Impact of building height regulations on outdoor thermal comfort: a simulation and statistical-based study of residential zones in mediterranean context

• ENVI-met parameterisation incorporating field- and laboratory-derived soil data advances OTC modelling beyond standard database inputs. • ENVI-met modelling reveals significant OTC differences across LCZs of Ljubljana. • Mean OTC varies by up to 12.44 °C between LCZs on hot summer days. • Tree shade reduces heat stress by up to 8.43 °C in Ljubljana's urban landscape. Owing to the specific thermal conditions of the urban environment, such as a high proportion of impervious surfaces, low tree cover, high building density, and low surface albedo, residents in these areas experience altered outdoor thermal comfort (OTC). Although these conditions generally contribute to elevated heat stress during hot summer days, this phenomenon varies spatially and temporally. Numerous studies have examined OTC indices across different cities using various modelling techniques; however, the preparation of spatial input data is often insufficiently addressed. Therefore, the study aims to quantify and assess OTC across selected Local Climate Zones (LCZs) in Ljubljana, as well as the effect of existing tree shading on OTC improvement, by advancing a modelling workflow that explicitly incorporates detailed field-derived urban soil characteristics into ENVI-met simulations. This was achieved through interdisciplinary field and laboratory measurements combined with urban microclimatic modelling. The fieldwork included micrometeorological measurements, soil sampling, surface albedo measurements, and green infrastructure mapping. The results revealed statistically significant differences in Universal Thermal Climate Index (UTCI) and Physiological Equivalent Temperature (PET) indices between 13:00 and 15:00 local time across the LCZs. LCZ A exhibited the lowest levels of heat stress, whereas LCZ 8 experienced the highest. The average differences in UTCI and PET between these two zones were 9.23 °C and 12.44 °C, respectively. Further analysis demonstrated that existing tree shade significantly improved OTC. Across all LCZs, the average thermal comfort improved by 5.67 °C (UTCI) and 8.43 °C (PET) under tree shade compared to areas exposed to direct solar radiation.

Assessing the vertical synergies between outdoor thermal comfort and air quality in an urban street canyon based on field measurements

Human thermal comfort is influenced by different climatic parameters. The effect of rain and snow events on human thermal comfort has been less explored in the available literature. The work presented here investigates outdoor and indoor thermal comfort using the physiological equivalent temperature (pet) and wind chill temperature (WCT) indices and Givoni bioclimatic chart for rainy and snowy days as well as a day prior to and a day post snow and rain events in Ardabil. Results indicated that snow and rain events have cooling effects on both indoor and outdoor thermal sensation. The cooling effect of rainy and snowy days is higher than a day prior to and a day post events. Also, the cooling effect of the snow and rain increases by the intensity of the events (> 10 mm/day). Based on the PET and WCT outputs, the cooling effect of the snow events with intensity higher than 10 mm a day is about 1.77 and 0.80 °C less than events under 10-mm a day intensity. The same pattern was observed for rain events. Analysis of the cooling effect of event duration on outdoor thermal comfort indicated that the events with more than 2-day duration have more cooling effect on thermal sensation. Finally, due to different cooling effects of snow and rain events on indoor thermal sensation, different types of bioclimatic strategies should be used inside the buildings during snowy and rainy days in Ardabil.

Studies of outdoor thermal comfort in northern China

Evaluation of urban form influence on pedestrians' wind comfort

The effect of vegetation in outdoor thermal comfort in archaeological area in urban context

