Adaptive Thermal Comfort Model Research Articles

Influence of environmental variables on thermal comfort and air quality perception in office buildings in the humid subtropical climate zone of Brazil

This study evaluates the influence of environmental variables on users’ thermal comfort and air quality perception in the humid subtropical climate of Florianópolis, southern Brazil. A building with central air-conditioning system and three mixed-mode buildings, which alternated between natural ventilation and air-conditioning modes, were investigated. Statistical analyses were performed considering environmental data collected in situ between 2014 and 2016 – using microclimate stations, a portable thermo-anemometer and a CO2 analyser – and users’ subjective responses obtained by means of an electronic questionnaire. Results showed a direct influence of air temperature and humidity ratio and indirect influence of air movement on thermal comfort. In addition, thermal, air movement and humidity sensation, preference and acceptability affected thermal comfort and air quality perception, highlighting the importance of carrying out a complete assessment of users’ perception of the thermal environment. This work supports the use of the ASHRAE 55 adaptive thermal comfort model for mixed-mode buildings under natural ventilation operation. Based on the results obtained in this study, the use of hybrid ventilation strategy is recommended for energy savings due to reducing the use of air-conditioning and improving indoor air quality as there is a decrease in air pollutants level.

Towards Sustainable Development: Building’s Retrofitting with PCMs to Enhance the Indoor Thermal Comfort in Tropical Climate, Malaysia

Building sector is associated with high energy consumption and greenhouse gas emissions, which contribute to climate change. Sustainable development emphasizes any actions to reduce climate change and its effect. In Malaysia, half of the energy utilized in buildings goes towards building cooling. Thermal comfort studies and adaptive thermal comfort models reflect the high comfort temperatures for Malaysians in naturally conditioned buildings, which make it possible to tackle the difference between buildings’ indoor temperature and the required comfort temperature by using proper passive measures. This study investigates the effectiveness of building’s retrofitting with phase change materials (PCMs) as a passive cooling technology to improve the indoor thermal environment for more comfortable conditions. PCM sheets were numerically investigated below the internal finishing of the walls. The investigation involved an optimization study for the PCMs transition temperatures and quantities. The results showed significant improvement in the indoor thermal environment, especially when using lower transition temperatures and higher quantities of PCMs. Therefore, the monthly thermal discomfort time has decreased completely, while the thermal comfort time has increased to as high as 98%. The PCM was effective year-round and the optimum performance for the investigated conditions was achieved when using 18mm layer of PCM27-26.

Influence of perceived control on thermal comfort in winter, A case study in hot summer and cold winter zone in China

Psychological impact is widely regarded as one of the most important factors in adaptive thermal comfort model. According to perceived control theory, perceived control is an important part of psychological impact. In order to explore the effect of perceived control on thermal comfort in the Hot Summer and Cold Winter (HSCW) zone in China, a field study and a climate chamber experiment were conducted. The field survey on thermal comfort was carried out in two residential buildings with split air-conditioners and central heating systems respectively in HSCW zone in winter. The results show that the thermal neutral temperatures of residents in residential buildings with split air-conditioners and central heating systems are 16.9 °C and 18.6 °C. From the perspective of thermal comfort, the central heating system in northern China is not suitable for direct application in southern China. Then, the effect of perceived control on thermal comfort was tested in a climate chamber. The results show that when the indoor operative temperature deviates from 18 °C, the thermal sensations of subjects with perceived control are closer to thermal neutral than those without perceived control. The effect of perceived control has a linear relationship with indoor operative temperature. The experimental results show that the perceived control can improve the thermal comfort of residents in winter. It is suggested to provide residents various ways to effectively control the thermal environment through windows and controllable terminal of heating systems, which can improve the thermal comfort of residents and reduce heating energy consumption.

