Thermal Comfort In Office Buildings Research Articles

Influencing factors of long-term thermal comfort in office buildings

Influencing factors of long-term thermal comfort in office buildings

The Effects of Exterior Glazing on Human Thermal Comfort in Office Buildings

As a major component of the building envelope, the energy-saving design of exterior windows is key to energy savings in office buildings. The conventional design of exterior windows mainly focused on their impact on heating and cooling energy but ignored the indoor thermal comfort problems caused by the direct solar radiation transmitted by windows and the fluctuation of their internal surface temperatures. This study analyzed the influence of exterior windows on the indoor thermal environment of office buildings by carrying out field experiments. The experiments were carried out in a typical office building in Xi’an during December and January. The impact of exterior windows on human thermal comfort was studied from two perspectives: longwave radiation from the surface of window glass and solar shortwave radiation. It was found that solar radiation was the main cause of temperature fluctuations on the internal surface of windows and created non-uniform thermal environments. The mean radiant temperature fluctuations in the near-window area could reach up to 7.8 °C due to outdoor solar radiation in winter. Solar radiation transmitted by windows directly affects thermal sensations. Since conventional thermal comfort models or indices underestimated the thermal sensations of occupants in the presence of solar radiation, the additional thermal loads caused by solar radiation needed to be taken into account. The allowable operative temperature range for maintaining thermal comfort should be reduced by 0.5 °C when occupants are exposed to solar radiation.

The effect of the glass planes on thermal comfort in office buildings: a case study

One of the most important aspect in architecture is the selection of exterior material. This materialsurface faces directly with building’s surrounding climate and environment, transferring the heat through its wall and roof significantly so it requires more consideration from the planners. Widely use of glasses as building’s exterior impacts its heat absorbing thereby it needs more power for air conditioning in order to keep the interior temperature productively workable. The objective of this research is to observe the impact between glass partition and interior thermal condition, how the habitants react, and also the ideal temperature for both users and building’s OTTV. Correlational research combines results from thermal observation and user’s perceptionin order to get its convenience thermal condition and to know its OTTV so we can issue the standard

A comprehensive optimization study of personal cooling radiant desks integrated to HVAC system for energy efficiency and thermal comfort in office buildings

Personal comfort systems (PCS) maintain the occupant's preferred thermal environment and expand his thermal comfort experience under varying environmental conditions. Among PCSs, radiant-based systems are popular due to their comfort and energy efficiency. A personal cooling radiant desk (PCRD) in conjunction with conventional heating, ventilation, and air conditioning (HVAC) has proven to reduce energy costs. A system's energy and thermal performance, however, depends on various factors making it important to identify the optimal design parameters of a PCRD coupled with HVAC system in an office space. To optimize the energy and thermal performance of the PCRD-HVAC system, a numerical/mathematical model is developed simulating different design parameters. The model uses an artificial neural network (ANN), combined with a multi-objective genetic algorithm (MOGA) to identify the optimal design parameters. The decision variables include the supply temperature, the temperature, and the flow rate of chilled water flowing inside the desk. The study's findings show that the optimal design parameters achieved a balance between thermal comfort and energy efficiency. The recommended design parameters result in an annual energy consumption of 3880 kWh and a predicted percentage of dissatisfied individuals (PPD) of 6 %. The experiment is carried out to validate the model showed a maximum relative error of only 12.54 %. The results of this study have important implications for designing sustainable cooling solutions for office spaces in hot climates. The successful optimization of the PCRD system highlights the importance of balancing energy efficiency and thermal comfort in designing sustainable cooling solutions.

Solar radiation-based method for early design stages to balance daylight and thermal comfort in office buildings

There is a lack of facade design methods for early design stages to balance thermal comfort and daylight provision that consider the obstruction angle as an independent variable without using modeling and simulations. This paper aims to develop easy-to use solar radiation-based prediction method for the design of office building facades (i.e., design parameters: room size, window-to-floor ratio, and glazing thermal/optical properties) located in urban canyons to balance daylight provision according to the European standard EN 17037:2018 and thermal comfort through specific cooling capacity. We used a simulation-based methodology that includes correlation analyses between building performance metrics and design parameters, the development of design workflows, accuracy analysis, and validation through the application of the workflows to a new development office building facades located in Tallinn, Estonia. The validation showed that the mean percentage of right/conservative predictions of thermal comfort classes is 98.8% whereas for daylight provision, it is higher than 75.6%. The use of the proposed prediction method can help designers to work more efficiently during early design stages and to obtain optimal performative solutions in much shorter time: window sizing in 73,152 room combinations in 80 s.

