Summer Thermal Comfort Research Articles

Energy performance and summer thermal comfort of traditional courtyard buildings in a desert climate

AbstractCourtyards have been traditionally used as a passive design strategy in desert climates. However, few studies have quantified the thermal performance of this building archetype. This paper explored the indoor and outdoor thermal conditions of a typical courtyard house in Iran. The study was performed in two phases. The first phase showed the effect of the position of the zones located in four sides of the courtyard on their indoor energy use and indoor thermal comfort. The results showed that the east and west sides of the courtyard require the highest cooling demand due to the solar radiation in summer time. Furthermore, maximum discomfort hours occurred in the east zone. In the second phase, hourly air temperature inside and outside of the courtyard were compared during the longest day of the year (21st of June). The results showed that inside of the courtyard was 1.2 °C cooler than the outside on average. Moreover, it was observed that the temperature fluctuations outside of the courtyard were higher than the inside. To sum up, the results showed that courtyards can provide a cooler microclimate in summer time.

Summer thermal comfort and overheating in the elderly

Atypically warm summers such as 2003 and 2018 are predicted to become normal by 2050. If current climate projections are accurate, this could cause heat-related mortality to rise by 257% by 2050, the majority of which will be in vulnerable groups such as the elderly. However, little is known about the temperatures achieved in the homes of the elderly even in typical summers, and even less on whether these are comfortable. This study examines, for the first time, the validity of current thermal comfort models in predicting summer comfort levels in the 65+ demographic over a typical and an atypically warm summer. This was achieved through the first longitudinal study of thermal conditions in homes of the elderly in the South West UK, utilising repeated standardised monthly thermal comfort and health surveys with continuous temperature monitoring in both living and bed rooms. Results show that neither the PMV/PPD model (ISO 7730) nor the adaptive model (ISO 15251) accurately predict true thermal comfort in our sample. Overheating analysis using CIBSE TM59 (based on ISO 15251) suggests significantly more homes (50% living room, 94% bed room = 94% overall) overheated during the atypically warm summer, compared to the typical summer (3% living room, 57% bed room = 57% overall). These are worrying results, especially for the elderly, given the projected increases in both the severity and the frequency of extreme summers in a future, changed, climate. Practical application: This paper provides new data on the performance of the homes of the elderly in both a typical and atypically warm summer. Our results could be considered for building performance evaluation in homes with elderly occupants to mitigate overheating risk. Crucially, we not only examine the impact of CIBSE criteria on these homes but also look at thermal acceptance, which is important to understand the true impact of elevated temperatures in this demographic.

Broadening human thermal comfort range based on short-term heat acclimation

Elevating indoor temperature set-points can reduce cooling energy use. Short-term heat acclimation (HA), the artificially induced adaptation developed in three consecutive days, is an effective method to increase the occupants' acceptance to hot environments. However, the quantitative study on the effects of short-term HA on thermal comfort is lacking. To this end, simulated experiments were conducted in a climate chamber to test the difference of subjects' thermal comfort before and after short-term HA. The subjects were instructed to do intermittent treadmill exercise under hot conditions to reach a HA state. During the trials, core temperature, ratings of perceived exertion (RPE), and ratings of thermal sensation (RTS) were measured. Perceptual strain index (PeSI) was used to assess the effect of short-term HA. The results showed that short-term HA could improve subjects’ adaptability to warmer environments without sacrificing thermal comfort. Furthermore, a HA zone was defined based on the predicted percentage of dissatisfied (PPD) of 10%. The upper limit of the HA zone was 2.1 °C higher than that of the summer thermal comfort zone in ASHRAE Standard 55–2017. This finding suggests that a higher temperature set-point could be considered into the control of air-conditioning systems, contributing to building energy conservation.

