SURVEY ON INDOOR AIR QUALITY IN CONTEMPORARY RESIDENTIAL BUILDINGS IN JAPAN

Transcription

1 SURVEY ON INDOOR AIR QUALITY IN CONTEMPORARY RESIDENTIAL BUILDINGS IN JAPAN Teruaki Mitamura 1, Haruki Osawa 2, Yasuo Kuwasawa 2, and Hisashi Miura 2 1 Department of Architecture, Ashikaga Institute of Technology, Ashikaga, Japan 2 Building Research Institute, Tsukuba, Japan ABSTRACT In order to facilitate rational development on the efficient new ventilation system with new detectors against the health problems caused by VOC in residential buildings, authors studied to clarify the actual IAQ conditions around occupied area. To grasp the contemporary circumstances and transfer-mechanisms of VOC in houses, the actual data regarding the pollutants and its movement were collected in 9 detached houses in Tochigi prefecture. In this paper, investigated results for indoor thermal environment, ventilation and indoor chemical pollutants are described. In this study, an interesting decreased trend of average concentration of formaldehyde was found. Steady appearance of alternative chemicals such as various carbonyls, and frequent observation of unexpected TVOC value over 4µg/m 3 are discussed. A composition ratio of VOCs and its characteristic were analyzed. The results of this research were compared with that of the past nationwide research in Japan. As a result, comparing two constructions between Japanese conventional method and 2 4 method, each characteristic of indoor air pollutions was identified. The characteristic of indoor chemical pollutions in 9 houses in Tochigi prefecture was similar with that of the past nationwide research in Japan. KEYWORDS Chemical pollution, Ventilation, Field survey, Wooden construction INTRODUCTION In Japan, many research works for indoor chemical pollutants have been carried out for sometimes, and recently the guideline for indoor VOC concentrations has been formulated. The Building Standard Law on Sick House Issues wad amended on July 1, 23. Under the said law, it is prohibited to use chlorpyrifos as an insecticide, and the use of the plywood emitting much formaldehyde is limited. The most important point of the new building standard law on Sick House Issues was the obligation to install the mechanical ventilation system. In this respect, its effect on the Japanese type of houses is still not clear. A matter of concern is the state of indoor chemical pollution after enforcement of the new building standard law on Sick House Issues. The purpose of this study was to investigate the actual condition of indoor air quality and the performance of the ventilation equipment in houses built after enforcement of the new building standard law on Sick House Issues. METHODS Investigated houses Nine detached houses in Tochigi Prefecture of Japan were investigated. These houses were built after enforcement of the new building standard law on Sick House Issues. The mechanical ventilation system was installed in all houses. Outlines of the nine investigated houses are shown in Table 1. Investigated period was from February to March, 26. Corresponding Author: Tel: ext.551, Fax: address: mitamura@ashitech.ac.jp

2 ID Construction time (Year.Month) Table 1 Outline of the investigate houses Floor area [m 2 ] Construction method Ventilation system Air tightness [cm 2 /m 2 ] A Forced supply & exhaust 2.34 B Forced supply & exhaust -* C Forced supply & exhaust 3.53 D Forced supply & exhaust -* E Forced supply & exhaust 3.42 F Japanese conventional Forced exhaust.79 G Forced supply & exhaust 3.7 H Japanese conventional Forced exhaust 4.16 I Forced supply & exhaust -* *: not measured Measurement of indoor air temperature, humidity and CO 2 concentration A small thermo recorder was used to measure indoor air temperature and humidity. The infrared CO 2 monitor was used to measure indoor CO 2 concentration. Indoor air temperature, humidity and CO 2 concentration were measured in the living room and bedroom. Measurement of air tightness and airflow of the ventilation system Air tightness in buildings was measured by the depressurized method. The hot wire anemometer was used to measure airflow at the mechanical fan, air inlet and outlet. Measurement of chemical pollutants Concentrations of formaldehyde and VOCs were measured in the living room and bedroom. In addition, chemical pollutant in the space of the inside wall was also measured. Indoor chemical pollutant was measured at the height of 1.1m above the floor. For the measurement in the space of inside wall, the sampling tube was put into the crack of the removed consent box on the wall. The measurement method of chemical pollutants is shown in Table 2. Table 2 Measurement method of formaldehyde and VOCs Item Location Sampler Sampling method Formaldehyde Indoor air Active (.1 l/min, 24 hours) DNPH cartridge Space of the inside wall Active (1. l/min, 3 min.) VOC Indoor air Active (.1 l/min, 24 hours) Charcoal absorption tube Space of the inside wall Active (1. l/min, 3 min.) RESULTS AND DISCUSSION Indoor air temperature and CO 2 concentration Variation of indoor and outdoor air temperature is shown in Figure 1. Average temperature in the living room was ranging from 17 to 22 C, which was higher than that of the bedroom. Indoor air temperature in House D was comparatively low, because only an old couple was staying in the other room during daytime and their bedroom was not heated. Daily range of temperature in all houses was varying from 7 to 1 C, which was comparatively large because of the intermittent heating in most houses. Variation of indoor CO 2 concentration is shown in Figure 2. Average concentration in Houses C, D, E and F were comparatively low, because air conditioning and floor heating system were used in those houses. The range of concentration in other houses was quite large. In those houses, the open type kerosene fan heater was used.

