Adaptive Comfort Model Research Articles

Urban heat islands’ effects on the thermo-energy performance of buildings according to their socio-economic factors

Urban areas experience the urban heat island (UHI) effect, which affects the thermal comfort and energy consumption of buildings. These consequences could vary depending on the socio-economic status of the neighbourhoods. Few studies have investigated how UHI affects socio-economically contrasting districts in thermal comfort and energy performance. Therefore, the primary goal of this research is to evaluate and compare the energy efficiency and thermal comfort conditions of residential buildings in the same city (Temuco, Chile) but located in socio-economically contrasting neighbourhoods. Urban weather files were first modelled in four urban zones using UWG software. Also, EnergyPlus building simulations were conducted to evaluate discomfort hours in adaptive comfort models and energy performance. The results showed annual average UHI intensities between 1.5 and 2.5 K. Urban–rural cooling energy load differences ranged between 12.47% and 38.92%, while heating energy load differences ranged between -20.47% and -81.95%. These distinctions depended on the urban zone, residence model analysed, or energy building standard applied. Similarly, urban-rural differences in thermal comfort times varied from 0.5% to 100%. Results illustrate that the risk of overheating could increase in socio-economically vulnerable areas. This issue could worsen if urban segregation continues to generate poor urban design in low-income districts.

Using setpoint temperatures based on adaptive thermal comfort models: The case of an Australian model considering climate change

It has recently become clear that using adaptive thermal comfort models to determine setpoint temperatures is a successful energy-saving method. Global models like ASHRAE 55 and EN16798-1 have been used in recent experiments using adaptive setpoint temperatures. This work, however, has taken a different route by concentrating on a region-specific Australian adaptive comfort model. The goal is to compare the energy implications of the use of setpoint temperatures based on the Australian local comfort model compared to the worldwide adaptive ASHRAE 55 model to highlight the significance of choosing the most fitting comfort model for making accurate predictions. All of Australia's climate zones are taken into account, as well as mixed-mode building operation scenarios, current and future scenarios, namely the years 2050 and 2100 for Representative Concentration Pathways (RCP) 2.6, 4.5, and 8.5. It has been found that the Australian-model-based adaptive setpoint temperatures taking into account mixed-mode significantly lowers energy demand when compared to the ASHRAE 55 adaptive model (average energy-saving value of 63 %). Considering climate change, the Australian model has an average energy demand of 13–26 kW h/m2·year, and an average increase of 1–13 kW h/m2·year. In the case of ASHRAE 55 model, energy demand decreases in future scenarios and average values range between 3 and 11 kW h/m2·year. Therefore, setting setpoint temperatures in accordance with the Australian regional adaptive comfort model is a very efficient method for energy conservation. These differences raise awareness on the importance of the selection of the appropriate adaptive thermal comfort model.

Thermal comfort in university classrooms in humid subtropical climate: Field study during all seasons

Ensuring students thermal comfort has complex implications involving student performance and energy consumption costs. Existing models may not be suitable for predicting the thermal comfort of university students. This study aimed to compare the thermal comfort responses of university students in air-conditioned and naturally ventilated classrooms located in a humid Brazilian subtropical climate with the analytical and adaptive models. The study was conducted in 28 classrooms of two universities located in a humid subtropical climate in southern Brazil. Environmental variables were measured using a microclimatic station, while personal variables were obtained through student responses in electronic questionnaires between September 2022 and July 2023. In classrooms operating with natural ventilation, the mean thermal neutrality temperatures were 19.8 °C and 21.4 °C in Joinville and São José, respectively. When operating with air-conditioning, the mean thermal neutrality temperatures were 21.8 °C and 22.1 °C in Joinville and São José, respectively. Even when they answered “neutral” on the thermal sensation questionnaire, students reported that they preferred the cooler environment. Classroom occupant densities less than 1.00 did not influence the students’ thermal sensation. In general, the PMV/PPD model was not able to predict the thermal comfort of university students. The adaptive comfort model proved adequate to predict the thermal comfort of students when classrooms were naturally ventilated.

