Outdoor Thermal Environment Research Articles

Research on Summer Indoor Air Conditioning Design Parameters in Haikou City: A Field Study of Indoor Thermal Perception and Comfort

Escalating global climate change and the intensification of urban heatwaves have led to an increase in summer air conditioning cooling energy consumption. This phenomenon is particularly critical in tropical regions, as it may trigger an energy crisis. The rational setting of indoor thermal design parameters can help conserve energy to the maximum extent while ensuring thermal comfort for occupants. This study selected Haikou City, a unique tropical city in China, as the research location. Indoor environment measurements and a questionnaire survey were conducted with participants, and the outdoor thermal environment sensitivity, population attributes and differences in thermal sensation, thermal neutral temperature, and comfort range were calculated and analyzed. The following results were obtained. Based on the overall population, long-term residence, and temporary residence classification, the indoor thermal comfort needs of residents in tropical cities in Haikou were effectively identified. The actual thermal neutral temperature of the overall population is 25.7 °C, and 90% of the acceptable thermal comfort temperature range is 23.2 °C–28.0 °C. The actual thermal neutral temperature of the regular residents is 27.3 °C, and 90% of the acceptable thermal comfort temperature range is 23.3 °C–31.4 °C. The actual thermal neutral temperature of the temporary population is 25.5 °C, and 90% of the acceptable thermal comfort temperature range is 23.0 °C–28.0 °C. These research results have an important reference value for improving the setting of the temperature of air conditioning in tropical areas in summer and further reducing energy consumption, which is conducive to sustainable development.

Research on wet physical properties of permeable concrete pavement with different porosity

ABSTRACT Permeable concrete pavement has been widely used in building ‘sponge cities’. Porosity has a great influence on wet physical properties such as permeability, water retention, and evaporative cooling performance of permeable concrete, and further research is needed. In this paper, permeable concrete specimens with target porosity of 20%, 24%, and 28% were made for indoor experimental research, including water permeability, water retention, and evaporation tests. The research results show that permeable concrete with a porosity of 28% has the best permeability among the three types of porosity. In the range of 20–28% porosity, as the porosity increases, the water retention performance of permeable concrete first strengthens and then weakens. The evaporative water loss of permeable concrete has the worst cooling performance on its surface temperature and the best cooling performance on its internal temperature. The air humidity above permeable concrete continues to decrease over time. The greater the porosity of the specimen, the later the air humidity above it becomes lower than the indoor ambient humidity. The work of this paper provides data support for permeable concrete pavement to improve outdoor thermal environment.

A Study on the Effect of Green Plot Ratio (GPR) on Urban Heat Island Intensity and Outdoor Thermal Comfort in Residential Areas

Greenery impacts the urban thermal environment, but the benefits of the three-dimensional green volume of space have not been effectively evaluated. In this paper, we analyzed the impact of 3D greenery on urban heat island intensity and thermal comfort in residential areas from the perspective of the green plot ratio (GPR). We selected a typical residential area, set up simulation models, and then analyzed the effect of different GPR values on the outdoor thermal environment using the validated ENVI-MET simulation. The results showed that increasing GPR in residential areas can effectively reduce the intensity of urban heat island and improve thermal comfort. When the GPR reaches 0.5 and 1.5, the thermal comfort level of the building overhead space and the north–south street space decreases from “very strong thermal stress” to “strong thermal stress”. When the GPR reaches 2.5, the outdoor thermal comfort of the east–west street space and courtyard space is reduced to “hot”. When the GPR is higher than 0.5, the urban heat island intensity in the north–south street space decreases by one level, from “very strong” to “strong”. When the GPR reaches 3.5, all four types of spaces have “moderate” urban heat island intensity. Increased GPR exacerbates urban heat island intensity to some extent and worsens outdoor thermal comfort due to the nocturnal insulating effect of plants. Based on the results, the study proposes the bottom-line control of the GPR index from the perspective of urban heat island mitigation and thermal comfort improvement. This paper points out the benefits of GPR in residential areas in improving the human environment, which is of great practical value for developing urban residential environment from “increasing quantity” to “improving quality”.

