1、NA-04-2-1 Thermal Comfort and Adaptation in Semi-Outdoor Environments Junta Nakano, D.Eng. Associate Member ASHRAE ABSTRACT Designing semi-outdoor environments such as atria or open-style cafes is apopular technique in modern architecture to provide occupants with natural outdoor elements in an arti
2、- jcial environment. Occupants are likely to expect a thermal environment differing from the indoors, and thermal adapta- tion is expected to play a major role in achieving comfort. Seasonal jeld surveys were conducted in four semi-outdoor environments for short-term occupancy with different levels
3、of environmental control. Observations were made on occupancy conditions and clothing adjustments. Sets of 2,248 question- naires and corresponding thermal environmental data were also collected throughout the survey. Clothing adjustment was afected largely by outdoor temperature and less by the imm
4、e- diate thermal environment. Number of occupants and time of occupancy decreased following the daily mean air tempera- ture decrease in non-air-conditioned semi-outdoor environ- ments. Occupants in semi-outdoor environments were tolerant of a two to three times wider range ofenvironmental condition
5、s compared to thatpredicted by PPD. INTRODUCTION Atria or terraces designed to introduce sunlight and fresh air are built in modem architecture to attract people from aesthetic aspects or to add diversity to the architectural envi- ronments. These moderately controlled, semi-outdoor envi- ronments o
6、ffer the occupants the amenity of naturalness within an artificial environment and function as a temporal refuge from tightly controlled indoor thermal environment. Planning of semi-outdoor environments is distinct in a way that comfort should be achieved without deteriorating the benefits of natura
7、l outdoor elements. Although little work has Shin-ich Tanabe, D.Eng. Member ASHRAE been done on thermal comfort in such environments, it is likely that people expect environments differing from the indoors, and the thermal comfort conditions may differ from that of indoor steady state. The atrium in
8、 modem architecture gained its fame in the 1960s when architect John Portman designed a series of large- scale atrium hotels in the U.S. Engineers have empirically derived environmental criteria for designing semi-outdoor spaces appropriate for the scope of their application (Mills 1990; SHASE 2000)
9、. Although many studies have dealt with the heat load calculations and the detailed thermal environ- ment prediction techniques for thermal system design of atria to accomplish these practical criteria (Kat0 et al. 1995), the actual comfort conditions have not been investigated in large numbers. The
10、 semi-outdoor environment falls between the environ- mental engineering categories of the “indoor environment,” where the thermal environment is controlled to satis the ther- mal comfort of the occupants, and the “outdoor environment,” where occupants need to adjust themselves to achieve thermal com
11、fort. As the thermal environment is not intended to be fully controlled in the semi-outdoor environments, thermal adaptation, especially behavioral adaptation, is expected to play a major role in the process of achieving thermal comfort. However, the form or process of adjustment may change dependin
12、g on circumstances. For example, if the thermal envi- ronment does not match their expectation and other forms of adaptation are not sufficient to maintain their comfort, occu- pants may choose not to stay at all under voluntary occupancy conditions. Knowledge of adaptation characteristics is requir
13、ed for different design objectives, and short-term occu- pancy, lasting no more than an hour, was intended to be the Junta Nakano is a research associate and Shin-khi Tanabe is a professor in the Department of Architecture at Waseda University, Tokyo, Japan. 02004 ASHRAE. 543 main purpose of occupan
14、cy for the semi-outdoor environ- ments in this study. In order to investigate thermal comfort conditions and thermal adaptation in semi-outdoor spaces from the viewpoint of short-term occupancy, four architectural environments with different levels of environmental control were selected. Four season
15、al field surveys were carried out from summer of 2001 to spring of 2002 to examine the seasonal differences. - Space O T P METHODS Dimension Location Description Survey Area (floor area * height) N3540 E 13941 office + Arcade 830m2* 16m shopping mall sunken garden 650 m2 no roof N3541 E 139”42 depar
16、tment store wooden deck 1 SOO m2 no roof N35”40 E 13941 office + closed atrium i,600m2 x 18 m shopping mall Survey Design Four semi-outdoor architectural environments with different levels of environmental control were selected for the survey in Tokyo, Japan. Air-conditioned atria (HVAC spaces), spa
17、ces P and B, and non-air-conditioned spaces (non-HVAC spaces), spaces O and T, were selected to have a common basic feature-large-scale precincts open to the public, designed for roaming and resting of the visitors. Both air-conditioned atria were spacious and furnished with greenery to create outdo