Adaptive Comfort Potential in Different Climate Zones of Ecuador Considering Global Warming

Ecuador is a country with several climate zones. However, their behaviour is similar throughout the year, with no peaks of extreme temperatures in the various seasons. This paper is a first approach to study the adaptive comfort behaviour in several areas and populations of the country. Considering the ASHRAE 55-2020 model, energy simulation programmes are applied not just to the current climate scenario but also to the climate change scenarios of 2050 and 2100. The results of locations are analysed and compared to determine their performance. Thanks to their climate characteristics, adaptive comfort models could be applied as a passive strategy, using natural ventilation for building indoor comfort improvement, particularly social dwellings. According to previous studies, some prototypes have not considered the climate determinants in each region. Given the geographic situation of the study areas, the adaptive comfort model could be applied in all cases. Percentages of application of natural ventilation and heating and cooling degree hours have similar behaviours according to the climatic region, with a variation greater than 30% among them.

Development of ReShadS, a climate-responsive shading system: Conception, design, fabrication, and small-scale testing

Integrating computational technologies to produce dynamic and intelligent architecture that can enhance building thermal performance and meet users' requirements and routines is broadly classified as responsive architecture. This seems to be a viable solution for façades, reducing energy demand during the building operational phase. However, scientific content regarding responsive components' fabrication, operation, and performance evaluation is not yet consolidated. This paper comprehensively presents the design and fabrication processes of a low-cost responsive shading system prototype, accounting for materials' characterization, software, responsive functionality, and its performance evaluation regarding thermal and illuminance management. The analysis is based on the Adaptive Comfort Model and Useful Daylight Illuminance parameters. Preliminary results indicate the system's feasibility in managing temperature and illuminance within the comfort zone by 58 % and 82 % of data points, respectively. The resulting prototype and the responsive management strategy contribute to the emerging responsive architecture field toward reducing building energy consumption.

Optimization control strategy for mixed-mode buildings based on thermal comfort model: A case study of office buildings

Mixed-mode (MM) buildings reduce air conditioning (AC) energy consumption while maintaining indoor thermal comfort through the appropriate use of natural ventilation (NV). The objective of this investigation was to propose a method to determine the best NV operation range suitable for MM buildings and further to propose a change-over control strategy. First, the usual natural ventilation operating range (NV-range) was obtained based on the upper and lower comfort temperature limits of the adaptive comfort model. The usual NV-range was extended by adding threshold conditions, and then, it was divided into nine natural ventilation operation subranges (NVOSs). Second, the comfort and energy performance of each NVOS were analyzed through a co-simulation for an MM office building in Xi'an, China, as an example to obtain the optimal NV-range for the local climate. The results showed that the proposed optimal NV-range reduced the number of discomfort hours by 248.33 h while increasing the energy savings by 13.29% compared to those of the commonly used NV-ranges. Finally, the control scheme with the adaptive comfort model changed to the PMV model (ACM-PMV-CS) with the addition of a 1.5-h transition period was proposed in order to solve the problem of using the steady-state PMV model directly in the AC mode under the frequent switching conditions between the NV and AC modes. The results showed that ACM-PMV-1.5 h transition period resulted in a reduction in the number of discomfort hours (248.33 h) and a 35.46% increase in the energy savings compared to those of ACM-PMV-CS without a transition period.

Thermal comfort of students in naturally ventilated secondary schools in countryside of hot summer cold winter zone, China

People experience four seasons every year, and their thermal comfort usually changes with the season. However, a little is known about the dynamic characteristics of secondary students’ thermal comfort in the countryside under different seasons. This study aims to investigate thermal comfort of students in the countryside under various seasons and reveal the underlying mechanism. One year long-term field study was conducted in a countryside secondary school in Hengyang City, located in the hot summer and cold winter zone of China. A paper questionnaire was used to collect subjective thermal comfort. The surrounding physical environment was also measured. A total of 450 subjects voluntarily participated and returned 2349 valid datasets. The results indicated students had the lowest acceptance rate with temperature (71.9 %), humidity (74.9 %), and velocity (70 %) in summer season. Neutral temperature was 25.7 °C in summer, 19.2 °C in transition, and 14.9 °C in the winter. An inverted U relationship was found between perceived air quality and air temperature. Cold extremities (53.0 %), shivering (37.2 %), and stuffy nose (60.4 %) were prevalent in winter. Adaptive comfort model was only effective in the summer in naturally ventilated secondary school buildings. Estimated learning performance was the highest in transition and lowest in summer. Behavioral adaptation was determined by the relationship between air velocity clothing insulation and operative temperature. The findings of this study provide fundamental knowledge of thermal environment, subjective comfort, and health status in naturally ventilated educational buildings in countryside area. Engineers and designers can use professional comfort indicators to guide their future construction or renovation.

