COMPARISON OF STRATEGIES TO IMPROVE INDOOR AIR QUALITY AT PRE-OCCUPANCY STAGE IN NEW APARTMENT BUILDINGS

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1 Proceedings: Indoor Air 25 COMPARISON OF STRATEGIES TO IMPROVE INDOOR AIR QUALITY AT PRE-OCCUPANCY STAGE IN NEW APARTMENT BUILDINGS SS Kim 1, DH Kang 1, DH Choi 1, MS Yeo 2, KW Kim 2* 1 Department of Architecture, Graduate School of Seoul National University, Seoul, Korea 2 Department of Architecture, Seoul National University, Seoul, Korea ABSTRACT The indoor air quality of new apartment buildings, which is known to cause sick housing syndrome, has become a major concern among residents as well as construction companies in Korea. Recently, a regulation that limits formaldehyde and VOCs concentration levels in new apartment buildings, the Indoor Air Quality Management Act, came into effect. The construction companies are required to measure the concentration and give public notification before the residents move in. In this study, the effects of air cleaning and ventilation are evaluated to compare the applicable strategies to improve indoor air quality at the pre-occupancy stage. Six residential units were tested under three conditions : one unit was shut tightly, another unit was naturally ventilated, and four units were exposed to different types of decomposing substances. INDEX TERMS New Apartment Buildings, Pre-occupancy Stage, Ventilation, Decomposing Substances INTRODUCTION In the past several decades, rapid urbanization and high population density in Korea have increased the demand for housing. With the increase in the housing supply rate and quality of life, the focus of construction activities has gradually shifted from finding ways to construct more housing to improving the quality of housing. In Korea, the multi-family residential building, which is generally referred to as apartment building, has become the prevalent housing type. These buildings are usually constructed on a massive scale by numerous construction companies. Recently, as the residents needs for the quality of housing have increased, the so-called sick housing syndrome due to the poor indoor air quality of newly constructed apartment buildings has also become a major concern among residents. In order to resolve this matter, the regulation concerning the limitations of formaldehyde and VOCs concentration in newly constructed apartment buildings, Indoor Air Quality Management Act (hereafter referred to as the IAQ Act ) was enforced by the Ministry of Environment in Korea and came into effect of May 3, 24. According to this Act, construction companies, which supply the new apartment buildings with over 1 units, are required to measure the concentrations levels of 7 toxic substances and give public notification before the residents move in. With the enforcement of the government, indoor air quality in newly constructed houses has recently become an important issue at the national level, and has drawn great attention among residents and construction companies. Thus to meet the requirements of the government regulation, the construction companies are hastily finding ways to lower the emission level of formaldehyde and VOCs in apartment buildings. There are several ways to reduce formaldehyde and VOCs concentration in indoor air of new apartment buildings : such as controlling the source by using low-emission building materials that emit smaller amounts of contaminants ( Source Control ), regulating indoor air with fresh outdoor air by natural and mechanical ventilation ( Dilution Control ), and finally cleaning indoor air by air cleaning devices or using decomposing chemical substances ( Air-cleaning Control )(Guo et al. 23, Jalas 23, Sekhar and Keong 23). Although it is widely known that using low-emission building materials is the most effective solution for improving indoor air quality(us EPA 1991, Shaw et al. 1999), this Source Control is not a solution applicable to all apartment buildings of which designs were already completed or which had been constructed prior to the enforcement of the regulation. Therefore, the solutions that can be applied at the pre-occupancy stage are * Corresponding author snukkw@snu.ac.kr 633

