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Existing building retrofitting for Indoor PM2.5 Concentration Control on Smog Days: Case study in China
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10th International Symposium on Heating, Ventilation and Air Conditioning, ISHVAC2017, 19-22 October 10th International Symposium on Heating, Ventilation Air Conditioning, ISHVAC2017, 19-22 October 2017, Jinan,and China 10th International Symposium on Heating, Ventilation 2017, Jinan,and China Air Conditioning, ISHVAC2017, 19-22 October 2017, Jinan, China
Existing Existing building building retrofitting retrofitting for for Indoor Indoor PM2.5 PM2.5 Concentration Concentration Control Control on on Existing building retrofitting for Indoor PM2.5 Concentration Control on Smog Days: Case study in China Smog Days: Case study in China Smoga Days: Case study ina China a,* a Yiyi Chua, Peng Xu a,*, Zhiwei Yanga, and Weilin Lia Yiyi Chu , Peng Xu , Zhiwei Yang , and Weilin Li Yiyi Chu , Peng Xu , Zhiwei Yang , and Weilin Li
a a
Department of Mechanical Engineering, Tongji University, aShanghai201800, China a a a,* Department of Mechanical Engineering, Tongji University, Shanghai201800, China
a
Department of Mechanical Engineering, Tongji University, Shanghai201800, China
Abstract Abstract Abstract Severe smog days in many parts of developing countries，such as China and India, have drawn worldwide attention. This study aims at Severe smogvarious days inbuilding many parts of developing countries，such as Chinatoand India,indoor have drawn attention. This study aims as at integrating retrofitting methods of existing buildings control PM2.5worldwide concentrations. Methods are such integrating retrofitting methods of existing buildings toand control PM2.5 concentrations. Methods are such Severe smogvarious days inbuilding manyroom parts of developing countries，such as China India,indoor haveofdrawn worldwide attention. This aims as at airtightness improvement, pressure control, recycling air filtration, and combinations the above. The study verifies thestudy effectiveness airtightness improvement, room pressure control, recycling air filtration, and combinations of the above. The study verifies the effectiveness integrating various building retrofitting methods of existing buildings to control indoor PM2.5 concentrations. Methods are such as 3 in of each control method to reduce the indoor PM2.5 concentration below 25 μg/m3 building. Measurements are conducted for different in building. Measurements are conducted for time different of each control method to room reduce the indoor PM2.5 concentration belowand 25 μg/m airtightness improvement, pressure control, recycling air filtration, ofintheShanghai, above. The study verifies thefirst effectiveness outdoor particle concentration scenarios under different control strategies atcombinations an apartment China. This is the that 3 in building. outdoor particle concentration scenarios under different control strategies at an apartment in Shanghai, China. This is the first time that Measurements are conducted for different of each control method to reduce the indoor PM2.5 concentration below 25 μg/m various existing residential building retrofitting strategies are integrated jointly and different control methods are tested to ensure indoor air various existing residential building retrofitting areconclusions integrated jointly and different control are tested ensure indoor air outdoorunder particle concentration scenarios under different control strategies apartment Shanghai, This the first occupants time that quality different outdoor conditions. The strategies results and canatbean used in manyin parts ofmethods the China. worlds, whenisto building quality under different outdoor conditions. The results and conclusions can be used in many parts of the worlds, when building occupants various existing residential building retrofitting strategies are integrated jointly and different control methods are tested to ensure indoor air choose proper retrofitting methods to control their indoor air quality. choose retrofitting methods controlThe their indoorand airconclusions quality. quality under different outdoor conditions. results can be used in many parts of the worlds, when building occupants © 2017proper The Authors. Published by to Elsevier Ltd. © 2017proper The Authors. Published by Elsevier Ltd. Published by Ltd. choose retrofitting methods to theircommittee indoor airof quality. Peer-review under responsibility ofElsevier thecontrol scientific the 10th International Symposium on Heating, Ventilation and Air Peer-review responsibility of Elsevier the scientific scientific committeeof ofthe the10th 10thInternational InternationalSymposium Symposiumon onHeating, Heating,Ventilation Ventilationand and Air © 2017 The Authors. Published by Ltd. committee under responsibility of the Conditioning. Conditioning. Peer-review under responsibility of the scientific committee of the 10th International Symposium on Heating, Ventilation and Air Air Conditioning. Conditioning. Keywords: Indoor PM2.5 control; Residential building retrofit; Control strategies integration; Filtration model validation. Keywords: Indoor PM2.5 control; Residential building retrofit; Control strategies integration; Filtration model validation. Keywords: Indoor PM2.5 control; Residential building retrofit; Control strategies integration; Filtration model validation.