Influence of outdoor temperature on thermal adaptation: Annual neutral temperature and thermal sensitivity

Building evaluation and guidance for naturally ventilated buildings rely on adaptive comfort models and standards. This study aims to establish an analytical and predictive thermal sensation and adaptation method. The proposed approach is based on the Griffiths method, which reveals a sinusoidal pattern in the neutral temperature and Griffiths coefficient throughout the year. Calculating the daily neutral temperature and evaluating thermal sensitivity through the Griffiths method highlight the delayed response of neutral temperature to outdoor temperature. With the input of operative and outdoor temperature, the Griffiths method predicts adaptive thermal sensation better than the PMV model. The regular fluctuations of neutral temperatures and Griffiths coefficients provide new research ideas and references for designing naturally ventilated buildings. Further research works are still required to check the method’s applicability in the presence of various climate characteristics.

Data-driven research into the inaccuracy of traditional models of thermal comfort in offices

The accurate prediction of thermal sensation among office workers, at design and post-occupancy stages, is crucial for controlling indoor temperature efficiently and correcting deficiencies in workspaces, ensuring healthy and productive working conditions. Traditional analytical comfort models are still the best tool for this purpose given their potential for interpretation. However, their reliability is undermined by their poor accuracy. Based on 304 data series of point-in-time measurements of quantitative and qualitative comfort-related parameters collected in an experimental campaign in three office buildings, one air-conditioned and two in free evolution, in San Luis Potosí (Mexico), this work aims to identify the major error-causing factors of steady and adaptive comfort models. The divergences between predicted and reported thermal sensation were set as a dependant variable of two multiple regressions, one for each model. Eighteen independent demographic, environmental, contextual and subjective variables were considered. No multicollinearity problems were identified. Our findings show that contextual factors and humidity perception were relevant in the adaptive model error. Clothing insulation highly impacted the accuracy of both models while age and body mass were not statistically significant for either of them. Metabolic rate was the factor with the greatest influence in the error of the steady model. Although not covered, other influential factors played a key role in models’ accuracy and further research is needed to integrate these in a new generation of more accurate and flexible analytical models.

Assessing the energy saving potential of using adaptive setpoint temperatures: The case study of a regional adaptive comfort model for Brazil in both the present and the future

Assessing the energy saving potential of using adaptive setpoint temperatures: The case study of a regional adaptive comfort model for Brazil in both the present and the future

Impact of different thermal zone data simplification for model calibration on monitored-simulated performance gaps

The paper analyses the impact of different simplification approaches for model verification purposes considering a reference demo case of a municipality school located in Torre Pellice (Italy), which has been monitored with room detail since April 2021. The target variable of the calibration process is the indoor air temperature: firstly, results validity is checked on an unoccupied free-running period; secondly, occupied standard behaviours and adapted to real-use ones are adopted to test the simplification choices impact on indoor thermal comfort indicators (e.g. the Adaptive Comfort Model). Several model simplification actions on both building-level construction and zoning approaches are considered. Results of this demo case demonstrate the usability of simplified models, which can be adopted instead of more detailed and time-consuming full models for performance gap detections and other analyses.

