Poor Thermal Comfort Research Articles

Study on winter thermal comfort of membrane structure gymnasium in severe cold region of China

Recently, membrane structures have been increasingly used in gymnasiums. However, an uneven distribution of indoor thermal environment exists in membrane-structure gymnasiums, resulting in poor thermal comfort for indoor personnel. Therefore, the indoor thermal environment of a membrane-structure gymnasium was assessed and some improvement measures are proposed herein. The adopted research method mainly comprised a combination of field tests and questionnaires, which aimed at collecting the indoor and outdoor environment parameters and the subjective vote values of different people to establish a thermal comfort model. The results of the thermal comfort model analysis showed that among the applicable population in the membrane-structure gymnasium, the sports group exhibited the highest thermal comfort, followed by the audience group, and the thermal comfort of post-exercise group was relatively poor. To ensure thermal comfort for all three studied groups, the proposed operative temperature range of the gym should be approximately between 10.07–13.34 °C. This study provides a reference for the application and operation of the membrane structures on sports buildings.

Incipient Chiller Fault Diagnosis Using an Optimized Least Squares Support Vector Machine With Gravitational Search Algorithm

Operational faults in centrifugal chillers will lead to high energy consumption, poor indoor thermal comfort, and low operational safety, and thus it is of significance to detect and diagnose the anomalies timely and effectively, especially for those at their incipient stages. The least squares support vector machine (LSSVM) has been regarded as an effective algorithm for multiclass classification. One of the most difficult issues in LSSVM is parameter tuning. Therefore, this paper reports a development of a gravitational search algorithm (GSA) optimized LSSVM method for incipient fault diagnosis in centrifugal chillers. Considering the inadequacies of conventional principle component analysis (PCA) algorithm for nonlinear data transformation, kernel principle component analysis (KPCA) was firstly employed to reduce the dimensionality of the original input data. Secondly, an optimized “one against one” multi-class LSSVM classifier was developed and its penalty constant and kernel bandwidth were tuned by GSA. Based on the fault samples of seven typical faults at their incipient stages in chillers from ASHRAE RP 1043, the proposed GSA optimized LSSVM fault diagnostic model was trained and validated. For the purpose of demonstrating the priority of the proposed fault diagnosis method, the obtained results were compared to that of using the LSSVM classifier optimized by another two algorithms, namely, the conventional cross-validation method and particle swarm optimizer. Results showed that the best fault diagnosis performance could be achieved using the proposed GSA-LSSVM classifier. The overall average fault diagnosis accuracy for the least severity faults was reported over 95%.

Indoor Environmental Quality Evaluation Strategy as an Upgrade (Renovation) Measure in a Historic Building Located in the Mediterranean Zone (Athens, Greece)

The assessment of indoor environmental quality in historic buildings converted to museums is a significant tool in deep energy renovation processes, as it provides insights for the microclimatic conditions in the interiors of the building where vast numbers of visitors walk every year and where artifacts that are vulnerable to pollution are exhibited. In this work, aiming to contribute to the development of an energy retrofitting protocol applied in the Mediterranean region (HAPPEN MedZeb protocol) for museums hosted in historic buildings by providing useful data, an experimental campaign to evaluate the indoor environmental quality of a museum housed in a historic building located in Athens took place from February 2019 to April 2021 and was divided into two periods. The findings revealed high concentrations of volatile organic compounds as well as poor thermal comfort levels since the sensors recorded low acceptable percentages of T values within the limits from 7 to 33% for the entire experimental period. Based on the findings, recommendations for retrofitting interventions are made.

Temperature Sensing Optimization for Home Thermostat Retrofit.

