Outdoor Thermal Environment Research Articles

Thermal Comfort and Restorative Benefits of Waterfront Green Spaces for College Students in Hot and Humid Regions

Global climate change presents a serious threat to the sustainable development of human society, highlighting the urgent need to develop effective adaptation strategies to mitigate the impact of climate-related disasters. Campus waterfront green spaces, integral to the blue-green infrastructure, have been demonstrated to facilitate stress recovery. However, in hot and humid regions, severe outdoor thermal conditions may impair students’ mental and physical health and cognitive function, leading to symptoms such as increased stress, anxiety, and depression. This study examined the influence of outdoor thermal environments on health recovery by selecting three different waterfront green spaces in this climate: Space A (medium water body, sky view factor (SVF) = 0.228), Space B (large water body, SVF = 0.808), and Space C (small water body, SVF = 0.292). The volunteers’ thermal comfort and the restorative benefits of these spaces were evaluated via the perceived restorativeness scale (PRS), heart rate (HR), and electrodermal activity (EDA). We found variations in the neutral physiological equivalent temperature (PET) across the spaces, with values of 28.1 °C (A), 28.9 °C (B), and 29.1 °C (C). The lowest skin conductance recovery rate (RSC) at 0.8811 was observed in Space B, suggesting suboptimal physiological recovery, despite higher scores in psychological recovery (fascination) at 15.23. The level of thermal comfort in this hot and humid region showed a negative correlation with the overall PRS score, the “being away” dimension, and heart rate recovery (RHR). At a lightly warm stress level, where PET increased from 31.0 to 35.7 °C, RSC peaked between 1.45 and 1.53 across all spaces. These insights provide guidance for urban designers and planners in creating waterfront green space designs that can improve the urban microclimate and promote thermal health, achieving sustainable health.

Improvement of thermal environment in the outdoor atrium by employing the spray system

Outdoor atriums have recently been applied with increasing frequency for natural illumination, but they produce a harsh thermal environment easily in summer. Moreover, overheating of the outdoor atrium necessitates air-conditioning to moderate indoor thermal comfort. Simultaneously, the substantial heat emissions from air-conditioning outdoor units worsen the outdoor thermal environment, creating a vicious cycle. Traditional passive evaporative methods involving water and greenery, while capable of regulating the thermal environment, suffer from low evaporative efficiency and pose significant challenges. To improve thermal environment in outdoor atriums, the spray system was employed due to its high cooling efficiency, especially in open or semi-open spaces. In this study, a comparative experiment was conducted to evaluate the effectiveness of using a spray system for evaporative cooling in open outdoor spaces. Furthermore, employing high-efficiency evaporative cooling through spraying to disrupt the vicious cycle of indoor and outdoor thermal environments. The dual goals include regulating indoor and outdoor thermal conditions while also mitigating the local heat island effect. Temperature and humidity distribution within the atrium and adjacent hallways were monitored, along with the impact on air-conditioning operation consumption in neighboring offices. Results showed that the spray system significantly improved the thermal environment in the outdoor atrium, reducing the average and peak air temperatures by 0.94–2.83 °C and 2.92–5.21 °C, respectively. It also resulted in a drop in the average temperature by 0.56–1.62 °C and the peak temperature by 2.31–3.25 °C in adjacent hallways. This effectively eased the issue of overheating in these areas while raising the comfort level in adjacent office spaces. The predicted mean vote decreased from 1.46 to 0.87, indicating a significant improvement in thermal environment in neighboring offices. Furthermore, the daily energy consumption was reduced by 10.6–12.4% in neighboring offices. This study provided the valuable guidance for improving thermal environments within outdoor atrium.