1. Introduction 1. Introduction 1. Introduction Epidemiologic evidence has shown a relationship between particle pollution exposure and adverse health effects, which has Epidemiologic evidence has shown a relationship between particle pollution exposure and adverse health effects, which has drawn increasing attention regarding methods for controlling PM2.5 pollutants indoors. Brook R D. [1] provided evidence that Epidemiologic evidence regarding has shownmethods a relationship between PM2.5 particlepollutants pollution indoors. exposureBrook and adverse health effects, which that has drawn increasing attention for controlling R D. [1] provided evidence PM is capable of acutely increasing blood pressure and that exposure to PM has tremendous public health implications. Hwang B drawn increasing attention regardingblood methods for controlling PM2.5 to pollutants indoors. Brook R D. [1] provided evidence that PM is capable of acutely increasing pressure and that exposure PM has tremendous public health implications. Hwang B F et al. [2] conducted a two-year study of 12-year-old Taiwanese children and concluded that long-term exposure to PM2.5 may PM of acutely increasing blood andTaiwanese that exposure to PMand hasconcluded tremendous public healthexposure implications. Hwang B F et is al.capable [2] conducted a two-year study of pressure 12-year-old children that long-term to PM2.5 may have a detrimental effect on the development of lung function in children. Yuming Guo et al. [3] explored the association F et al. conductedeffect a two-year of 12-year-old Taiwanese and concluded thatetlong-term exposurethe to PM2.5 may have a [2] detrimental on thestudy development of lung function children in children. Yuming Guo al. [3] explored association between PM2.5 and the hospital emergency room visits in Beijing, China for cardiovascular diseases. There are also many other have a detrimental on theemergency development ofvisits lung in function children. Yuming Guo diseases. et al. [3]There explored the many association between PM2.5 and effect the hospital room Beijing,inChina for cardiovascular are also other epidemiological studies on particular hazards reviewed in [4]. between PM2.5 and the on hospital emergency visitsinin[4]. Beijing, China for cardiovascular diseases. There are also many other epidemiological studies particular hazardsroom reviewed Since people spend approximately 80%~90% of their time indoors, indoor pollution becomes very important to human health, epidemiological studiesapproximately on particular hazards reviewed [4]. indoors, indoor pollution becomes very important to human health, Since people spend 80%~90% of theirintime and various studies from different academic fields on PM2.5 have attracted attention. Some building retrofit measures have been people spend approximately 80%~90% their time have indoors, indoorattention. pollutionSome becomes very retrofit important to human health, andSince various studies from different academic fieldsofon PM2.5 attracted building measures have been proposed by many researchers to reduce indoor PM2.5 concentrations. For example, Fang Wang et al. [5] presented a statistical and various from different academic fields on PM2.5 have attracted attention. Fang SomeWang building retrofit measuresahave been proposed bystudies many researchers to reduce indoor PM2.5 concentrations. For example, et al. [5] presented statistical analysis of the available data of PM2.5 in four residential dwellings with different building airtightness levels and HVAC-filter proposed many researchers reduceinindoor PM2.5 concentrations. Fordifferent example,building Fang Wang et al. [5] presented a statistical analysis ofbythe available data oftoPM2.5 four residential dwellings with airtightness levels and HVAC-filter combinations, which revealed that the enhanced airtightness and the improvement of filter efficiency for both makeup air and analysis of the which available data ofthat PM2.5 in four residential dwellings different building levels HVAC-filter combinations, revealed the enhanced airtightness and thewith improvement of filter airtightness efficiency for bothand makeup air and indoor recirculated air decrease indoor PM2.5 concentration significantly. Zhihua Zhou et al. [6] also proposed a method for combinations, whichairrevealed the enhanced airtightness and the improvement of filter both makeup air and indoor recirculated decreasethat indoor PM2.5 concentration significantly. Zhihua Zhou et efficiency al. [6] alsofor proposed a method for indoor recirculated air decrease indoor PM2.5 concentration significantly. Zhihua Zhou et al. [6] also proposed a method for * * *
Corresponding author. Tel.:86-13601971494 Corresponding author. Tel.:86-13601971494 E-mail address:[email protected] Corresponding author. Tel.:86-13601971494 E-mail address:[email protected] E-mail address:[email protected]
1877-7058 © 2017 The Authors. Published by Elsevier Ltd. 1877-7058 2017 The Authors. Published by Elsevier Ltd. 1877-7058©©under 2017responsibility The Authors. Published by Elsevier Ltd. of the Peer-review of the scientific committee 10th International Symposium on Heating, Ventilation and Air Conditioning. Peer-review under responsibility of scientific thebyscientific committee of the 10th International Symposium on Heating, Ventilation and Peer-review© under the committee 1877-7058 2017responsibility The Authors. of Published Elsevier Ltd. of the 10th International Symposium on Heating, Ventilation and Air Conditioning.
AirPeer-review Conditioning. under responsibility of the scientific committee of the 10th International Symposium on Heating, Ventilation and Air Conditioning. 10.1016/j.proeng.2017.10.290
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controlling infiltration of PM2.5 from outdoors and reducing indoor emissions, based on the experimental results of a typical residential building with different voids of windows and doors and different indoor emission sources. Although the above measurements have been performed to control indoor PM2.5 concentrations to some extent, these methods consider only certain factors and these measurements alone cannot ensure the indoor PM2.5 concentration can be controlled under the standard healthy value of 25 μg/m3 continuously, which is at levels below the current standards of the World Health Organization (WHO) (10 μg/m3 of annual average PM2.5, 25 μg/m3 daily), especially when the outdoor concentration is higher than 200 μg/m3. To help address this gap in knowledge, and provide appropriate retrofitting strategies for existing residential buildings, we conducted thorough experiments in a residential building in Shanghai in China and intend to (1) integrate various indoor PM2.5 concentration control methods; (2) quantitatively measure indoor and outdoor particle concentrations and survey the variation of I/O ratio under outdoor PM2.5 concentration ranges in order to determine a successful retrofitting method that ensures the PM2.5 concentration remains below 25 μg/m3 under any outdoor pollution. 2. Indoor PM2.5 control methods The significance of PM2.5 is strongly related to airborne particle concentration, size distribution, and chemical or biological composition, which depend on factors broadly classified as sources, transformation processes and removal mechanisms. Accordingly, the indoor PM2.5 control methods consist of three aspects including source control, outdoor/indoor transportation control and indoor active control. Some of these aspects are easy to control and others are uncontrollable, as shown in detail in Fig. 1.
