Evaluation of the outdoor thermal environment in redevelopment buildings in front of Osaka Station based on observations

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Albert Townsend
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1 Academic Article Jurnal f Heat Island Institute Internatinal Vl. 9-2 (2014) Evaluatin f the utdr thermal envirnment in redevelpment buildings in frnt f Osaka Statin based n bservatins Kentar Ayama *1 Sae Kygku *1 Sintar Nakayama *1 Riek Yagi *1 Hideki Takebayashi *1 Etsuk Ishii *1 Makik Kasahara *2 Shing Tanabe *2 Makt Kuyama *2 *1 Graduate Schl f Engineering, Kbe University *2 Nikken Sekkei Ltd. Crrespnding authr: Kentar AOYAMA, 144t001t@stu.kbe-u.ac.jp ABSTRACT Several technlgies used as cuntermeasures against urban heat islands, such as green cver and water surfaces, are being applied t redevelpment buildings in frnt f central Osaka Statin. In this study, we evaluated the utdr thermal envirnment by fcusing n the effects f wind velcity and MRT, which is reflective f slar radiatin shielding, in an pen plaza with water surfaces, a rftp garden with plants, and a sunken garden placed between high-rise buildings. In the pen plaza, SET* was high due t high MRT and reduced by slightly strng wind at sme measurement pints. In rftp garden, SET* was high due t high MRT and nt reduced s much by wind with a little variatin in each measurement pint. In the sunken garden, SET* was lw due t lw MRT, because slar radiatin is shielded by plants and high-rise buildings at mst f the measurement pints, while wind velcity is lw due t wind resistance ffered by plants. T cnclude, the imprvement f MRT is the mst significant factr fr the imprvement f the utdr thermal envirnment during the daytime. Key Wrds : Outdr thermal envirnment, Wind velcity, MRT, SET*, Redevelpment buildings 1. Intrductin Several technlgies used as cuntermeasures against urban heat islands, such as green cver and water surfaces, are being applied t redevelpment buildings in frnt f central Osaka Statin. With regards t a previus study, Akagawa et al.(1) analyzed the utdr thermal envirnment f a rftp garden n a large cmmercial building. In subsequent research, Akagawa et al.(2) als cmpared standard effective temperature at an area shielded by bjects, trees, and semi-pen spaces in a large, artificial green space. standard effective temperature is transcribed int SET*. SET* was fund t be lwest in semi-pen spaces in the mrning and evening, and in spaces shielded by trees in the daytime. As well, SET* was highest in spaces shielded by varius bjects, due t lw wind velcities in the daytime and high air temperatures at night. The authrs cncluded that ventilatin and slar radiatin shielding can effectively imprve the utdr thermal envirnment. Hwever, they did nt discuss whether ventilatin r slar radiatin shielding was mre imprtant fr the imprvement f the utdr thermal envirnment. In this study, we evaluated the utdr thermal envirnment by fcusing n the effects f wind velcity and mean radiative temperature, which is reflective f slar radiatin shielding, in an pen plaza with water surfaces, a rftp garden with plants, and a sunken garden placed between high-rise buildings. Mean radiative temperature is transcribed int MRT. 2. Measurement 2.1 Measurement methd The selected measurement perid was frm 22 t 26, Air temperature, relative humidity, surface temperature, wind directin and velcity, and thermal images were btained by a thermistr, capacitive humidity sensr, infrared thermmeter, windsck, ht-wire anemmeter, and therm-camera. Measurements were made at 10:00, 13:00, 17:00, and 20:00 in 5 r 6 measurement pints in each f the fllwing areas: pen plaza, rftp garden, and sunken garden. We selected these 3 areas in the redevelpment building cmplex because several

urban heat island cuntermeasure technlgies, such as green Table 1 Measurement elements, measurements, and analytical cver and water surfaces, had already been

There are tw tall buildings t Air temperature Measured at 5 sec., averaged in 5 min.

There is little vegetatin present, and pen Surface temp. Measured n grund and wall surface spaces and water surfaces are dminant.

, averaged in 30 sec. redevelpment building cmplex. The sunken garden, where View factr Calculated by fisheye pht at 1.

The measured variables and the measurement and analytical methd are shwn in Table 1. We carried ut the measurements by mving between the measurement pints.

The measurement pints were selected with cnsideratin f surface cver, ventilatin, and slar radiatin shielding.

