Journal of Heat Island Institute International Vol. 12-2 (2017)

Academic Article

Thermal Environment and Mental State in Premises Woods
in Urban Tokyo Area
Atsumasa Yoshida*1, Shoko Hashida*2, Shinichi Kinoshita*3*1Department of Mechanical Engineering, Osaka Prefecture University*2Graduate School of Frontier Sciences, The University of Tokyo3* Department of Mechanical Engineering, Osaka Prefecture University
Corresponding author: Atsumasa Yoshida, ayoshida@me.osakafu-u.ac.jp
ABSTRACT
Thermal environment parameters within premises woods in an urban area were measured for one monthduring the summer. These data were compared to similar data from the top of an adjacent building. Premises woods
effectively decrease daytime solar irradiation and reduce wind speed. The differences between air and black-bulb(globe) temperatures inside and outside the premises woods were significantly larger during the day than at night.
Fifteen data collection locations within the different land-use types of the premises woods were selected forcontinuous data collection. There were small differences in air temperature throughout the premises woods.
Humidity varied across land-use types within the premises woods. Study participants rated thermal comfort andmental state to be higher in the premises woods than in an adjacent park.
Key Words: Urban tree canopy, Woodland, Thermal environment, Thermal comfort, Field measurement, Thermal design,
Spatial distribution, Psychological effect, Landscape impression

woods, analysis of spatial distribution and factors contributing to1. Introduction

the thermal environment was insufficient. Therefore, in theIn Japan, the group of trees surrounding a farmhouse are called

present study, we used an adequate number of data collection‘premises woods’ and this land-use type is found across thelocations in the same premises woods, and conducted continuouscountry. Premises woods were artificially created for disastermeasurements over approximately one summer month. To

prevention, providing functions such as windbreaks, snow

elucidate the psychological effects of premises woods, and theprotection, and fire prevention. These areas also provide shade,

impressions people have of them, we also conducted afirewood, a timber supply, and a familiar wooded area for people

human-subject experiment(3). We aimed to comprehensivelyliving nearby(1). Recent research has focused on the thermal

evaluate the thermal environment mitigation function ofenvironment mitigation function of premises woods, rather thanpremises woods for thermal environment design.

on the woods’ disaster prevention functions.
In the premises woods remaining within urban areas, mature

2. Data collection locations and methods

trees provide air purification, cool air during the summer, and aenvironmental

The premises woods used in this study were a 1.1 ha area

measurements in urban premises woods during summer andlocated 300 m northwest of the Hoya Station, Nishitokyo

winter, calculated the human thermal load, and evaluated the(Figures 1 and 2). They were classified into five land-use types:

thermal sensation(2). We compared thermal environmental data

forest, wild plant, main house, bamboo grove, and yard (Figurefrom premises woods and a neighboring open space to determine3). The leaf area index (LAI) was measured in the premises

if there were diurnal and/or seasonal changes. However, thewoods in the summer and winter. The LAI values in the winternumber of data collection days was insufficient, and thewere much lower than those in the summer, except in the main

connection to meteorological conditions was unclear. Becausehouse and bamboo grove areas (Table 1). The forest is a mix ofthere was only one data collection location within the premises

evergreen and deciduous trees. The total number of trees

richecosystem.

We

conducted

thermal- 115 -growing in the forest area of the premises woods exceeded 300.

block solar radiation, and were naturally ventilated at a height ofMany trees were taller than 20 m, with branch heights exceeding

1.0 m in each location (Figure 6). Soil temperature meters were

2 m. The crowns covered the sky, and the average LAI wasplaced in the forest, the main house, and bamboo grove areas

3.74–4.89. The ground was covered by dry leaves andand on the rooftop of the adjacent building. Measurements fromundergrowth. A two-story Child Welfare Center is located

all instruments and locations were taken at 10- minute intervals.

adjacent to the premises woods; the roof of this building isconcrete and partially covered by planted vegetation. Theaverage sky view factor of these premises woods was 18.4%,

Residential section

and the sky view factor of the rooftop was greater than 90%.