Residential areas are the basic unit related to the living quality of urban residents, and their comfort is one of the key concerns of residents. Greening has always been an important means to improve the living environment of residential communities. In this paper, ENVI-met V4 simulation software is verified and used to discuss the influence of the residential scale and green ratio on the outdoor thermal environment. By comparing the difference in outdoor thermal comfort with or without greening measures in residential blocks of different scales, the effects of vegetation on optimizing the outdoor thermal comfort of different scale residential blocks are investigated. The meteorological parameters selected for this case study analysis include a wind speed of 2.5 m/s at 10 m height and an air temperature range of 28 °C to 35 °C. The results show that the wind speed and air temperature in the residential area are less affected by the residential scale and more affected by the greening rate. There are obvious differences in the improvement in outdoor thermal comfort by vegetation at different times. With the increase in residential area scale, the improvement effect of vegetation on outdoor thermal comfort also increases, which in 5 × 5 blocks residential area is 0.2–0.5 °C, higher than that in 2 × 2 blocks small-scale residential area. A modified index, PET (Physiological Equivalent Temperature) drop per green ratio, is proposed for cost performance. Reasonable and feasible greening suggestions for residential buildings are summarized.

How does shade infrastructure affect outdoor thermal comfort during hot, humid summers? Evidence from Nanjing, China

The study of street geometry has gained significant attention in recent years, with researchers investigating the effects of design factors on pedestrian thermal comfort in hot and arid climates.This research investigates how introducing vegetation to pedestrian path design influences thermal comfort on a street section in residential neighborhoods in Riyadh, Saudi Arabia.The case studies explore location-specific investigations to understand pedestrian path design scenarios with variations of vegetation and their placement while focusing on their impact on outdoor thermal comfort, furthermore, using Envi-met 5.6.1 to analyze and compare existing case studies and offer optimized outdoor samples supporting thermal conditions.By examining the influence of vegetation on outdoor thermal comfort, identifying environmental parameters that affect thermal comfort, and comparing their impact on physiological equivalent temperature (PET) recommendations to improve pedestrians' physical health and impact their well-being.This study emphasizes the significance of vegetation in shaping pedestrians' outdoor thermal comfort in hot and arid climates, with design factors such as type, height, width, and distance.Understanding these factors and their crucial roles in determining thermal conditions and their immediate impact on pedestrian thermal comfort can inform urban design strategies aimed at enhancing pedestrian comfort and promoting sustainable and livable urban environments

Urban parks are an important component of urban public green space and a public place where a large number of urban residents choose to conduct outdoor activities. An important factor attracting people to visit and stay in urban parks is its outdoor thermal comfort, which is also an important criterion for evaluating the liability of the urban environment. In this study, through field meteorological monitoring and a questionnaire survey, outdoor thermal comfort of different types of landscape space in urban parks in Chengdu, China was studied in winter and summer. Result indicated that (1) different types of landscape spaces have different thermal comforts, (2) air temperature is the most important factor affecting outdoor thermal comfort; (3) because the thermal sensation judgment of outdoor thermal comfort research in Chengdu area, an ASHRAE seven-sites scale can be used; (4) the neutral temperature ranges of Physiological Equivalent Temperature (PET) and Universal Thermal Climate Index (UTCI) in Chengdu in winter and summer were obtained through research; (5) and UTCI is the best index for evaluating outdoor thermal comfort in Chengdu. These findings provide theoretical benchmarks and technical references for urban planners and landscape designers to optimize outdoor thermal comfort in urban areas to establish a more comfortable and healthy living environment for urban residents.

Semi-private open spaces are indispensable as they enhance society’s growth and contribute to individuals’ health and well-being, thereby improving the quality of life in residential neighbourhoods. However, at present, the integration of such open spaces into the planning of housing projects is often neglected and results in incidental open spaces in the built environment. These incidental open spaces, if designed and integrated carefully, can enhance thermal comfort and community activities significantly. Therefore, this study aims to assess the impact of semi-private open spaces on outdoor thermal comfort in a residential neighbourhood in Kochi, India. A low-rise residential neighbourhood was selected for the study, and the semi-private open spaces were categorized into six typologies based on location, shape, proportions, orientation, aspect ratio, sky view factor, and albedo. Further, the outdoor thermal comfort conditions of these typologies were assessed through simulations in Envi-Met software for a critical summer day. The comfort conditions were assessed through comfort indices namely physiological equivalent temperature and mean radiant temperature (MRT) and were compared to arrive at appropriate design recommendations for semi-private open spaces. The study found a significant correlation between orientation, aspect ratio, sky view factor, and shading with outdoor thermal comfort. The study found a sky view factor of 0.3–0.5, an aspect ratio greater than 1.5, orientation of open spaces in the N-S axis, and shading by trees with canopies above 2.5 m height as appropriate design strategies to reduce the heat stress in semi-private open spaces in low-rise residential neighbourhoods. The study recognizes the importance of integrating planned semi-private open spaces in the local building regulations which can improve the quality of open spaces and enhance public health and well-being while contributing to a better microclimate.