Experimental Research on Using Form-stable PCM-Integrated Cementitious Composite for Reducing Overheating in Buildings

This paper investigates the potential of using form-stable phase change material (FS-PCM) integrated cement mortars in building envelopes to prevent overheating and to improve summer thermal comfort. The FS-PCM integrated cement mortar was applied as the interior surface plastering mortar of a full-scale test hut and compared with identical test huts built on cement plasterboard (OCB) and gypsum plasterboard (GPB). The test huts were exposed to outdoor climatic conditions, and indoor thermal behaviours were continuously monitored throughout the summer period. The effects of PCM in reducing the overheating was analysed by the intensity of thermal discomfort (ITDover) and frequency of thermal discomfort (FTDover) for overheating during the summer days. The comparison between different test huts showed that the application of PCM integrated cement mortars reduced the peak indoor temperature by up to 2.4 °C, compared to GPB and OCB test rooms. More importantly, the analysis of overheating effects revealed that at lower intensive thermal discomfort levels, FS-PCM largely reduces FTDover. As the intensity of thermal discomfort increases, the reduction in ITDover becomes dominant. At highly intensive thermal discomfort levels, the reduction was neither apparent in the intensity of thermal discomfort nor the period of discomfort.

Influence of the Mega-Urban Heat Island on Spatial Transfer of Summer Thermal Comfort: Evidence from Tianjin, China

Influence of the Mega-Urban Heat Island on Spatial Transfer of Summer Thermal Comfort: Evidence from Tianjin, China

Appraisal of thermal comfort in rural household kitchens of Punjab, India and adaptation strategies for better health

There is increasing evidence of adverse health impact of solid biomass fuel, and its use may hinder thermal comfort, which may lead to lower quality of life. Hence, current study aims to assess the thermal comfort at a rural location of Punjab, India. The indoor air temperature and relative humidity in rural households during winter varied from 11.9–25.2 °C and 63.4–90.5% respectively, during pre-summer it ranged between 21.3 and 27.4 °C and 48.4–78.4% while during summer it ranged between 28.4 and 37.8 °C and 13.7–63.8% respectively. The PMV of the households ranged between −0.85 to 0.69 (winter), −0.32 to 0.4 (pre-summer) and 0.53 to 1.25 (summer) for American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) 55-2017 and −0.56 to 1.11 (winter), 0.04 to 0.99 (pre-summer) and 1.21–2.36 (summer) for European Committee for Standardization (CEN) European standard EN15251 while the Predicted Percentage of Dissatisfied ranged between 5 and 20% (winter), 5–8% (pre-summer) and 11–38% (summer) for ASHRAE 55-2017 and 5–31% (winter), 5–26% (pre-summer) and 36–90% (summer) for EN15251 guidelines. On the other hand, Adaptive thermal comfort (ATC) during winter and pre-summer was comfortable for 80 and 90% acceptable limits (ASHRAE-2017) and ranged between too cool to comfortable for EN15251 (Class I, II and III) while during summer thermal comfort for occupants was comfortable for ASHRAE 2017 and EN15251 (Class I, II, III) but did not comply with EN guidelines in some households using either clean fuel or chullah. Thermal comfort sensation was observed to be slightly cool to neutral during winter, neutral during pre-summer and slightly warm during summer according to Predicted Mean Vote method. The results were also compared using a thermal comfort and household survey and found to be similar with the model results. Climate change is leading to changes in temperature which may have an impact on the built environment. Hence, the current study suggests formulating policies on the uses of household fuel and design of kitchen with proper ventilation to increase thermal comfort which in turn will also reduce air pollutants.

Space Design for Thermal Comfort and Energy Efficiency in Summer

Space Design for Thermal Comfort and Energy Efficiency in Summer

Output of part I:

In part 1, a literature review was done to summarise and introduce the theoretical background knowledge of thermal comfort and passive cooling technology. The adaptive thermal comfort was explained because it is applicable to a free-running building which is the studied object of this research. The basic theory and design standards of adaptive thermal comfort were reviewed. A brief overview of passive cooling techniques was given. The techniques were then reviewed based on their relationships with urban morphology, building shape, layout, opening and “elements”. The study started with a Chinese vernacular building (chapter 4) because these always use the passive way to achieve a comfortable living environment under the limitations of technology at that time. Firstly, the spatial design strategies for passive cooling of a Chinese vernacular house were investigated in a field survey. The design of modern rural houses under free-running conditions compared with the Chinese vernacular house. It was found that the modern rural house did not achieve a satisfactory thermal summer environment under free-running conditions, while the vernacular house did. Furthermore, the vernacular house was deeply analysed by field measurements and dynamic thermal simulations. It was found that the particular spatial design of the vernacular house has its own building microclimate, which is important for the occupants’ thermal summer comfort. The concept of building microclimate was identified. In this study, the scale of “building microclimate” refers to a type of microclimate, involving the indoor space and the spaces around the indoor spaces of a particular building. It is the extension of the indoor climate. The spatial scale is smaller than the urban fabric. It rarely covers an area more than several hundred meters wide, but is bigger than an indoor space alone. It is limited to one particular building, whether a small house or a big stadium. The building microclimate is mainly defined by the spatial and the thermo-physical properties. Similar to the influence of urban morphology on urban microclimate, the spatial configuration influences the building microclimate significantly. To have a particular microclimate at the building scale, some key factors of spatial configuration such as spatial diversity, spatial arrangement and boundary conditions between spaces should be identified. The spatial design of modern house is different from the vernacular house due to the evolution of people’s lifestyle over a long period. Can a modern house have a good building microclimate? To answer this question, the spatial design and thermal environment of a modern house were analysed through field survey and simulation. It was found that a modern house can also have its own microclimate and that the microclimate of this particular building can provide considerable thermal comfort for the occupants in summer under local climate conditions. Adaptive actions, for example movement, can explain why occupants can achieve thermal comfort in a building microclimate with diverse spaces. To find the relationship between the occupants’ spatial perception and thermal perception, a questionnaire was put forward. It was found that the spatial openness of a particular space significantly affects the occupants’ visual perception, wind speed perception and thermal perception. It was revealed that the occupants’ spatial perception and thermal perception are associated. The strongest correlation is between spatial openness and visual perception and wind speed perception. That means spatial boundary conditions can strongly influence occupants’ comfort perception, and subsequently influence the occupants’ spatial choice and movement in a particular thermal environment, given the opportunity, as Humphreys (1997) pointed out: when people are free to choose their location, it helps if there is plenty of thermal variety, giving them the opportunity to choose the places they like. The fundamental assumption of the adaptive approach is expressed by the adaptive principle: “if a change occurs such as to produce discomfort, people react in ways which tend to restore their comfort”. Nicol et al. (2012) proposed that there are at least five basic types of adaptive actions. One important adaptive action is selecting a different thermal environment. Occupant movement in a particular building microclimate is significant for thermal comfort. Occupants can change their location for different activities. Movement is possible between buildings, between rooms, around rooms, out of the sun and into the breeze, and so on (Nicol et al., 2012).

Coupling occupants’ behaviour and natural ventilation potential analysis in the design of a Chinese rural house

In chapter 11, the VGA analysis method proposed by the author was used for the evaluation of the layout designs of Chinese rural houses proposed by the local government. Type 10 was selected as best design type, because it can most easily achieve thermal summer comfort for occupants in passive ways. The optimised layout has a high potential to achieve natural cross-ventilation, especially in the public spaces, which are important for the local occupants’ thermal summer comfort in hot and humid climates. Chapter 11 also shows occupants’ movement behaviour in the spaces. The public spaces in the house are the most attractive spaces for occupants. This is related to the occupants’ spatial perception. This helps the occupants to enjoy the natural ventilation in the public spaces because there is a high potential to achieve natural ventilation there. In this chapter, the optimised layout design of chapter 11 will be developed for a new rural house design in the studied area. The focus of the design is still on the occupants’ behaviour and natural ventilation potential with respect to the spatial configuration. This study will demonstrate how to use the VGA analysis method for the optimisation of spatial configuration, coupling occupants’ behaviour and natural ventilation analysis to design practice.