Optimization of university timetables considering students’ thermal sensation in classrooms

In northern China, university classrooms are often densely populated, and students have limited means of thermal adaptation during lectures. Considering the significant differences in the thermal environment of the classroom throughout different periods, changing the patterns of classroom utilization is a feasible way to improve students’ thermal comfort during classes and ensure learning efficiency. A university teaching building in Xi'an is considered an example in this study. The indoor and outdoor thermal environment parameters of the teaching building were measured in the autumn semester, and the students’ thermal sensation was investigated. On this basis, a model for optimizing university timetables was developed to minimize students’ thermal discomfort in classrooms. The study results showed: 1) During non-heating seasons, students felt comfortable in all periods, except for the third class period (14:00–15:30), during which they felt slightly hot. During the heating season, students felt slightly cold in the first class period (8:30–10:00), slightly hot in the third class period, and comfortable in the second (10:30–12:00) and fourth (16:00–17:30) class periods. 2) Compared to the general schedule, the optimized timetable decreased first period classes by 14 and increased fourth period classes by 13, with minimal changes elsewhere. Adopting this approach, students’ thermal discomfort time during classes in the autumn semester was shortened by 6.16%. 3) The students’ thermal discomfort time reduction rate obtained by timetabling optimization during the non-heating season, heating season are 0.78%, 8.91%, respectively. The effect of reducing students’ thermal discomfort is more pronounced during the heating season.

Comprehensive analysis on the thermal comfort of various greening forms: a study in hot-humid areas

The potential impact of greening on improving thermal environments is widely recognized. However, few studies have comprehensively evaluated the influence of different forms of greening, such as various tree crown widths, green facades, green roofs, and their combinations, on both outdoor and indoor environments. In this study, we conducted an extensive investigation within a residential precinct at Guangzhou University by combining on-site measurements and numerical simulations with the ENVI-met model. Physiologically Equivalent Temperature (PET) and Temperature Humidity Index (THI) were used to assess outdoor thermal comfort. The results indicated that planting trees had a greater impact on improving the outdoor thermal environment than green facades and green roofs, and this effect increased with the crown width of the trees, with a maximum potential reduction of 4.8 °C (0.2 °C) in PET (THI). Green facades can bring a change of up to 101.9 W m−2 in sensible heat flux, resulting in a reduction of up to 1.8 °C in indoor Ta (air temperature). Conversely, green roofs composed of grass exhibit minimal effects in both outdoor and indoor environments. Finally, we provide recommendations for the construction and renovation of projects in residential areas, with a focus on hot-humid areas.

Assessing and enhancing the applicability of standard effective temperature in outdoor thermal sensation prediction for continental climates

Accurate thermal sensation prediction is crucial for assessing outdoor thermal environments. This study aims to enhance the applicability of the standard effective temperature (SET*) in continental climates for a more comprehensive evaluation of outdoor thermal comfort. Taking Zhengzhou, China as an exemplar, a comprehensive 12-day survey involving questionnaire surveys and microclimatic measurements was conducted in residential communities during the summer, autumn, and winter seasons. Based on this, the relationship between the SET* and thermal sensation was explored. Furthermore, the SET*-original thermal sensation scale was modified using linear and probit regression, and the accuracy of modified scale was assessed using predicted accuracy percentage (PAP) and mean absolute error (MAE). The results indicated that the SET*-original scale performs poorly in predicting thermal sensation in continental climates (P = 27.3 %, MAE = 1.24). The modified scale using probit regression model was better suited for continental climates (P = 39.5 %, MAE = 0.87). It outperformed the modified scale obtained through a linear regression model, with PAP increasing by 5.9 % and MAE decreasing by 0.04. The SET*-modified scale extended thresholds at the colder end and significantly enhanced predictive accuracy for colder conditions, making it more suitable for predicting thermal perception in continental climates.

Planning for heat-resilient educational precincts: Framework formulation, cooling infrastructure selection and walkable routes determination

To create a heat-resilient education precinct, this study developed a framework for campus heat solutions to enhance the heat mitigation and adaptation capacity of campus stakeholders. The campus heat solution framework consists of preparation, mitigation and adaptation, thermal environment and comfort assessment, information-sharing platform, heat action plan, and post-assessment. An empirical study in Chongqing University, China based on field experiments, numerical simulations, and post-processing of outdoor thermal environments and comfort was conducted, to demonstrate the applicability of the framework in actual educational precincts. The results indicated the spatiotemporal variability of surface temperature and outdoor thermal comfort, exhibited the right time and proper cooling infrastructure selection, and identified the adaptive walkable paths. For instance, the universal thermal climate index (UTCI) with sun exposure had a mean value of 46.8 °C and a maximum value of 51.4 °C at 14:00, while the mean UTCI of the tree, sunshade and pavilion were 8.1 °C, 9.3 °C and 10.6 °C lower than that of the full exposure means, respectively. Therefore, before 10:00 or after 18:00, choosing locations under trees, sunshades, or pavilions can ensure better thermal comfort at high temperatures. In comparison, from 10:00 to 13:00, it is essential to choose sunshades or pavilions, and from 13:00 to 18:00, it is preferable to choose only pavilions. Moreover, a suitable walkable path was determined based on cumulative heat stress. Overall, this study is expected to provide a reference for building healthy and comfortable educational precincts and enhance the understanding of heat resilience planning.