Outdoor thermal comfort and adaptation in severe cold area: A longitudinal survey in Harbin, China

The modification effects of street trees on outdoor thermal comfort in summertime according to tree planting types and road direction were analyzed using a computer simulation program, ENVI-met. With trees, the air temperature and wind speed decreased, and the relative humidity increased. In the case of mean radiant temperature (<italic>T_mrt</italic>) and human thermal sensation, physiological equivalent temperature (PET) and universal thermal climate index (UTCI), there was a decrease during the daytime. The greatest change among the meteorological factors by trees happened in <italic>T_mrt</italic>, and PET and UTCI showed similar patterns with <italic>T_mrt·</italic>The most effective tree planting type on thermal comfort modification was low tree height, wide tree crown, high leaf area index, and narrow planting interval (LWDN). <italic>T_mrt</italic>, PET and UTCI showed a large difference depending on shadow patterns of buildings and trees according to solar altitude and azimuth angles, and building locations. When the building shade areas increased, the thermal modification effect by trees decreased. In particular, results on the east and west sidewalks showed a large deviation over time. When applying the LWDN, the northwest, west and southwest sidewalks showed a significant reduction of 8.6-12.3°C PET and 4.2-4.5°C UTCI at 10:00, and the northeast, east and southeast sidewalks showed 8.1-11.8°C PET and 4.4-5.0°C UTCI at 16:00. On the other hand, when the least effective type (high tree height, narrow tree crown, low leaf area index, and wide planting interval) was applied, the maximum reduction was up to 1.8°C PET and 0.9°C UTCI on the eastern sidewalks, and up to 3.0°C PET and 0.9°C UTCI on the western ones. In addition, the difference in modification effects on <italic>T_mrt</italic>, PET and UTCI between the tree planting types was not significant when the tree effects were reduced by the effects of buildings. These results can be used as basic data to make the most appropriate street tree planting model for thermal comfort improvement in urban areas in summer.

Influence of university campus spatial morphology on outdoor thermal environment: A case study from Eastern China

Many developing countries are experiencing rapid urban growth, resulting in a high demand for social housing schemes. In Egypt, newly built communities and potential extensions are incompatible with its hot climate due to low aspect ratios, high sky view factors values (SVF) and less shaded areas, which negatively affect outdoor thermal comfort at the pedestrian level. This study aims to find a relationship between density (represented in SVF), Physiological Equivalent Temperature (PET) and orientation through a sensitivity analysis to improve the thermal comfort of outdoor spaces in new cities. The research was held on the peakiest summer day using a validated ENVI-met simulation model for a residential area in New October city. The simulation results of 36 scenarios with a total of 37,138 spatial grids were examined through sensitivity analysis to quantify the impact of densification parameters like building coverage ratio, floor area ratio, building height variation, and orientation on PET. PET was found to be more sensitive to densification in cardinal directions. With Higher mid-range densities PET at cardinal orientation reached up to 10℃ higher than in diagonal. Also, the results revealed that optimizing density and building heights could improve average PET (08:00 to 18:00) in diagonal orientation with up to 8℃ in the mid-range densities. However, orientation is insignificant in low densities. Out of the tested parameters, densification was found to be the most impactful strategy than height variation. These results can aid in developing public and private housing schemes that are more climate responsive.