning and risk assessments.

Intra-urban microclimate investigation in urban heat island through a novel mobile monitoring system.

Monitoring microclimate variables within cities with high accuracy is an ongoing challenge for a better urban resilience to climate change. Assessing the intra-urban characteristics of a city is of vital importance for ensuring fine living standards for citizens. Here, a novel mobile microclimate station is applied for monitoring the main microclimatic variables regulating urban and intra-urban environment, as well as directionally monitoring shortwave radiation and illuminance and hence systematically map for the first time the effect of urban surfaces and anthropogenic heat. We performed day-time and night-time monitoring campaigns within a historical city in Italy, characterized by substantial urban structure differentiations. We found significant intra-urban variations concerning variables such as air temperature and shortwave radiation. Moreover, the proposed experimental framework may capture, for the very first time, significant directional variations with respect to shortwave radiation and illuminance across the city at microclimate scale. The presented mobile station represents therefore the key missing piece for exhaustively identifying urban environmental quality, anthropogenic actions, and data driven modelling toward risk and resilience planning. It can be therefore used in combination with satellite data, stable weather station or other mobile stations, e.g. wearable sensing techniques, through a citizens' science approach in smart, livable, and sustainable cities in the near future.

Sustainable production and consumption in remote working conditions due to COVID-19 lockdown in Italy: An environmental and user acceptance investigation.

In response to the disruptive changes brought upon our society by the COVID-19 pandemic, most work activities and service providers had to resort to remote working. This is credited to reduce emissions for transportation, however the role of forced confinement within dwellings, especially if not designed for hosting working stations, deserves to be properly evaluated in terms of both user acceptance and long-term environmental impact. In this work, a dedicated survey campaign is used for investigating the potential pros and cons of remote working. In more detail, logistic regression and generalized linear models are used for capturing the effect of several independent variables on user acceptance of remote working. At a later stage, the main greenhouse gas emissions produced by each participant before and during remote working are assessed. According to the obtained results, the greater the distance between their home and workplace, the higher the acceptance score declared by the survey participants about remote working. Additionally, higher incomes and better-quality lifestyles with larger devotion to leisure activities also provide higher acceptance. Finally, the existence of a comfortable room to be used for work activities plays a crucial role on the declared acceptance. From an environmental point of view, remote working is always sustainable in case of long commuting distances (above 10 km) are avoided on a daily routine. In conclusion, a sensible use of remote working could reduce the environmental impact of any organization employing desk-workers as well as improve their work satisfaction and lifestyle.

Data collected by coupling fix and wearable sensors for addressing urban microclimate variability in an historical Italian city.

This article presents the data collected through an extensive research work conducted in a historic hilly town in central Italy during the period 2016-2017. Data concern two different datasets: long-term hygrothermal histories collected in two specific positions of the town object of the research, and three environmental transects collected following on foot the same designed path at three different time of the same day, i.e. during a heat wave event in summer. The short-term monitoring campaign is carried out by means of an innovative wearable weather station specifically developed by the authors and settled upon a bike helmet. Data provided within the short-term monitoring campaign are analysed by computing the apparent temperature, a direct indicator of human thermal comfort in the outdoors. All provided environmental data are geo-referenced. These data are used in order to examine the intra-urban microclimate variability. Outcomes from both long- and short-term monitoring campaigns allow to confirm the existing correlation between the urban forms and functionalities and the corresponding local microclimate conditions, also generated by anthropogenic actions. In detail, higher fractions of built surfaces are associated to generally higher temperatures as emerges by comparing the two long-term air temperature data series, i.e. temperature collected at point 1 is higher than temperature collated at point 2 for the 75% of the monitored period with an average of +2.8 °C. Furthermore, gathered environmental transects demonstrate the high variability of the main environmental parameters below the Urban Canopy. Diversification of the urban thermal behaviour leads to a computed apparent temperature range in between 33.2 °C and 46.7 °C at 2 p.m. along the monitoring path. Reuse of these data may be helpful for further investigating interesting correlations among urban configuration, anthropogenic actions and microclimate variables affecting outdoor comfort. Additionally, the proposed dataset may be compared to other similar datasets collected in other urban contexts around the world. Finally, it can be compared to other monitoring methodologies such as weather stations and satellite measurements available in the location at the same time.