18、or- like settings similar to the non-HVAC spaces. Personal envi- ronmental control was unavailable either in HVAC spaces B equipped with fixed windows and centrally controlled HVAC systems or open-aired non-HVAC spaces. The details of the selected environments are listed in Table 1, and perspective
19、views are presented in Figure 1. Surveys from 1O:OO to 18:OO each day were conducted for four days per space per season. Four seasonal surveys lasted from the summer of 2001 to the spring of 2002 for a total of 64 days to examine any seasonal differences. Three survey methods were integrated into th
20、e survey design: (I) investiga- tion ofthe occupancy conditions, (2) questionnaire survey, and (3) measurement of the thermal environment. The present survey was focused on “short-term occupants,” defined as the visitor who actually sat down in the survey area, and passersby or standing persons were
21、 left out of scope. Occupancy periods were measured throughout the day by randomly selecting the visitors sitting in the area and record- ing the time of their arrival and departure. A daily mean occu- pancy period was derived from approximately 100 observations per day. The number of occupants with
22、in the survey area was also counted every ten minutes. Questions concerning the background information, purpose of stay, and frequency of visit were included in the questionnaire. N3535 E 13944 office + closed arium 4,200 m2 x 40 m shopping mall Table 1. Description of Survey Areas Environmental Con
23、trol Non-HVAC Non-HVAC HVAC HVAC Non HVAC Space “O” Space “T” c 4 HVAC S pac e I P ” Space “B” c Figure I Perspective views of the survey areas. Non-HVAC spaces Qej) and HVAC spaces (right). 544 ASHRAE Transactions: Symposia Outdoor condition The questionnaire sheet, written in plain Japanese, also
24、included questions concerning the approximate length of stay, activity within the previous 15 minutes, clothing items worn at the moment, general comfort (seven scales, from “very comfortable” to “neutral” to “very uncomfortable”), thermal sensation (ASHRAE scale), thermal preference (McIntyre scale
25、), and thermal acceptability. Field studies on clothing are typically conducted by the surveyors visual observation or by asking the occupants to choose their clothing items on a garment checklist. However, mistakes could happen, espe- cially in short-term occupancy spaces where a respondent may hav
26、e worn a coat prior to occupancy and removed it at the time of questionnaire. A combination of the two methods was employed to correct apparent mistakes, and visual observation of a surveyor was recorded simultaneously using the same checklist. Each clothing item in the questionnaire was assigned an
27、 insulation value according to IS0 9920 (IS0 1995) and summed for total insulation. A mobile measurement cart equipped with batteries for fll-day operation was devised to measure the immediate ther- mal environment around the occupant at heights of 0.1, 0.6, 1.1, and 1.7 m above ground. Measurement
28、items are given in Table 2. Radiant environment was evaluated by measuring the directional total radiation (0.3-4.0 m) and solar radiation (0.4- 1.1 m) separately for six directions (up, down, front, back, left, right) at 1.1 m above floor level. Orientation of the sensors was also recorded for each
29、 measurement. Outdoor conditions were recorded separately. After obtaining the consent of an occupant to answer the questionnaire, another surveyor pushed the cart near the respondent to measure the surrounding environment for ten minutes. A five-minute average prior to the end of each measurement w
30、as regarded as the representative thermal envi- ronment for that respondent. A view of the survey is presented in Figure 2. A total of 2248 occupant responses and corre- sponding sets of thermal environment data were collected throughout the entire survey. Calculation of Mean Radiant Temperature Dir
31、ectional longwave radiation Ldif;k (W/m2) was calcu- lated by subtracting the measurement value of the Pyranometer Air temperature Thermistor Humidity RH sensor Solar radiation Solar meter ASHRAE Transactions: Symposia Figure 2 View of questionnaire suniey and thermal environment measurement. Survey
32、or on the right asked the occupant to answer the questionnaire, and surveyor on the left measured the surrounding thermal environment with the mobile measurement cart. Inet,k (W/m2)fiom the measured total (W/m2) for each direction. The subscript krepresents the six directions for up, down, right, le
33、ft, front, and back. Ldif,k = Rnei,k-net,k (1) In the HVAC spaces P and B, where direct solar radiation rarely reached the occupant, the measured solar radiation was considered to be difise radiation. For the non-HVAC spaces O and T, direct solar radiation normal to the sunray (W/m2) was calculated