Optimizing educational environments: microclimate analysis and energy efficiency through courtyard orientation in UAE schools

Sustainable school design is becoming increasingly important worldwide, particularly in the UAE, where schools are significant energy consumers. This study explores the impact of courtyard orientation on microclimate and energy consumption in UAE schools, utilizing a standardized template applied across 70 existing schools. By employing advanced simulation tools, ENVI-met and IES-ve software, the research provides a comprehensive analysis of air temperature and energy use related to different courtyard orientations, specifically on key dates of September 21st and March 21st, representing seasonal variations. The results indicate that North-facing courtyards consistently provide cooler microclimates compared to other orientations. Specifically, North-facing courtyards showed temperature reductions of 1.31°C in September and 1.9°C in March compared to the least favorable orientations. This orientation recorded the lowest average mass temperatures of 29.36°C in September and 25.13°C in March, surpassing the West-facing orientation by 0.39°C and 0.45°C, respectively. The primary factor for this improvement is the reduced solar radiation exposure on East-West aligned courtyards, which significantly lowers the heat gain. Additionally, the study assessed Physiologically Equivalent Temperature (PET) readings and cooling demands, both of which were found to be lower in North-facing courtyards. Cooling load reductions varied between 1% and 4%, depending on the day, further emphasizing the efficiency of this orientation. These findings suggest that strategic courtyard orientation is a critical design consideration for enhancing thermal comfort and energy efficiency in school buildings. The implications of this research are significant for sustainable design and construction practices. By highlighting the benefits of optimal courtyard orientation, this study offers practical solutions for reducing energy consumption and improving the indoor and outdoor thermal environments of schools. These insights contribute to the broader goal of developing greener, more sustainable educational facilities, particularly in hot climates like the UAE. This research not only informs architects and urban planners but also supports policymakers in implementing effective sustainability strategies in the educational sector.

Adjustment of outdoor thermal environment in a Central Business District with high-reflective material and rooftop greening

Adjustment of outdoor thermal environment in a Central Business District with high-reflective material and rooftop greening

Optimization of temperature prediction algorithms and simulation of future neighborhood-scale thermal environments in Chongqing

With climate change and urbanization, predicting the outdoor thermal environment of residential areas has become increasingly crucial, particularly during extreme weather conditions. Existing studies lack a comprehensive approach to optimizing temperature prediction algorithms for Chongqing and simulating extreme thermal environments at the neighborhood scale for future decades. This study employed various algorithms, including Levenberg-Marquardt optimization, Monte Carlo simulation, ARIMA modeling, and SARIMA prediction, to simulate and forecast temperature data for the central urban area of Chongqing from 2014 to 2023. By assessing metrics such as root mean square error (RMSE), R-squared (R2), and mean absolute percentage error (MAPE), the most effective prediction algorithm was identified. Results indicate that the Levenberg-Marquardt optimization algorithm, known for its nonlinear curve fitting capabilities, demonstrated superior performance in both the test and training sets, achieving an RMSE of 0.82 °C, MAPE of 1.81 %, and R2 of 0.75. This algorithm was subsequently used to forecast the outdoor temperature trend in Chongqing from 2024 to 2050, while also simulating the outdoor wind field, temperature distribution, building surface temperatures, and wind speeds in a residential district at neighborhood scale for 2030, 2040, and 2050 at a building density of 40 %. Findings reveal that peak pedestrian-level temperatures could reach 45.62 °C, and peak roof surface temperatures could reach 93.93 °C under extreme conditions. Furthermore, the study proposes practical recommendations for building layouts and cooling strategies. These findings are expected to improve residential planning in Chongqing, enhance residents' quality of life, and provide insights for other regions facing future temperature changes.

Thermal Environments of Residential Areas: Sunlight and Building Shadow in a Chinese City with Hot and Humid Summers

With a primary focus on sunlight and building shadows, we studied the impact of residential building orientation angles, building heights, and area combinations, as well as the underlying surface materials, on the outdoor thermal environment in Changsha, a city located north of the Tropic of Cancer. On the basis of Changsha’s regulations, the research results indicate that building orientation angles of 15–45° and 315–345° can generate more building-shadow areas and have a better effect on improving the outdoor thermal environment. Based on the study of many common residential block building layouts in Changsha, we believe that, for point-pattern residential blocks, an increase in building lengths can be very effective for increasing building-shadow areas and thermal comfort. For row-pattern residential blocks, an increase in building heights can be regarded as more effective for increasing building-shadow areas and reducing air temperatures. Shadow areas formed on impervious surface material areas, such as concrete pavements, reduce the air temperature more than shadow areas formed on natural surfaces, such as grasslands. For the planning and regeneration of residential areas, urban planners should focus on placing more green spaces in areas which are seldom or never covered by building shadows; they should also focus on installing more impervious surfaces in areas covered by building shadows. These strategies are beneficial for making full use of building shadows to reduce air temperatures in residential areas.