Implementation of ISO/DIS 52016-3 for adaptive façades: A case study of an office building

Adaptive building envelope technologies can increase the energy efficiency of buildings. Adaptive facades can be controlled automatically and respond to environmental changes. There is no standard method for evaluating control strategies for adaptive façade elements, particularly for dynamic shadings. Therefore, the ISO/DIS 52016–3 recommended different default control strategies to compare the energy use of various building variants. ISO/DIS 52016–3 presents the procedures for considering the effect of adaptive building envelope elements in calculating the energy needs for heating, cooling, internal temperatures, and sensible and latent heat loads. This paper presents a comprehensive study of the impacts of the newly published ISO/DIS 52016–3 on energy performances and thermal comfort in office buildings with adaptive facades. The simulations were performed for an office room in Brussels with four scenarios: no shading and fixed shading (fixed horizontal louvers) with static control, external roller blinds, and Venetian blinds employing automatic control strategies suggested by ISO/DIS 52016–3. Energy Management Systems (EMS) as a user-customized coding plugin in EnergyPlus was utilized for implementation of each control strategy algorithm. The findings indicated that in the case of roller blinds, the energy performance of the selected office was improved by 19.47% compared to the fixed shading. This study shows that the chosen roller blinds performed the best in decreasing the annual cooling loads with a value of 63.9%, 44.12%, and 8.2% compared to scenarios of no shading, fixed shading, and Venetian blind, respectively. Furthermore, the results showed that the fixed shading would occasionally outperform automated Venetian blinds.

Development of an adaptive model for thermal comfort in the office buildings of Nagasaki City, Japan

Thermal comfort in office buildings is instrumental in improving the productivity of employees while maintaining their health. The primary objectives of this research were to analyze the comfort temperature in Japanese office buildings and investigate its relationship with outdoor air temperature. Additionally, we examined the differences in comfort temperatures with respect to closed and opened windows to factor in the increase in the opening of windows during the COVID-19 pandemic when air-conditioning systems were operated. We investigated the environmental conditions of office buildings and the thermal comfort of the occupants through monthly visits to each office building over a year. Field data were collected from four office buildings located in Nagasaki City, with 1047 votes obtained from 143 participants. The survey indicated that the occupants were highly satisfied with the thermal environment in their offices. The correlation between indoor comfort temperature and outdoor temperature was high in the FR mode. Based on the analysis, we developed an adaptive model for office buildings in Nagasaki City and compared it with existing adaptive models used for buildings in other regions of Japan. The proposed model is useful for energy-saving designs that bring out human adaptive capacity.

Development of the adaptive model for thermal comfort in office buildings of Aichi prefecture, Japan

This study was undertaken to investigate seasonal adaptation to temperature in Japanese offices, with a view to suggesting an adaptive model for them. We measured temperatures in seven office buildings and conducted thermal comfort transverse surveys of occupants for over a year in the Aichi prefecture of Japan. We collected 1,228 samples. The occupants were found to be highly satisfied with the thermal environment in their offices. Even though the Japanese government recommends the indoor temperature of 28 °C for cooling and 20 °C for heating, we found that the comfort temperature was 2.8 °C lower in cooling mode and 4.3 °C higher in heating mode, in line with the actual indoor temperatures. The monthly variation in the temperature in the investigated offices was significantly lower than had been found in dwellings. An adaptive relationship can be derived to estimate the indoor comfort temperature from the prevailing outdoor temperature for similar office buildings.