Fig. 1. Indoor PM2.5 concentration control methods.
2.1. Airtightness improvement Building airtightness, defined as the resistance to air leakage through unintentional openings in the building envelope, is a fundamental building property that impacts infiltration. Air leakage is an important factor we must consider at first due to its principle effects for ingress of outdoor pollutant – dust, noise, particles, etc. In this paper, we focus on the airtightness improvement which could maximally prevent outdoor particles itself. 2.2. Pressure control with mechanical ventilation According to ASHRAE standard 62.1 [7], maintaining a positive pressure indoors with a mechanical ventilation system, which follows the same goal of airtightness improvement, is a possible approach to prevent outdoor particles from penetrating into the indoor environment. This method has been widely used in specialized care environments such as hospitals [8]. The current standard for suitable indoor pressurization value is intended for industrial facilities such as clean rooms. The relevant code for residential buildings is not available. We can take the low end of the clean room code as a reference in order to obtain a reasonable pressurization value of approximately 5 Pa for residential buildings. The ventilated building will maintain positive pressure as long as the supply airflow rate is greater than the return airflow rate and the wind pressure effect is minimized by enhancing the supply airflow rate.
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2.3. Air filter Historically, standards for evaluating the results of the reference filter test have been developed in response to the needs of the times. ANSI/ASHRAE Standard 52.2 [9] provides filter minimum efficiency reporting value (MERV) rating recommendations to evaluate the performance of air cleaners. Azimi P et al [10] used nearly 200 outdoor particle size distributions from literature to estimate PM2.5 removal efficiencies of a wide range of MERV-rated single-pass HVAC filters. The average removal efficiency values are shown in Fig. 2.
PM2.5 Removal Efficiency
120% 100% 80% 60% 40% 20% 0% MERV Fig. 2. Estimates of PM2.5 removal efficiency of outdoor origin for filters tested according to ASHRAE 52.2-2012 0.
3. Case Study and Results An apartment on the 6th floor, located on Tian Yueqiao Road, Xuhui district in Shanghai, was selected to be retrofitted according to the methods mentioned above for this study. The apartment measures 110 m2 of gross floor and 2.6 m clear height from floor to ceiling. This is a typical apartment building in many China cities. The experiment was conducted during the winter season from November, 2016 to February, 2017. 3.1. Airtightness improvement As mentioned above, good airtightness ensures less infiltration. So it is necessary to improve the airtightness of the apartment at first to reduce the source of PM2.5. The single entrance door has been replaced with a double door, and the single glazing windows were replaced with high quality double glazing windows. Some of the remaining windows were well sealed. To evaluate the effect of the airtightness improvement, the blower door test was used to measure the airtightness of the building envelope. And ACH50, the air change per hour rate when the house is under 50 Pa pressure, is measured by the test. The ACH50 value before and after the airtightness improvement are 9.5 and 6.4 respectively. The airtightness improvement can decrease the ACH value to effectively prevent the ingress of outdoor particles. Fig. 3 (a) and (b) illustrate the changes in Ci before and after airtightness improvement, respectively. The average I/O ratio became 0.53 after the retrofitting, which was lower than that when the building was not well sealed, indicating the decrease of outdoor particle invasion. In addition, we observed that indoor PM2.5 concentration could be kept lower than 25 μg/m3 when outdoor PM2.5 concentration was in a relatively low level after airtightness improvement. However, when outdoor PM2.5 concentration grew higher, indoor PM2.5 concentration could not be controlled in a healthy range, other measures must be taken to decrease the indoor PM2.5 concentration.
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Fig. 3. (a) Ci, Co and I/O before airtightness improvement; (b) Ci, Co and I/O after airtightness improvement.
3.2. Pressure control with mechanical ventilation As mentioned above, a fresh air system with a high efficiency PM2.5 removal filter was chosen to be installed on the balcony of the apartment to achieve micro-positive pressure control. The fan has two grades, high air volume with 216.8 m³/h and low air volume with 170.3 m³/h. Each pressurized value of the two grades was calculated due to the relationship between indoor-outdoor pressure difference and infiltration air flow obtained by the blower door test which are 2 Pa and 1 Pa separately. The PM2.5 removal efficiency for the filter was 84.1%, which lies between MERV 14 and MERV 16. Fig. 4 (a) illustrates that the low air volume fan starts at 7:39 when outdoor PM2.5 concentration has a mean value of 130 μg/m3. Because the air cleaning was on before the experiment, Ci is very low at the beginning (approximately 19 μg/m3), though the outdoor PM2.5 concentration was at approximately 140 μg/m3. However, when Co decreased, Ci also decreased, but with a slight rise lagging behind Co variation. After Co increased, Ci rose again. Similarly, the I/O ratio fluctuated with an average value of 0.25. It is worth noting that low air flow could maintain indoor PM2.5 concentration below 25 μg/m3 while Co was under 120 μg/m3. And from Fig. 4 (b), we observed that high air volume fresh air unit cannot keep indoor PM2.5 concentration in a healthy level while Co increased above 160 μg/m3.
Fig. 4. Ci, Co and I/O with low air volume (starting at 7:39); (b) Ci, Co and I/O with high air volume (starting at 23:21).