34、from the global radiation (Udagawa and Kimura 1978). Time, date, location, andreadings oftheupward direction of the Pyranometer I,nel,up were used as the input vari- ables. From the orientation of each sensor, direct solar radiation entering each direction dick was calculated by trigonometric functi
35、on. These values were subtracted from each directional Pyranometer reading to derive difise solar radiation Idif;k (W/m2). 545 Idif,k = Inet,k-Idir,k (2) Longwave radiation and diffuse solar radiation were assumed to be absorbed by the effective radiation area. Long- wave emissivity of the clothed b
36、ody E was assumed to be 1, and shortwave absorptance u was assumed to be 0.66. Directional diffuse total radiation RdKk (W/m2) was weighted according to the projected area of the human body (Olesen et al. 1989) and averaged for diffuse total radiation Rd$ (W/m2). Since ali respondents were seated, a
37、 value of 0.696 was used as the effective radiation area factorf,f(Fanger 1970). Rd$,k = ELd$,ktard$,k (3) (4) Rdrf = fefffcl 0“27(Rd$up + Rdif,down) + o“8(Rdif,righr + Rdif,lefr + Rdrffront + Rdif,back) The direct total radiation on the person Rdir (W/m2) was assumed to be IdiKfi, absorbed by the b
38、ody surface area directly lit by the sun. A constant value of 0.2 was used for y, irradi- ated area expressed as fraction of the Dubois area, since only small differences existed for the irradiated area of a seated person for different solar altitudes. Ratio of y, of clothed person to y, of nude per
39、son,f, was also assumed to be a constant value of 1.1 (Breckenridge and Goldman 1972). dir = a .fa . Idij-,n (5) Net radiation on the person R (W/m2) was calculated by the sum of Equations 4 and 5. R Rdir + Rdif (6) Surface temperature of an imaginary uniform enclosure MRT (“C) was derived from the
40、following equation (o is the Stefan Boltzmann constant 5.67 x lo-* (W/m2.K4). RESULTS (7) Outdoor Climate Figure 3 shows the daily mean outdoor temperature and humidity of all survey days extracted from the meteorological database. The Tokyo area belongs to the temperate climate zone, having four di
41、stinctive seasons. The climate is hot and humid in summer, cold and dry in winter, and intermediate in spring and autumn. The general seasonal description applied to the seasonal classification of the present survey. Daily mean variation of outdoor temperature was calcu- lated for each season from t
42、he meteorological data of survey days. Daily minimum temperature was generally observed at around 6:OO and the maximum at 14:OO. Differences between the daily maximum and minimum temperatures were approx- imately 5.5“C in autumn and winter and 4C in summer and spring, showing that the daily temperat
43、ure fluctuation was larger during autumn and winter seasons. Thermal Environment Thermal environmental characteristics of the occupied zone were examined from the data of the mobile measurement cart. The results are presented according to the two environ- mental control classifications. The relation
44、ship between outdoor air temperatures and air temperatures of the occupied zone (measured around the questionnaire respondent with the mobile measurement cart) are given in Figure 4a. Air temper- ature closely coincided the outdoor temperature in the non- HVAC spaces. Links between the two temperatu
45、res were also observed in the HVAC spaces, but the occupied zone was generally kept between 15C and 29C by air conditioning. Mean radiant temperatures (MRT) of the occupied zone are plotted against air temperature of the occupied zone in Figure 4b. MRT approximated the air temperature in the HVAC sp
46、aces, while prominently higher values were recorded in the non-HVAC spaces due to solar radiation. Humidity ratios of the occupied zone and outdoors are presented in Figure 4c. Mild humidity control was confirmed in the HVAC spaces, especially when the outdoor humidity was high. Relative frequency o
47、f air velocity observed within the occupied zone is shown in Figure 4d. Majonty of the mean air velocity measured in the HVAC spaces was below 0.3 m/s, while the peak frequency of 0.6 ds and maximum value of 2.6 m/s were observed in the non-HVAC spaces. 8 9101112123456 Month Figure 3 Daily mean outd
48、oor air temperature und humidity ratio of all survey days. 546 ASHRAE Transactions: Symposia 20 O O O 10 20 30 40 O 10 20 30 40 Outdoor air temperature 1C) Air temperature of occupied zone (“e) 60 5 50 C 40 a! 30 - o a G f 20 c lw Q) 10 E - O O 5 IO 15 20 0.0 0.4 OB 1.2 lb 2.0 2.4 Outdoor humidity r
49、atio (g/kg) Air vdocitv Lmlcl Figure 4 Thermal environment characteristics of survey areas. Occupancy Conditions The analysis of questionnaires showed that the percent- age of males to females was equal in the non-HVAC spaces, while 60% were females in the HVAC spaces. More than 80% of the entire occupants were engaged in voluntary activities such as “resting” and “eating.” The contrary would be “wait- ing, where an occupant is required to wait in the environment regardless of hidher comfort condition. The percentage of “waiting” plus “others” was l
