Thermal Comfort Research Articles

Application of supervised and unsupervised learning for enhancing energy efficiency and thermal comfort in air conditioning scheduling under uncertain and dynamic environments

Air conditioning (AC) plays a major role in building energy management because it generally requires a large amount of energy to maintain indoor thermal comfort. The main objective of this study is to develop a novel method for scheduling AC operations to minimize energy costs and ensure the thermal comfort of occupants under uncertainty. The key challenge is the uncertainty and variability in time-series data and their serial dependence in determining AC operation. To address this challenge, we propose an optimization-informed learning approach that integrates unsupervised and supervised learning techniques with a stochastic optimization model. This method derives energy-efficient and thermal comfort-aware AC operation schedules through a comprehensive interpretation of uncertainties and variabilities in time-series data. Numerical experimental results demonstrate that the proposed approach can reduce energy costs by up to 15.6% and decrease thermal comfort violations by up to 63.6% compared to the Deep Q-learning method, while also reducing energy costs by 1.8% and decreasing thermal comfort violations by 37.5% compared to the forecast data-driven AC scheduling method.

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.

Optimizing active chilled beam systems in the South Korean Climate: Comparative analysis of cooling energy and thermal comfort by set-point temperature

In this study, the feasibility of implementing the active chilled beam system (ACBS) in South Korea has been analyzed, and an appropriate control strategy has been proposed. While ACBS is increasingly adopted in North America and Europe, its spread in South Korea has been slow due to different climatic characteristics and a lack of diverse understanding and analysis. Furthermore, research discussing the effects of key system parameters on ACBS is notably scarce. Therefore, this study aims to assess the impact of air handling unit discharge air temperature (AHU DAT) and ACBS entering chilled water temperature (ACBS ECWT) on ACBS and propose a control strategy suitable for the South Korean climate. The applicability of ACBS, compared with existing HVAC systems using this control strategy, has been evaluated. The study incorporates two methodologies: firstly, the impact of control variables has been assessed, and a suitable control strategy has been proposed through a sensitivity analysis of these variables. Secondly, the feasibility of applying ACBS, in comparison with conventional HVAC systems, has been evaluated from the perspectives of energy and thermal comfort. It has been found that system parameters, tailored for the South Korean climate, can maintain a level of thermal comfort like existing HVAC systems while achieving up to 18% in energy savings. Overall, this research not only demonstrates the potential applicability of ACBS in hot and humid climates like South Korea but also emphasizes the need for controlling key system parameters

Research on indoor thermal comfort of traditional dwellings in Northeast Sichuan based on the thermal comfort evaluation model and EnergyPlus

Northeast Sichuan is in the hot summer and cold winter area (HSCW), making its traditional dwellings highly valuable for study. Due to the lack of an appropriate indoor thermal comfort evaluation model, this study developed a suitable model by combining field measurement, questionnaire, and dynamic simulation. The study also investigated the indoor thermal environment of traditional dwellings in the area. The results indicate that in summer, the average indoor air temperature in the bedroom is 25.3°C, and for 81.4% of the summer period, the bedroom operative temperature (top) is below the highest acceptable top of 29.2°C. In contrast, in winter, the average indoor air temperatures in both the bedroom and the hall are below 9.0°C, with only 9.6% of the winter period having bedroom top exceeding the minimum acceptable top of 12.2°C. These findings suggest that there is significant room for improvement in the winter indoor thermal environment. Additionally, the summer neutral top for occupants is 27.0°C, which is higher than the predicted value of 25.4°C, while the winter neutral top is 14.2°C, which is lower than the predicted value of 19.3°C. This indicates that both the traditional dwellings and their occupants have adapted to the local climate to some extent. This study aims to provide a theoretical framework and research basis for optimizing the indoor thermal environment of traditional dwellings in this area.

Analysis of Urban Forest Distribution in Makassar City and its Effects on Microclimate Conditions and Thermal Comfort in the Surrounding Area

Analysis of Urban Forest Distribution in Makassar City and its Effects on Microclimate Conditions and Thermal Comfort in the Surrounding Area

Optimization design of layout dimension for residential buildings weighing up daylighting, thermal comfort, and indoor air quality with a low-carbon decision-making

Optimization design of layout dimension for residential buildings weighing up daylighting, thermal comfort, and indoor air quality with a low-carbon decision-making

Limits of a single surrogate model development methodology to represent housing stocks

Surrogate models for predicting housing stock thermal comfort, and operational cost, energy or emissions have increasingly gained popularity due to the potential to identify solutions to accelerate and optimise construction. In addition to the potential opportunity to progress towards climate goals and increase resource efficiencies by identifying areas of interest, they are much less time consuming than brute-force simulations of millions of scenarios. Although they are popular due to their promise, analysis of scalability limits for surrogate model development methodologies have been left out. Without this analysis, assurance that these may be used over differing housing stock scales cannot be provided. This work uses black-box model interpretation as well as common predictive performance metrics to assess the scalability of the development methodology presented.The novelty of this work stems from its comparison of the performance of a development methodology through training a learning algorithm with a progressively varied dataset to illustrate its scalability. This validates the use of a single surrogate model to represent numerous bottom-up archetypes used to represent a housing stock.