3.3. Air purifier Except for indoor pressure control, which introduces outdoor air that must be cleaned by a filter before entering indoors, an air purifier, circulating indoor air repeatedly through filters to clean indoor air, is another active way to control indoor air quality. Therefore, an air purifier with a high efficiency filter 99%, reported by the manufacturer, was chosen to be installed in the living room of the apartment. Similarly, the air purifier also has two grades for different recirculating air volumes which are 350.24 m³/h and 158.98 m³/h respectively. Fig. 5 (a) shows the variations of Ci and Co with an average outdoor PM2.5 concentration of 86 μg/m3. During the first 3 h, Ci decreased while Co increased slightly. However, with the continued growth of Co, Ci stopped decreasing and
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continued rising, indicating that an air purifier with low circulated air volume could not keep indoor PM2.5 concentration under 25 μg/m3 when outdoor PM2.5 concentration was over 80 μg/m3. The I/O ratio fluctuated between 0.15-0.59 with an average of 0.33. Fig. 5 (b) show the results when an air purifier with high circulated air volume was used and the outdoor PM2.5 concentration was approximately 125 μg/m3. The I/O ratio was with an average of 0.29.
Fig. 5. Ci, Co and I/O with low circulated air volume (starting at 8:59); (b) Ci, Co and I/O with high circulated air volume (starting at 17:46).
3.4. Combination control From the above data analysis, the three measures—airtightness improvement, pressure control with mechanical ventilation and air purifier—were not effective if used alone when outdoor pollution was high. Therefore, integrated application of the three measures has been considered and tested.
Fig. 6. Ci, Co and I/O with combination control (starting at 22:46).
Fig. 6 combines airtightness improvement, pressure control with low air volume, and an air purifier with high circulation air volume, in order to control indoor PM2.5. Under the combination control mode, C_i declined rapidly from 66 μg/m3 to 10 μg/m3 with higher outdoor PM2.5 concentration, and kept steady decline even C_o showed a modest increase at approximately 4:00 pm. The I/O ratio declined from 0.41 to 0.01 with an average value of 0.05, which is much lower than that of the isolated operation mode of the earlier scenario, indicating that only the combined operation is effective when outdoor PM2.5 is high. 4. Conclusions The air pollution problem will continue to be a problem in many parts of developing countries. It will take a long time to improve outdoor environment governance, for example, in London and LA, where the smog problem has lasted for more than 30 years. In the near future, the primary task is to improve the indoor air quality and protect people from suffering caused by poor quality air. In this paper, we investigated the influence of different indoor PM2.5 control strategies—airtightness improvement, indoor positive pressure control with a fresh air system, and an air purifier, on indoor particle concentrations within a residential
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building in Shanghai in China. Based on the results of both experimental measurements and modeling, we draw the following conclusions, and their implications are summarized below. In general, the experimental results showed that the indoor PM2.5 concentration can be maintained below 25 μg/m3 continuously under different outdoor PM2.5 concentrations by choosing appropriate control methods. The airtightness improvement is the premise for control, since it will reduce the source and the load. The two control strategies of pressure control and air purification can be used alone when outdoor PM2.5 concentrations are not high. However, each of them has their own limitations. When outdoor PM2.5 concentration is relatively high (usually over 200 μg/m3), the combined control method must be used instead of the single control method to control indoor air quality. A relatively small fresh air volume should be chosen to make sure that the indoor air is kept pressurized. It is advisable that a high efficiency filter (larger than 84.1%) for the fresh air system be selected when the outdoor PM2.5 is higher than 100μg/m3. In regard to other areas with more severe pollution, a higher efficiency filter for the fresh air system should be considered. References [1] Brook R D. You are what you breathe: evidence linking air pollution and blood pressure, Curr. Hypertens Rep. 7 (6) (2005) 427-434. [2] Hwang B F, Chen Y H, Lin Y T, et al. Relationship between exposure to fine particulates and ozone and reduced lung function in children, Environ. Res. 137 (2015) 382-390. [3] Guo Y, Jia Y, Pan X, et al. The association between fine particulate air pollution and hospital emergency room visits for cardiovascular diseases in Beijing, China, Sci. Total Environ. 407(17) (2009): 4826-4830. [4] Li Z, Wen Q, Zhang R. Sources, health effects and control strategies of indoor fine particulate matter (PM2.5): A review, Sci. Total Environ. (2017). [5] Wang F, Meng D, Li X, et al. Indoor-outdoor relationships of PM2.5 in four residential dwellings in winter in the Yangtze River Delta, China, Environ. Pollut. 215 (2016) 280-289. [6] Zhou Z, Liu Y, Yuan J, et al. Indoor PM2. 5 concentrations in residential buildings during a severely polluted winter: A case study in Tianjin, China, Renew. Sust. Energ. Rev. 64 (2016) 372-381. [7] ASHRAE Standard 62.1, 2013. Ventilation for Acceptable Indoor Air Quality, American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), Atlanta. [8] Leung M, Chan A H S. Control and management of hospital indoor air quality, Med. Sci. Monitor 12 (3) (2006) 17-23. [9] ASHRAE Standard 52.2, 2007. Method of testing general ventilation air-cleaning devices for removal efficiency by particle size, American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), Atlanta. [10] Azimi P, Zhao D, Stephens B. Estimates of HVAC filtration efficiency for fine and ultrafine particles of outdoor origin, Atmos. Environ. 98 (2014) 337-346.