Adaptive thermal comfort in the offices of three climates of North-East India

Buildings not only provide shelter to the occupants but also security, safety and comfort, as well as signifying economic and socio-cultural status. The high energy intensity of buildings has become a matter of concern worldwide in the context of climate change and global warming. Adaptive comfort principles and guidelines afford greater design opportunities for reduced energy intensity without compromising occupant thermal comfort and indoor environmental quality performance. However, thermal adaptation opportunities of office occupants in the North-Eastern part of India are rarely addressed by previous thermal comfort studies conducted in the Indian subcontinent. A yearlong questionnaire-based adaptive thermal comfort study with concurrent indoor environmental measurements was conducted in naturally ventilated office buildings located in three locations, i.e., Tezpur, Imphal and Shillong, representing the climatic zones of North-East India. A total of 2326 valid questionnaire responses were collected. ASHRAE Class-II field study protocols, seven-point thermal sensation and five-point preference scales were used to collect objective and subjective comfort assessments. It was found that the clothing insulation (clo) levels worn by occupants varied non-linearly with indoor temperatures. The estimated preferred temperatures for building occupants in Tezpur, Imphal and Shillong were 24 °C, 23.5 °C and 22 °C, respectively. Probit analysis of thermal sensation data indicated that the indoor temperature stimulus associated with a shift of one thermal sensation unit differed between the warm and cool side of the 7-point thermal sensation scale. Increasing indoor air velocity up to 0.8m/s shifted the upper threshold of discomfort to 32 °C. It was also found that 80% of office occupants were comfortable within the temperature range of 25 °C–30 °C. The adaptive comfort model derived from the current database shows lower sensitivity of subjects to outdoor temperature changes compared to existing International standards like ASHRAE Standard 55 or EN16798. The present study demonstrates the potential for low-energy, naturally ventilated office design strategies in similar climatic conditions in North-East India and other parts of the world. Above all, it enriches the worldwide thermal comfort database.

Multi-Performance Characterization of a Modular Wooden House

Although not a new concept, modular construction has been the target of increasing interest and investment in recent years. Modular wood construction systems have economic and environmental advantages, as wood is a natural and locally available raw material with interesting thermal properties. In this context, the BlueWoodenHouse Project, a closed cooperation project between academy and industry, aims to improve the actual knowledge of modular wood construction in Portugal. Among other objectives, the project aims to characterize the solutions, systems, and materials used in wooden modular construction, specifically in a modular wooden, single-family house in full use. Afterward, the house was monitored for 1 year (temperature, relative humidity, and CO2) and the data collected were analyzed and the interior thermal comfort was evaluated. The results of CO2 concentration monitoring indicate adequate air renewal rates, except for some periods in the bedroom, during the night. Additionally, application of the adaptive comfort model proposed by the EN 16798-2 standard resulted in a percentage of time in discomfort due to overcooling ranging between 31.3% and 38.6%. However, most of these periods may correspond to times when there is no occupancy of these spaces.

Low-energy resilient cooling through geothermal heat dissipation and latent heat storage

Conventional passive cooling techniques provide limited benefits in extremely hot climates in southern Asia, characterised by high daytime and night temperatures and frequent climate-related disruptions, such as power cuts. This study proposes and demonstrates a novel low-energy and resilient cooling solution for extremely hot regions in southern Asia. The novelty lies in the combination of geothermal heat dissipation and latent heat storage, specifically designed for the particular conditions of extremely hot climates in Southern Asia; considering the influence of climate-related disruptions such as power cuts, whose frequency is increasing in the region; and using discomfort hours as an indicator to measure the passive survivability of buildings in the absence of air-conditioning (following the adaptive comfort model). A numerical model was developed in TRNSYS for optimal sizing and configuration of the phase change material (PCM) integrated into a ceiling panel using a typical multi-family building archetype in three climatic regions of Pakistan. A parametric numerical analysis was performed concerning different PCM melting temperatures, amount of PCM, convective heat transfer capacity, and equivalent thermal conductivity. Moreover, daytime was considered the period with a higher probability of power cuts. The results showed how integrating PCM-based ceiling panels with geothermal heat dissipation can mitigate discomfort hours by 28 % in extremely hot climates, 55 % in very hot climates, and 91 % in hot climate areas with intermittent access to electricity. Latent heat storage maximised the benefits of geothermal heat dissipation by extending thermal comfort periods by 13 % and 18 % in extremely hot and very hot climates compared to the scenario without PCM. This low-energy resilient cooling solution, integrating PCM as a cool battery, can keep the home cool for longer when electricity is unavailable. This study demonstrates the importance of considering the specific climate-related disruptions from these extremely hot regions in building design, such as extreme heat events or power cuts, to enhance the heat resilience capacity of cities.