Energy and exergy analysis and performance optimization of buildings integrated with transpired solar collectors and phase change materials

Transpired solar collectors (TSCs) are one of the cost-effective air heating technologies that can be easily installed on building facades to provide heated fresh air to condition indoor space. The economics of TSCs can be further enhanced by integrating with phase change materials (PCMs). This study presents the performance investigation and optimization of a building-integrated TSC and PCM system (TSC-PCM). The interactions between PCM thermal properties, their locations in the building envelope, and TSC design parameters were investigated. Based on the modeling of the TSC-PCM by using energy balance and enhanced enthalpy method, a series of orthogonal tests, which varied PCM type, thickness, and location within building envelopes, and TSC suction flow rate were conducted. Multivariate testing, through the Taguchi method, was then applied to identify the optimal design combination. The results showed that the suction flow rate of the TSC-PCM on the external wall showed the highest influence on enhancing indoor thermal performance (up to 77.6%), followed by PCM location on the external wall (up to 9.2%). The optimized TSC-PCM system improved the thermal comfort increase index (TCI) to 3.7 and achieved a maximum thermal efficiency of 401.8%, with an exergy improvement of 26.9% in comparison with the use of the TSC-only. The optimized TSC-PCM system increased the average indoor room temperature to 18.8 oC, which was 6.8% and 18.2% higher than the use of the TSC-only and a baseline without using PCM and TSC, respectively.

Optimization of building thermal environment in industrial heritage landscape regeneration design simulation based on image visual visualization

With the increasing attention paid to the regeneration design of industrial heritage landscape, how to effectively improve the thermal energy environment in these areas has become a research hotspot. The thermal efficiency of buildings not only affects the energy consumption, but also relates to the comfort of users and the sustainable development of the region. This study aims to explore the optimization method of building thermal energy environment based on image visual visualization, so as to achieve efficient regeneration of industrial heritage landscape, and improve the thermal energy performance and environmental adaptability of buildings through scientific design and simulation means. Through the use of computer aided design (CAD) and building information modeling (BIM) techniques, combined with heat flow simulation and visual image analysis, a detailed thermal environment assessment is carried out for selected industrial heritage buildings. Through data collection and analysis, we take into account factors such as sunlight, ventilation and heat loss in the building to develop an optimization plan. The simulation results show that the energy consumption of buildings with optimized thermal environment design is significantly reduced and the indoor thermal comfort is greatly improved. Visual tools effectively help the design team identify problem areas and provide intuitive data support for all parties during the design process. The optimization method of building thermal energy environment based on image visual visualization provides a new idea for the regeneration design of industrial heritage landscape, which helps to realize the dual goals of protecting the historical value and meeting the needs of modern environmental protection.

Avaliação da resiliência térmica de edificações em sobreaquecimento nos cenários presente e de alterações climáticas

Abstract Thermal resilience refers to a building’s capacity to adapt to extreme thermal variations, maintaining a healthy environment for its occupants. This study aims to assess the thermal resilience of a naturally ventilated low-income residential building in overheating conditions within a region of savannah tropical climate. Various indices, including adaptive thermal comfort, Indoor Overheating Degree (IOD) and Exceedance Hours (HE), Heat Index (HI), and Standard Effective Temperature (SET) were calculated in current and climate change scenarios using two models, a standard building (HISp) and a building that incorporates passive bioclimatic strategies (HISe).It was demonstrated that thermal insulation and low absorption strategies significantly contribute to indoor environmental quality, reducing the risk of overheating exposure in all evaluated scenarios. Despite reducing discomfort hours and critical thermal stress levels, the idealized strategies do not provide adequate habitability conditions for the occupants. Overheating will become even more severe in projected future scenarios. Among the two dwellings, HISe demonstrates a superior potential to mitigate the risk of overheating compared to HISp in all the scenarios evaluated.