Theoretical Minimum Thermal Load in Buildings

Summary Building cooling and heating accounts for a large portion of total global energy use and requires commensurate amounts of resources, which contribute significantly to global warming. Traditionally, addressing this issue has meant improving the efficiency of equipment supplying the thermal energy, reducing envelope heat transfer, and reducing air infiltration. However, this approach is already reaching practical limits. In this perspective, we explore (1) how to reduce thermal load in buildings theoretically and (2) how to achieve that reduction and dramatically lower the energy required to support building loads practically. First, we discuss our framework developed for calculating the theoretical minimum thermal load (TMTL) in buildings. Our analysis shows that current thermal loads in buildings are more than an order of magnitude higher than the TMTL. We also introduce an approximate formula to calculate energy savings from zonal control of thermal load, which shows that the majority of zonal control benefits can be achieved with fewer than 10 zones. Then, we discuss pros and cons of various approaches and strategies to achieve the TMTL. We conclude our perspective with some longer-term R&D ideas, such as thermally adaptive clothing and thermal storage to help approach the TMTL, while providing the additional benefit of interacting with the renewable grid of the future.

Forecasting the impact of climate change on thermal comfort using a weighted ensemble of supervised learning models

This work presents a weighted ensemble of supervised learning models for estimating the days of the year where compliance with the Adaptive Model of thermal comfort is exceeded. The ensemble combines several gradient boosting on decision tree algorithms and Bayesian logistic regression. In a presented case study, the model is trained on three summers of hourly weather data and indoor air temperature data of a south-facing, naturally-ventilated office in Vancouver, Canada. The model is then used to predict thermal comfort exceedance under a possible climate change scenario. It is found that the ensemble outperforms its individual models in terms of accuracy, precision, and similar metrics. In eight of nine trials using the ensemble to re-assess known history, the ensemble predicts total comfort-exceeding days within a margin of one day. Under the RCP 8.5 global climate change scenario, the model predicts annual comfort-exceeding days will double before the 2050s, by that point exceeding current local thermal comfort compliance guidelines. Future applications of the presented methodology may assist other areas of data-driven forecasting, such as peak energy demand prediction. It may also assist analysis of emerging space cooling solutions such as radiant cooling of free-running buildings.

An investigation of indoor thermal environment in semi-cold region in Japan – Validity of thermal predictive indices in Nagano during the summer season

Thermal comfort can be evaluated using two models—heat balance models and adaptive thermal comfort models. A heat balance model is based on the results of laboratory research. Furthermore, the most common predictive index is the Predicted Mean Vote (PMV). However, PMV cannot be used to predict occupants' thermal sensation well in naturally ventilated buildings. In a previous study, it was considered that the prediction accuracy is improved by associating PMV with two-node models or the psychological and behavioral adaptations of occupants. Our aim here was to evaluate the validity of the prediction accuracy of indices. Three predictive indices were compared in terms of occupants' thermal sensation (TSV): PMV, Predicted Mean Vote Gagge (PMVG), which was modified by Gagge, and predicted thermal sensation (TSENS), which is related to the two-node model. In summer, questionnaire-based subjective votes and thermal environment surveys were conducted in a naturally ventilated high school. Regression analysis showed that PMV and TSENS tended to underestimate TSV, whereas PMVG predicted TSV more accurately than PMV and TSENS. TSV was predicted more accurately PMVG, which is based on the two-node model. In addition, the adaptive predicted mean vote (aPMV), which considers occupants’ adaptive abilities, was used to predict TSV. At high temperatures, the predictive accuracy was improved. Finally, the thermal environment of a naturally ventilated classroom was evaluated using an adaptive thermal comfort model. By modifying the upper limit of the acceptable range, we showed the possibility of applying it more accurately in this study.