A typical meteorological day database of solar terms for simplified simulation of outdoor thermal environment on a long-term

The simulation of the outdoor thermal environment long-term, represented by the annual conditions, can describe outdoor thermal environment characteristics more completely. To simplify the simulation, Typical Meteorological Year (TMY) or Principal Component Analysis (PCA) methods are often used to generate a Typical Meteorological Day (TMD) as input conditions for a simplified simulation of the outdoor thermal environment in the long term. However, the results of these typical days are accidental, the time interval between the typical days is heterogeneous, and these typical days cannot be linked together to represent a data sequence used to describe meteorological features in the long term. By combining knowledge of Solar Terms in the traditional Chinese calendar with the CSWD (the Chinese standard year) method, a meteorological element data sequence of a typical weather day (Solar Terms Typical Meteorological Day, STTMD) can be generated. There are 24 typical days obtained by the STTMD method. In the traditional Chinese calendar, they have a definite time order, and the time interval between the typical days is about 15 days. Connecting these typical days can form a hypothetical meteorological year, which is used to simplify the description of the annual meteorological characteristics with the maximum probability of occurrence. Based on meteorological observation data from 1981 to 2010, the STTMD data series of 61 stations in China were generated. These data were used to form a simple national climate division, and then the meteorological representation of different divisions was analyzed. Meteorological representativeness analysis for these subtions indicated the good accuracy of STTMD data. The method can simplify the numerical simulation process for those studied on long-term and can be extended to applications such as outdoor comfort evaluation and urban building energy consumption.

The impact of roof systems on cooling and building energy efficiency

The excessive warming in the built environment, due to urbanization and anthropogenic heat emissions, has adverse effects on building energy consumption. Diverse technology using, e.g., vegetated roofs or innovative roof materials, have been proposed and implemented to ameliorate both indoor and outdoor thermal environments and reduce energy consumption. In this study, we apply a state-of-the-art urban canopy model to simulate the thermal performance of multiple roof technology, viz. the white, green, and hybrid roofs, in the contrasting urban environments of Princeton, NJ and Phoenix, AZ, USA. In addition, we estimate the combined energy-water saving potential for green roofs with five different irrigation schemes. It is found that green roofs can achieve a combined energy-water saving of $9.68 m−2 roof area in Phoenix with moisture-controlled irrigation, and $5.23 m−2 in Princeton without irrigation. These results can help to promote building energy efficiency by adapting to flexible and sustainable roof technology for heat mitigation.

Effects of landform and building layout on outdoor thermal environment: a case study of mountain villages in severely cold regions

ABSTRACT In the global context of climate change and frequent occurrence of extreme temperature variations, the impact of harsh climates on the outdoor thermal environment in remote, cold, mountainous villages is particularly pronounced, leading to many negative effects. The geoorphology of the village sites and their building layouts are important factors affecting the outdoor thermal environment. Therefore, exploring the spatiotemporal characteristics of these factors is significant for optimizing village construction and improving living environments. In this study, taking Fangjialiang Village in a cold mountainous area as an example, we analysed the outdoor thermal environment from a spatiotemporal perspective through comprehensive field investigations and measurements. The findings obtained are summarized as follows: (1) Landform elements were limited by boundary and azimuth constraints (difference in time temperature decay rate between the valley interior and valley edge area: ΔK = 0.48°C/m). (2) The temperature inversion phenomenon in the valley was significant (the average rate of temperature increase with elevation was 0.037°C/m). (3) The vertical distribution of the temperature was more susceptible to the influence of the difference in elevation inside the village (ρ≈–0.48). The average rate of temperature decrease with elevation is 0.489°C/m. (4) A compact building layout could sustainably weaken the effects of topographic elements (e.g. the average temperature sequenced as: closed internal courtyard (Avg = 14.60°C)> semi-open horizontal village street (Avg = 13.58°C)> fully open space (Avg = 13.11°C)). Therefore, the results of the study further revealed the coordinated relationship between the natural environment and rural settlements, proved the integrated effects of village siting and building layout, and provided useful insights for the construction and living environment optimization of mountain villages.