Most existing residential buildings adopt one single-zone thermostat to control the heating of rooms with different thermal conditions. This solution often provides poor thermal comfort and inefficient use of energy. The current market proposes smart thermostats and thermostatic radiator valves (TRVs) as cheap and relatively easy-to-install retrofit solutions. These systems provide increased freedom of installation, due to the use of wireless communication; however, the uncertainty of the measured air temperature, considering the thermostat placement, could impact the final heating performance. This paper presents a sensing optimization approach for a home thermostat, in order to determine the optimal retrofit configuration to reduce the sensing uncertainty, thus achieving the required comfort level and minimizing the retrofit’s payback period. The methodology was applied to a real case study—a dwelling located in Italy. The measured data and a simulation model were used to create different retrofit scenarios. Among these, the optimal scenario was achieved through thermostat repositioning and a setpoint of 21 °C, without the use of TRVs. Such optimization provided an improvement of control performance due to sensor location, with consequent energy savings of 7% (compared to the baseline). The resulting payback period ranged from two and a half years to less than a year, depending on impact of the embedded smart thermostat algorithms.

How Can Scientific Literature Support Decision-Making in the Renovation of Historic Buildings? An Evidence-Based Approach for Improving the Performance of Walls

Buildings of heritage significance due to their historical, architectural, or cultural value, here called historic buildings, constitute a large proportion of the building stock in many countries around the world. Improving the performance of such buildings is necessary to lower the carbon emissions of the stock, which generates around 40% of the overall emissions worldwide. In historic buildings, it is estimated that heat loss through external walls contributes significantly to the overall energy consumption, and is associated with poor thermal comfort and indoor air quality. Measures to improve the performance of walls of historic buildings require a balance between energy performance, indoor environmental quality, heritage significance, and technical compatibility. Appropriate wall measures are available, but the correct selection and implementation require an integrated process throughout assessment (planning), design, construction, and use. Despite the available knowledge, decision-makers often have limited access to robust information on tested retrofit measures, hindering the implementation of deep renovation. This paper provides an evidence-based approach on the steps required during assessment, design, and construction, and after retrofitting through a literature review. Moreover, it provides a review of possible measures for wall retrofit within the deep renovation of historic buildings, including their advantages and disadvantages and the required considerations based on context.

Building Reconstruction of Historical and Cultural Protection Area Based on Green Technology

With the continuous intensification of urban expansion, the transformation and utilization of existing building resources has gradually attracted attention from all walks of life. The Lifen building is the epitome of Wuhan's residential culture for nearly a century. After the baptism of time, the use function and structural safety of the Lifen building can no longer meet people's living needs today. Therefore, further research is needed on how to combine the protection and renovation of the Lifen building. This article takes Kunhouli, Jiang’an District, Wuhan as an example. Through field research and semi-open interviews with local residents, it is found that the current Kunhouli has poor thermal comfort, traffic congestion, outdated infrastructure, and lack of public space. And poor construction quality. According to the regional and cultural characteristics of Lifen, combined with the concept of green building and green analysis software, it is updated and transformed to promote the protection of Lifen while improving the living environment of Lifen, providing reference for the development of Wuhan Lifen's building renovation.

Dynamic performance of displacement ventilation in a lecture hall

An accurate temperature gradient calculation is essential for displacement ventilation (DV) system design since it directly relates to thecalculation of the required supply airflow rate. Inaccurate temperature prediction can cause poor thermal comfort and wrong sizing of the ventilation and cooling systems. A heat balance-based method is usually applied in displacement ventilation (DV) design when overheating is the primary indoor climate concern. The temperature gradient in DV systems is usually calculated with lumped-parameter nodal models. Several simplified nodal models were developed and implemented in the various building simulation software to estimate the temperature stratification in rooms with DV. Recent studies reveal that the multi-nodal models provide the most accurate temperature gradient prediction. However, the majority of dynamic calculation methods assumes either complete mixing of zone air or linearised temperature gradient. The present study introduces the dynamic temperature gradient model for DV and investigates the effect of thermal mass on the temperature stratification. The model was validated with the experimental results of a lecture room with displacement ventilation. The room air temperature measurements were conducted during three weeks at 20 different heights. The supply air temperature and occupancy rate were recorded during each scheduled lecture. The developed dynamic nodal model is able to calculate the air temperatures in the occupied zone accurately. The effect of the thermal mass and changing heat gains on the room air temperature stratification is analysed for the lecture room with DV.