④ForestFor the investigation of human psychological impressions, weused a nearby park as a reference location for the yard area③

within the premises woods. A lawn was located at the center of●⑦

Public road⑤

Main house② ⑧⑭

the park where the sky view factor was 50% or greater, with the⑯rate of visible greenery 60%.

① ⑩ ⑨Childwelfare⑪
centerbuilding Wild plant

Measurements were taken continuously from August 1 to 28,
2014. Weather stations installed in the forest area of theN

Bamboogrove⑫⑥

Parking lotx⑮

Yard

Parkinggarage⑬
Public roadParkx

premises woods, and on the rooftop of the adjacent building(Figures 4 and 5), measured air temperature, relative humidity,

Residential section

wind direction, wind speed, global solar radiation, global

100m

infrared radiation, and black-bulb temperature (globetemperature). Measurements were taken at 1.2 m above theFig. 2 Plan of the premises woods ●: Weather station, ×: Humanground. Air temperature and humidity sensors were stored in a

subject experiment, ①-⑯: air temperature and relative

white radiation shield, and naturally ventilated. Wind direction

humidity data collection points

and wind speed were measured using a wind vane and athree-cup anemometer, respectively. The starting wind speed forTable 1 Leaf area index values for various areas within the-1

premises woods

the anemometer was 0.4 ms . Measurements of solarreflectance on the ground surface were made separately. The
solar reflectance of the premises woods was 30.8%.

Area

Forest(center part)

Forest(west part)

Forest(north part)

Thermo-hydrometers and soil-temperature meters were installedsummer

4.89±0.07

4.28±0.17

3.74±0.34

in each area within the premises woods (ten in the forest area;

winter2.69±0.12

1.85±0.20

2.06±0.07

the main house area) and on the rooftop of the adjacent building

Area

Wild plant

Main house

Bamboo grove(one). The thermo-hydrometers were stored in birdhouses tosummer

2.36±0.10

1.94±0.11

5.35±0.17

winter0.54±0.16

1.30±0.04

4.97±0.20

Area

Yard

one each in the wild plant, yard, and bamboo grove areas; two inBACN

summer

3.17±0.11

winter

0.84±0.29

A: Premises wood
B: Child welfare centerbuildingHoya station
C: Park200 m
Fig. 1 Premises woods and surrounding areas A: Premises
woods, B: Adjacent building (child welfare center), C: Park
(retrieved from Google Maps)(a) Forest area

- 116 -

(b) Wild plant area

Fig. 4 Weather station inside the premises woods(c) Main house area

Fig. 5 Rooftop of the building adjacent to the premises woods(d) Bamboo grove area
Fig. 6 Sensors installed in birdhouses to measure air temperatureand humidity in the premises woods

3. Human-subject experiment methods
Twenty-two healthy seniors (4 males and 18 females) ranging
from 68 to 86 years old, and 4 healthy students (3 male and 1female) ranging from 18 to 21 years old, participated in ahuman-subject experiment on August 18, 2014 within a nearbypark and in the yard area of the premises woods (Figure 7). The(e) Yard area

data collected were thermal sensation, comfort, sense of healing,

Fig. 3. Land-use areas in premises woods

psychological self-reporting using the Profile of Mood States- 117 -(POMS) method developed by McNair et al.(4), and scenic
impression according to the SD method(5).
Thermal sensation, comfort, and a sense of healing were allmeasured on relative scales (Figure 8). The right ends of thescales were labeled ‘hot’, ‘comfortable’, and ‘there is a sense ofhealing’, respectively, and the value of +3 was assigned. The left
ends of the scales were labeled ‘cold’, ‘uncomfortable’, and‘there is no sense of healing’, respectively, and a value of -3 wasassigned. Using these scales, study participants were asked toindicate their experiences, and results were assigned numericalvalues within 0.1 increments.
The POMS method evaluates mood via a questionnaire
composed of 65 items. This method allows quantification of aperson’semotions

andmoodundergivenconditions.

