monitoring of winter thermal environment of university student apartment … · ·...

Monitoring of Winter Thermal Environment of University Student

Apartment in Xi’an

HUANG Jie

1, LIU Yu

1, WU Xinlan

1

1. Northwestern Polytechnical University, China

E-mail: [email protected]

Abstract: The indoor thermal environment of student apartment has great impacts on students’ daily life. By

monitoring of the indoor air temperatures and humidity of a university student apartment in the winter time, the

performance of indoor thermal environment of the student apartment at different times of a day and different

positions of the room are revealed; plan, layout and some details of the building and management system are

identified as the main issues that are closely related to the performance of indoor thermal environment, of the

student apartment and suggestions for their improvement are provided.

Keywords: Student apartment; Indoor thermal environment; Monitoring; Xi’an

1. Introduction

In China, the study of comfort of thermal environment mainly concentrated on residential buildings,

especially on the high-rise residential buildings. There is still a lack of study on the university student apartment,

which is a relatively small part of residential buildings. Student dormitory turning into apartment has been an

inevitable trend in China’s universities, which puts forward higher requirements on the qualities of such

buildings. The lack of theoretical research and investigation on such buildings may cause blindness in their

problems, and cannot satisfy the increasing demands of the quality of living environment of today’s university

students.

Student apartment is one of the main places for students to study and live, its thermal environment condition

will directly affect students' learning efficiency, as well as their physical and mental health. In order to

understand the indoor thermal environment of university student apartment in Xi’an city, the author of this paper

conducted a monitoring research in the new student apartment of one university in Xi’an in between November

15-25, 2012.

Fig1. Location of the university in Xi’an Fig2. Location of the apartment in the university

2. The object and method of monitoring

2.1. Object of monitoring A graduate student apartment is chosen as the object for monitoring in this study. The building was

constructed in 2006, each unit of it has four bedrooms, one living room and two bathrooms, It was originally

designed as standard 2 bed hotel rooms for academic staff to have a rest when there is a need. Since 2012, the

Advances in Sciences and Engineering

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sixth floor (top floor) on the south side was transformed into graduate student apartment, due to a great increase

in the number of students. After the transformation, in each unit, the four bedrooms become four student

dormitories, while the living room and bath rooms are retained and shared by the students living in the apartment.

Each dormitory contains four students, with four desks on one side and four bunk beds on the other side. Every

unit has the same layout.

The main monitoring object in this research is dormitory D (with red color marked in Fig3). . This dormitory

room is located to the north of the apartment and receives less direct solar radiation than that to the south, so it is

more representative for investigation of indoor thermal environment in wintertime.

2.2 Method of monitoring The monitoring in this research is mainly aimed at different functional locations in the room, including

temperature and humidity of student desk space, upper berth space, lower berth space, window and outdoor

spaces.

In this study, five Hobo brand H08-004-02 Temperature-Humidity Recorders (THR) had being used to

monitor the thermal conditions of student apartment. Each device recorded once in every half hour for 10 days

from November 16th to 25th, 2012. The locations of four of the THRs are shown in Figure 4, and the fifth one

was placed in the open balcony to record the outdoor air condition. A total of about 480 sets of data were

collected, in which the data of ten consecutive days were identified as typical for the weather, so were picked up

and analyzed.

3. Analysis of outdoor air temperature and humidity

3.1 Basic climate conditions of Xi’an city Xi 'an area belongs to the warm temperate semi-humid continental monsoon climate, with hot-rainy summer,

cold-drier winter, mild climate, four distinct seasons and moderate rainfall. The annual average temperature is

between 13.0℃ and 13.4℃; the coldest January average temperature is about -0.4℃ to 0.9℃; the hottest July

average temperature is about 25℃ to 26.6℃. The annual extreme minimum temperature is -20.6℃ (January

11th, 1995); the annual extreme maximum temperature is 43.4℃ (June 19th, 1966). Annual rainfall is about

558mm to 750mm, increasing from north to south. The annual sunshine hours are 1983 to 2267 hours; the annual

prevailing wind direction is northeast. The main meteorological disasters include drought, water logging, hail,

high winds, dry hot wind and low temperature damage.