ScienceDirect ScienceDirect ScienceDirect Procedia Engineering 00 (2017) 000–000
Available online at www.sciencedirect.com Procedia Engineering 00 (2017) 000–000 Procedia Engineering 00 (2017) 000–000
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Procedia Engineering 205 (2017) 3222–3227
www.elsevier.com/locate/p www.elsevier.com/locate/p rocedia rocedia www.elsevier.com/locate/p rocedia
10th International Symposium on Heating, Ventilation and Air Conditioning, ISHVAC2017, 19-22 October 10th International Symposium on Heating, Ventilation Air Conditioning, ISHVAC2017, 19-22 October 2017, Jinan,and China 10th International Symposium on Heating, Ventilation 2017, Jinan,and China Air Conditioning, ISHVAC2017, 19-22 October 2017, Jinan, China
Existing Existing building building retrofitting retrofitting for for Indoor Indoor PM2.5 PM2.5 Concentration Concentration Control Control on on Existing building retrofitting for Indoor PM2.5 Concentration Control on Smog Days: Case study in China Smog Days: Case study in China Smoga Days: Case study ina China a,* a Yiyi Chua, Peng Xu a,*, Zhiwei Yanga, and Weilin Lia Yiyi Chu , Peng Xu , Zhiwei Yang , and Weilin Li Yiyi Chu , Peng Xu , Zhiwei Yang , and Weilin Li
a a
Department of Mechanical Engineering, Tongji University, aShanghai201800, China a a a,* Department of Mechanical Engineering, Tongji University, Shanghai201800, China
a
Department of Mechanical Engineering, Tongji University, Shanghai201800, China
Abstract Abstract Abstract Severe smog days in many parts of developing countries，such as China and India, have drawn worldwide attention. This study aims at Severe smogvarious days inbuilding many parts of developing countries，such as Chinatoand India,indoor have drawn attention. This study aims as at integrating retrofitting methods of existing buildings control PM2.5worldwide concentrations. Methods are such integrating retrofitting methods of existing buildings toand control PM2.5 concentrations. Methods are such Severe smogvarious days inbuilding manyroom parts of developing countries，such as China India,indoor haveofdrawn worldwide attention. This aims as at airtightness improvement, pressure control, recycling air filtration, and combinations the above. The study verifies thestudy effectiveness airtightness improvement, room pressure control, recycling air filtration, and combinations of the above. The study verifies the effectiveness integrating various building retrofitting methods of existing buildings to control indoor PM2.5 concentrations. Methods are such as 3 in of each control method to reduce the indoor PM2.5 concentration below 25 μg/m3 building. Measurements are conducted for different in building. Measurements are conducted for time different of each control method to room reduce the indoor PM2.5 concentration belowand 25 μg/m airtightness improvement, pressure control, recycling air filtration, ofintheShanghai, above. The study verifies thefirst effectiveness outdoor particle concentration scenarios under different control strategies atcombinations an apartment China. This is the that 3 in building. outdoor particle concentration scenarios under different control strategies at an apartment in Shanghai, China. This is the first time that Measurements are conducted for different of each control method to reduce the indoor PM2.5 concentration below 25 μg/m various existing residential building retrofitting strategies are integrated jointly and different control methods are tested to ensure indoor air various existing residential building retrofitting areconclusions integrated jointly and different control are tested ensure indoor air outdoorunder particle concentration scenarios under different control strategies apartment Shanghai, This the first occupants time that quality different outdoor conditions. The strategies results and canatbean used in manyin parts ofmethods the China. worlds, whenisto building quality under different outdoor conditions. The results and conclusions can be used in many parts of the worlds, when building occupants various existing residential building retrofitting strategies are integrated jointly and different control methods are tested to ensure indoor air choose proper retrofitting methods to control their indoor air quality. choose retrofitting methods controlThe their indoorand airconclusions quality. quality under different outdoor conditions. results can be used in many parts of the worlds, when building occupants © 2017proper The Authors. Published by to Elsevier Ltd. © 2017proper The Authors. Published by Elsevier Ltd. Published by Ltd. choose retrofitting methods to theircommittee indoor airof quality. Peer-review under responsibility ofElsevier thecontrol scientific the 10th International Symposium on Heating, Ventilation and Air Peer-review responsibility of Elsevier the scientific scientific committeeof ofthe the10th 10thInternational InternationalSymposium Symposiumon onHeating, Heating,Ventilation Ventilationand and Air © 2017 The Authors. Published by Ltd. committee under responsibility of the Conditioning. Conditioning. Peer-review under responsibility of the scientific committee of the 10th International Symposium on Heating, Ventilation and Air Air Conditioning. Conditioning. Keywords: Indoor PM2.5 control; Residential building retrofit; Control strategies integration; Filtration model validation. Keywords: Indoor PM2.5 control; Residential building retrofit; Control strategies integration; Filtration model validation. Keywords: Indoor PM2.5 control; Residential building retrofit; Control strategies integration; Filtration model validation.