2 urban heat island cuntermeasure technlgies, such as green Table 1 Measurement elements, measurements, and analytical cver and water surfaces, had already been applied at thse sites. methds The pen plaza is lcated n the suthern tip f the Element Measureent and analysis methd redevelpment building cmplex. There are tw tall buildings t Air temperature Measured at 5 sec., averaged in 5 min. the nrtheast and suth f the pen plaza, while the western side Relative humidity Measured at 5 sec., averaged in 5 min. f the plaza is pen. There is little vegetatin present, and pen Surface temp. Measured n grund and wall surface spaces and water surfaces are dminant. The rftp garden (GL Wind directin Recred mst frequent wind directin + 45 m) is n the rf f the suthernmst building in the Wind velcity Measured at 1 sec., averaged in 30 sec. redevelpment building cmplex. The sunken garden, where View factr Calculated by fisheye pht at 1.5m plants are prevalent, is lcated between the nrthernmst and Thermal image Taken t capture panramic view suthernmst high-rise buildings. The measured variables and the measurement and analytical methd are shwn in Table 1. We carried ut the measurements by mving between the measurement pints. Figure 1 shws the measurement pints and phts taken via fisheye lens in each area. The measurement pints were selected with cnsideratin f surface cver, ventilatin, and slar radiatin shielding. Six measurement pints in the pen plaza were numbered frm 1 t 6, five measurement pints in the rftp garden were labeled A t E, and six measurement pints in the rftp garden were labeled a t f. (a) Air temperature (b) Relative humidity (a) (c) Grund surface temperature (b) Rftp garden (d) Wind velcity (c) Fig. 2 Air temperature, relative humidity, grund surface Fig. 1 Lcatin f the measurement pints and phts taken via temperature, and wind velcity at 13:00 n 25, 2013 fisheye lens

2.2 Measurement results In the daytime, the air temperature increased in the fllwing rder: pen plaza, rftp garden, and sunken garden. At night, the temperature was lwest in the rftp garden.

The wind velcity was high during the daytime at several measurement pints in the rftp garden.

Air temperature, relative humidity, grund surface temperature, and wind velcity in each measurement pint at 13:00 n 25, 2013, is shwn in Figure 2.

3 2.2 Measurement results In the daytime, the air temperature increased in the fllwing rder: pen plaza, rftp garden, and sunken garden. At night, the temperature was lwest in the rftp garden. Differences in relative humidity were small; hwever, relative humidity values were greatest at the measurement pints lcated near water surfaces in the pen plaza and sunken garden. The wind velcity was high during the daytime at several measurement pints in the rftp garden. In the daytime, the artificial grund surface temperature in the pen plaza and rftp garden was high due t slar radiatin absrptin. Air temperature, relative humidity, grund surface temperature, and wind velcity in each measurement pint at 13:00 n 25, 2013, is shwn in Figure 2. minimum MRT, and abut 8 C due t the differences between measured maximum and minimum wind velcity. The effect f wind velcity n SET* was fund t be greater than that f MRT. MRT cmpnents at each measurement pint are shwn in Figure 4. MRT was primarily affected by grund surface temperature, wall surface temperature, and direct slar radiatin. In particular, the grund surface temperature dminated MRT. The grund surface temperature was lw at measurement pints 1 and 3, where slar radiatin was shielded in the mrning. The wind vectrs are shwn in Figure 5. Wind directins varied depending n the bstacles present arund the measurement pints. The characteristics f the thermal envirnment at each 3. Calculatin f SET* Measured values f fur envirnmental elements; air temperature, surface temperature, relative humidity, and wind velcity, were used fr calculating SET*. SET* is cmmnly used as an indicatr f the utdr thermal envirnment, particularly in Japan. Therefre, we have fcused n SET* in this study. We set a metablic rate f 2.0 Mets, with the assumptin f a certain walking pace, and we set the amunt f clthing at 0.6 cl, assuming the use f summer clthes. Thrugh the sensitivity analysis f SET* fr changes in fur envirnmental elements, it was bserved that MRT and wind velcity are the dminant factrs in SET*. Therefre, we evaluated the utdr thermal envirnment by fcusing n the effects f wind velcity and MRT. MRT was calculated with surface temperature, view factr, direct slar radiatin, and diffuse slar radiatin. We divided the measured glbal slar radiatin int direct and diffuse slar radiatin fr this purpse. MRT was an instantaneus value and wind velcity was averaged ver 30-secnds, based n measurements taken at ne-secnd intervals. The effects f MRT and wind velcity n SET* in all areas at 13:00 during 25 is shwn in Figure 3. The thermal cmfrt f SET* is shwn in accrdance with the study results f Ishii et al.(3). In the pen plaza, MRT was high and the variatin in wind velcity was large. In the rftp garden, MRT was als high, while the wind velcity was generally high. In the sunken garden, the variatin in MRT was large as well, but the wind velcity was lw. Fig. 3 Effects f MRT and wind velcity n SET* in all areas at 13:00 n 25, 2013 Fig. 4 Cmpnents f MRT in the pen plaza at 13:00 n 25, Discussin f SET* 4.1 The variatin in SET* in the measurement pints was abut 4.5 C due t the differences between measured maximum and Fig. 5 Wind vectrs in the pen plaza at 13:00 n 25,