3 Air flow rate of the ventilation system Air flow rate of the ventilation system is shown in Figure 3. Air flow rate in House B was comparatively small, because air filter of the supply fan in the living room was clogged. Air flow balance between supply and exhaust was all different in each house. Supply air flow in House F and H was at the lower limit of the anemometer. In those houses, forced exhaust ventilation system was installed. Concentrations of Formaldehyde and VOCs Concentration of formaldehyde is shown in Figure 4. Although formaldehyde was detected in all houses, indoor air concentration was lower than 1 µg/m 3 of the guideline value. Concentration in the space of the inside wall was also at low level. It is deemed that measures for the source of formaldehyde were taken after enforcement of the new building standard law on Sick House Issues. Concentration of VOCs is shown in Figure 5. (ethanol) were detected in all houses, and its concentration was particularly high in Houses A, B and G. Concentration of halogens (p-dichlorobenzene) in the bedroom of House A was high because of the use of an insecticide in the closet and chest of drawers. Concentration of terpenes (α-pinene) in House F was quite high. It could be because a source of terpenes was the wooden flooring material. The characteristic in Houses F and H of Japanese conventional construction method was high concentration of α-pinene and ethanol. The number of rooms that the concentrations of TVOC were over the guideline value of 4 ug/m 3 was 7 rooms (5 houses) out of the total of 18 rooms (9 houses). Temperature ( C) Left:, Middle:, Right: Outdoor MAX. Ave.+SD Ave.-SD MIN. Figure 1 Variation of indoor and outdoor temperature >25 CO2 Concentration (ppm) Left:, Right: MAX. Ave.+SD Ave.-SD MIN. Figure 2 Variation of indoor CO 2 concentration

4 Air flow rate (m 3 /h) Exhaust Supply * *: not measured Figure 3 Air flow rate of the ventilation system Concentration of formaldehyde (µg/m 3 ) Figure 4 Concentration of formaldehyde Concentration of VOCs (µg/m 3 ) TVOC:391, 2721, 131 Figure 5 Concentration of VOCs Aliphatic Aromatic

5 Comparison with the results of the past nationwide research in Japan In order to grasp the trend of indoor VOCs pollutant, results of this research was compared with that of the past nationwide research in Japan. The past nationwide research was carried out during winters of 21 and 22 (T. Mitamura et al. 25). The number of the investigated houses was 49 (87 rooms). Investigated areas were Hokkaido and Tohoku regions as cold area, and Kanto and Kyushu regions as warm area. About 8 percents of investigated houses were airtight (αa is less than 4. cm 2 /m 2 ). The average composition ratio of VOCs is shown in Figure 6. The composition ratio of the steel construction was different from other construction methods. The ratios of aliphatic and halogens were low, and the ratio of aromatic was high comparing with other construction methods. Comparison of results between this research (9 houses in Tochigi) and the past nationwide research is shown in Figure 7. The characteristic of the composition ratio of VOCs for Japanese conventional method and 2 4 construction method was identified. Comparing results between this research and the past nationwide research, both results of the trend of the composition ratio for Japanese conventional method were similar, except that the ratio of terpenes in this research was quite high. Similarly, both results for 2 4 construction method were similar whereby the ratio of alcohols was high. Average of the composition ratio (%) Aliphatic Aromatic All houses(n=87) Conventional method (n=4) 2 4 method(n=19) Steel construction(n=6) Reinforced Concrete (n=22) Figure 6 Average of the composition ratio of VOCs in the past research Average of the composition ratio (%) Aliphatic Aromatic Past research (n=4) This research(n=2) Average of the composition ratio (%) Aliphatic Aromatic Past research (n=19) This research (n=7) (a) Japanese conventional method (b) 2 4 construction method Figure 7 Comparison of results between this research (9 houses in Tochigi) and the past research

6 CONCLUSIONS The open type kerosene fan heater was used and intermittent heating was carried out in most of the investigated houses. Therefore, the change of indoor temperature was large and indoor CO 2 concentration was high in some of houses. Distinctive characteristics for the detected VOCs pollutant and the composition ratio were clearly found in Japanese conventional method and 2 4 construction method. Comparing with the results of the past nationwide research, the trend of the composition ratio of VOCs in each construction method was almost similar. For future study, the target of the investigated house will be expanded to include other areas and other construction methods, as well as maintaining the investigated database continuously. ACKNOWLEDGEMENTS This study was carried out as part of the project by the New Energy and Industrial technology Development Organization. Authors would like to acknowledge the occupants of the investigated houses. REFERENCES 1. H. Osawa, et al. (26) Study on Indoor Air Quality in Contemporary Residential Buildings Part 1. Summary of First Measurement and its Basic Analysis, Technical Papers of Annual Meeting the Society of Heating, Air-Conditioning and Sanitary Engineers of Japan, (in Japanese) 2. T. Mitamura, et al. (26) Study on Indoor Air Quality in Contemporary Residential Buildings Part 2. Analysis and Comparison with Results of the Past National Wide Research, Technical Papers of Annual Meeting the Society of Heating, Air-Conditioning and Sanitary Engineers of Japan, (in Japanese) 3. T. Mitamura, et al. (25) Investigation of Indoor Chemical Pollutants and Ventilation Rate in Japanese Houses, Proceedings of Indoor Air 25,