3.2 The results of outdoor temperatures and humidity 3.2.1 Temperature

During the monitoring period, the weather were generally stable, but the variation of daily air temperatures is

very obvious (up to nearly 20℃). The lowest temperatures usually occur at around 6:00 am, and the lowest

temperature of the ten consecutive days was 2.5℃ , occurred at about 7:00 am on the 24th; the highest

temperatures usually occurs at around 11:00 am, and the highest temperature of ten consecutive days was 22℃,

occurred at about 11:30 am on the 18th. Analyzing the monitoring data, it is found that the variation of diurnal

temperatures has a close relationship with the weather condition, big temperature variations usually occur in

sunny days, temperature variations usually occur in rainy days.

Fig3. Apartment layout plan

Fig4. Locations of the Temperature-

Humidity Recorders (the outdoor recorder is

not included in the figure)


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Table1. Statistics of outdoor temperature in ten days

3.2.2 Humidity

The variation of outdoor humidity was very large during the monitoring period, and was inversely

proportional to the temperatures. The outdoor humidity also had close relationship with weather conditions.

Specific data shows that the highest humidity (84%) occurred at about 4:00 am on the 25th; while the lowest

humidity (23%) occurred several times at about 10:00 am. Comparison of the data shows that, when the

temperature was higher, the humidity was lower; when the diurnal temperature variation was larger, the changes

in humidity was more obvious. In the rainy weather the daily average humidity was increased, but not

particularly obvious.

Table2. Statistics of outdoor humidity in the ten successive days

4. Analysis of indoor air temperatures and humidity

4.1 Basic conditions of the monitoring In the 10 successive days, situations and conditions of the monitored department had changed. In the early 1-

3 days, heating was just provided and as not very stable (stopped several times); in the mid 3-4 days, the weather

became very cold, even affected activities of students in the apartment; in the last 3 days, the weather was quite

stable, the heating system also become stable, and the indoor temperatures reached the heating standard of Xi’an

and relatively city. Therefore, data collected on Nov. 23rd (within the last three days) was selected for further


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analysis in this paper. During the monitoring period, the window on the exterior wall was closed, and the door

between living room and dormitory was opened or closed in need, the living room also had heating supply.

4.2 Analysis of indoor air temperatures

In general, the indoor temperatures at different locations were relatively stable, all about 19℃. When the

outdoor temperatures fluctuation was up to 16℃，the indoor temperature fluctuation was only about 2℃.

reasons for this phenomenon were analyzed as the following: (1) the heating supply system is stable, and

achieves the requirement of comfortable indoor environment; (2) the performance of building envelop insulation

is relatively good, which prevent indoor additional heat loss; (3) the per capita living space was small, about 4 ㎡,

so larger amount of body heat per unit area.

Due to the influence of students’ body heat, when there are more activities in the room, the temperature in

different place will be 1℃ to 2℃ higher than no people in the room. So the indoor temperature is higher from

8:00 pm to 1:00 am, according to students’ behavior.

Locations for the monitoring of indoor temperatures include the desk space, the lower berth space, the upper

berth space and the window interior surface, which involves the main indoor activity areas of students. The

collected data shows that, the difference of temperatures among the three main living areas is small; however, the

difference of temperatures between the three main living areas and the window glass are is significant. The

temperature of window glass area was about 6℃ lower than the other indoor areas, and about 6℃ higher than

the outdoor air temperature. Overall, the indoor temperatures were relatively stable, and not notably affected by

the variation of outdoor temperature.

Except the obvious difference between the temperature of window and living spaces, there are also some

small differences among three living areas. As can be seen from the statistics table, during the main sleeping

period, 1:00 am to 9:00 am, the temperatures of lower berth and desk are almost the same, but upper berth is

0.5℃ lower than others. During the activity period, the temperature of desk is 0.8℃ higher than lower berth, and

1.3℃ higher than upper berth, because students didn’t sleep and the main activities were occurred around the

desk, such as study and using PC.

In the apartment, except solar radiation, city heating supply and human activities, some digital devices also

can emit heat, especially computers. So the temperature of computer desk is higher than other places. The

apartment researched is on the top floor of the building, so the roof has some impact on the indoor thermal

environment. Under normal circumstances, the hot air will be in the upper space of the interior, but the result of

monitoring data shows that upper berth was 0.5℃ lower than lower berth. It is not difficult to find that the roof

and exterior walls had cold radiation to the interior space, especially to the upper berth.