Study on Behavioural Adaptation for the Thermal Comfort and Energy Saving in Japanese Offices

Office workers use a variety of adaptive opportunities to regulate their indoor thermal environment. The behavioural adaptations such as window opening, clothing adjustments, heating/cooling use are one of the important factors for the adaptive thermal comfort. It is well-known that they are the most important contributors in the adaptive thermal comfort model. Thus, if we understand the behavioural adaptation properly, we can explain the mechanism of the adaptive model. In addition, the indoor thermal environment is often adjusted using the air conditioning in Japanese office building to improve the thermal comfort and productivity. Thus, it is necessary to conduct research on the behavioural adaptation in the offices because the occupant behavior is different to the dwellings.
 In order to record the seasonal differences in behavioural adaptation and to develop an adaptive algorithm for Japanese offices, we measured temperatures in 11 office buildings and conducted the thermal comfort and occupant behaviour survey for over a year in Japanese offices. We collected 4,660 samples from about 1350 people.
 The proportion of ‘open window’ in the free running mode (neither heating or cooling being used) is significantly higher than that of the air-conditioned mode. The behavioural adaptation is related to the outdoor air temperature. The behavioural adaptation predicted by the regression analysis is in good agreement with the measured data. These findings can be applied to the building thermal simulation to predict the behavioural adaptation and energy use in office buildings.

Climate Change Effects on Belgian Households: A Case Study of a Nearly Zero Energy Building

Overheating in residential building is a challenging problem that causes thermal discomfort, productivity reduction, and health problems. This paper aims to assess the climate change impact on thermal comfort in a Belgian reference case. The case study represents a nearly zero energy building that operates without active cooling during summer. The study quantifies the impact of climate change on overheating risks using three representative concentration pathway (RCP) trajectories for greenhouse gas concentration adopted by the Intergovernmental Panel on Climate Change (IPCC). Building performance analysis is carried out using a multizone dynamic simulation program EnergyPlus. The results show that bioclimatic and thermal adaptation strategies, including adaptive thermal comfort models, cannot suppress the effect of global warming. By 2050, zero energy buildings will be vulnerable to overheating.

Influence of the Improvement in Thermal Expectation Levels with Adaptive Setpoint Temperatures on Energy Consumption

A sustainable use of active heating, ventilation, and air conditioning (HVAC) systems is crucial for minimum energy consumption. Currently, research studies are increasingly applying adaptive setpoint temperatures, thus reducing considerably the energy consumption without influencing comfort levels excessively. Most of them, however, are focused on the limit values of adaptive comfort standards without considering the tolerance in users’ adaptation capacity. This research study analyzed various tolerance ranges in the recent adaptive thermal comfort model from EN 16798-1:2019 used in setpoint temperatures. The study focused on the south of Europe, considering 47 cities in Spain, 18 cities in Portugal, 13 cities in Greece, and 20 cities in Italy. In addition, such cities were analyzed in three climate scenarios: present time, 2050, and 2100. The results showed that values prefixed by EN 16798-1:2019 for new buildings (tolerance of 0.00 °C) produced significant savings with respect to the static model and that each progressive improvement in users’ thermal expectations in 0.25 °C increased the energy consumption between 6.57 and 9.31% in all scenarios analyzed. Even applying a thermal tolerance of 1.50 °C, energy savings are currently produced with respect to the static model. This tendency increases in future scenarios until a thermal tolerance of 1.75 °C. The results of this paper provide greater knowledge about the possible energy increase that the improvement in users’ expectations would produce.

Initial Assessment of Indoor Environmental Condition and Thermal Comfort of Malaysia Heritage Mosque

Heritage mosques are the gems of the country as they preserve the history of local communities and nation. Many studies have been executed on the architectural characteristics of Malaysia heritage mosques. However, the empirical studies on its indoor environmental condition and thermal comfort are still lacking. Therefore, the objective of this study is to identify the indoor environmental condition and thermal comfort of Malaysia heritage mosque by using the field measurement method. The selected heritage mosque for this study is Masjid Tanah, which is located at Masjid Tanah, Alor Gajah, Melaka. Two multiparameter ventilation meters were used in the field measurement. The variables measured were air temperature and air velocity, while the indoor predicted comfort temperature was calculated using the adaptive thermal comfort model equation. The results show that the average indoor air temperatures were lower than the average outdoor air temperatures throughout the measurement. This is also similar with the indoor air velocities which were lower than the outdoor wind speeds at all times. Meanwhile, the results also demonstrate that the average indoor air temperatures were also lower than the indoor predicted comfort temperatures during the morning hours until 1 pm. The overall findings indicate that the architectural characteristics of the selected heritage mosque has a good response to the local climate. However, some improvements are necessary in enhancing the indoor thermal comfort. The findings can be used as guides for achieving a more comfortable indoor environmental condition of heritage mosques, as well as the modern mosques also.

