Conference Agenda

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Session Overview
Poster introductions 03: Thermal comfort
Thursday, 26/Aug/2021:
11:15am - 11:35am

Session Chair: Dr. Jiyun Song, University of Hong Kong
Location: Room 2 - Room 011, Building: 116

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11:15am - 11:18am

Analysis of Draught Discomfort Prediction Models

Seyed Mohammad Hooshmand1, Seyed Alireza Zolfaghari1, Jørn Toftum2

1University of Birjand, Iran; 2Technical University of Denmark

One of the common local thermal discomforts that happen in an indoor environment is draught. Because of the importance of draught, many studies have been carried out to develop equations to calculate the draught rate. But because these equations are obtained from experimental tests in narrow experimental windows, their accuracy under wider environmental conditions should be analyzed. In this paper, the accuracy of equations obtained from the literature were investigated. Each equation predicted the draught rate with high accuracy and mean error of 5.3, 6.8, and 2.2% under the thermal conditions in which the equation was obtained. When applying the equations to different thermal conditions, the mean and maximum errors significantly increased and showed errors in predicting the draught rate with a maximum deviation of 63.5, 51.6, and 49.7%. These equations in some cases, even could not predict the draught rate of the reported draught discomfort percentage. Based on the results, each equation had its limitations and none of the studied equations could accurately predict the draught rate in all experimental conditions. An index that considers all relevant parameters in predicting draught discomfort can lead to a better draught rate prediction.

11:18am - 11:21am

Thermal comfort environment for migrants: a long-term follow-up climate chamber experiment

Yu Dong1,2, Yuan Shi3, Yanfeng Liu2, Jørn Toftum1

1Technical University of Denmark, Denmark; 2Xi’an University of Architecture and Technology, China; 3China Mobile Group Design Institute Co., Ltd, China

Migration between different climate regions may change people's thermal experience and their thermal adaptation. However, few studies have explored the thermal adaptation process and the suitable indoor thermal environment of migrants. In this study, we conducted a long-term tracking comparative experiment on thermal adaptation of migrants moving from severe cold (SC) regions, hot summer and cold winter (HSCW) regions, and hot summer and warm winter (HSWW) regions to cold region of China. A two-year climate chamber experiment was conducted to follow migrants' progressive thermal adaptation, such as different weeks, months and seasons after they migrated. The results show that the thermal sensation of migrants was significantly associated with their origin, the time after migration and air temperature. In addition, with the increase time after migration, the thermal sensitivity of HSCW and SC migrants showed a significant upward and downward trend, respectively. Two years after migration, the thermal comfort limits of migrants from SC, HSWW and HSCW were almost identical at 23.5-27.8°C, 23.8-27.8°C, and 23.5-27.6°C. The results provides insight to the progression of thermal adaptation and helpful to guide the design of indoor climate for immigrants with different thermal experiences.

11:21am - 11:24am

Prediction of indoor air temperature for assessment of thermal stress

Jørn Toftum1, Jose Joaquin Aguilera Prado1, Boris Kingma2, Hein Daanen3, Chuansi Gao4, Lars Nybo2

1Technical University of Denmark, Denmark; 2University of Copenhagen, Denmark; 3Vrije Universiteit Amsterdam, Netherlands; 4Lund University, Sweden

Climate change is expected to increase the frequency and intensity of extreme weather events. Individualized and timely advice on how to cope with thermal stress is therefore needed to encourage protective strategies and reduce morbidity and even mortality among vulnerable populations. Such advice can be based on integration of human thermal models, weather forecasts and individual user characteristics. The current study focused on development of an algorithm to predict indoor air temperature and assess indoor thermal exposure with incomplete knowledge of the actual thermal conditions. The algorithm will be used in a mobile application that translates thermal stress into coping strategies at individual level.

Outdoors, thermal stress in hot or cold exposures can be evaluated with local weather forecasts and personal information on clothing and activity. Indoors, prediction of thermal stress requires knowledge of the indoor air temperature, which is the result of a heat balance including external and internal heat gains, ventilation and building properties. The suggested method provides discrete predictions of temperature through a decision tree classification algorithm with six simple building descriptors and three parameters harvested from weather forecast services. The data used to train and test the algorithm was obtained from field measurements in seven Danish households and from building simulations considering three different climate regions ranging from temperate to hot and humid.