Knowledge Visualization in Outdoor Thermal Environment Studies: A Comprehensive Review and International Comparison

This review highlights the escalating challenges of outdoor thermal discomfort and urban heat islands due to urbanization and climate change, impacting sustainability and health. Analyzing global research trends, it reveals methodological differences between Chinese and Western scholars, with the former focusing more on quantitative analysis and the latter on diverse approaches including adaptation strategies. It underscores the importance of using emerging technologies like GIS, AI, and remote sensing for precise mapping, scenario modeling, and environmental monitoring. These tools offer innovative, data-driven solutions for urban planning, essential for addressing thermal impacts. The paper calls for enhanced Sino-Western cooperation and interdisciplinary research to develop context-specific, sustainable strategies for improving urban thermal environments.

Quantifying influence of rainfall events on outdoor thermal comfort in subtropical dense urban areas

Existing research on outdoor thermal comfort in urban areas focuses on meteorological factors such as temperature, relative humidity, wind speed, and radiation on sunny or cloudy days. However, climate conditions before, during, and after rainfall events can cause changes in meteorological factors in subtropical regions. Rainfall is an atmospheric condition with a large influence on thermal comfort, particularly in subtropical areas with abundant rain. Big data on temperature, relative humidity, wind speed, precipitation, and total cloud cover from the Taipei Weather Station under the Central Weather Administration from June to August each year from 2011 to 2020 were analyzed, dividing the data into categories based on precipitation. Using a k-means clustering algorithm, we quantified the relationships between meteorological factors and apparent temperature as well as physiological equivalent temperature in different rainfall scenarios. The results indicate that rainfall in the summers of subtropical oceanic climates indeed influence outdoor thermal comfort in urban areas: 37.7% of the rainfall weather patterns improved thermal comfort and 62.3% of the rainfall weather patterns reduced thermal comfort. RWP 46 represent the weather conditions that most significantly improve thermal comfort, at 1:00 PM, with a rainfall of 15 mm, there is a decrease in ΔAT by 14.4 °C and ΔPET by 22.1 °C. With the hot, humid, and rainy climate conditions in Taiwan, apparent temperature is the most accurate index of thermal comfort. KEY POLICY HIGHLIGHTS Rainfall events may affect outdoor thermal comfort in subtropical cities. Different rainfall weather patterns have different impacts on urban outdoor thermal environments. 62.3% of rainfall weather patterns resulted in worsened thermal comfort, for low and concentrated rainfall resulting in a stuffier thermal environment.

Gaussian Mixture Model based classification for analyzing longitudinal outdoor thermal environment data to evaluate comfort conditions in urban open spaces

Global warming and the urban heat island effect have led to a decline in the quality of urban open spaces. Although many studies have been conducted on the thermal environment of urban open spaces, there is a lack of a detailed analysis of the time dimension. This study is to propose a method for analyzing long-term time series data on thermal environment, to more comprehensively evaluate the comfort of urban open spaces. We employed thermal environment data from urban open spaces in Melbourne and conducted a time series comfort analysis using a Gaussian mixture model. The research findings indicate that urban open spaces surrounded by low-rise buildings exhibit the highest thermal comfort, whereas those encompassed by a combination of buildings and green spaces exhibit the lowest comfort level. More importantly, we discovered similarities in the comfortable time periods across the five types of urban open spaces, with the majority falling between 6:00 AM and 10:00 AM. These discoveries can assist in achieving a more objective evaluation of the thermal environment in urban open spaces and provide scientific guidance for urban planning and landscape design, thus enhancing the quality of life for urban residents.