Investigative Study on Adaptive Thermal Comfort in Office Buildings with Evaporative Cooling Systems (ECS) under Dry Hot Climate

Evaporative cooling systems (ECS) in buildings, which are driven by cleaner and more sustainable energy, had been widely applied in recent years especially for the dry hot regions in summer. In this study, an investigation was conducted for office buildings by using ECS in Urumqi (China) from July to August 2021. Through subjective survey and objective measurements, 577 initial questionnaires and measured data were obtained. Outcomes showed that the indoor expectative temperature (Te) was received by 26.6 °C, 0.7 °C lower than neutral temperature (Tn). And the acceptable intervals for the 90% and 80% level were obtained at 27.1–28.9 °C and 26.4–30.3 °C, respectively. It appeared to possess a wider scope than that calculated by PMV algorithm, which further indicted that subjects have adapted to the local climate. Furthermore, the adjustment PMV models (ePMV, APMV) were found to have an effectively narrow gap comparing to the actual thermal sensation vote (TSV). The appropriate usage intervals of ePMV and APMV were quantified by Top < 27.6 °C/Top > 29.8 °C, 27.6 °C < Top < 29.8 °C, respectively. These findings may provide reference values for the revision of local energy-saving standard to some extent.

Investigation of personal thermal comfort in office building by implementation of smart bracelet: A case study

Thermal comfort is significant factor in the overall satisfaction level and affects directly the building energy performance within heating and cooling systems. Through this work, the short-term field investigation of smart monitoring devices was applied for personal thermal comfort investigation. The conceptual approach was presented for the case of specific office building. The low cost sensing technology was implemented in this investigation as key advantage of herein considered approach. The users wore smart bracelets which monitored physiological parameters, i.e. skin wrist temperature and heart rate during the day in office facility. Simultaneously, the environmental parameters were measured (air temperature, relative air humidity and CO2 concentration). Field survey (subjective response from occupants) was conducted as well. Wrist skin temperature from the individual users has a positive correlation with thermal comfort evaluation for female (0.54) and male (0.36) user. Additionally, for the data from male user, the CO2 concentration in the office had a positive correlation as well (0.45). The positive correlation between examined parameters endorse the application of the proposed measuring technology (wearable device) for detection of personal thermal comfort. The proposed approach represents a basis for further development of novel regulation approach for heating/cooling systems in buildings, since it allows more complex evaluation of the personal thermal comfort factors.

Analysis of the long-term effects of solar radiation on the indoor thermal comfort in office buildings

Windows play a critical role in building energy consumption and thermal comfort. Although many different models have been adopted for developing standards for indoor thermal comfort evaluation, the impact of solar radiation on occupant thermal sensation is still overlooked. In this study, the SMRT-Air temperature deviation method, in which the impact of solar radiation can be assessed based on the deviation of the solar-adjusted mean radiant temperature from air temperature, was developed to help the designer conveniently evaluate the impact of solar radiation on indoor thermal comfort in initial design stage. This method was applied to evaluate the effect of solar radiation on occupants in office buildings under different orientation and climate zones in China. The results show that the effect of solar radiation on thermal comfort is more severe in cold climate zones. Controlling the amount of solar radiation transmitted by windows facing east and west is more critical than for windows oriented in other directions. An appropriate decrease SHGC of windows from the current standard requirements can reduce over 86% discomfort times when SHGC decrease to 0.3 in all climate zones. The outcomes of this study can help designers implement appropriate measures for improving indoor thermal comfort.

Assessment of Air Quality Perception and Its Effects on Users’ Thermal Comfort in Office Buildings

Since people spend most of their time in indoor environments, the objective of this work was to study indoor air quality and its effects on users’ thermal comfort. Based on previous data from a building with a central air-conditioning system and two mixed-mode buildings located in the humid subtropical climate of Florianópolis, southern Brazil, statistical analyses were performed. Each user’s subjective answer obtained through a questionnaire was combined with the corresponding environmental conditions measured by instruments. Results showed that improvement in air quality was associated with the reduction of air temperature and humidity ratio. Also, there was a significant influence of thermal and humidity sensation on air quality satisfaction. Users felt more satisfied or neutral with air quality for being in thermal comfort, and not because of the CO2 concentration—which means that air quality perception is influenced by factors other than CO2. This study recommends implementing an air exchange device in split air-conditioners with air recirculation commonly used in mixed-mode buildings in Brazil. It is important to provide suitable indoor ventilation to reduce pollutant concentration, ensure good air quality and prevent respiratory diseases.