Optimisation of air-distributor channel structural parameters based on Taguchi orthogonal design

Air distributors are a typical kind of ventilation terminal that are widely used in air-conditioning systems. However, the high flow resistance of traditional air distributors leads to huge energy losses and poor indoor thermal comfort. Therefore, this paper uses experimental and numerical methods to examine the influence of key structural parameters on the resistance coefficient of air distributors. First, a resistance-coefficient test is carried out, and based on the test results a computational fluid dynamics model is developed. Second, a Taguchi design table is created and numerical simulation data are collected. Finally, the prediction results of Mean Response and Assisted Regression are compared. The resistance coefficient of prediction combination of Assisted Regression model is lower, so the optimal scheme is as follows: d = 90 mm, D = 155.5 mm, and h = 96.5 mm. The predicted resistance coefficient is 1.503, and the difference between the predicted and simulation results accords with the 95% confidence interval. These findings show that numerical simulation and the analysis method based on the orthogonal design presented in this paper enable the optimal design of an air distributor.

Urban transformation and heat island: Potential of urban design alternatives to mitigate the effects of urban overheating in Austrian cities

Ongoing urbanization worldwide present a big challenge for the quality of urban life. This development poses great challengesfor cities due to the growing demand for more living space and supporting infrastructure, resulting in environmental pollution, higher anthropogenic waste heat and poor outdoor thermal comfort. To accommodate this rapid expansion of urban areas, the city authorities need to adopt a more climate-sensitive approach to urban transformation. In this regard, the present contribution investigates the potential of specific planning and adaptation strategies to attenuate the urban overheating for distinct urban locations in Vienna and Linz, Austria, over a hotsummer period. For this purpose, we applied the parametric modelling environment Rhinoceros 3D and a number of built-in algorithms in the Rhino’s plug-in Grasshopper for dynamic simulation of urban microclimate. The results were compared based on the meanradiant temperature (MRT) averaged over a 24-hour cycle and differentiated into day-and night-time shares. The results reveal a notable potential of selected greening measures to positively influence outdoor thermal conditions. The effectiveness of thesemeasures, however, seem to be time-dependent, whereby a more pronounced cooling effect was noted during the daytime, attributed to the solar shielding effect.

Energy-Saving Transformation Design of Existing Residential Buildings in Qinba Mountainous Areas

Through investigation, it is found that some existing buildings in Qinba Mountain have high energy consumption and poor indoor thermal comfort. The cost of demolishing and rebuilding is relatively high. Therefore, it is an important issue for the current urban residential development to study suitable local reconstruction strategies. Taking an old community in Hanzhong City of Qinba Mountain as an example, the field test of indoor and outdoor thermal environment in winter and summer was carried out for one house. The current situation of indoor thermal environment in Qinba mountain city buildings in winter and summer was analyzed. The environmental conditions are not ideal. This article uses DesignBuilder software to carry on the comprehensive transformation design to the wall of this existing building, the roof, the outer window and so on, and carries on the simulation analysis to its indoor thermal environment, the result shows that the enclosing structure has a greater influence on the thermal environment of the local building; the transformation model was obtained: 30mm EPS insulation layer was added to the wall, 50mm EPS insulation layer was installed on the roof, and plastic window (6+13A+6) was used as the outer window. After the renovation, the indoor temperature was increased by 11%-21%. This result can provide a certain theoretical reference for the energy-saving reconstruction of the existing residential houses in the Qinba Mountains.