Building microclimate and summer thermal comfort in free-running buildings with diverse spaces

In this paper, the authors first clarify the definition of building microclimate in free-running buildings and the relationship with summer thermal comfort. Next, field measurements were conducted to investigate the microclimate in a Chinese traditional vernacular house. Subsequently, the results of measurements were compared with a dynamic thermal and a CFD simulation in order to determine the building microclimate and thermal comfort of the present vernacular house over the period of an entire summer. The field measurements show the present Chinese vernacular house has its own independent building microclimate in summer, which is in accordance with the main character of microclimate in terms of different distributions of solar gain, air temperature and wind velocity in different spaces. The simulation results of the vernacular house could be matched well with the field measurements. According to the simulations, at night, a comfortable temperature could be obtained throughout most of the summer period whereas in the daytime the operative temperature was higher than the comfortable temperature for one-third of the summer period. Wind velocity in the semi-outdoor and outdoor spaces however, improves the thermal comfort significantly. The thermal comfort environment can thus not only change in time but also in space. This example of the vernacular building shows that it is possible to create comfortable conditions for the inhabitants when not only the indoor climate is taken into account but the whole building microclimate as defined in this paper. This paper also shows that the simulations can predict the building microclimate.

Conclusion

The main objective of this dissertation is to find the main factors of building spatial configuration that affecting the thermal summer environment, the possibility of occupants to achieve thermal comfort there in, and to propose a spatial design method as the passive cooling strategy for summer thermal comfort. In accordance with the objective, the research questions were put forward in section 1.5 of chapter 1. For every sub-question, there is a respective chapter to answer it, see figure 1.3 in section 1.6 of chapter 1. In chapter 8, some conclusions of part I of this dissertation were summarised. In this chapter, the research questions are answered. In addition, the limitation of this research and recommendations for future practice and research will be mentioned as well.

Performance of Wood-Based Panels Integrated with a Bio-Based Phase Change Material: A Full-Scale Experiment in a Cold Climate with Timber-Frame Huts

The relatively low thermal mass of timber frame buildings is a limiting factor for their energy efficiency and for the thermal comfort. The aim of this study is to assess the performance of wood-based wallboards integrated with PCM (Phase Change Materials) in a cold climate (Québec, Canada), from the heating season to the summer. Two timber-frame test huts, of 2 × 2.5 × 3 m, were built following the National Building Code of Canada and placed in the LAVAL University Campus. The first hut was equipped with wood-based panels integrated with the commercial bio-based PCM Puretemp®23 with a 23 °C melting point. The second hut was equipped with standard interior wood panels. Large double glaze windows were installed facing south. Dry indoor air temperatures were recorded for both huts and for the heating season, heating consumptions were monitored. The behaviour of the two huts was compared and PCM panels efficiency was evaluated over several seasons. A reduction of heating consumption was observed for cold months. For the heating season, panels were found to be more efficient as the months were getting milder. By gathering solar energy during the day, they allowed to reduce the test-hut heating consumption, by a maximum of 41% in May. In summer, the PCM panels had a positive impact in order to reduce the hut overheating. However their efficiency was found limited by a poor ability of discharge during the night. The solidification of the PCM was often impossible to achieve due to unsuitable night conditions. The results presented in this study will improve the knowledge concerning wood/PCM composites performance and concerning PCMs issues in cold climates. This study exposes the potential of wood-based panels integrated with PCM to achieve winter energy savings and enhance the summer thermal comfort of a timber-frame building, for a cold Canadian climate.

Climate change and summer thermal comfort in China

Heat escape-motivated travel, called “sunbird” tourism, has become increasingly important with global warming and associated urban heat island effects. This study proposes a new method based on defining “comfortable” calendar days, to identify regions thermally suitable for “sunbird” tourism (namely northern Northeast China, eastern Inner Mongolia Plateau, northern Xinjiang Province, eastern Qinghai-Tibet Plateau, and Yungui Plateau) and their comfortable periods in China. From 1961–1990 to 1987–2016, comfortable periods have extended by 5 to over 20 days in eastern Qinghai-Tibet Plateau and parts of Yungui Plateau, but shortened by 5 to over 20 days in northern Northeast China and eastern Inner Mongolia Plateau, corresponding to 9 and 21 locations respectively becoming suitable and no longer suitable for “sunbird” tourism. Moreover, comfortable periods are now much earlier in the eastern Inner Mongolia Plateau and have dramatically altered in terms of their temporal distribution over the eastern Qinghai-Tibet Plateau. Finally, we discuss the implications for tourism.