From BIM to thermal comfort: Leveraging BIM for rapid outdoor comfort assessments

This study introduces a novel system within a Building Information Modeling (BIM) environment to rapidly evaluate Outdoor Thermal Comfort (OTC). Traditionally, direct microclimate analysis in the design phase is hindered by cumbersome and resource-intensive processes. By utilizing information from BIM and integrating the COMFA thermal energy budget model, this approach facilitates immediate OTC evaluation. The system automates the Sky View Factor simulation using 3D modeling techniques and utilizes BIM model data to assess the thermal environment. Tested on a university campus, it effectively processes geospatial BIM data to compute microclimate parameters and estimate OTC using COMFA. This research represents a significant advancement in BIM-integrated OTC analysis, streamlining the design feedback process and aiding practitioners in improving outdoor thermal environments amidst climate change challenges.

Experimental study of a novel Radiative cooling-Dual phase change material roof under hot summer and warm winter climate

In hot summer and warm winter climates, phase change materials (PCMs), with their ability to absorb and store thermal energy, can effectively reduce indoor temperature fluctuations and lower cooling loads when applied to roofs. Therefore, this study proposes a novel Radiative cooling-Dual phase change material (RC-DPCM) roof and conducts experimental research on its regulation of indoor and outdoor thermal environments. This energy-efficient roof integrates radiative sky cooling with PCM latent heat storage technologies within a compact building envelope. The innovative dual-PCM configuration can store heat from both indoor sources and outdoor solar radiation during the day through integrated PCM layers. At night, radiative cooling materials emit heat to the deep universe, helping the PCM layers complete solidification. The thermal performance of the RC-DPCM roof was tested in hot summer and warm winter climates compared to other roof designs: a single layer of aluminum (AL) roof, the Aluminum-Thermal insulation (AL-TH) roof, the Radiative cooling (RC) roof, the Radiative cooling-Outside phase change materials (RC-OPCM) roof, and the Radiative cooling-Inside phase change materials (RC-IPCM) roof. Results showed that the RC-DPCM roof significantly improved indoor thermal comfort and efficiency. Compared with the AL roof, the RC-DPCM roof reduced the average indoor temperature by 1.13 °C (or 2.49 °C during working hours) and continuously dissipated heat from the indoor environment to the ambient environment, reducing the cooling load. Additionally, the RC-DPCM roof achieved a 172.9 % average cooling load reduction during working hours, outperforming other roofs, thus demonstrating its potential as an innovative solution for sustainable and energy-efficient buildings. The RC-DPCM roof effectively reduced peak indoor temperatures and cooling load, demonstrating its potential as an innovative solution for sustainable and energy-efficient buildings.

Do blue-green roofs yield optimal thermal performance? Synergy analysis of the combination of green roofs and water retention layer

Blue-green roofs can potentially enhance the outdoor thermal environment in urban areas and reduce indoor energy consumption. By integrating a water retention layer with green roofs, blue-green roofs maximize environmental benefits through rainwater storage and increased evapotranspiration. This study evaluates the thermal performance of blue-green roofs during summer and examines their potential for microclimate improvement and energy savings. The study investigates the individual and interactive effects of the blue-green roof components by measuring the upper and lower surface temperatures with incremental application of soil, blue, and green layers and analyzing their synergistic benefits. The results indicate that blue-green roofs exhibited a cooling effect of up to 7.5 °C on the upper surface temperature and up to 17.4 °C on the lower surface temperature, showing the greatest potential for improving indoor and outdoor thermal comfort. The synergistic effect of the blue-green roof was −0.80 °C on the upper surface and +1.59 °C on the lower surface. This research provides an in-depth investigation into the thermal performance of blue-green roofs in both indoor and outdoor spaces, highlighting their synergistic effects through incremental application. This contributes to climate-responsive architectural design and practices aimed at enhancing energy efficiency in building retrofitting for hot climates.