1. Introduction 1. Introduction 1. Introduction Epidemiologic evidence has shown a relationship between particle pollution exposure and adverse health effects, which has Epidemiologic evidence has shown a relationship between particle pollution exposure and adverse health effects, which has drawn increasing attention regarding methods for controlling PM2.5 pollutants indoors. Brook R D. [1] provided evidence that Epidemiologic evidence regarding has shownmethods a relationship between PM2.5 particlepollutants pollution indoors. exposureBrook and adverse health effects, which that has drawn increasing attention for controlling R D. [1] provided evidence PM is capable of acutely increasing blood pressure and that exposure to PM has tremendous public health implications. Hwang B drawn increasing attention regardingblood methods for controlling PM2.5 to pollutants indoors. Brook R D. [1] provided evidence that PM is capable of acutely increasing pressure and that exposure PM has tremendous public health implications. Hwang B F et al. [2] conducted a two-year study of 12-year-old Taiwanese children and concluded that long-term exposure to PM2.5 may PM of acutely increasing blood andTaiwanese that exposure to PMand hasconcluded tremendous public healthexposure implications. Hwang B F et is al.capable [2] conducted a two-year study of pressure 12-year-old children that long-term to PM2.5 may have a detrimental effect on the development of lung function in children. Yuming Guo et al. [3] explored the association F et al. conductedeffect a two-year of 12-year-old Taiwanese and concluded thatetlong-term exposurethe to PM2.5 may have a [2] detrimental on thestudy development of lung function children in children. Yuming Guo al. [3] explored association between PM2.5 and the hospital emergency room visits in Beijing, China for cardiovascular diseases. There are also many other have a detrimental on theemergency development ofvisits lung in function children. Yuming Guo diseases. et al. [3]There explored the many association between PM2.5 and effect the hospital room Beijing,inChina for cardiovascular are also other epidemiological studies on particular hazards reviewed in [4]. between PM2.5 and the on hospital emergency visitsinin[4]. Beijing, China for cardiovascular diseases. There are also many other epidemiological studies particular hazardsroom reviewed Since people spend approximately 80%~90% of their time indoors, indoor pollution becomes very important to human health, epidemiological studiesapproximately on particular hazards reviewed [4]. indoors, indoor pollution becomes very important to human health, Since people spend 80%~90% of theirintime and various studies from different academic fields on PM2.5 have attracted attention. Some building retrofit measures have been people spend approximately 80%~90% their time have indoors, indoorattention. pollutionSome becomes very retrofit important to human health, andSince various studies from different academic fieldsofon PM2.5 attracted building measures have been proposed by many researchers to reduce indoor PM2.5 concentrations. For example, Fang Wang et al. [5] presented a statistical and various from different academic fields on PM2.5 have attracted attention. Fang SomeWang building retrofit measuresahave been proposed bystudies many researchers to reduce indoor PM2.5 concentrations. For example, et al. [5] presented statistical analysis of the available data of PM2.5 in four residential dwellings with different building airtightness levels and HVAC-filter proposed many researchers reduceinindoor PM2.5 concentrations. Fordifferent example,building Fang Wang et al. [5] presented a statistical analysis ofbythe available data oftoPM2.5 four residential dwellings with airtightness levels and HVAC-filter combinations, which revealed that the enhanced airtightness and the improvement of filter efficiency for both makeup air and analysis of the which available data ofthat PM2.5 in four residential dwellings different building levels HVAC-filter combinations, revealed the enhanced airtightness and thewith improvement of filter airtightness efficiency for bothand makeup air and indoor recirculated air decrease indoor PM2.5 concentration significantly. Zhihua Zhou et al. [6] also proposed a method for combinations, whichairrevealed the enhanced airtightness and the improvement of filter both makeup air and indoor recirculated decreasethat indoor PM2.5 concentration significantly. Zhihua Zhou et efficiency al. [6] alsofor proposed a method for indoor recirculated air decrease indoor PM2.5 concentration significantly. Zhihua Zhou et al. [6] also proposed a method for * * *
Corresponding author. Tel.:86-13601971494 Corresponding author. Tel.:86-13601971494 E-mail address:[email protected] Corresponding author. Tel.:86-13601971494 E-mail address:[email protected] E-mail address:[email protected]
1877-7058 © 2017 The Authors. Published by Elsevier Ltd. 1877-7058 2017 The Authors. Published by Elsevier Ltd. 1877-7058©©under 2017responsibility The Authors. Published by Elsevier Ltd. of the Peer-review of the scientific committee 10th International Symposium on Heating, Ventilation and Air Conditioning. Peer-review under responsibility of scientific thebyscientific committee of the 10th International Symposium on Heating, Ventilation and Peer-review© under the committee 1877-7058 2017responsibility The Authors. of Published Elsevier Ltd. of the 10th International Symposium on Heating, Ventilation and Air Conditioning.
AirPeer-review Conditioning. under responsibility of the scientific committee of the 10th International Symposium on Heating, Ventilation and Air Conditioning. 10.1016/j.proeng.2017.10.290
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controlling infiltration of PM2.5 from outdoors and reducing indoor emissions, based on the experimental results of a typical residential building with different voids of windows and doors and different indoor emission sources. Although the above measurements have been performed to control indoor PM2.5 concentrations to some extent, these methods consider only certain factors and these measurements alone cannot ensure the indoor PM2.5 concentration can be controlled under the standard healthy value of 25 μg/m3 continuously, which is at levels below the current standards of the World Health Organization (WHO) (10 μg/m3 of annual average PM2.5, 25 μg/m3 daily), especially when the outdoor concentration is higher than 200 μg/m3. To help address this gap in knowledge, and provide appropriate retrofitting strategies for existing residential buildings, we conducted thorough experiments in a residential building in Shanghai in China and intend to (1) integrate various indoor PM2.5 concentration control methods; (2) quantitatively measure indoor and outdoor particle concentrations and survey the variation of I/O ratio under outdoor PM2.5 concentration ranges in order to determine a successful retrofitting method that ensures the PM2.5 concentration remains below 25 μg/m3 under any outdoor pollution. 2. Indoor PM2.5 control methods The significance of PM2.5 is strongly related to airborne particle concentration, size distribution, and chemical or biological composition, which depend on factors broadly classified as sources, transformation processes and removal mechanisms. Accordingly, the indoor PM2.5 control methods consist of three aspects including source control, outdoor/indoor transportation control and indoor active control. Some of these aspects are easy to control and others are uncontrollable, as shown in detail in Fig. 1.
