key: cord-0793937-hhfzae7o
authors: Su, Yuan; Cheng, Haoyuan; Wang, Zhe; Wang, Linwei
title: Impacts of the COVID-19 lockdown on building energy consumption and indoor environment: A case study in Dalian, China
date: 2022-03-28
journal: Energy Build
DOI: 10.1016/j.enbuild.2022.112055
sha: 295c75123714d7abbed90a357b12f3c4be1dff44
doc_id: 793937
cord_uid: hhfzae7o

Restricting social distancing is an effective means of controlling the COVID-19 pandemic, resulting in a sharp drop in the utilization of commercial buildings. However, the specific changes in the operating parameters are not clear. This study aims to quantify the impact of COVID-19 lockdowns on commercial building energy consumption and the indoor environment, including correlation analysis. A large green commercial building in Dalian, China's only country to experience five lockdowns, has been chosen. We compared the performance during the lockdown to the same period last year. The study found that the first lockdown caused a maximum 63.5% drop in monthly energy consumption, and the second lockdown was 55.2%. The energy consumption per unit area in 2020 dropped by 55.4% compared with 2019. In addition, during the lockdown, the compliance rate of indoor thermal environment increased by 34.7%, and indoor air quality was 9.5%. These findings could partly explain the short-term and far-reaching effects of the lockdown on the operating parameters of large commercial buildings. Humans are likely to coexist with COVID-19 for a long time, and commercial buildings have to adapt to new energy and health demands. Effective management strategies need to be developed.

The pandemic lockdown has also had a meaningful impact on energy consumption 2 worldwide. Fig. 1 shows the power demand changes in some countries in the first three quarters of electricity consumption increased by 5% [23] .

23 Fig. 2 shows the year-over-year changes in electricity demand in some countries' first three 24 quarters of 2020. Spain is one of the EU countries most affected by the epidemic. From 25 mid-March to the end of April, its electricity consumption dropped by 13.49% from the previous 26 five years' average. [24] . Industrial electricity consumption in the UK fell by 17% from April to 27 June 2020 compared with the same period last year, and commercial building electricity demand 1 Due to the lockdown situation, these parameters are essential performance references for 2 buildings in similar events in the future. Especially in China, it has a large population base, and 3 coastal cities with cold chain logistics have a higher probability of being infected than ordinary 4 cities, such as Dalian. It will have a considerable impact on the energy and indoor environment of 5 the commercial building, as lockdowns will be frequent. Dalian Municipal Government issued a notice requiring that all public places be closed and strictly 10 controlled if infected persons are in the area. [48] But public spaces in other areas are often closed 11 to prevent unforeseen situations.

In this study, Dalian, the only city in China that has currently experienced five pandemic 13 lockdowns, was selected. The research was based on investigating the building operation status of 14 a commercial building in 2019-2020 and the data collection of the energy consumption monitoring 15 system. We use statistical controlled variables to select typical months and days for comparison 16 before and after the lockdown, including hourly energy consumption and sub-metering. 

In 2019, the particular electricity consumption fluctuated. The energy consumption level on 29 working days was the same, with the electricity consumption ranging from 694kWh to 831kWh, 30 which was higher than the same period in 2020. After the first lockdown in 2020, the special 31 electricity consumption will gradually increase. On the one hand, the project's operation has 32 improved and steadily adjusted to the normal operation state. On the other hand, considering that 33 the epidemic has just eased, buildings are usually sterilized due to policy restrictions. The increase 34 in electricity consumption is mainly reflected in the special electricity consumption. 

The correlation heatmap before lockdown is shown in Fig.9 . We found a significant positive 20 correlation between building energy consumption and all environmental factors, except indoor 21 humidity. Analysis of the data found that the building interior humidity remains at 80-84% 22 throughout the day on a typical day. Its changing trend is not much related to energy consumption. Fig. 11-12 shows that the lockdown affects indoor air quality. The compliance rate during the 6 lockdown increased by 9.5% on average. The concentration of PM2.5 and CO 2 decreased during 7 the lockdown in office, public and exhibition hall areas: PM2.5 decreased by 28% on average, and 8 CO 2 decreased by 12%. When the COVID-19 was well controlled, the number of occupants 9 gradually increased. For instance, office workers resume their daily work. Due to the pandemic 10 lockdown, the ventilation of the buildings has been improved. The air quality has become better.

Among them, the average recovery rate of the office area is the largest, which is 23%. 12 14 1 Fig. 11 . The overall distribution of PM2.5 in buildings 2 3 Fig. 12 . The overall distribution of indoor CO 2 in buildings 4 5 As shown in Fig.13-15 , before the pandemic lockdown, the average concentration of PM2.5 6 in the exhibition hall was 19.9-30.5 μg/m 3 . The standard deviation was 36.2, and the distribution 7 was scattered, with the peak value reaching 87.7 μg/m 3 in some areas. Compared with the IAQ 8 standard, the incompliance rate was 8.2%. [50] After that, affected by the lockdown, the PM2. the approximate level before the pandemic, but the peak value decreased by 35% compared with 22 before the pandemic. This is caused by the fact that not all the venue staff have returned to work.