- At measurement pint 4, SET* was lw because the wind velcity was high, due t a lack f bstructins in the center f the pen plaza.

4 measurement pint were as fllws: - At measurement pint 2, SET* was lw because the wind velcity was high due t the wind passage in high-rise buildings. - At measurement pint 3, SET* was high because the wind velcity was lw, due t shielding by trees. - At measurement pint 4, SET* was lw because the wind velcity was high, due t a lack f bstructins in the center f the pen plaza. - At measurement pints 5 and 6, SET* was high because the wind velcity was lw, due t the presence f a glass fence between the grund and water surfaces. At measurement pint 5 r 6, any imprvement f MRT derived frm water surfaces was nt bserved. Therefre, we analyzed the relatinship between the distance frm the water surface bundary and MRT, using a view factr as an indicatr. The relatinship between the distance frm the water surface bundary and MRT is shwn in Figure 6. We calculated the view factr by the water surface by changing the distance frm the water surface bundary, with a height f 0.88 m assuming a child s stature, and a height f 1.5 m assuming an adult s stature. If the distance was clser than 2 m and 3.5 m t the water surface bundary, the imprvement f MRT by the water surface was cnfirmed at bth 0.88 m and 1.5 m heights. Fig. 6 Relatinship between the distance frm the water surface bundary and MRT, at 0.88 m (child) and 1.5 m (adult) height Fig. 7 Cmpnents f MRT in the rftp garden at 13:00 n 25, Rftp garden The variatin in SET* in the measurement pints was abut 3 C, due t differences between the measured maximum and minimum MRT, and abut 2.5 C due t differences between the measured maximum and minimum wind velcity. The effect f MRT n SET* was fund t be mre significant than that f wind velcity. The MRT cmpnents at each measurement pint are shwn in Figure 7. The MRT was primarily affected by plant surface temperature, grund surface temperature, and direct slar radiatin. The grund surface temperature dminated MRT, similar t the results btained frm the pen plaza. Wind vectrs are shwn in Figure 8. The primary wind directin n the rftp garden was frm the suthwest. The wind velcity was high at measurement pints A and B n the windward side, and slightly lwer at measurement pints C, D, and E n the leeward side, due t the wind resistance ffered by plants and bstacles. The characteristics f the thermal envirnment n each measurement pint were as fllws: - At measurement pints A and C, SET* was lw because the MRTs were lw, due t lw grund surface temperatures n brick and stne. - At measurement pint B, SET* was lw because the MRT was lw, due t the large view factr f plants. - At measurement pint D, SET* was high because the MRT Fig. 8 Wind vectrs in the rftp garden at 13:00 n 25, 2013 Fig. 9 Cmpnents f MRT in the sunken garden at 13:00 n 25, 2013 was high, due t high grund surface temperatures n the wd deck. - At measurement pint E, SET* was high because MRT was high, due t high grund surface temperatures n stne