Natural ventilation usability under climate change in Canada and the United States

ABSTRACT Natural ventilation can be incorporated into buildings to decrease energy use and the associated greenhouse gas emissions of buildings. However, mechanical cooling has largely replaced natural ventilation in commercial buildings in Canada and the US. This study evaluates the potential for natural ventilation under climate change. To this end, a typical office space in a mixed-mode building in 14 cities representing the major climate zones in Canada and the US was simulated to assess the usability of natural ventilation under the predicted climatic data for the years 2050 and 2080. A rule-based model for change-over between natural and mechanical ventilation modes was developed on the basis of the adaptive thermal comfort model. The potential impact of occupants was also simulated using an existing stochastic occupants’ window use model. The simulation results show that the natural ventilation usability with rule-based control generally decreases under climate change. The stochastic model indicated the risk of overheating resulted from inefficient window use. Climate change leads to higher cooling energy use, which can be reduced considerably, especially in temperate climates, using natural ventilation with rule-based control. However, the stochastic model yielded to the reduction in the energy saving rates.

Energy poverty analyzed considering the adaptive comfort of people living in social housing in the central-south of Chile

Energy poverty (EP) occurs when there are no energy services available or not at an affordable price, or when homes are not capable of maintaining minimum thermal comfort conditions. It is associated with a series of adverse consequences for the people's health and with a higher number of deaths in winter in most European countries. The objective of this research was to study whether the thermal comfort levels, the state of the dwellings, the heating systems, the energy expenses, the respiratory illnesses and the medical expenses reported by social housing inhabitants in central-south Chile, were correlated, to determine which variables or combination of variables are more related with EP situations. To define the thermal comfort limits, a recently published adaptive thermal comfort model for low income housing in Chile was used. The results show that a third of those surveyed were not capable of keeping their home comfortable for at least 80% of the time and more than a fifth were incapable of doing so 65% of the time. Only 10% of those who were capable of keeping comfort levels more than 90% of the time, spend less than US$ 40 a month, which represents 10% of the minimum Chilean wage. Reducing the time that temperatures are below the lower comfort limit to 10% can mean a reduction in the number of respiratory illnesses and medical expenses.

Energy flexibility for heating and cooling in traditional Chinese dwellings based on adaptive thermal comfort: A case study in Nanjing

Human thermal adaptation is widely recognized to achieve building energy saving. However, the energy-saving potential of traditional dwellings based on adaptive thermal comfort of residents in cooling and heating periods has not been fully explored. This paper takes the traditional dwellings in the Small West Lake area in Nanjing, China as an example, and explores the thermal comfort of local residents. Then, based on the annual thermal neutral temperature of local residents, a dynamic control strategy of temperature setting points throughout the cooling and heating periods was proposed, and compared with the traditional constant indoor condition from the perspective of heat transfer. The results show that the proposed dynamic controlling method can reduce the energy consumption for maintaining heating or cooling by 26.87%–36.51% in the whole year under the climatic environment of Nanjing, China. The average thermal neutral temperatures are 27.63 °C in summer and 14.44 °C in winter. The thermal sensitivity of residents in traditional Chinese dwellings in winter is lower than that in summer. This study shows the applicability of the adaptive thermal comfort model to traditional Chinese dwellings and a relaxation in the presence of strict set-point temperatures. It is recommended to consider the adaptive thermal comfort of residents into the design of air conditioning or heating systems, which can achieve great energy-saving effect.