2 Proceedings: Indoor Air 25 Air-cleaning Control and Dilution Control. In this study, the effects of air cleaning and ventilation methods were investigated to compare and verify the strategies applied to improve the indoor air quality at the pre-occupancy stage in new apartment buildings. RESEARCH METHODS A case study was carried out to evaluate and compare the strategies to improve indoor air quality in new apartment buildings. A residential unit type with an area of 85m 2 was selected, because it is the most common and preferred choice among the various unit types. Six residential units, finished with the same materials and furnished, were selected from the same apartment complex located at Yong-In in the southern part of Seoul. As shown in the unit plan in Figure 1, all of the rooms can be ventilated by natural means of opening windows and doors, but mechanical ventilation systems were not equipped. In Korea, the radiant floor heating systems (Ondol) are widely used and HVAC systems are not usually adopted in the low-rise (a building with not more than 25 floors) apartment buildings but only in high-rise residential complex buildings. Kitchen /Dining Bedroom 3 Bedroom 2 P1 Living Room Bedroom 1 Figure 1. Floor plan of the test unit The experiments were divided into 6 cases as shown in Table 1. Six housing units were tested prior to occupancy, where one unit was made shut tightly, another was naturally ventilated, and the others were exposed to four different types of decomposing substances from 13 th to 21 st, September 24. Measurements on the temperature, humidity, formaldehyde and VOCs concentration levels were conducted in the middle of living rooms at location P1 (Figure 1). On one day before and on the 1 st, 3 rd, 7 th day after applying the air cleaning and ventilation methods, a series of measurement were taken to investigate how each control method affected the indoor air quality as shown in Table 2. Particular attention was given to the residential units to ensure that there are no external factors that could act as an intervening factor to this experiment. Table 1. The six experimental cases Shut tightly Under natural Applied with decomposing substances cross-ventilation Photocatalyst Aircatalyst Nano-ceramic Negative-ion Table 2. The measurement test schedule Test No. T1 - T2 T3 T4 Date 13/Sep./4 14/ Sep./4 15/ Sep./4 17/ Sep./4 21/ Sep./4 Application of Schedule One day ventilation and 1 st day after 3 rd day after 7 th day after before application decomposing application application application substances The measurements were conducted according to the measuring method of the IAQ Act. In the morning, all units were naturally ventilated by opening windows for 3minutes, and then were tightly shut for 5 hours with all interior doors, drawers and doors of furniture open in order to ensure that the indoor air is sufficiently mixed. The measurements were taken at about 1 p.m. When the concentrations were measured, all the fans in bathrooms 634

3 Proceedings: Indoor Air 25 and kitchen were turned off. Formaldehyde was collected using DNPH cartridges. 15 liters of air samples were taken for 3 minutes, and the samples were analysed using HPLC. VOCs were collected using TenaxTA tubes. 4.5 liters of air samples were taken for 3 minutes, and the samples were analysed using thermal desorber and GC-MS. Among the various VOCs, toluene, benzene, ethylbenzene, xylene, styrene, and p-diclolobenzen levels were analysed. TVOC levels were analysed, and relative humidity and temperature in the units were also measured. RESULTS The concentrations were monitored at one day before and on the 1 st, 3 rd, and 7 th day after applying adsorbents. Table 3 shows the initial environmental condition and formaldehyde and VOCs concentration levels on the 1st day of the measurement (T1). At present, officially recommended or tentative air concentration levels and corresponding indoor air quality standards for formaldehyde and VOCs are not yet being released in Korea. In this study, indoor air quality for the test units was assessed according to the existing recommendations of other countries or international organizations. It is shown that formaldehyde levels ranged from 29µg/m 3 to 457µg/m 3, which are 2~5 times higher than that of recommended thresholds in all units. It should be noted that most standards and guidelines typically recommend a threshold limit level of 1µg/m 3 (Japan Ministry of Health, Labour, and Welfare ; WHO Guideline Europe 2). TVOC and toluene levels also reached fairly high levels from 517µg/m 3 to 192µg/m 3, of which the tentative or recommended level is between 4µg/m 3 and 6µg/m 3 (Japan MHLW ; FiSIAQ 2). However, it is observed that ethylbenzene, xylene, styrene, and p-diclolobenzene levels are very low to the extent that they are almost negligible. Especially, p-diclolobenzene was not detected at all. Table 3. The initial concentration levels of test units(t1) Temp( C) R. H. (%) Formaldehyde(µg/m 3 ) TVOC(µg/m 3 ) Toluene(µg/m 3 ) Benzene(µg/m 3 ) Ethylbenzene(µg/m 3 ) Xylene(µg/m 3 ) Styrene(µg/m 3 ) The ratios of concentration level to initial concentration level were plotted in Figures 2, 3, and 4. Figure 2 shows the variation of formaldehyde concentration ratio with the passage of time. Figures 3 and 4 show the variation of TVOC and toluene concentration ratio respectively. Although the measured data of each residential unit is different, the concentration curves show similar trends with indoor temperature variation, with the exception of a few cases. In the unit which was shut tightly during the experiments, the concentration of all types of indoor pollutants increased considerably compared to other cases. In the units for case 5 and case 6, TVOC concentration levels were very higher than those of other units due to the large volume of other unknown VOCs besides the 6 analysed VOCs. It can be seen that all of the cases considered that the measured concentration levels of TVOC and toluene were higher than the recommended values. 635