Mitigating urban heat island effects using trees in planters with varied crown shapes

Urban downtown areas are often overheated and contribute to the creation of urban heat island (UHI) phenomenon. Implementation of trees is considered an effective way to mitigate UHI and improve outdoor thermal comfort (OTC) in densely built-up areas.This study aims to investigate the potential of applying additional trees in planters to mitigate UHI effects and improve OTC in open urban areas. Simulation of OTC is performed for hot summer days using Universal Thermal Climate Index (UTCI). In this study, we have devised a method to determine favourable locations for a predetermined number of additional trees, with different crown shapes (cylinder, sphere and cone), to improve OTC conditions. In the proposed method, an evolutionary algorithm based on natural selection was used as it is effective for solving problems that have a large number of combinations. The method considers the geometry of the built environment, the geometry, locations and number of additional trees, weather data and UTCI simulation.The method was applied to three different urban morphologies located in the downtown of Novi Sad, Serbia. The results show that, depending on urban geometries and morphologies, different crown shapes lead to different UTCI reduction. Cylinder-shaped and sphere-shaped tree crowns showed to be the most effective in reducing heat stress. The positioning of additional trees reduced the UTCI values at single manikin locations by up to 6.11 °C, indicating that the process of determining their locations is crucial for mitigating the heat and improving OTC conditions during hot summer days.

Optimizing Trombe Wall performances: The impact of L-shaped fins on solar heating efficiency and building thermal comfort

Optimizing Trombe Wall performances: The impact of L-shaped fins on solar heating efficiency and building thermal comfort

Evaluating common supply air temperature setpoint reset strategies with varying occupancy patterns and behaviours

The supply air temperature (SAT) setpoint of a multi-zone variable air volume (VAV) air handling unit (AHU) systems significantly affects the system’s performance. ASHRAE Guideline 36 introduces a so-called trim and respond logic defining the SAT reset behaviour of these systems. The trim and respond logic for SAT reset relies on demand-based feedback. Many studies have assessed ASHRAE Guideline 36, however there is a literature gap in addressing the performance of the trim and respond SAT reset with varying occupancy patterns and behaviours. This paper studies four SAT reset strategies under different thermal preferences and irregular occupancy patterns: (1) constant 13°C SAT, (2) SAT reset based on outdoor air temperature (OAT), (3) trim and respond, and (4) trim and respond combined with OAT reset. Different cases of zone-level setpoints and irregular occupancy schedules have been simulated in EnergyPlus with the studied SAT setpoint reset methods. The results show that varying setpoints across different zones lead to higher energy use with all studied SAT reset strategies. The highest variation in energy use was accompanied with constant SAT, with a standard deviation of 16 kWh/m2, and the highest variation in averaged discomfort fraction was accompanied with OAT reset, with a standard deviation of 5.3%. Both trim and respond methods achieved better comfort results with varying setpoints. These findings establish a basis for future work on developing a SAT reset strategy that utilizes occupant-centric control (OCC) that optimally balances thermal comfort and energy use.

Field Experiment on Transient Thermal Comfort in a Chinese Railway Station – High Temperature Exposures

Thermal alliesthesia describes the phenomenon where the perception of a given environmental thermal stimulus can be either pleasant or unpleasant, depending on the individual's internal thermal state relative to homeostasis. Quantifying the thermal alliesthesia effect in human thermal perception of periodic transient metabolic rates and thermal environmental exposures can potentially enhance the thermal experience of temporarily occupied built environments, such as a railway station. A field experiment was conducted in a railway station in southern China during hot and humid summer months. Sixteen college-age participants were recruited to undergo simulations of entering the railway station after having been exposed to various intensities of heat, and then sitting quietly in the station waiting hall. Thermal environmental parameters, thermal physiological parameters, and subjective perceptions of participants were registered throughout each field experiment. The results indicate that the effect of prior heat exposures on skin temperatures and subjective perceptions were extinguished within 10 minutes after participants entered the station. Step-changes from low-to-high intensity activity induced a more immediate and pronounced change in metabolic heat production, compared to the reverse scenario. A transient thermal perception model is proposed with the input parameters including the environmental temperature and metabolic rate transients, inter alia. The algorithm in the model indicates that thermal alliesthesia induced by temperature step-change within transition spaces could be negligible, whereas metabolic transients exert a more decisive influence. The study provides insight into the alliesthesia experienced in transitional spaces and guidance for designs and operations of HVAC systems.