Numerical simulation of the effect of street trees on outdoor mean radiant temperature through decomposing pedestrian experienced thermal radiation: A case study in Guangzhou, China

Street trees have often been proposed to improve the outdoor thermal environment. However, due to the combined effects generated by street trees, the impacts of street trees on the thermal radiation field in a street canyon and mean radiant temperature (Tmrt) reduction have not been systematically analyzed in previous studies. In this paper, we developed a Tmrt decomposition model using first-order Taylor series expansion to decompose the various factors of the street trees on Tmrt reduction and quantify their individual and combined effects in Guangzhou, China. Our results showed that street trees significantly reduce Tmrt and severe heat stress events (Tmrt ≥ 60 °C). For 80% tree crown cover, the maximum decrease of Tmrt by 26.2 °C - 42.1 °C and the severe heat stress events decreased by 197 h - 500 h over the course of a year at different sidewalk locations, compared to the street canyon without trees. During the daytime, the interception of radiation (especially short-wave radiation) by street trees was the primary determinant in reducing Tmrt, with a contribution that mostly exceeded 70%. Additionally, the shading effects of street trees decreased the short-wave radiation reflected from urban surfaces, contributing about 20% to Tmrt reduction. Lastly, our results also showed the leaf area index played an important role in the Tmrt reduction. Our study quantified the individual and combined effects of each factors of reducing Tmrt by street trees, which will better understand the thermal benefits of urban street trees.

Effect of the thermal environment on mortality: analysis of longitudinal data from Cyprus (2009–2018)

Exposure to a suboptimal outdoor thermal environment is associated with increased morbidity and mortality. This study aimed to examine the effect of the thermal environment on all-cause mortality in Cyprus. Daily mortality data were obtained from 2009 to 2018. Hourly meteorological data were retrieved from the ERA5-Land reanalysis database and air pollutant concentrations were obtained from the official air quality network of the Republic of Cyprus. Air temperature (Tair), the physiologically equivalent temperature (PET), and the universal thermal climate index (UTCI) were used to assess the thermal environment. Associations of Tair, PET, and UTCI with daily mortality were examined using negative binomial regression while adjusting for air quality. Mortality in the cold period (December to March) increased by 3.3% for each 1 °C decrease in Tair and by up to 1.8% for each 1 °C decrease in PET and UTCI (p value < 0.001). In the warm period (April to November), a 1 °C increase in Tair or in PET and UTCI was associated with an increase in mortality of up to 1.4% and 1.1% (p value < 0.001), respectively. The effect (increase in mortality) was more pronounced when the analysis focused on winter (3.6% per 1 °C decrease in Tair, 2.4% per 1 °C decrease in PET, and 2% per 1 °C decrease in UTCI) and summer (4.1% per 1 °C increase in Tair, 2.4% per 1 °C increase in PET, and 1.2% per 1 °C increase in UTCI). Males in cold periods and the elderly (older than 64 years) were more vulnerable. Awareness about the effects of the thermal environment on mortality, including those during the cold months of the year, should be enhanced.

Spatial and temporal variations of microclimate and outdoor thermal comfort in informal settlements of warm humid Dar es Salaam, Tanzania

In developing countries, urbanization is dominated by the growth of informal settlements which represents 40–80% of major cities. The challenges brought up by the growth of informal settlements spans from social-economic to environmental. Previously, upgrading of the informal settlements focused on social-economic aspects such as provision of necessary services for the residents, whereas the quality of the outdoor thermal environment has not received much attention. This paper entails to investigate the potential of upgrading the outdoor thermal environment in informal settlements in the warm humid city of Dar es Salaam, Tanzania through examining the influence of addition of trees with different Leaf Area Index (LAI) and incremental increase of buildings heights. The study uses simulation as a method for analysis of the warm season and calculates the Physiological Equivalent Temperature (PET) as a thermal index. Results show substantial improvement of both microclimate and outdoor thermal comfort. Incremental increase of buildings heights in a street canyon to 12, 18, and 24 m leads to the reduction of PET by 2.5, 2.8, and 3.8 °C respectively at 2:00 p.m. Similarly, applying LAI's of 2, 4, and 6 m2/m2 leads to reduction of the mean radiant temperature by 7.9, 10.1, and 12.2 °C; while PET was reduced by 3.9, 4.7, and 5.6 °C respectively at 2:00 p.m. Nonetheless, upgrading of informal settlements shows marginal influence on the reduction of air temperature. Despite the noted thermal improvement in the studied area, the thermal comfort limits of the warm season were difficult to reach. The findings suggest that addition of vegetation is the economically most effective way for upgrading thermal conditions in informal urban fabric areas.