Investigation of Influencing Factors on Air Leakage of Canadian Dwellings

Air leakage is one of the main influencing factors in buildings’ thermal performance. The adverse effects of poor air leakage include higher energy costs, consumption in space heating and cooling, poor thermal comfort, corrosion, and the growth of molds due to air leakage induced condensation. The main objective of this study is to investigate the characteristics of air leakages of Canadian homes related to construction methods, age, size and climatic zones. The air leakage test results of 226,000 dwellings in three provinces of Canada were analyzed. Statistical analysis was utilized to compare the mean of air leakage with respect to different factors. Generally, the air leakage decreased by 40% in the period from 1960 until 2018, which has shown a remarkable effect of new construction techniques on air leakage. Investigations also indicated that the average air leakage rate of homes constructed by using the onsite technique is approximately 25% to 60% higher than those prefabricated in modular or panels, varying with respect to the workmanship and construction quality control. This study concluded that the prefabricated construction techniques could decrease the air leakage rate significantly, which will have a remarkable effect on buildings’ thermal performance as well as home’s heating and cooling costs. The findings contribute to estimating the effects of influencing factors on air leakage, also it is useful in performance simulations, HAVC sizing and energy management. And recommend the use of the prefabricated in modular or panel’s construction method to achieve better and acceptable air leakage performance.

Robust evaluation method of thermal deviation of air distribution

Air distribution (e.g., mixing ventilation) is widely used to provide indoor thermal comfort. The thermal deviation is defined as the deviation between the thermal condition and thermal preference, and a thermal deviation closer to zero indicates a more comfortable thermal environment. The thermal deviation is significantly affected by uncertainties in the thermal preference and cooling load. However, the conventional design method of air distribution evaluates the thermal deviation in a deterministic manner, which could result in an improper design with poor thermal comfort. This study innovatively proposes a robust thermal deviation evaluation method and uses it for the design optimization of air distribution. Monte Carlo simulations are employed to treat uncertainties in the thermal preference and cooling load. From the Monte Carlo simulations, the thermal deviation D0.95 is quantified with a confidence level of 0.95. The thermal deviation D0.95 should be minimized to optimize the design of air distribution robustly. Tests based on experiments of an energy efficient air distribution, i.e., stratum ventilation, have been conducted to validate the evaluation method proposed. Results show that the robust design based on the evaluation method proposed can ensure thermal comfort, while the conventional design risks thermal discomfort due to the uncertainties. Compared with the robustly optimized variable-air-volume system of stratum ventilation, the robustly optimized constant-air-volume system of stratum ventilation improves thermal comfort by 8.5% with the thermal deviation D0.95 reduced from 0.682 to 0.624. Therefore, the evaluation method proposed contributes to designing and comparing air distributions robustly for thermal comfort improvement.

Path Analysis of Energy-Saving Technology in Yangtze River Basin Based on Multi-Objective and Multi-Parameter Optimisation

The Yangtze River Basin in China is characterised by hot- and cold-humid climates in summer and winter, respectively. Thus, increased demand for heating and cooling energy according to the season, as well as poor indoor thermal comfort, are inevitable. To overcome this problem, this study focused on the influence of passive design and heating, ventilation, and air conditioning equipment performance on the energy performance of residential buildings, and explored potential energy-saving technology paths involving passive design and improved coefficient of performance through a multi-objective and multi-parameter optimisation technique. A large-scale questionnaire survey covering a typical city was first conducted to identify family lifestyle patterns regarding time spent at home, family type, air conditioner use habits, indoor thermal comfort, etc. Then, the actual heating and cooling energy consumption and information of model building were determined for this region. Subsequently, the design parameters of an individual building were simulated using Energyplus to investigate the cooling and heating energy consumption for a typical residential building with an air conditioner. The results indicated an improvement of approximately 30% in energy efficiency through optimisation of the external-wall insulation thickness and the external-window and shading performance, and through use of appropriate ventilation technology. Thus, a multi-objective and multi-parameter optimisation model was developed to achieve comprehensive optimisation of several design parameters. Experimental results showed that comprehensive optimisation could not only reduce cooling and heating energy consumption, but also improve the thermal comfort level achieved with a non-artificial cooling and heating source. Finally, three energy-saving technology paths were formulated to achieve a balance between indoor thermal comfort improvement and the target energy efficiency (20 kWh/(m2·a)). The findings of this study have implications for the future design of buildings in the Yangtze River Basin, and for modification of existing buildings for improved energy efficiency.