A new adaptive thermal comfort model for the Romanian climate

Adaptive thermal comfort refers to the ability that the occupants of a building have to accustom themselves to specific thermal conditions. The notion of human thermal comfort (HTC) is therefore introduced and defined by a simple mathematical equation. In the evaluation process of actual buildings and in the design of new ones, adaptive HTC equations translate into a substantial reduction in energy consumption and maintenance costs to the buildings. Specialised databases provide adaptive HTC equations that are regarded as standard over large geographical areas. However, in particular climate regions, new adaptive HTC equations have to be established. This paper aims to find an HTC equation specific to the Romanian climate (Köppen climate type D – temperate continental climate). In order to achieve that, a field survey was conducted between 2013 and 2014 in several naturally ventilated buildings (two university buildings from Bucharest, a passive office building and a residential house). The input data consist of questionnaire surveys as well as measurements of comfort parameters.

Development of an adaptive thermal comfort model for energy-saving building design in Japan

In order to quantify the seasonal differences in the comfort temperature and to develop a domestic adaptive model for highly insulated Japanese dwellings, thermal measurements and a thermal comfort survey were conducted. We collected 19,081 thermal comfort votes from 94 residents of 69 flats. The results suggest that the residents are highly satisfied with the thermal environment of their dwellings. People are highly adapted to the thermal condition of the dwellings, and the comfort temperature has seasonal variation. An adaptive model for these dwellings was derived from the data, to relate the indoor comfort temperature to the prevailing outdoor temperature. Perhaps because of the high insulation of the condominiums, the seasonal differences of comfort temperature and the regression coefficient of the adaptive model are smaller than those of detached houses. Adaptive building design and adaptive thermal comfort of people are important for energy-saving building design.

Adaptive Thermal Comfort Model in Naturally Ventilated Buildings

An investigation was carried out in naturally ventilated buildings in Zunyi, China, which was located in HSCW climate zone, covering the period of wintertime, from November, 2018 to January, 2019 and yielded 1177 datasets in total. Base on the gathered data, the adaptive thermal comfort model using Griffith’s method taking into account running mean outdoor temperature was developed. 55.9% of data points representing proposed comfort temperatures were not within comfort zones specified in ASHRAE 55 standard and CEN 15251. The proposed adaptive comfort model provides guides on building simulation with more accuracy and indoor thermal environment optimization in this area.

A field study of adaptive thermal comfort in primary and secondary school classrooms during winter season in Northwest China

Current thermal comfort evaluation models are based on the average level of an entire society, which is difficult to use as a direct guide for the design of classroom thermal environments in primary and secondary schools. Research was made on a group of pupils during winter in rural areas in Northwest China to analyze their thermal comfort level and regulation of their thermal adaptability under controlled and uncontrolled environments. Using questionnaire surveys and field measurements, 781 sets of valid data in controlled conditions and 345 sets in uncontrolled conditions were collected. Along with the measured air temperature, relative humidity, air velocity, globe temperature, and clothing level, a significant difference was observed between the thermal sensation vote and predicted mean vote. The preferred temperature and comfortable temperature range were obtained by analyzing the actual percentage of dissatisfied pupils and their thermal expectations. The result subsequently indicated that the comfortable temperature ranges for 90% of the pupils was 13.0–18.0 °C. The upper limit of comfortable temperature was 3.0 °C lower than the lower limit of the current recommended international standard in winter, and the clothing insulation was approximately 0.5 clo higher than the recommended value. By considering the influence of outdoor climate on the behavioral habits, psychological expectations, and physiological regulation, an adaptive thermal comfort model for primary and secondary school students in cold environments is proposed. The findings can serve as a guideline for the design and evaluation of heating systems in primary and secondary schools in rural areas.