Effect of greening vacant houses on improvement in thermal environment using ENVI-met simulation: A case study on Busan metropolitan city

This study aimed to analyze the improvement in outdoor thermal environment by greening of persistently vacant housing and open areas in a densely built old downtown area of Busan Metropolitan City using ENVI-met. Simulation was performed for a summer day by constructing four scenarios for four areas considering the building density and slope direction. The results indicate that compared to the current scenario, the concrete scenario had the worst thermal environment, where the average temperature, mean radiant temperature (MRT), and physiological equivalent temperature (PET) increased by 0.04°C, 1.49°C, and 0.51°C, respectively. In contrast, the tree scenario exhibited the most significant improvement. The average temperature, MRT, and PET decreased by 0.03°C, 1.66°C, and 0.65°C, respectively. Moreover, the removal of vacant houses in dense residential areas improved ventilation, and PET decreased by approximately 8°C locally. Planting trees higher than the demolished vacant houses mitigated the thermal environment considerably. The effect of greening was the strongest in the residential areas located on the south-facing slope with the worst thermal environment. This study provides essential data for implementing greening as a smart reduction strategy in the sustainable management of vacant houses.

Quantification of summertime thermal stress and PET range in a tropical Indian city

Outdoor environments are rapidly deteriorating in tropical cities, affecting social and commercial activities. Thermal comfort plays a main role in encouraging people to use outdoor spaces. The present study evaluated objective and subjective measurements to assess outdoor thermal stress benchmarks (sensation, comfort and tolerance) in Nagpur city. Summertime micrometeorological surveys were conducted across 13 different locations which recorded 1445 respondents. Physiological equivalent temperature (PET) was used to evaluate objective thermal stress levels of respondents. Strong R2 (> 0.82) was found for PET against thermal sensation, comfort and tolerance. Neutral PET (NPET) was found to be 29.29 °C and NPET range as 26.33–32.25 °C. Thermal acceptability range (TAR) for 88% was found to be 24.61–34.52 °C. Neutral thermal comfort (NTC) and neutral thermal tolerance (NTT) were found to be 30.56 °C and 26.67° respectively using linear regression (LR). The range for NTC and NTT were 27.65–33.48 °C and 22.77–30.58 °C respectively. The study demonstrated higher tolerance of respondents towards extreme temperatures in hot dry climates when compared to those in temperate climates. The attributes of various benchmarks and ranges provide useful insights to optimize outdoor thermal environment and can contribute towards planning and designing sustainable cities.

Impacts of high-albedo urban surfaces on outdoor thermal environment across morphological contexts: A case of Tianjin, China

The urban heat island (UHI) effect can exacerbate various environmental challenges related to high temperatures in urban areas. Increasing urban surface albedo is an effective strategy to mitigate UHI. However, the efficacy of high-albedo urban surfaces across varying urban contexts remains poorly understood. In this study, we leverage Urban Weather Generator to systematically simulate the effects of high-albedo roads, walls, and roofs on urban microclimate across Tianjin. Our simulation covers a typical meteorological year, representing typical weather conditions from January to December. Our results reveal that increasing road albedo is more effective in mitigating UHI in fringe areas, whereas increasing wall and roof albedo is more effective in mitigating UHI in central areas. Local climate zones with an urban aspect ratio of about 0.5 can obtain a maximum reduction of road surface temperature (-6 °C) and wall surface temperature (-3 °C). The temperature changes induced by albedo changes show evident seasonal characteristics: the road temperature decreases significantly in summer, while the wall temperature decreases significantly in spring and autumn. Our results could help guide UHI mitigation policies and urban planning in cities hoping to enhance urban surface albedo to balance urban growth and climate resilience.

Research on the wind environment in an enclosed courtyard: Effect of the opening position, size and wind angle

With the urbanization process in China, outdoor thermal environments are drawing increasing attention, of which comfortable pedestrian height wind environments are crucial for urban outdoor spaces. Few studies have been conducted on the comfort wind zone ratio (CWZR)11Abbreviations: CFD, computational fluid dynamics; CWZR, comfort wind zone ratio; MWSR, mean wind speed ratio; SWZR, static wind zone ratio. models for openings in enclosed courtyards. We quantitatively analyzed the effects of different opening positions, sizes, and wind angles on the wind environment of campus enclosed courtyards via computational fluid dynamics (CFD) simulations, and CWZR models were established for different opening sizes and wind angles. The results are as follows: (1) The opening position, opening size and wind angle significantly affected the outdoor wind environment. (2) Under the dominant wind direction in summer, the cross-opening position better improved the courtyard wind environment than the symmetrical opening. The courtyard CWZR significantly increased with increasing inlet opening size and increased with decreasing outlet opening size. (3) A wind angle from 2° to 47° is the recommended angle for typical courtyard opening types, and the maximum courtyard CWZR occurred at a wind angle of 10°. The study results could guide courtyard building design and courtyard wind environment optimization and enrich the theoretical study of outdoor wind environments.