Modelling of room air temperature profile with displacement ventilation

An accurate temperature gradient calculation is essential for displacement ventilation (DV) system design, since it directly relates to the calculation of supply air flow rate. Several simplified nodal models were developed and implemented in the various building simulation programmes to estimate the temperature stratification in rooms with displacement ventilation. However, the most commonly used models do not take into account the types and locations of the heat loads in rooms with DV. As a result, the calculated air temperature in the occupied zone can defer from the real one by 2–3 °C, which causes poor thermal comfort and inadequate sizing of the ventilation and cooling systems. In the present study, the nodal model was proposed to provide a simplified technique to predict the vertical temperature gradient in rooms with DV. In addition, the effect of the room height and locations of the indoor heat sources were studied for the typical office environment. The measurement data were compared with the existing nodal models and the proposed nodal model in terms of predicting the occupied zone temperatures. The presented nodal model demonstrates an accurate calculation of the temperature gradient for the typical heat loads and combinations of them.

An exploration aboutthe Solar Energy Utilization and the Enclosure SystemRenovation for Rural Residential Buildings in Cold Areas of Northern China——Taking the rural residential renovation design in Zhujialin Village, Linyi as an example

Rural areas in the cold regions of northern China generally suffer from excessive energy consumption, poor thermal comfort, and low thermal efficiency of heating equipment. In order to improve the comfort of ruralresidential buildings, renovation design has become an indispensable part of the current beautiful rural construction.This paper comprehensively analyzes the current situation of rural residential buildings in cold regionsbytaking the transformation ofa farmhouse in Zhujialin of Linyi City as an example. Moreover, the methods of energy-saving renovation of rural houses are explored from two aspects of solar energy utilization and enclosing system renovation. The research provides a feasible reference for energy-saving renovation of other rural areas in the cold regions of northern China.

Dynamic design model of displacement ventilation

An accurate temperature gradient calculation is essential for displacement ventilation (DV) system design, since it directly relates to the calculation of the required supply air flow rate. Inaccurate temperature prediction can cause the poor thermal comfort and w sizing of the ventilation and cooling systems. Several simplified nodal models were developed and implemented in the various building simulation software to estimate the temperature stratification in rooms with DV. Recent studies reveal that the multi-nodal models provide the most accurate temperature gradient prediction. However, the most building simulation software uses the air models with only one air node. The present study introduces the dynamic temperature gradient model for DV and investigates the effect of thermal mass on the temperature stratification. The model was validated with the experimental results of the lecture room with displacement ventilation. The room air temperature measurements were conducted during three weeks at 20 different heights. The supply air temperature and occupancy rate were recorded during each scheduled lecture. The developed dynamic nodal model is able to accurately calculate the air temperatures in occupied zone. The effect of the thermal mass and varied heat loads on the indoor air temperature stratification is analysed for the lecture room with DV.

Fault Diagnosis of Components and Sensors in HVAC Air Handling Systems With New Types of Faults

Air handling systems are the key sub-systems of heating ventilation and air conditioning (HVAC) systems. They condition and deliver air to satisfy human thermal comfort requirements and provide acceptable indoor air quality. Faults in their components and sensors may lead to high-energy consumption, poor thermal comfort, and unacceptable indoor air quality. Additionally, new types of faults may falsely be identified as known types. Identifying failure modes and their severities with low false identification rates is thus critical to know what faults occur and how severe they are. However, this is challenging, since 1) classifying both failure modes and fault severities generates many categories of failures, leading to high computational requirements; 2) updating model parameters to adapt to changing environments requires accurate recursive equations that are hard to obtain; and 3) model errors and measurement noise may cause high false identification rates in detecting new types of faults. In this paper, failure modes are identified by hidden Markov models (HMMs) and fault severities are estimated by filtering methods, leading to a decrease in the number of HMM states and low computational requirements. To adapt to changing environments, a new online learning algorithm is developed. In this algorithm, HMM parameters are obtained based on their posterior distributions given new observations, thereby avoiding the need for accurate recurrence equations. To identify new fault types with low false identification rates, a robust statistical method is developed to compare current HMM observations with those expected from existing states to obtain potential new types, and then confirm new types by checking whether observations have a significant change. Physical knowledge is then used to find the reason for the new fault type. Experimental results show that failure modes and fault severities of both known and new types of faults are identified with high accuracy.