Thermal comfort study in prefab construction site office in subtropical China

In urbanization, prefab buildings for office use are extensively applied on construction sites due to its convenience and flexibility. In order to study the adaptive thermal comfort in prefab construction site offices (PCSO),combined thermal parameter measurement and questionnaire survey were conducted on selected construction sites in Guangzhou during summer and winter seasons. 1179 valid questionnaires were collected. The relationship between Predicted Mean Vote (PMV) and the thermal sensation was studied; thermal comfort zones and preferred temperatures in summer and winter seasons were identified. The results show that the indoor thermal environment of the PCSOs was always unacceptable for occupants in summer. However, the percentage of acceptability is much higher in winter. The comfort temperatures in summer and winter are 26.2 °C and 21.1 °C, respectively. In summer, the upper limit of the acceptable temperature is 29.3 °C, and the comfortable temperature range is from 25.0 °C to 28.2 °C, which is different from the thermal comfort zone of ASHRAE–55. An adaptive thermal comfort model for PCSO is established, which is beneficial for reliably evaluating the indoor thermal comfort of PCSO in Guangzhou and other locations with similar environmental conditions.

Adaptive thermal comfort models for homes for older people in Shanghai, China

This research focused on adaptive thermal comfort in homes for older people in the hot summer and cold winter climate zone of China. A field study was conducted throughout the four seasons beginning in January 2014 and ending in April 2017 in Shanghai, China. The survey included simultaneous measurements of outdoor and indoor environmental parameters and an assessment of the participants’ sensations using questionnaires. A total of 19 homes for older people and 64 buildings were surveyed; 1040 measured data points and subjective questionnaires were obtained. The sensation ratings were analyzed, and thermal comfort temperature was calculated using regression methods. Results showed that thermal comfort assessments of older people in Shanghai should use –0.2 < TSV < +0.2 as the standard, yielding acceptable temperature ranges for older people of 14.1–19.4 ℃ in winter, 23.8–27.0 ℃ in summer, and 20.6–31.7 ℃ in mid-season. Adaptive thermal comfort models in different seasons showed that, first, the predictions of the winter and summer models were both reliable. Second, the thermal adaptive models of the mid-season intersected with the ASHRAE 55 model at 20.5 ℃ and was within the applicable range of the mid-season model (10–20.8 ℃); under the same outdoor temperature conditions, the neutral temperatures predicted by the EN15251 model and the ASHRAE 55 model were higher than the predicted values of the mid-season thermal adaptive model. Third, the slopes of both the winter and summer thermal adaptive models were slightly lower than those of the GB/T50785-2012 model. These results can be used to assess indoor thermal comfort in homes for older people and help create age-friendly building environments in China.

Analysis of Energy Consumption in Different European Cities: The Adaptive Comfort Control Implemented Model (ACCIM) Considering Representative Concentration Pathways (RCP) Scenarios

Reports of Intergovernmental Panel on Climate Change have set various greenhouse gas emissions scenarios, through which the evolution of the temperature of the planet can be estimated throughout the 21st century. The reduction of the emissions from the different activities carried out by mankind is crucial to mitigate greenhouse gas emissions. One of the most significant activities is users’ behaviour within buildings, particularly the use of Heating, Ventilation and Air-Conditioning systems. Modifying users’ behaviour patterns to guarantee acceptable thermal conditions inside buildings could lead to considerable energy saving percentages, and adaptive thermal comfort models could be an opportunity to achieve important savings. For this reason, this study analyzes the potential to apply adaptive thermal comfort models to use artificial air-conditioning systems by modifying setpoint temperatures. The analysis was conducted in five major European cities (Barcelona, Berlin, Bern, Rome, and Vienna) and in five climate change scenarios in the year 2050. The results showed that, in general, the energy saving achieved by adaptive strategies was larger in the cities with a greater cooling demand. Also, in both Representative Concentration Pathways (RCP) of the Fifth Assessment Report (AR5) considered, the energy saving were decreased in the cities of Barcelona and Rome, with values lower than those of the Fourth Assessment Report (AR4) scenarios considered, whereas in the cities of Berlin, Bern, and Vienna, the saving in the RCP scenarios is greater than those in the other scenarios.