The Ventilation Capacity of Earthen Vernacular Buildings With Timber Projections (Sachnisi) in Dense Urban Canyons – Findings From a Field Study in the Mediterranean

Vernacular architecture employs numerous elements for enhancing natural ventilation, especially in the Mediterranean climate. However, the cooling effectiveness of natural ventilation also relies on occupant behaviour and is highly determined by urban scale attributes. Still, airflow in real, inhomogeneous historic urban settings is rarely integrated in the thermal comfort studies of historic buildings. In this study, a multi-scale approach is adopted in order to assess the role of ventilation in establishing thermal comfort in earthen buildings, in real field conditions. This is achieved by addressing field monitoring of air velocity, temperature and relative humidity in: a) a dense (packing density λp=0.60) and inhomogeneous historic neighbourhood in Nicosia, Cyprus (measurement at a reference height); b) the street-canyon (measured at the mid-height of a narrow canyon with aspect ratio 2); and c) the interior of a typical adobe building with semi-open, pass-through spaces (portico) and closed timber projections with multiple openings, called sachnisi. Building ventilation was addressed as a function of in-street and rooftop airflow. Indoor thermal comfort was assessed in the case of specific ventilation patterns, comparing three adaptive comfort models. The results highlight the complexity of airflow in real inhomogeneous urban canopies and demonstrate that air velocity level in the street canyon is approximately one third of the reference free-stream wind velocity, while indoor air velocity remains at minimum levels. The study also reveals the contribution of night-time ventilation in cooling. Finally, spatial differentials of indoor environmental conditions in the portico were recorded for the first time, demonstrating the role of the sachnisi as a wind-capture element.

Adaptive thermal comfort model and active occupant behaviour in a mixed-mode apartment. A synergy to sustainability.

The adaptive comfort model was mainly developed for naturally ventilated buildings, but few recent studies explore its applicability in mixed-mode buildings. The present study uses the adaptive thermal comfort model (EN15251) in a dynamic thermal simulation (EnergyPlus) parametric analysis of a mixed-mode apartment, in an attempt to determine the energy savings. Two simulation models were created. The first one makes full use of mechanical heating and cooling systems when the required temperature is not reached. The second one adopts a hybrid approach, resembling the existing operation of residential buildings in Greece. The primary regulator of the indoor conditions is the occupant through his/her interaction with the building shell and only when this is not effective the mechanical systems are activated. The internal thermal gains in both models were determined based on the detailed recording of the real conditions in a typical apartment. Many design parameters (window size, thermal insulation position and thickness, orientation, airtightness, glazing properties and shading) along with different occupant behavioural patterns (derived from a questionnaire campaign) have been examined in sensitivity analysis. Machine learning algorithms, such as the Random Forest, were also incorporated to identify most important parameters. Results indicate that airtightness, occupant behaviour and shading are the most important parameters for primary energy consumption for cooling, while airtightness, window size and shading for the total of heating and cooling primary energy consumption.

Comparing economic benefits of HVAC control strategies in grid-interactive residential buildings

Energy consumption in buildings continues to rise with increased deployment of energy-consuming equipment such as Heating, Ventilation, and Air Conditioning (HVAC) amid a growing world economy. Renewable energy is projected to comprise a majority of the future electricity supply, but the intermittent nature of renewables means that consumption must respond to dynamic supply for optimal utilization. This paper proposes a novel HVAC control strategy for residential buildings using the adaptive comfort model, considering occupancy through probability and real-time information, and optimizing the HVAC schedule to reduce cost, maintain thermal comfort, and respond to the dynamic availability of renewable energy while being generalizable to different situations. To validate this approach, the Universal CPS Environment for Federation (UCEF) co-simulation platform is used to connect advanced building controls with the building energy simulation software EnergyPlus. Simulations are performed for a residential building in Sacramento, CA during a typical summer week. Economic impacts, energy consumption, and thermal comfort are analyzed for traditional, adaptive, and occupancy-based control strategies under demand-based, tiered, and fixed electric tariff systems. Simulation results show that occupancy consideration, adaptive thermal comfort, and optimization can reduce cost by 50.1 %, electricity consumption by 52.9 %, and discomfort by 56.2 % compared to traditional fixed setpoints. The ability of the proposed HVAC control strategy to shift energy consumption away from peak times under a demand-based tariff system is qualitatively analyzed and findings suggest that maximum load-shifting on a grid-scale is attained using occupancy consideration with optimized control and demand-based pricing. For individual residential buildings, similar economic benefits can be gained using the less-complex adaptive HVAC control strategy with existing tiered or simple electric tariff systems.