Numerical and Experimental Investigation of the Thermal Comfort of an Office Building Equipped with Hybrid Downdraft Evaporative Cooler

In office buildings, provision of thermal comfort for occupant’s high intellectual concentration, efficiency and productivity is imperative. This study experimentally and numerically investigates the thermal comfort performance of HDEC system equipped to an office building. The experiment was carried out in September, October and November for 24 working days and the thermal comfort Predicted Mean Vote (PMV) index being the objective function was determined using Centre for Built Environment thermal comfort tool. DesignBuilder CFD simulation software was employed to numerically determine the PMV index of the test office using ASHRAE Standard-55 thermal comfort range of PMV=±0.5. Minitab 19 software was used to validate the numerical results against the experimental results. The Pearson correlation coefficient and the P-value at 95% confidence level were 0.717 and 0.00 respectively while the RMSE computed was 0.653 indicating a good agreement between the numerical and the experimental results. Both PMV results indicate that the HDEC system is suitable for the provision of thermal comfort in office buildings and any other similar building.

End-to-end deep meta modelling to calibrate and optimize energy consumption and comfort

In this paper, we propose a new end-to-end methodology to optimize energy performance and thermal comfort in office buildings, without any renovation work. The process is decomposed into three steps: metamodel training, model calibration and optimization. We introduce and train a metamodel on thousands of weather and building settings scenarios, using samples from a physical simulation model. Its much faster computation time allows for the calibration of two weakly instrumented buildings with a derivative free optimization procedure. Using historic data from these buildings, we estimate up to 60 unknown parameters defined by energy managers, such as heat capacity, window area or exposition. Energy consumptions are finally minimized while maintaining a target thermal comfort using the Pareto front provided by a multi-objective optimization algorithm. Our approach allows the computation of the entire calibration-optimization pipeline on several types of buildings. Moreover, the numerical experiments illustrate how it may ensure a significant gain in energy efficiency, up to almost 10%, while being computationally much more appealing than simulation programs.

Assessment of Passive Cooling Potentials to Enhance Thermal Comfort in Office Buildings in Dry Sub-Humid Climate

The importance of optimizing thermal comfort in interior spaces through passive means cannot be over-emphasized, especially in tropical regions in order to lower energy demand for cooling and to promote sustainable practices in Sub-Sahara Regions like Nigeria. This paper aimed at assessing the potential of passive cooling potentials in selected Nigerian Universities’ buildings in the North-East sub-region. In this study, quantitative method of data collection was adopted. Three cases were studied such as Administrative Building of Gombe State University (GSU), Senate Building of Abubakar Tafawa Balewa University, Bauchi (ATBU) and Administrative Building of Modibbo Adama University of Technology, Yola (MAUTECH). The results of the study are presented in simple percentages, tables, figures and frequencies in adherence to the checklists derived from Contemporary Methods of Passive Cooling established by Santamouris & Kolokotsa as follows: MAUTECH’s Administrative Building scored 45% while ATBU Senate Building assessed to have 48% and GSU Administrative Building got 55%. This connotes that, designers should embrace passive elements in design and construction of office buildings in Nigeria as two of the three case studies fell below 50%.

Application of wearable sensory devices in predicting occupant’s thermal comfort in office buildings during the cooling season

The mitigation of adverse health consequences, improvement of life quality and the work environment with consequential benefits to wellness and performance of the occupants, arise the need for innovations in predicting thermal comfort in the actual time during which a requirement occurs. Late researches in this field largely neglect user engagement in building energy performance. In this paper, the wearable sensory devices are deployed to provide real-time information in a spatially distributed indoor environment during the cooling season in office buildings. The results imply that wearable devices are an efficient tool for collecting individualized human sensation data such as a precise metabolic equivalent of task (MET) and occupant’s activity level which could generate total energy expenditure of an occupant. In addition to sensor data, documenting indoor environmental conditions such as air temperature, relative humidity and a level of carbon dioxide (CO2), could be utilized as useful inputs that complete the more sensibly provided feedback of occupants’ work environmental surroundings. Furthermore, this could provide a potentially significant opportunity for achieving a personal indoor environment that is most preferred.