Effect of optimal allocation of urban trees on the outdoor thermal environment in hot and humid areas: A case study of a university campus in Guangzhou, China

The process of urbanization in developing countries has had an ecological impact, destroying the outdoor thermal environment, especially in hot and humid areas where high summer temperatures are a nuisance for human outdoor activities. The role of urban greening in improving the regional microclimate has been confirmed by many studies. To improve the outdoor thermal environment, taking a university campus in Guangzhou as an example, the tree species and tree geometric parameters were analyzed, the ENVI-met model was established, and a simulation platform was calibrated based on the measured data, which improved the accuracy of the simulation platform. In this simulation platform, the maximum root mean square errors of air temperature and humidity were as low as 1.49 °C and 5.63 %, respectively. To reveal the influence of the physical morphology of tree species and their community characteristics on the outdoor thermal environment, six typical greening tree species and 37 green space configurations were established, and the influence of each tree species and their spatial configurations on the cooling effect of the outdoor environment was simulated. The results showed that the leaf area index, crown width, and tree height had a great influence on the ground temperature and sensible heat flux under the tree canopy, and the cooling effect of the tree group was improved when the height of the trees exceeded 10 m, with an ideal canopy coverage of 30 %. Optimizing the green space configuration reduced the temperature at pedestrian height (1.5 m) in the study area by up to 1.5 °C, and a reduction of 0.5 °C was observed over approximately 50 % of the green area during the peak summer temperatures (14:00–16:00), mitigating the microclimate heat environment. This study can enable urban planners to determine the type, quantity, and spatial allocation of green vegetation to improve the urban thermal environment.

Comprehensive optimization of urban building cluster morphology based on microclimate: A two-level optimization approach

Building cluster morphology plays a crucial role in shaping urban microclimate. Due to the global warming and urban expansion, urban microclimate environment has encountered several problems, like extreme heat or cold stress events. The practical design of building clusters often involves multi-scale, multi-faceted problems and contradiction points which is always challenging to solve. This paper proposes a “two-level” optimization framework for the layout and form design of building clusters in the aspect of engineering applications. A case design project is used to demonstrate the effectiveness of the proposed framework through detailed seasonal simulation. Results show that, comparing with the base case, the candidate design plan (i.e., Plan C) is attractive given the mean UTCI of the selected locations is lower by 0.73 °C in the cooling season noon and higher by 1.91 °C in the heating season at night. Results also indicate that the layout of a building cluster has greater impacts on the outdoor thermal environment during the heating season than the cooling season. Considering Plan C still has a heat/cold stress, further refinements have been performed on the local micro climate to adjust the wind corridor and solar radiation at the lower-level of architectural form. Finally, comprehensive design strategies have been synthesized for the building cluster design.

Influence of greenery configuration on summer thermal environment of outdoor recreational space in elderly care centers

Greenery can improve the outdoor thermal environment in elderly care centers during heat wave in summer. However, it lacks quantitative results and rules. This study investigated the summer outdoor thermal environment of four representative elderly care centers in Tianjin to establish the thermal demand of seniors. The different thermal effects of greenery types (GTs) were revealed in elderly care centers. To improve the quality of the outdoor recreational space, this study utilized numerical simulation to quantitatively establish the influence of tree-shrub coverage rate (TSCR) on the thermal comfort of seniors. The results showed that the thermal neutral physiologically equivalent temperature (PET) of elderly people was 27.0 °C in summer, and the thermal acceptance range of PET was 23.6–36.8 °C. Shrubs overall could significantly increase the tree's ability to improve the outdoor thermal environment. Furthermore, this study proposed different TSCR strategies. TSCR of the elderly care center should be greater than 31.5% to obtain great thermal acceptance for the elderly in summer; when the TSCR of the elderly care center could not reach 31.5% due to the reality, TSCR = 10.0% was the efficient strategy to improve outdoor thermal comfort. This research provided a scientific reference for the greenery configuration plan of elderly care centers in summer.