The approach was able to correctly predict approximately 68% of the most frequent temperature levels. Solar irradiation, outdoor running mean temperature and the number of occupants in a room were the parameters that were most important and increased the accuracy of the indoor air temperature prediction, whereas building related parameters (construction year and floor area) only had a minor influence. The findings suggest that it is possible to develop a simple method that predicts indoor air temperature with reasonable accuracy.

11:24am - 11:27am

The Role of Complex Airflow Simulation Tools for Overheating Assessment of Passive Houses

Vitor Leite Goncalves, Tarek Rakha

School of Architecture, Georgia Institute of Technology, Atlanta, GA, USA

To meet the energy target goal of the Energy Performance Building Directive COM/2016/0765, sustainable buildings have become of greater interest in recent times to reduce buildings’ primary energy demand. European Passive Houses, when compared to standard buildings, are characterized mainly by an increased insulation level, airtight building envelope, and a heat recovery system that greatly reduces the energy usage during the winter but can lead to significant overheating during the hotter summer days. Since in the Passive House concept thermal comfort during the summer completely relies on natural ventilation to provide indoor cooling, the adequacy of this modeling technique to simulate airflow within the building needs to be investigated. This research analyzes the effect of simplifications commonly made in airflow modeling techniques to the overheating assessment of Passive Houses by collecting measured indoor temperature data and performing the overheating evaluation on a Passive House case study. Its outcome was then compared against the results obtained from simulations utilizing Building Energy Modeling (BEM) alone, BEM coupled with an Airflow Network Model (AFN), and BEM coupled with an AFN with the addition with the wind pressure coefficient values obtained from Computational Fluid Dynamics (CFD) simulation. Results showed that the default infiltration and natural ventilation input values commonly utilized in literature, when compared to those obtained from either the AFN or AFN+CFD, are significantly overestimating the natural ventilation potential of the buildings (30% increase), resulting in a lower number of overheating hours and inaccurate overheating evaluation outcomes. Therefore, the paper concludes that the use of at least an AFN is necessary when estimating the overheating hours of Passive Houses under climate change conditions, which is critical when pondering that global warming factors will affect heat stress experiences in future European Passive Houses.

11:27am - 11:30am

Improving thermal comfort conditions in K-12 educational buildings in hot and humid climate: a case study in Cucuta, Colombia.

Diana Carolina Guerrero, Hua Ge, Bruno Lee

Concordia University, Canada

The school buildings in Colombia are designed and built based on geographical locations, available materials, and regional construction systems. However, external weather conditions and building design can have a significant impact on the indoor thermal conditions of classrooms and the thermal comfort of students, which affects the academic performance and productivity of students. This paper investigates the thermal comfort performance for an educational building, located in a hot and humid city in Cucuta, Colombia. The selected school is a representative building of Colombian educational facilities, which was built under the architectural and structural guidelines established by the national government. This school is a concrete structure without mechanical cooling. It has features such as vertical louvers and light shelves to provide solar shading and cross ventilation. However, field observation discovered that 82% of the time students experienced thermal and visual discomfort in elementary classrooms. To investigate the potential causes and provide mitigation strategies, a whole building energy simulation is conducted. DesignBuilder is used to evaluate the indoor thermal conditions of the school building based on existing building configuration and compared to field observation. ASHRAE 55 adaptative model is used for the evaluation of thermal comfort. It is found that in these classrooms 79% of the time the thermal conditions are outside the acceptable range during the year. The effect of mitigation measures i.e. occupancy, wall insulation, shading, and natural ventilation rates on indoor thermal conditions are investigated through simulations. It is found that occupancy and natural ventilation rate have a significant impact on the indoor temperature and relative humidity, and thus the thermal comfort. While increasing wall insulation level and shading. Passive design strategies are proposed in optimizing the school building design to meet ASHARE-55 requirements.

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