Fig. 1. Indoor PM2.5 concentration control methods.
2.1. Airtightness improvement Building airtightness, defined as the resistance to air leakage through unintentional openings in the building envelope, is a fundamental building property that impacts infiltration. Air leakage is an important factor we must consider at first due to its principle effects for ingress of outdoor pollutant – dust, noise, particles, etc. In this paper, we focus on the airtightness improvement which could maximally prevent outdoor particles itself. 2.2. Pressure control with mechanical ventilation According to ASHRAE standard 62.1 [7], maintaining a positive pressure indoors with a mechanical ventilation system, which follows the same goal of airtightness improvement, is a possible approach to prevent outdoor particles from penetrating into the indoor environment. This method has been widely used in specialized care environments such as hospitals [8]. The current standard for suitable indoor pressurization value is intended for industrial facilities such as clean rooms. The relevant code for residential buildings is not available. We can take the low end of the clean room code as a reference in order to obtain a reasonable pressurization value of approximately 5 Pa for residential buildings. The ventilated building will maintain positive pressure as long as the supply airflow rate is greater than the return airflow rate and the wind pressure effect is minimized by enhancing the supply airflow rate.
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2.3. Air filter Historically, standards for evaluating the results of the reference filter test have been developed in response to the needs of the times. ANSI/ASHRAE Standard 52.2 [9] provides filter minimum efficiency reporting value (MERV) rating recommendations to evaluate the performance of air cleaners. Azimi P et al [10] used nearly 200 outdoor particle size distributions from literature to estimate PM2.5 removal efficiencies of a wide range of MERV-rated single-pass HVAC filters. The average removal efficiency values are shown in Fig. 2.
PM2.5 Removal Efficiency
120% 100% 80% 60% 40% 20% 0% MERV Fig. 2. Estimates of PM2.5 removal efficiency of outdoor origin for filters tested according to ASHRAE 52.2-2012 0.
3. Case Study and Results An apartment on the 6th floor, located on Tian Yueqiao Road, Xuhui district in Shanghai, was selected to be retrofitted according to the methods mentioned above for this study. The apartment measures 110 m2 of gross floor and 2.6 m clear height from floor to ceiling. This is a typical apartment building in many China cities. The experiment was conducted during the winter season from November, 2016 to February, 2017. 3.1. Airtightness improvement As mentioned above, good airtightness ensures less infiltration. So it is necessary to improve the airtightness of the apartment at first to reduce the source of PM2.5. The single entrance door has been replaced with a double door, and the single glazing windows were replaced with high quality double glazing windows. Some of the remaining windows were well sealed. To evaluate the effect of the airtightness improvement, the blower door test was used to measure the airtightness of the building envelope. And ACH50, the air change per hour rate when the house is under 50 Pa pressure, is measured by the test. The ACH50 value before and after the airtightness improvement are 9.5 and 6.4 respectively. The airtightness improvement can decrease the ACH value to effectively prevent the ingress of outdoor particles. Fig. 3 (a) and (b) illustrate the changes in Ci before and after airtightness improvement, respectively. The average I/O ratio became 0.53 after the retrofitting, which was lower than that when the building was not well sealed, indicating the decrease of outdoor particle invasion. In addition, we observed that indoor PM2.5 concentration could be kept lower than 25 μg/m3 when outdoor PM2.5 concentration was in a relatively low level after airtightness improvement. However, when outdoor PM2.5 concentration grew higher, indoor PM2.5 concentration could not be controlled in a healthy range, other measures must be taken to decrease the indoor PM2.5 concentration.
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Fig. 3. (a) Ci, Co and I/O before airtightness improvement; (b) Ci, Co and I/O after airtightness improvement.
3.2. Pressure control with mechanical ventilation As mentioned above, a fresh air system with a high efficiency PM2.5 removal filter was chosen to be installed on the balcony of the apartment to achieve micro-positive pressure control. The fan has two grades, high air volume with 216.8 m³/h and low air volume with 170.3 m³/h. Each pressurized value of the two grades was calculated due to the relationship between indoor-outdoor pressure difference and infiltration air flow obtained by the blower door test which are 2 Pa and 1 Pa separately. The PM2.5 removal efficiency for the filter was 84.1%, which lies between MERV 14 and MERV 16. Fig. 4 (a) illustrates that the low air volume fan starts at 7:39 when outdoor PM2.5 concentration has a mean value of 130 μg/m3. Because the air cleaning was on before the experiment, Ci is very low at the beginning (approximately 19 μg/m3), though the outdoor PM2.5 concentration was at approximately 140 μg/m3. However, when Co decreased, Ci also decreased, but with a slight rise lagging behind Co variation. After Co increased, Ci rose again. Similarly, the I/O ratio fluctuated with an average value of 0.25. It is worth noting that low air flow could maintain indoor PM2.5 concentration below 25 μg/m3 while Co was under 120 μg/m3. And from Fig. 4 (b), we observed that high air volume fresh air unit cannot keep indoor PM2.5 concentration in a healthy level while Co increased above 160 μg/m3.
Fig. 4. Ci, Co and I/O with low air volume (starting at 7:39); (b) Ci, Co and I/O with high air volume (starting at 23:21).