The main types of space used in public areas are coffee shops, book bars, etc., which are 24 densely populated. Before the pandemic, the PM2.5 value in this area was 22% higher than that in 25 offices and exhibition halls on average. It ranged from 28.8 to 46.0 μg/m 3 with a peak value of 26 131.6 μg/m 3 . Moreover, before the epidemic, PM2.5 in public areas did not meet the standard 27 from 11:00 to 14:00, above the standard by 37%. During this time, the staff will gather here to 28 relax, and the fresh air system alone may not meet the standard requirements. We suggest that 29 windows be opened appropriately to increase natural ventilation to maintain good air quality. At The CO 2 concentration in public and office areas before, during and after the pandemic were 2 similar. Affected by office workers returning to work, it quickly rose to the previous level after the 3 lockdown, floating around 450ppm. Due to the closure of venues in the outbreak, the CO 2 value in 4 each space was maintained at 400ppm. The exhibition hall is the primary use space, and the 5 average distribution of CO 2 before the pandemic is 488.5-540.9 ppm. On average, the peak value 6 is 11% higher than office and public space, and the standard deviation is 29.6. After the lockdown, 7 it rebounded slightly, and the change was smaller than that of the office and public. Generally 8 speaking, the CO 2 compliance rate of each space in the building is 100%. As shown in Fig. 18 -20, during the non-heating season before the epidemic, the temperature 5 of the exhibition hall area was maintained at 21.2°C. The public space was at 23.7°C, and the 6 office area was at 24.2°C. The overall fluctuation was slight. However, according to the 7 specification, the compliance rate of the exhibition hall area was relatively low, which was 41.3%.

8 [50] Over-cooling was identified in the exhibition hall area during some periods, which will 9 increase unnecessary building energy consumption without improving comfort. We recommend 10 adjusting the central air-conditioning settings to ensure that the indoor temperature is appropriate 11 while meeting energy-saving requirements.

After the COVID-19 outbreak, the temperature in each space rose slightly, and the overall 18 Similar to temperature changes, the humidity of venues remains stable in daily management.

However, the moisture in public, office and exhibition halls exceeded the standard by 13% on 20 average in a non-heating season before the lockdown. The public area has the highest relative 21 humidity of 81.6-82.9%. Dalian had a higher ambient humidity level in the summer before the 22 pandemic. Indoor humidity is greatly affected by outdoor; dehumidification is necessary to control 23 the relative humidity. During the COVID-19 outbreak, the humidity in the exhibition hall area was 24 the lowest at 40% because it was winter. After the pandemic, the humidity in public spaces is 25 relatively high in some periods, caused by users opening windows for ventilation and outdoor 26 water vapor entering the room.

Generally speaking, the humidity compliance rate before the pandemic was 32.4%, and the 28 compliance rate during and after the pandemic was about 85.7%. Humidity in summer should be 29 considered in buildings to improve the running performance of equipment. The lockdown situation provides a unique chance to test the operational performance of 3 commercial buildings. This paper studies the energy consumption pattern and indoor air quality of 4 a large green commercial building in Dalian, China, by caring its performance before, during, and 5 after the COVID-19 outbreak. The data covered typical months of the first and second lockdown 6 in 2020, while the operational data for 2019 was used as a benchmark.

7

The results showed that during the lockdown period, the energy consumption of the large 8 commercial building was significantly reduced. The first lockdown resulted in a monthly energy 9 consumption decline of 63.5%, and the second lockdown was 55.2%. Compared with 2019, 10 building energy consumption decreased by an average of 55.4% in 2020. During the lockdown, 11 improvements in outdoor air quality affected the indoor environment. The indoor thermal 12 environment and air quality compliance rate increased by 34.7% and 9.5%, respectively. In 13 addition, we also found that before the lockdown, the indoor air quality of the building did not 14 meet the standard, and problems such as insufficient dehumidification and excessive cooling in 15 summer needed to be solved urgently. Although this study is a regional example, it can provide a 16 reference for the energy performance of buildings in similar mass and climatic regions under 17 emergency events so that managers can formulate reasonable energy management policies and 18 discover energy-saving potential.

Due to the strict lockdown, few studies currently use large amounts of measured data. It is 20 also difficult to know whether the lockdown affects the correlation of building and environmental 21 parameters. This study shows that pre-lockdown building energy consumption has a significant 22 positive correlation with almost all environmental factors. After lockdown, the interference of the 23 outdoor environment to indoors has increased, and some of them have reached a very high level. 

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