Ventilative Cooling in a School Building: Evaluation of the Measured Performances

The test lecture rooms on Katholieke Universiteit Leuven (KU Leuven) Ghent Technology Campus (Belgium) are a demonstration case of Annex 62: Ventilative Cooling of the International Energy Agency’s Energy in Buildings and Communities programme (IEA EBC). The building is cooled by natural night ventilation and indirect evaporative cooling (IEC). Thermal comfort and the performances of ventilative cooling are evaluated. Long-term measurements of internal temperatures, occupancy, opening of windows and IEC were carried out in the cooling season of 2017. The airflow rates through the windows in cross- and single-sided ventilation mode were measured by both tracer gas concentration decay and air velocity measurements. In addition, the air flow pattern is visualized by measuring air temperatures in the room. The results show that good thermal summer comfort was measured except during heat waves and/or periods with high occupancy. Both nighttime ventilation and IEC operate very well. IEC can lower the supply temperature by day significantly compared to the outdoor temperature. The Air Changes Rates (ACR) of the night ventilation greatly depends on wind direction and velocity. The air temperature profile showed that the air is cooled down in the whole lecture but more in the upper zone. The extensive data monitoring system was important to detect malfunctions and to optimize the whole building performance.

Experimental case study on the effect of the urban morphology on urban microclimate and outdoor thermal comfort

The present study aims at testing the influence of the urban morphology on the external weather conditions and the urban microclimate by treating quantitative aspects of the outdoor thermal comfort. This is based on a site investigation aims at studying the correlation between the geometry of the street, its orientation and the evolution of the physical variables: air temperature (Ta), Mean Radiant Temperature (MRT), Relative Humidity (RH), Wind speed (Ws). The measures were the subject of a campaign carried out in the urban fabric of the ksar of the red village in the wilaya of Biskra in Algeria. The objective is to define the most efficient urban geometry in term of summer thermal comfort by studying the real impacts of the urban form on the solar control and microclimatic conditions. The evaluation of the thermal comfort in these external spaces is carried out by analyzing physiologically equivalent temperature (PET) values calculated by Rayman Pro 2.1 software based on the measured microclimatic parameters.

Experimental case study on the effect of the urban morphology on urban microclimate and outdoor thermal comfort

The present study aims at testing the influence of the urban morphology on the external weather conditions and the urban microclimate by treating quantitative aspects of the outdoor thermal comfort. This is based on a site investigation aims at studying the correlation between the geometry of the street, its orientation and the evolution of the physical variables: air temperature (Ta), Mean Radiant Temperature (MRT), Relative Humidity (RH), Wind speed (Ws).The measures were the subject of a campaign carried out in the urban fabric of the ksar of the red village in the wilaya of Biskra in Algeria. The objective is to define the most efficient urban geometry in term of summer thermal comfort by studying the real impacts of the urban form on the solar control and microclimatic conditions. The evaluation of the thermal comfort in these external spaces is carried out by analyzing physiologically equivalent temperature (PET) values calculated by Rayman Pro 2.1 software based on the measured microclimatic parameters.

Effect of urban morphology on thermal comfort in outdoor spaces: the case of the red village-El Kantara-Biskra

Climate urban design is today a topical issue dealt with in many recent studies. This paper aims to test the influence of urban morphology on external climatic conditions and the urban microclimate by dealing with the quantitative aspects of thermal comfort and the assessment of the thermal environment from an objective point of view. This is based on an on-site investigation based on the correlation between the geometry of the street, its orientation and the evolution of the physical variables (Ta, Tg, HR, Va). The measures were the subject of a campaign carried out in the urban fabric of the Ksar of Dachra El- Hamra (the red village), the first nucleus of the city of El Kantara in the wilaya of Biskra. The objective is to define the most efficient urban geometry in terms of summer thermal comfort by studying the true impacts of urban form on solar control and microclimatic conditions in arid regions. The evaluation of the thermal comfort in these external spaces is carried out by analyzing the calculated physiological temperature (PET) values based on the measured microclimatic parameters. The analysis of the results obtained from the investigation enabled us to demonstrate the considerable effect of the sky view factor, calculated by Rayman Pro 2.1 software, on the thermal fluctuations in the street.