Energy efficiencies model for thermal comfort in urban applications

Improving people's standard of living has increased their requirements for the environment. Increasing air temperature in urban areas due to urban heat islands (UHI) has been a global concern since industrialization. Apart from suitable facilities and landscapes, a comfortable outdoor thermal environment can improve the efficiency of urban space use. Ensuring outdoor comfort is an integral part of the design agenda where the UHI phenomenon plays a significant role. A study has been conducted on a residential building campus to analyze the effect of these heat island countermeasures (individual and combined) with the help of the simulation tool Grasshopper. A 3D reference model of a small residential campus is developed. The outdoor thermal comfort level is studied for this case, and Universal Thermal Climate Index (UTCI) is evaluated. Further, several UHI mitigation strategies such as wall and roof reflectivity, vegetation, plantation, pavement configuration, and shading are applied to find their effect on the micro-climate and outdoor thermal comfort. Based on the simulation outcomes, urban geometry is identified as the most influential design factor in decreasing the urban heat island effect and outdoor thermal comfort. The study's principal objective is to develop a simulation framework including all mitigation strategies and find the best case for UHI reduction.

The Annual Effect of Landscapes on the Indoor Thermal Environment in Residential Areas—A Case Study in Southern Hunan

Landscape elements are crucial to the quality of the built environment. Thermal comfort is one of the important paths through which landscape elements affect the quality of the built environment. Most studies investigate the impacts of the landscape on the outdoor thermal environment, while ignoring the impacts on the indoor environment. A residential area in Chenzhou, a typical city having a hot summer and cold winter climate, was taken as an example to reveal the effect on the indoor thermal environment of landscapes. The annual distribution of the indoor thermal environment was analyzed with the “Envi-met+IDW” model, which was created to evaluate the annual thermal impact. Analytical results show that, from the perspective of the annual cycle, the camphor tree has the best performance in regulating the indoor thermal environment, followed by water and the palm. Manila grass has a very weak impact on indoor thermal comfort throughout the year. Camphor trees, water, and palm extend the “acceptable temperature” by 523 h, 416 h, and 388 h respectively. However, the camphor tree also has the strongest cooling effect on indoor environments during winter, increasing the “heating demand temperature” by 289 h.

Assessment of the estimation methods of Tmrt in semi-outdoor spaces in humid sub-tropical climates: An empirical study in Wuhan, China

Studies have been conducted on the mean radiant temperature (Tmrt) estimation methods using globe thermometers for measuring outdoor thermal environments in various climate regions. Yet, given the unique thermal environments of semi-outdoor spaces, these Tmrt estimation methods may not be appropriate for the spaces with shading effects. This study aims to assess the thermometric and radiative methods for Tmrt estimation in semi-outdoor spaces in humid sub-tropical climates, taking data from six-directional radiation measurements as validations. During the typical summer and winter days in Wuhan, China, the measurements were carried out in semi-outdoor spaces facing south and west, with an open square for comparison, including air temperature, humidity, wind velocity, black-globe temperature, and long- and short-wavelength radiation fluxes obtained from four-component net radiometers. It was found the maximum mean deviation of diurnal Tmrt values estimated by the black-globe thermometer method in semi-outdoor spaces was 7.1 °C, which exceeded the threshold required by ISO7726, where the shortwave radiation was regarded as the dominant interference factor. To improve the accuracy and cost-effectiveness of Tmrt estimation, we proposed linear empirical equations to calibrate the Tmrt estimated by black-global thermometer method that the root mean square error (RMSE) of the Tmrt deviations can generally vary from 2.22 to 2.72 °C. Contributing to the thermal comfort research, this study proposed an empirical method for estimating Tmrt in semi-outdoor spaces in humid subtropical climates, which can generate satisfactory results in accordance with ISO7726 standards with cost-effective instrumentation.

Field Investigation on Adaptive Thermal Comfort in Rural Dwellings: A Case Study in Linyi (China) during Summer

A large number of people in China still live in rural villages. The indoor environment of these rural dwellings directly affects the quality of life of the occupants. Nevertheless, constrained by the quality of dwelling construction, rural buildings have poorer indoor environments and, at the same time, have a higher operating energy consumption. However, inadequate attention has been given to the summer thermal environment in cold regions. This work has been carried out around the thermal environment of rural residences in cold regions during summer. Field measurements, questionnaires, and data analysis were used in this study. We recorded the indoor and outdoor thermal environment parameters on a typical summer day in the Linyi rural area. Moreover, the subjective sensations and thermal adaptive behaviors of the participants were recorded in detail with a questionnaire. Linear regression showed that the neutral temperature for residents in summer was 27.52 °C, with acceptable temperatures ranging from 25.14 °C to 29.9 °C. Age and gender differences were found to affect the occupants’ sensation of thermal comfort and humidity, as well as their thermal adaptive behavior. In addition, a thermal adaptive model has been constructed in the study, which will further enrich the thermal adaptive investigation and provide a scientifically sound reference for the renovation and development of the local rural areas.