Improving the Performance Attributes of Plug-in Hybrid Electric Vehicles in Hot Climates through Key-Off Battery Cooling

Ambient conditions can have a significant impact on the average and maximum temperature of the battery of electric and plug-in hybrid electric vehicles. Given the sensitivity of the ageing mechanisms of typical battery cells to temperature, a significant variability in battery lifetime has been reported with geographical location. In addition, high battery temperature and the associated cooling requirements can cause poor passenger thermal comfort, while extreme battery temperatures can negatively impact the power output of the battery, limiting the available electric traction torque. Avoiding such issues requires enabling battery cooling even when the vehicle is parked and not plugged in (key-off), but the associated extra energy requirements make applying key-off cooling a non-trivial decision. In this paper, a representative plug-in parallel hybrid electric vehicle model is used to simulate a typical 24-h duty cycle to quantify the impact of hot ambient conditions on three performance attributes of the vehicle: the battery lifetime, passenger thermal comfort and fuel economy. Key-off cooling is defined as an optimal control problem in view of the duty cycle of the vehicle. The problem is then solved using the dynamic programming method. Controlling key-off cooling through this method leads to significant improvements in the battery lifetime, while benefiting the fuel economy and thermal comfort attributes. To further improve the battery lifetime, partial charging of the battery is considered. An algorithm is developed that determines the optimum combination of key-off cooling and the level of battery charge. Simulation results confirm the benefits of the proposed method.

Improving indoor air quality and thermal comfort in office building by using combination filters

Poor indoor air quality and thermal comfort condition in the workspace affected the occupants’ health and work productivity, especially when adapting the recirculation of air in heating ventilation and air-conditioning (HVAC) system. The recirculation of air was implemented in this study by mixing the circulated returned indoor air with the outdoor fresh air. The aims of this study are to assess the indoor thermal comfort and indoor air quality (IAQ) in the office buildings, equipped with combination filters. The air filtration technique consisting minimum efficiency reporting value (MERV) filter and activated carbon fiber (ACF) filter, located before the fan coil units. The findings of the study show that the technique of mixing recirculation air with the fresh air through the combination filters met the recommended thermal comfort condition in the workspace. Furthermore, the result of the post-occupancy evaluation (POE) and the environmental measurements comply with the ASHRAE 55 standard. In addition, the level of CO2 concentration continued to decrease during the period of the measurement.

Comfort metrics for an integrated evaluation of buildings performance

The capability of expressing all the different aspects of the building’s performance, besides and beyond the mere energy behavior is becoming more and more important, because of the increased expectations related to either new construction or the renovation of existing buildings.Even though building energy performance is one of the main aims of an appropriate design process or of a suitable management strategy during the operation phase, it can be strongly undermined by the underestimation of the role of the indoor environmental quality. Poor thermal or visual comfort not only affects occupant satisfaction, well-being and productivity, but also induces actions and operations that ultimately compromise the energy efficiency targets.In order to support the design approach, including, since the very beginning, the comfort conditions among the design requisites, a set of metrics is proposed in this work, considering either time constancy or spatial uniformity of a single comfort aspect −or of different aspects at the same time. These metrics have been applied to a simulated reference environment, in order to test their ability to represent the performance of the envelope components when comparing building configurations characterized by high solar and daylighting gains and different window and shading configurations.