Beyond thermal comfort in the hospital rooms. Investigation of thermal summer comfort in patients rooms: case of Biskra hospitals

In Algeria, the architectural design of hospitals is unfortunately not subject to clear and specific regulatory thermal strategy, it depends mainly on the architect own approach to the issue of comfort design, materials, etc. This research aims to investigate the present comfort conditions in typical hospital configuration and under specific climate conditions of hot and arid regions. Two different hospital designs have been investigated in Biskra. A main town is southeast of Algeria. The first case study being the oldest hospital in the town, build in the late 30s during the colonial era and renovated recently. The second hospital is a brand new hospital. A series of measurements of ambient air temperature, patient surveys and interviews have been initiated in two typical wards. The results show that thermal comfort sensations in these specific spaces depend not only on architecture, design and typical processes, but also on physiological, psychological and behavioral parameters which widely influence the perception of the patients.

Effect of long-term acclimatization on summer thermal comfort in outdoor spaces: a comparative study between Melbourne and Hong Kong.

The Universal Thermal Climate Index (UTCI) is an index for assessing outdoor thermal environment which aims to be applicable universally to different climates. However, the scale of UTCI thermal stress classification can be interpreted depending on the context. Previous studies validated the UTCI in individual cities, but comparative studies between different cities are scarce. This study examines the differences in thermal perception and clothing choices between residents from two climate zones over similar UTCI ranges in summer. We compared summer thermal comfort survey data from Melbourne (n = 2162, January-February 2014) and Hong Kong (n = 414, July-August 2007). We calculated the UTCI from outdoor weather station data and used t tests to compare the differences in thermal sensation and clothing between Hong Kong and Melbourne residents. When the UTCI was between 23.0 and 45.9°C, Melbourne residents wore significantly more clothing (0.1 clo) than Hong Kong residents. Hong Kong residents reported neutral to warm sensation at a higher UTCI range compared with the dynamic thermal sensation (DTS) model. Moreover, Melbourne residents reported warm and hot sensation at a higher UTCI range than the DTS model. Respondents in Melbourne also exhibited different responses to the mean radiant temperature under shaded and sunny conditions, while such a trend was not observed in Hong Kong. It would be advisable to define different thermal sensation thresholds for the UTCI scale according to different climate zones for better prediction of the outdoor thermal comfort of different urban populations.

The impact of increasing urban surface albedo on outdoor summer thermal comfort within a university campus

The impact of increasing urban surface albedo on outdoor thermal comfort was studied in two phases:Firstly, the thermal conditions of three locations with different ground surface materials were compared. The study used CFD modelling followed by a measurement campaign to validate the control simulation. It was observed that the physiological equivalent temperature (PET as the outdoor thermal comfort index) in the campus park (covered with grass) was 11.0 °C lower than the parking lot (paved with concrete) at 16:00 CET.As the next step, the albedo of the roofs and walls were increased from 0.2 (control) to 0.3, 0.4, 0.5 and 0.6. It was found that increasing the albedo made the open space of the courtyard uncomfortable due to the higher reflectivity of high-albedo materials. An increase of every 0.1 albedo of the surfaces led to 1.2 °C higher mean radiant temperature, and consequently, 0.8 °C higher PET. The study also showed that the increase of albedo radiated more sun to the ground surface. This increased average ground surface sensible heat flux (6.7 W/m2) and surface temperature (0.4 °C) during the day. This finding shows that the position and orientation of high albedo materials can significantly affect pedestrians' thermal comfort in urban open spaces.