A Bibliometric Analysis of the Outdoor Thermal Environment Based on CiteSpace

The outdoor thermal environment (OTE) is closely related to sustainable urban development and human living, and related research has attracted widespread attention. The research hotspots and research frontiers were obtained using CiteSpace to analyze 4473 relevant studies published in English from the Web of Science (WOS) core database from 1998 to 2023. The results show that (1) Hong Kong Polytechnic University, National University of Singapore, Chinese Academy of Sciences, Tsinghua University, and Harbin Institute of Technology are important in OTE research. China has the largest number of publications in the field of OTE, but the United States has the greatest centrality and significant influence. (2) The focus of OTE keyword clustering research is divided into four main categories: thermal environment perception, the thermal environment index, thermal environment quality, and thermal environment optimization. (3) The frontiers of OTE research have changed from focusing on environmental quality, thermal perception, numerical simulation, urban space, and thermal adaptation to thermal mitigation, energy conservation, energy consumption, and optimization strategies. Visualization research in the field of OTE helps to provide references for the direction of future research on improving climate change, human thermal comfort, urban planning, and pre-planning.

Agent-based modelling and simulation of elderly residents’ dynamic usage patterns in neighbourhood squares during summer

Understanding how elderly residents use neighbourhood squares is helpful for designing these public areas to maximize their usage and minimize heat exposure risks, especially given the global increase in heatwaves and initiatives for healthy aging in place. This study aims to explore the dynamic use of a neighbourhood square with multiple shade configurations by its elderly residents. In-situ observations and measurements in three squares in public housing estates in Hong Kong were conducted in hot summer days to learn the relationship between elderly users' usage behaviours and multiple driving factors, including outdoor thermal environment, level of social interaction, and different shade types. The relationship was then used to develop an agent-based model (ABM) to simulate the dynamic usage pattern in a square over a day. The result indicates that the dynamic usage pattern from 9:00 to 18:00 in a square emerges from interactions between elderly users’ behaviours and shade configurations, which can be reasonably estimated by the developed ABM. Based on the ABM simulation, shade configurations that cover 60 % of the square and create microclimates with a maximum mPET not exceeding 34.0 °C during summer days encourage square usage and mitigate heat-stress risks of elderly users. The prototype ABM enables the understanding of the complex usage pattern in a neighbourhood square and can potentially assist planning and optimization of shade configurations at the design/renewal stage.

Study on the Impact of Design Factors of Piloti Forms on the Thermal Environment in Residential Quarters

Study on the Impact of Design Factors of Piloti Forms on the Thermal Environment in Residential Quarters

Quantitative Study on the Effects of Street Geometries and Tree Configurations on the Outdoor Thermal Environment

Global warming and the urban heat island effect has aroused the attention of research on the outdoor thermal environment. As outdoor spaces often used by citizens, streets play an important role in improving the thermal environment. In this study, six factors relating to street geometries and tree configurations in Busan are measured and quantified to form 32 typical scenarios. The degree of importance of these six factors is evaluated based on ENVI-met simulation results, and GeoDetector is introduced to evaluate the interactions between the factors and their impacts on the outdoor thermal environment. This study confirms the significantly higher impact of street geometry factors on the air temperature and physiological equivalent temperature compared to tree configuration factors. Particularly, Hb/Ws shows the most significant impact during the research period. The impact of interactions between any two factors of street geometry is much higher than that of interactions between the geometry and tree configuration factors and that of interactions between the tree configuration factors. We recommend dynamically adjusting the relationship between street geometry and tree configurations in different situations to improve the outdoor thermal environment, especially at noon and in the afternoon.