Page 58 - JCAU-5-2

Journal of Chinese
Architecture and Urbanism Cooling energy-saving mechanism

according to different construction ages (built before 1980, standards and scientific guidance for the behavioral
built from 1980 to 2004, and built after 2004). The authors energy conservation of existing office buildings. The
selected 16 typical cities representing different climatic paper is structured as follows: Section 2 describes the
conditions in the US, calculated the optimal temperature research object (a model building) and research conditions
set-point under various climatic conditions, and adjusted (climate conditions, building parameters, temperature
the HVAC system based on the optimal set-point. They set-point, etc.) and introduces the quantitative analysis
then used the MATLAB program to simulate the energy method used in the paper to analyze the mechanism of
consumption of the system. The research results show that energy conservation. Section 3 gives the research results
under the three-size models, the construction age affects the of the macroscopic energy-saving effect. Section 4 analyzes
characteristics of building energy consumption. The newer the difference between energy-saving effects and energy-
the construction age, the better the envelope performance, saving mechanisms at the micro-scale. Section 5 discusses
and the lower the energy consumption, the smaller the the comparison of the energy-saving effect after adding
energy saving potential. The author applied different an internal heat source. Finally, Section 6 summarizes the
temperature set-points to three sizes of office building research results and conclusions.
models in 16 cities under different climatic conditions. The
results showed that compared with the baseline set-point of 2. Research model and procedures
22.5°C, the energy-saving effect varied to different degrees, The research model in the paper is a typical three-story
and the energy-saving effect was significant in hot areas. office building, whose plan and elevation are shown in
However, due to the complexity of climate condition types, Figures 1 and 2. The length of the building is 21.24 m, the
building size types, and optimal temperature set-point, the width is 14.04 m, the height is 11.9 m, the total area of
conclusions were not comparable. In addition, because of the building is 894.63 sqm, the total area of the envelope
the complexity of the problem, the author only studied the is 1065.96 sqm, the building volume is 3280.31 cubic
difference in relative energy saving rate and did not study meters, the shape coefficient is 0.3250, the window-wall
absolute energy saving, which significantly affected energy ratio of the north and south external walls is 0.29, and
cost and emission reduction. In the same city or region, the window-wall ratio of the east and west external walls
buildings with different envelope performances and is 0.07. For the other working conditions of building
different construction times coexist. The behavioral energy simulation, such as indoor air exchange rate (ACH)
conservation policy that advocates raising the temperature through mechanical ventilation system, internal heat gains
set-point of air-conditioners is aimed at people living in from indoor lighting, occupations and devices, and so on,
buildings completed at different times. However, it is not key parameters are obtained based on the benchmark
difficult to find out from the above studies that under the values according to the US DOE Reference Building and
same climatic conditions (the same city), there is little ASHRAE AS (2013) Standard of thermal environmental
research on the differences in the relative and absolute conditions for human occupancy (building’s daily office
energy-saving effect of buildings of different times with hours are 9:00 – 18:00) (ASHREA, 2013; Guo et al., 2019;
the same temperature set-point increase, and the profound Jin et al., 2023; Office of Energy Efficiency & Renewable
revelation of its energy-saving mechanism is even more Energy, n.d.).
blank. Therefore, the temperature set-point and the thermal To focus on the differences in the influence of a 1°C
characteristics of a building envelope are coupled in this increase in air-conditioning temperature set-point on
study. The thermal characteristics of building envelopes energy consumption of buildings of the same type in the
of different grades represent existing buildings built at same city but with different construction times under the
different times. New constructions and high construction condition of different envelope thermal characteristics,
level often lead to better thermal performance of building based on the general envelope structural requirements
envelopes (Feijó-Muñoz et al., 2019).
and related thermal engineering and energy-saving
Aimed at office buildings, this paper selects Guangzhou, design standards of the outer envelope of civic buildings
a typical Chinese city with hot summers and warm winters, of different times in China, in this paper, we assume that
to explore the relative and absolute energy-saving effect the building envelope thermal characteristics are divided
difference of increasing the temperature set-point of the into lower-grade, medium-grade, high-grade, and top-
air conditioner by 1°C for different grades of envelope grade. The envelope heat transfer coefficient of each grade
performance, and further investigate the energy-saving is listed in Table 1. Some scholars have shown that the
mechanism, which has practical engineering significance hotter the region, the higher the energy-saving potential
and values. The research results can provide a theoretical (Feijó-Muñoz et al., 2019; Jin et al., 2023). Therefore, this
reference for the revision of energy conservation paper focuses on the hottest region with hot summers

Volume 5 Issue 2 (2023) 4 https://doi.org/10.36922/jcau.0877