Table3. Indoor and outdoor temperature data on November 23

rd

4.3 Analysis of indoor air humidity From the statistical result, the indoor relative humidity was between 25% -55% on Nov.23rd. Some data

indicate that the effect of humidity on indoor thermal environment depends on temperature range, the total

evaporation cooling requirements, air flow velocity and clothing conditions. When the temperature is close to the

range from 20℃ to 25℃, humidity level has no obvious effect on physiological responses and thermal sensation


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reaction; the variation of relative humidity between 30% and 85% is almost imperceptible. Only when the

relative humidity in the air is nearly saturated state, people can obviously feel skin sticky and wet.

The overall variation trend of building interior humidity is roughly close to outdoor, but specific values are

different, because indoor humidity is related to indoor human activities more closely, while outdoor humidity

depends on climate. In the five sets of data, the variation of window humidity is the biggest, and it is not stark

inversely proportional to the temperature of window glass. Window minimum humidity of 26% occurred at

about 2:30 pm, when indoor activity was minimal; window maximum humidity of 82.5% occurred at about 7:30

am, students were sleeping, and breathing out of water vapor reached the maximum.

The general trends of humidity of the three main indoor space are the same, but the concrete numerical

values are different in different periods. During the sleeping period, the humidity of upper berth and lower berth

are both higher than desk. In other periods, three kinds of humidity are nearly the same. So it is easy to find that

indoor humidity is closely related to human activities, especially in the smaller per capita area room.

Table4. Indoor and outdoor humidity data on November 23

rd

4.4 Summary of the monitoring results

(1) In winter, the indoor temperature is affected by heating supply significantly, and the stability of indoor

thermal environment of student apartment has little relationship with the outdoor environment when the room

with heating supply. Therefore, it can reduce the discomfort caused by large variation of outside temperature

when apartment heating system has good thermal stability.

(2) During the monitoring period, the window was always closed in order to reduce the influence of outdoor

climate, but it led to a decline in the quality of indoor air of the apartment. In the actual operation, the window

should be opened to refresh indoor air when it doesn’t affect indoor thermal environment obviously, so as to

improve the quality of indoor air.

(3) It can be seen from the temperature data that energy consumption of heating will increase when the

thermal insulation property of window is poor in winter. Also, due to the per capita area is small and indoor

activity range is relatively fixed, it is easy to cause so uneven temperature distribution that lead to large

difference of experience and feeling. Generally, the feeling of spaces near doors and windows is colder than

middle area in the apartment.

(4) Because of the roof and outdoor air contact directly, the apartments located on the top floor are more

easily influenced by outside environment than other floors, especially the upper berth space near the roof.

(5) Indoor humidity is closely related with indoor personnel activities. In this high-density residential space,

the relationship between indoor humidity and temperature is different from outside environment, and the main

factor is indoor human activities.

5. Possible ways of improvement

Regarding the problems that have been identifies in the above mentioned monitoring and analysis, following

perspectives are recommended to explore for possible ways to improve the indoor thermal condition of student

apartment in winter time in Xi’an city and in other areas with similar climate conditions.


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5.1 Site planning perspective In site planning, the quality of indoor thermal environment can be improved by building a suitable outdoor

microclimate environment. Different orientation, shape, building interval, height, layout of road, distribution of

green space and so on will affect the microclimate, sunshine, natural ventilation and energy consumption of

students’ residential area. From the perspective of energy conservation and ecological environmental protection,

students’ residential planning should adapt to the outdoor climate and microclimate conditions, and create a

more favorable outdoor environment.

In winter in Xi’an, the climate is cold; day-and-night temperature variation is obvious; humidity is low. Some

thermal storage and humidity increasing measures can be added in the landscape design of student’s apartment.

For example, water features can be added in the landscape design that raise outdoor air humidity, and it can

release heat from water at night when the outdoor temperature comes down, while absorbing and storage solar

radiation and air heat at day.

In the aspect of solar radiation, building layout and orientation should be considered carefully. The amount

of solar radiation obtained by different orientation building surface is different, because solar radiation has a

straight direction. As can be seen, south elevation has the most solar radiation in winter in Xi’an, so south

orientation of building is favorable for heat absorption and preservation. Through the calculation of the best

orientation is south by east 10°in Xi’an, suitable orientation is south to south by west. The layout of the student

apartments should make full use of solar radiation.

The layout of different kinds of plants in the site also can affects indoor thermal environment. Evergreen

trees can be planted in the northwest corner of the apartment block, as a barrier to against the chill wind.

Combination of appropriate density plants is equivalent to the wind-break wall. In addition to play the important

role of wind-break wall, it also can avoid whirly wind on leeward side.