5 4.3 The variatin in SET* in the measurement pints was abut 9.5C due t the differences between the measured maximum and minimum MRT, and abut 3C due t the differences between the measured maximum and minimum wind velcity. The effect f MRT n SET* was dminant, as cmpared t wind velcity. The cmpnents f MRT at each measurement pint are shwn in Figure 9. There were few plants at measurement pint a, and mre plants present at measurement pint f. Slar rbital diagrams crrespnding t the date f 25 are shwn in Figure 10. At the majrity f the measurement pints, the slar radiatin was shielded by high-rise buildings and plants Fig. 10 Slar rbital diagrams frm the sunken garden n 25, 2013 thrughut the day. MRT was primarily affected by plant surface temperatures, direct slar radiatin, and grund surface temperatures. MRT Table 2 Averaged values f SET*, MRT, and wind velcity at was lw at mst f the measurement pints because f the large 13:00 n 25, 2013 view factr f plants, while MRT was high at measurement SET* MRT wind velcity pints a and d, due t the incidence f direct slar radiatin C 50.0 C 2.2 m/s The wind velcity at each measurement pint was lw, due t Rftp garden 38.6 C 50.3 C 2.1 m/s the wind resistance ffered by plants. 5. Discussin and Summary 33.1 C 38.0 C 0.9 m/s Table 3 Variatins in SET* due t differences in MRT and wind velcity at 13:00 n 25, 2013 The averaged value f SET*, MRT, and wind velcity in each due t difference due t difference in area at 13:00 n 25, 2013, is shwn in Table 2. The in MRT wind velcity 4.5 C 8.0 C in each area at 13:00 n 25, 2013, is shwn in Table 3. Rftp garden 3.0 C 2.5 C The averaged value f SET* in the sunken garden was the 9.5 C 3.0 C variatin in SET* due t differences in MRT and wind velcity lwest ut f the three measurement areas because the lwest MRT was present at this lcatin, despite the fact that the wind velcity was als the lwest at the same site. The imprvement Table 4 Averaged values f SET*, MRT, and wind velcity at 10:00, 17:00 and 20:00 n 25, 2013 in MRT due t slar radiatin shielding by plants and high-rise SET* buildings is mre effective fr the imprvement f the utdr thermal envirnment, rather than thrugh The averaged value f SET*, MRT, and wind velcity in each 10:00 study area fr ther measurement times and days, i.e., under alternative weather cnditins, are shwn in Tables 4 and 5. The tendency fr SET* t be lwer in the sunken garden during these 17:00 17:00 and 20:00 is lw due t the lw MRT derived frm radiative cling and a slightly strnger wind. T cnclude, the imprvement f MRT is the mst significant factr fr the imprvement f the utdr thermal envirnment during the daytime, althugh ventilatin enhancements are als imprtant fr the imprvement f the utdr thermal envirnment during the evening C 1.7 m/s 31.3 C 41.1 C 2.6 m/s 30.8 C 37.2 C 0.8 m/s 38.9 C 0.7 m/s 45.4 C Rftp garden 31.3 C 38.5 C 2.1 m/s 30.6 C 36.3 C 1.4 m/s 20: C Rftp garden measurement times and days is similar t the bservatins taken at 13:00 n 25. Hwever, the SET* in the rftp garden at wind velcity ventilatin enhancements. MRT 26.0 C 0.4 m/s 30.0 C Rftp garden 24.2 C 27.5 C 1.3 m/s 25.3 C 29.3 C 0.8 m/s

6 Table 5 Averaged values f SET*, MRT, and wind velcity at 13:00 n 22, 23, 24 and 26, 2013 SET* MRT wind velcity 35.3 C 46.8 C 2.6 m/s Rftp garden 34.8 C 48.1 C 3.4 m/s C 37.1 C 2.0 m/s 30.4 C 38.5 C 1.7 m/s Rftp garden 30.8 C 39.2 C 1.7 m/s C 36.3 C 1.9 m/s C 2.3 m/s Rftp garden 35.7 C 47.6 C 2.3 m/s C 32.9 C 1.2 m/s 34.6 C 43.6 C 2.4 m/s Rftp garden 34.6 C 45.4 C 3.0 m/s C 38.0 C 0.9 m/s References (1) H. Akagawa, K. Fukumi, T. Kubta, H. Takebayashi and M. Mriyama, Study n thermal envirnment and behavir f visitrs at a large rftp garden n a cmmercial building in summer, Jurnal f Envirnmental Engineering (Transactins f AIJ) 611, (2007) (2) H. Akagawa and H. Sugimt, Envirnmental evaluatin at large-scale greening area in urban canyn: Part 2 Investigatin f thermal envirnment in the district, Summaries f technical papers f annual meeting f AIJ D-1, (2011) (3) A. Ishii, T. Katayama, Y. Shitsuki, H. Yshimizu and Y. Abe, Experimental study n cmfrt sensatin f peple in the utdr envirnment, Jurnal f Architecture and Planning (Transactins f AIJ) 386, (1988) (Received Nv. 20, 2014, Accepted Dec. 27, 2014)

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