4 Proceedings: Indoor Air 25 Formaldehyde concentration ratio(%) Figure 2. Formaldehyde concentration ratios of 6 test units TVOC concentration ratio(%) Figure 3. TVOC concentration ratios of 6 test units Toluene concentration ratio(%) Figure 4. Toluene concentration ratios of 6 test units. DISCUSSION Based on the results of the experiments, it is shown that formaldehyde, TVOC and toluene levels reach fairly high levels compared to the existing tentative or recommended levels of other countries or organizations. The concentration levels of the other 5 VOCs, with the exception of toluene, were not so serious for all of the tested units. Based on this, it is clearly evident that formaldehyde, TVOC, and toluene are the primary indoor pollutants in these newly constructed apartment buildings in Korea. Although the specific effects of natural ventilation depend on how tight the building is and how much the wind flow is, etc, it was found that the increasing rate of concentration levels in naturally ventilated units could be controlled to 2/3 of the increasing rate in unventilated units. In the units for case 5 and case 6, formaldehyde concentration levels were decreased after applying the substances, and the increasing rates of TVOC concentration levels were relatively low. It was also found that the increasing rates of formaldehyde concentration levels in cases where the decomposing substances were applied were lower than those of other units that was shut tightly or ventilated naturally. However, for VOCs, it could not be found whether the indoor 636

5 Proceedings: Indoor Air 25 air quality in the units where decomposing substances were used had improved much more than other cases. Therefore, it can be concluded that using decomposing substances can be said to be an efficient strategy for mitigating the high formaldehyde concentration or restraining the increase of the formaldehyde concentration in new apartment buildings prior to occupancy(zhao and Yang 23). But, it is not yet confirmed whether this applies similarly to VOCs concentration. CONCLUSION AND IMPLICATIONS The indoor air quality of several residential units in a new apartment complex was investigated in this study. As formaldehyde, TVOC, and toluene are major indoor pollutants of concern in newly constructed apartment buildings, the construction companies must take into consideration the emission level of these pollutants. It is widely known that an architect s stipulation for selecting building materials is necessary for improving indoor air quality of new apartment buildings. If it is impossible to prevent such emission of pollutants, decomposing substances such as photocatalyst, and, dilution control such as natural and mechanical ventilation should be used as an alternative strategy. In this study, the effects of air cleaning and ventilation methods were evaluated to compare and verify the strategies applied to improve indoor air quality at pre-occupancy stage in new apartment buildings. The results demonstrated that ventilation is the most effective ways to control indoor air pollution caused by formaldehyde and VOCs emissions. During the pre-occupancy period sufficient ventilation has been proved to reduce the pollutant concentration levels in indoor air. The air cleaning method using decomposing substances to reduce formaldehyde levels indoors was also discussed. In cases where ventilation cannot be done continuously, the air cleaning strategy with decomposing substances would be alternative way for reducing the formaldehyde concentration level. In the future, a study on the evaluation of mechanical ventilation and bake-out among dilution control methods and air cleaners will be conducted to explore other ways or strategies that can be applied to new apartment buildings in the pre-occupancy stage. ACKNOWLEDGEMENTS The authors thank the Ministry of Environment of South Korea and the Korea Institute of Environmental Science and Technology for their support for this research (Core Environmental Technology Development Project for Next Generation, ). REFERENCES Anonymity FiSIAQ. 21. Classification of Indoor Climate 2 : Target values, design guidance and product requirements. FiSIAQ publication. Guo H.. Murray F. and Lee SC. 23. The development of low volatile organic compound emission house-a case study, Building and Environment. 38(12) : Jalas J. 23. Quality of indoor air and functionality of ventilation in day care centres, Proceedings of the 7th International Conference on Healthy Buildings Healthy Buildings 23, Singapore. Sekhar SC. and Keong LW. 23. Ventilation and IAQ performance of a typical split-system air conditioning unit in a residential apartment in Singapore, Proceedings of the 7th International Conference on Healthy Buildings Healthy Buildings 23, Singapore. Shaw CY. et al Improvement of indoor air quality in four problem homes, Building and Environment. 34(1) : US EPA Building Air Quality : A Guide for Building Owners and Facility Managers. WHO. 2. Air Quality Guidelines for Europe, 2 nd edition. WHO Regional Publications. Zhao J. and Yang X. 23. Photocatalytic oxidation for indoor air purification : a literature review, Building and Environment. 38(5) :