Influence of non-uniform distribution of fan-induced air on thermal comfort conditions in university classrooms in warm and humid climate, India

This study investigates how fan-induced non-uniform air movement affects thermal comfort conditions and productivity at different seats in different parts of a lecture hall. A four-month-long field study was conducted, involving 11 naturally ventilated lecture halls, 828 samples from the students, monitoring thermal environments, and measuring air movement at every seat. Thermal comfort conditions and productivity at every seat were obtained through questionnaire survey. During the study, outdoor temperature varied between 24.7 °C and 36.7 °C. From ANCOVA and cluster analysis, it was found that students seated farther from the fan experience less air velocity, resulting in a significant difference in comfort conditions and productivity. The thermal sensation of the students was found to be comparatively less in Zone-1 (Mean = 0.2, SE = 0.06) than Zone-2 (Mean = 0.53, SE = 0.05). In the zone near the fan, 8.1% of students voted hot sensation at 33°C–34 °C, whereas in the zone far from the fan, this number increased to 35.9%. The slope of the regression line plotted between thermal sensation and indoor operative temperature was found to be 0.368/°C. Regression analysis revealed that thermal comfort could be achieved up to 33.8 °C with an air velocity of 1.2 m/s. The acceptable temperature limit for 80% of students was between 23.4 °C and 29.7 °C. A narrower comfort band was observed compared to ASHRAE-55 and the Indian standard, indicating limited adaptive opportunities in lecture halls. An adaptive comfort model is proposed that includes the effect of air velocity.

Climate Change and Building Renovation: Effects on Energy Consumption and Internal Comfort in a Social Housing Building in Northern Italy

Climate change is becoming a crucial factor to consider within human activities and the building sector is particularly influenced by aspects of internal comfort and energy. In Italy, great attention has been paid to the energy refurbishment of buildings. However, such interventions are mostly focused on reducing heating energy consumption, thus neglecting summer season performance. Moreover, climate change is barely considered during the design phase. This issue is addressed in this work which analyzes some of the most common refurbishment interventions applied to a social housing building in Trieste, while also considering internal comfort during the summer season. A dynamic analysis of the building-plant system is carried out using EnergyPlus. Fanger, UTCI and the adaptive comfort models were used to represent internal health, while three TRY data sets were generated using two GCM–RCM projections to evaluate the influence of climate change. The results show that both building insulation and climatic change affect heating consumption reaching a 70% reduction. However, building insulation does not greatly affect internal comfort, although different models show different behavior to protect against external temperatures. On the contrary, climatic change influences the percentage of hours of discomfort, with a 20% increase for all of the models. The final consideration is that people’s internal health should always be considered when carrying out refurbishment activities.

A detailed view of the Adaptive-Comfort-Control-Implementation Script (ACCIS): The capabilities of the automation system for adaptive setpoint temperatures in building energy models

Recent research has looked into the potential for energy savings from adopting setpoint temperatures based on adaptive comfort. The recently suggested Adaptive-Comfort-Control-Implementation Script (ACCIS), a computational method that expands the use of air conditioning to adaptive comfort, can be used to accomplish this. The user's setup and an Input Data File (IDF) are used by ACCIS to convert PMV-based EnergyPlus models into adaptive setpoint models. The Adaptive Comfort Control Implemented Model (“accim”) Python module has been used to nest ACCIS, which was originally an Energy Management System (EMS) script. This research focuses on the creation of ACCIS and offers a more in-depth understanding of how the computational method functions based on the connections between the objects that compose it. Since all weather file quantity constraints have been overcome and studies can now be generated based on millions of simulations, ACCIS opens up new opportunities for performing energy simulations on a worldwide scale rather than only on a national or continental level. This potential is increased considering that, until recently only international models ASHRAE Standard 55 and European standard EN16798-1 were considered in ACCIS, but now a recent update allows to select local comfort models developed for specific areas. As a result, this potential is firstly demonstrated by means of the study of the 3 arguments that have the most important impact on the setpoint temperatures: the thermal comfort model, the acceptability levels and the behaviour of setpoint temperatures when adaptive comfort models are not applicable; and secondly by means of an actual example of use of accim.