Beyond the g-Value: A comparative study of solar control coated glass and spectrally selective glass in terms of building energy efficiency

The thermal efficiency of transparent envelopes is a key factor in building energy consumption and indoor thermal comfort, with the g-value being a critical metric for evaluating these effects. Solar control film glass and low-emissivity (Low-E) glass, recognized for their distinct advantages, are extensively used in construction. However, comprehensive research on their photothermal properties, especially regarding spectral and angular dependencies, remains limited. In this study, a meticulous field experiment was conducted under six distinct conditions during both winter and summer to examine the thermal performance between solar control coated glass (SCCG) and spectrally selective glass (SSG). The results show that, despite having similar heat transfer and solar heat gain coefficients, their indoor peak temperatures can differ by 1.2 °C to 5.6 °C under typical sunny conditions, and variations in cooling and heating energy consumption range from 6.9 % to 14.4 %. Further analysis reveals that the standard g-value overestimates the solar heat gain of SSG by approximately 10 %, with significant discrepancies in the direct transmission heat and secondary heat transfer of 17.8 % and 37.4 %, respectively. In contrast, the standard g-value is more suitable for SCCG, with a measured g-value that is only 1.2 % higher than the standard g-value. The spectral and angular dependencies of both glasses were also compared in this study, and SSG was found to have a strong spectral dependence and a higher angular dependence than SCCG. These findings indicate that SCCG is more beneficial for energy conservation in cold climates when the thermal parameters are identical. Moreover, the research underscores the limitations of current standards and calculation methods for evaluating solar heat gain in transparent envelopes, particularly for glasses with spectral selectivity.

Thermal Comfort–Based Differential Pricing for High-Rise Apartments in Hot and Humid Climates: A Multicriteria Decision-Making Approach

Thermal Comfort–Based Differential Pricing for High-Rise Apartments in Hot and Humid Climates: A Multicriteria Decision-Making Approach

Improving thermal comfort using personalized local conditioning: A large-scale retrospective questionnaire survey conducted during a heatwave in China

Improving thermal comfort using personalized local conditioning: A large-scale retrospective questionnaire survey conducted during a heatwave in China

Development of a tailored questionnaire instrument to evaluate thermal sensation of elderly people in India

Purpose India’s growing elderly population necessitates ensuring indoor thermal comfort because of their vulnerability to temperature-related illnesses and reduced capacity to regulate body temperature. Currently, thermal sensation (TS) assessment scales, designed for those between 20 and 60 years of age, may not accurately capture the preferences of elderly adults. To address the gap, this study aims to identify appropriate scaling methods to help the elderly understand the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE-55) seven-point TS scale clearly. Design/methodology/approach Four scaling methods – color, emoji, landscape images and regional images scales – identified from literature were analyzed using quantitative approaches. The differences between two age groups (<60 years and = 60 years) were examined using frequency distribution differences and independent sample t-test methods. Findings Results indicated that both younger/middle-aged (<60 years) and elderly individuals (= 60 years) were adept at identifying color and regional images scale, while emoji and landscape images scale posed challenges for the elderly. Furthermore, a tailored questionnaire instrument was developed to enhance the comprehension of TS questions for the elderly. One sample t-test results indicated that the proposed questionnaire instrument is a better fit to support ASHRAE-55 seven-point TS scale, making it particularly effective for the elderly population. Originality/value This research presents a novel, tailored questionnaire instrument that significantly enhances the elderly population’s comprehension of TS questions, thereby improving the accuracy of thermal comfort assessments and contributing to the creation of better indoor thermal environments for the elderly people.

An analysis of outdoor thermal comfort impact on pedestrian walking patterns at sub-hour timescales with agent-based modelling

PurposeThis study aims to analyse the impact of outdoor climate, building configuration and locations of public amenities on pedestrians’ walking behaviour and their outdoor thermal comfort. As outdoor climate can rapidly change within minutes, this study maintains that outdoor thermal comfort should be analysed at the pedestrian scale and within a short period to understand people’s walking behaviour and how it may affect urban activities.Design/methodology/approachThis research analyses the thermal stresses experienced by pedestrians and their walking patterns within a sub-hour timeframe in Darling Square, Sydney. The simulation incorporates multiple outdoor climate analyses with agent-based modelling (ABM) simulation; it runs on a parametric modelling platform to predict walking patterns according to the agents’ innate properties, goals and environmental constraints as the weather fluctuates.FindingsThis study demonstrates that mapping outdoor thermal comfort within a shorter timescale could reveal emergent walking patterns that inform pedestrians’ preferences of their surrounding environment and their walking behaviour.Practical implicationsThe findings could inform planners and stakeholders on how outdoor climate and building configuration affect pedestrian walking patterns for improving outdoor space quality during the design process or post-occupancy evaluation.Originality/valueThis study integrates ABM that incorporates multiple agents’ goals and innate properties and a micro-climate analysis on diverse context geometries under sub-hour periods, compatible with the pedestrian walking speed and distances at the neighbourhood scale.

A comparison of heating and cooling systems having radiant and ventilation systems regarding thermal comfort

A comparison of heating and cooling systems having radiant and ventilation systems regarding thermal comfort