Cultural heritage microclimate change: Human-centric approach to experimentally investigate intra-urban overheating and numerically assess foreseen future scenarios impact.

Microclimate change related events affect cities total environment and therefore citizens' wellbeing. In a framework of urban resilience challenge, it is important to guarantee thermally comfortable conditions to dwellers in outdoors but also to preserve cultural heritage masterpieces for tourism and local socio-cultural identity. This work couples an innovative field monitoring at multiple scales and a validated numerical modelling effort to identify indoor and outdoor critical conditions at the present time and in the future, according to IPCC climate change forecast scenarios. The authors focused the attention on the overheating risk of Gubbio historical city center, in central Italy. Experimental data analysis highlights the microclimate granularity of the case study with detected temperature discrepancies up to 2.5 °C observed at pedestrian height during the hottest hour, i.e. 2p.m. Collected data are then used to validate the numerical models of (i) the most significant building of the city and (ii) its surroundings to investigate indoor/outdoor thermal comfort stress due to climate change and local overheating. The combined analysis shows that indoor operative temperature reaches 32 °C on average in 80 years, compared to the current 29 °C value. In the outdoors, apparent temperature increases by about 10 °C on 2100, being responsible for a serious threat compromising socio-cultural life, human health and outdoor and recreational activities.

Effect of PCM on the Hydration Process of Cement-Based Mixtures: A Novel Thermo-Mechanical Investigation.

The use of Phase Change Material (PCM) for improving building indoor thermal comfort and energy saving has been largely investigated in the literature in recent years, thus confirming PCM’s capability to reduce indoor thermal fluctuation in both summer and winter conditions, according to their melting temperature and operation boundaries. Further to that, the present paper aims at investigating an innovative use of PCM for absorbing heat released by cement during its curing process, which typically contributes to micro-cracking of massive concrete elements, therefore compromising their mechanical performance during their service life. The experiments carried out in this work showed how PCM, even in small quantities (i.e., up to 1% in weight of cement) plays a non-negligible benefit in reducing differential thermal increases between core and surface and therefore mechanical stresses originating from differential thermal expansion, as demonstrated by thermal monitoring of cement-based cubes. Both PCM types analyzed in the study (with melting temperatures at 18 and 25 ∘ C) were properly dispersed in the mix and were shown to be able to reduce the internal temperature of the cement paste by several degrees, i.e., around 5 ∘ C. Additionally, such small amount of PCM produced a reduction of the final density of the composite and an increase of the characteristic compressive strength with respect to the plain recipe.

A new wearable monitoring system for investigating pedestrians' environmental conditions: Development of the experimental tool and start-up findings.

Urban population is predicted to increase rapidly and massively in the next decades, by producing also the exacerbation of urban scale climate change imputable to anthropogenic actions, such as urban heat island. In this view, urban pedestrians assume a key role in determining city livability in dense built environments, typically much more polluted than suburban or rural areas. Despite that, urban heat island experimental studies are pretty focused on data collected by means of permanent microclimate stations for environmental monitoring, also coupled with satellite measurements or mobile stations equipped over transportation media. This work deals with the development, experimental startup with field test and critical data analysis of a brand new wearable system for microclimate and air quality investigation, just developed with the purpose to characterize livability environmental conditions which affect urban population wellbeing. To this aim, the experimental tool definition and the first field test are carried out in a historical city centre in Italy, where cluster analysis is performed in order to also identify the role of urban design in affecting key microclimate parameters such as air temperature, solar radiation, daylight, air pollution and pedestrian thermal comfort in general. The analysis showed that very site-specific environmental conditions may be detected while several environmental spheres are investigated by the novel wearable system in summer conditions.