A longitudinal study of summertime occupant behaviour and thermal comfort in office buildings in northern China

The adaptive behaviour and thermal responses of building occupants can be responsible for significant uncertainties when comparing monitored and modelled building energy performance. A better understanding of the interaction of occupants and their buildings is necessary for managing this uncertainty and reducing discrepancies between predicted and actual energy use (commonly known as ‘the performance gap’). This paper presents the results from a longitudinal study during a summer season of ten mixed-mode offices located in Harbin, a city in northern China, which experiences severe winters and warm summers. The study collected data from on-line daily surveys, field measurements of the local environment, occupants' experiences and adaptive control behaviours. Occupant-building interactions were analysed through observing adaptive behaviour, perceived thermal sensations in the physical environment, architectural geometric variables and personnel characteristics. The driving mechanisms for behaviours and feelings were also studied. The results showed a high probability of window opening for both day and night, and a high frequency of the use of a mix of cooling options, including fans and air conditioning, accompanied by natural ventilation in the summer season. The active interaction of the offices' internal environments with the outdoor environment motivated more connections of occupant thermal feelings with the outdoor physical variables. Relative humidity levels were potential key predictors for window opening, and the geometric parameters of offices, occupants' fan use and perceived thermal feelings also showed a level of predictive ability. Evaluating the nature of occupant feelings and behaviours interactions may inform and improve results from building performance-based design.

Assessment of gender on requirements for thermal comfort in office buildings located in the Brazilian humid subtropical climate

This article aims to assess the effects of gender on requirements for thermal comfort in office buildings. Data were obtained from 83 field studies conducted over 2014 in three office buildings located in Florianópolis, southern Brazil. One of the buildings is fully air-conditioned and the other two operate under mixed-mode strategy, i.e., alternating from air-conditioning to natural ventilation. Data were measured by means of microclimate stations, and the occupants opinions were obtained through a questionnaire. There was no significant difference of clothing insulation for male and female subjects. Significant differences were found for thermal sensation, thermal preference, thermal acceptability and thermal comfort in the central air-conditioned building. In mixed-mode buildings, significant differences were found for thermal sensation and thermal preference responses of male and female subjects. However, during air-conditioning operation in mixed-mode buildings, significant differences were found for thermal preference and thermal acceptability responses of male and female subjects; and during natural ventilation operation, significant differences were found for thermal sensation and thermal preference. In contrast to what some previous studies have found this work indicates the existence of significant differences in the thermal comfort responses of male and female subjects.

Using Upper Extremity Skin Temperatures to Assess Thermal Comfort in Office Buildings in Changsha, China.

Existing thermal comfort field studies are mainly focused on the relationship between the indoor physical environment and the thermal comfort. In numerous chamber experiments, physiological parameters were adopted to assess thermal comfort, but the experiments’ conclusions may not represent a realistic thermal environment due to the highly controlled thermal environment and few occupants. This paper focuses on determining the relationships between upper extremity skin temperatures (i.e., finger, wrist, hand and forearm) and the indoor thermal comfort. Also, the applicability of predicting thermal comfort by using upper extremity skin temperatures was explored. Field studies were performed in office buildings equipped with split air-conditioning (SAC) located in the hot summer and cold winter (HSCW) climate zone of China during the summer of 2016. Psychological responses of occupants were recorded and physical and physiological factors were measured simultaneously. Standard effective temperature (SET*) was used to incorporate the effect of humidity and air velocity on thermal comfort. The results indicate that upper extremity skin temperatures are good indicators for predicting thermal sensation, and could be used to assess the thermal comfort in terms of physiological mechanism. In addition, the neutral temperature was 24.7 °C and the upper limit for 80% acceptability was 28.2 °C in SET*.

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.