3.3. Air purifier Except for indoor pressure control, which introduces outdoor air that must be cleaned by a filter before entering indoors, an air purifier, circulating indoor air repeatedly through filters to clean indoor air, is another active way to control indoor air quality. Therefore, an air purifier with a high efficiency filter 99%, reported by the manufacturer, was chosen to be installed in the living room of the apartment. Similarly, the air purifier also has two grades for different recirculating air volumes which are 350.24 m³/h and 158.98 m³/h respectively. Fig. 5 (a) shows the variations of Ci and Co with an average outdoor PM2.5 concentration of 86 μg/m3. During the first 3 h, Ci decreased while Co increased slightly. However, with the continued growth of Co, Ci stopped decreasing and
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continued rising, indicating that an air purifier with low circulated air volume could not keep indoor PM2.5 concentration under 25 μg/m3 when outdoor PM2.5 concentration was over 80 μg/m3. The I/O ratio fluctuated between 0.15-0.59 with an average of 0.33. Fig. 5 (b) show the results when an air purifier with high circulated air volume was used and the outdoor PM2.5 concentration was approximately 125 μg/m3. The I/O ratio was with an average of 0.29.
Fig. 5. Ci, Co and I/O with low circulated air volume (starting at 8:59); (b) Ci, Co and I/O with high circulated air volume (starting at 17:46).
3.4. Combination control From the above data analysis, the three measures—airtightness improvement, pressure control with mechanical ventilation and air purifier—were not effective if used alone when outdoor pollution was high. Therefore, integrated application of the three measures has been considered and tested.
Fig. 6. Ci, Co and I/O with combination control (starting at 22:46).
Fig. 6 combines airtightness improvement, pressure control with low air volume, and an air purifier with high circulation air volume, in order to control indoor PM2.5. Under the combination control mode, C_i declined rapidly from 66 μg/m3 to 10 μg/m3 with higher outdoor PM2.5 concentration, and kept steady decline even C_o showed a modest increase at approximately 4:00 pm. The I/O ratio declined from 0.41 to 0.01 with an average value of 0.05, which is much lower than that of the isolated operation mode of the earlier scenario, indicating that only the combined operation is effective when outdoor PM2.5 is high. 4. Conclusions The air pollution problem will continue to be a problem in many parts of developing countries. It will take a long time to improve outdoor environment governance, for example, in London and LA, where the smog problem has lasted for more than 30 years. In the near future, the primary task is to improve the indoor air quality and protect people from suffering caused by poor quality air. In this paper, we investigated the influence of different indoor PM2.5 control strategies—airtightness improvement, indoor positive pressure control with a fresh air system, and an air purifier, on indoor particle concentrations within a residential
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building in Shanghai in China. Based on the results of both experimental measurements and modeling, we draw the following conclusions, and their implications are summarized below. In general, the experimental results showed that the indoor PM2.5 concentration can be maintained below 25 μg/m3 continuously under different outdoor PM2.5 concentrations by choosing appropriate control methods. The airtightness improvement is the premise for control, since it will reduce the source and the load. The two control strategies of pressure control and air purification can be used alone when outdoor PM2.5 concentrations are not high. However, each of them has their own limitations. When outdoor PM2.5 concentration is relatively high (usually over 200 μg/m3), the combined control method must be used instead of the single control method to control indoor air quality. A relatively small fresh air volume should be chosen to make sure that the indoor air is kept pressurized. It is advisable that a high efficiency filter (larger than 84.1%) for the fresh air system be selected when the outdoor PM2.5 is higher than 100μg/m3. In regard to other areas with more severe pollution, a higher efficiency filter for the fresh air system should be considered. References [1] Brook R D. You are what you breathe: evidence linking air pollution and blood pressure, Curr. Hypertens Rep. 7 (6) (2005) 427-434. [2] Hwang B F, Chen Y H, Lin Y T, et al. Relationship between exposure to fine particulates and ozone and reduced lung function in children, Environ. Res. 137 (2015) 382-390. [3] Guo Y, Jia Y, Pan X, et al. The association between fine particulate air pollution and hospital emergency room visits for cardiovascular diseases in Beijing, China, Sci. Total Environ. 407(17) (2009): 4826-4830. [4] Li Z, Wen Q, Zhang R. Sources, health effects and control strategies of indoor fine particulate matter (PM2.5): A review, Sci. Total Environ. (2017). [5] Wang F, Meng D, Li X, et al. Indoor-outdoor relationships of PM2.5 in four residential dwellings in winter in the Yangtze River Delta, China, Environ. Pollut. 215 (2016) 280-289. [6] Zhou Z, Liu Y, Yuan J, et al. Indoor PM2. 5 concentrations in residential buildings during a severely polluted winter: A case study in Tianjin, China, Renew. Sust. Energ. Rev. 64 (2016) 372-381. [7] ASHRAE Standard 62.1, 2013. Ventilation for Acceptable Indoor Air Quality, American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), Atlanta. [8] Leung M, Chan A H S. Control and management of hospital indoor air quality, Med. Sci. Monitor 12 (3) (2006) 17-23. [9] ASHRAE Standard 52.2, 2007. Method of testing general ventilation air-cleaning devices for removal efficiency by particle size, American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), Atlanta. [10] Azimi P, Zhao D, Stephens B. Estimates of HVAC filtration efficiency for fine and ultrafine particles of outdoor origin, Atmos. Environ. 98 (2014) 337-346.