5.2 Architecture design perspective The requirements of the function of student apartment in university are quite simple. In architecture design, it

is important to reasonably handle the classification of thermal environment zones in the building. During all

functions in the apartment, the dormitory is the most demanding of thermal environment condition, so the

dormitory should be arranged in the best orientation and zone. In Xi'an area, relatively good orientation of

building is the south, so dormitories should be arranged facing south as far as possible, and other auxiliary rooms

arranged in the north. In addition, these auxiliary rooms also can be arranged near the gable ends, because the

thermal environment condition near gable ends is poor.

In the monitored dormitory, due to the huge difference between indoor and outdoor environment in winter, it

was seldom to open the window for natural ventilation that caused poor indoor air condition. In the design

process, the necessity of natural ventilation should be taken into account, and other forms of indoor ventilation

should be designed that don’t cause rapid change of indoor thermal environment when they in operation. For

example, some special vents can be installed in the exterior walls, and operated to promote ventilation when

indoor and outdoor air conditions (temperature, humidity) are not very different.

Building envelope structure likes a coat for interior space, and plays an important role in reducing the impact

of outdoor environment on the indoor environment and indoor heat loss. It helps to create a comfortable indoor

thermal environment. In the monitored data, the roof has significant impact on the indoor environment, so it

should be strengthened on the property of thermal insulation. Furthermore, the auxiliary functions can be

arranged on the top floor. The dorm windows mostly are the main way to indoor heat loss, they also should be

strengthened on the property of thermal insulation, and controlled on the area simultaneously. In the south facade,

the windows can be designed combined with solar house that reduces heat loss and promotes air flow.

5.3 Apartment management perspective In order to improve the overall living environment of student apartments, apartment management also needs

to be improved in addition to improvements of site planning and architecture design. The indoor environment

indicators can be added to the original management system, and complete service facilities are provided in the

apartment, so that it provides convenient conditions and comfortable environment for students. The monitored

apartment isn’t equipped with complete management system, the sliding door between living room and balcony

didn’t work for a long time and no one cared. So the indoor and outdoor space could not be isolated and most

indoor heat release to the outside through the convective outlet. Standardizing the construction and management

of student apartments, is also an important factor in the process of environmental improvement.

6. Conclusions and suggestions for further research


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The indoor thermal comfort environment of student apartment is affected by many factors. Its quality impacts

directly on students’ physical and psychological health, living quality and study efficiency. With the

development of living standard, the research of university student apartment mainly focuses on the architecture

forms and operation management. For buildings, it mostly talks about the change of architectural functions with

the social development; for the indoor thermal environment, it is lack of systematic exploration and research.

This paper introduces the monitoring results of student apartment and analyzes the monitoring data of

temperature and humidity, then it puts forward some suggestions for improvement of indoor thermal

environmental quality. Although temperature and humidity are important factors to the indoor thermal

environment, indoor environment is a complicated system, and it should be researched and improved in many

fields. It is expected that this paper can provides beneficial reference for in-depth research and exploration in

relative fields.

7. References

[1] WANG Yan, LONG Ensheng, MENG Xi, LI Pang. The Research of Thermal Environment of University

Student Apartment[J]. Refrigeration & Air Conditioning, 2011,25(z1): 156-159,163.

[2] XU Xiaolin, LI Baizhan. Influence of Indoor Thermal Environment on Thermal Comfort of Human Body[J].

Journal of Chongqing University (Natural Science edition), 2005.28(4): 102-105.

[3] XIA Bo. Research on the Indoors Thermal Environment of Student Dormitory in Universities[D].Xi’an:

Xi’an University of Architecture & Technology,2003.

[4] J. Wines,P. Jodidio. Green Architecture[M]. Taschen America Llc, 2000.

[5] WANG Zhaojun, WANG Gang, LIAN Leming. History and Status of Indoor Thermal Environment

Research[J]. Journal of Harbin University of Civil Engineering and Architecture .2000,06: 97-101.

[6] CHEN Liang. Research on the Influence of Indoor Thermal Environment on Body Physiology and Thermal

Comfort[D]. Chongqing University,2006.

[7] DING Yong, SU Yingying, LI Baizhan, SHEN Yan. The Effects Analysis of Natural Ventilation on

Improving Indoor Thermal Environment [J]. Industrial Construction, 2010,S: 46-50.

[8]LI Juan. Effective Ways for Improving the Indoor Thermal Environment Quality [J]. Journal of Xi’an

University of Architecture &technology (Natural Science edition), 2001,04: 365-368+374.


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