(a) Yard area of premises woods

Evaluations are made based on six mood categories:‘Tension-Anxiety’, ‘Depression-Dejection’, ‘Anger-Hostility’,‘Vigor’, ‘Fatigue’, and ‘Confusion’. To reduce the burden on theparticipants, a shortened version was developed by Yokoyama(6).
Although the questionnaire was reduced to 30 items instead of65, it was able to provide the same results as longer version,
with sufficient reliability and validity. Scores for each of the six
mood categories were totaled, and the score for ‘Vigor’ wassubtracted to obtain the Total Mood Disturbance (TMD) score.
This allowed the expression of the mental state of a subject witha single numerical value. For all categories other than ‘Vigor’,the lower the score, the better the mental state.
The SD method is a psychological test developed by Osgood etal.(5). In this research, we evaluated differences in the scenic(b) Park adjacent to premise woods

impression of the data-collection locations. There were 13Fig. 7 Fisheye photographs of data collection sites for the humanquestionnaire items, each item consisting of two antonymous

subject experimentadjectives, with a 7-step scale.
Participants were gathered in the yard area of the premises

0-3
ThermalThermalsensation
sensation
cold
Cold

woods at 9:30 a.m. Details on how to respond to thequestionnaire were provided before the participants were asked+3
hotHotto record their responses. The participants then took 2 minutes towalk to the park next to the premises woods and recorded theirFig. 8 Thermal sensation scale

responses again. The experiment was completed at 10:00 a.m.
The senior participants exercised lightly for 15 minutes prior togathering at the yard area as daily routine and rested 10 minutes

4. Results and discussion

at the same location before participating in the experiment.
Within the yard area, many of the participants faced southwest in

Figure 9 shows the comparison of environmental elements on

response to our request, toward the outside of the premises

sunny days in the premises woods with those from the rooftop ofwoods; at the park, they faced southeast toward the central lawn.

the adjacent building (the reference area). Global solar radiation,

The participants completed the response forms while standing.

infrared radiation, and wind speed were expressed as the ratio ofMeteorological data measured at 9 a.m. and 10 a.m. included thepremises

following mean values (for the premises woods and rooftop

temperature, and relative humidity were expressed with therespectively): air temperature (27.4 °C, 31.0 °C), global solar

equation: premises woods – reference area. Daytime values forradiation (15 Wm2, 411 Wm2), relative humidity (85%, 65%),

solar radiation, air temperature, and wind speed were lower in-1

-1

woods/referencearea.

Airtemperature,

globe

wind speed (1.0 ms , ≤ 0.4 ms ), and globe temperature

the premises woods than they were in the reference area (Figure(27.8 °C, 40.5 °C).

9). The relative humidity in the premises woods was higher than- 118 -absolute humidity was the same in both areas, based on air
temperature and relative humidity data. The global infrared
radiation in the premises woods was slightly higher than that inthe reference area because of the greater tree canopy in thepremises woods. Daytime globe temperature in the premises
woods was closely related to the subjects’ thermal sensation andwas lower than that in the reference area. This is because the5Premises wood－Roof [％]surface moisture and the transpiration of tree leaves. ThePremises wood－Roof [℃]

that in the reference area (Figure 9) because of the ground-0-5Daytime
Night-10-15-20

solar radiation decreased near the tree canopy and the surface
temperature decreased according to the solar radiation. Except

Air temperaturetemperature GlobeBlacktemperature
bulbAir(b)for wind speed, the differences between environmental variables
Premises wood－Roof [％]20

in the premises woods and the reference area were smaller atnighttime than they were during the daytime. This finding was
similar to the results of a previous study(2).
Figure 10 compares air temperatures and relative humidity
within the different land-use types of the premises woods during
the day and night. There were small differences in air
temperature between each area of the premises wood; the mean

DaytimeNight
151050values varied by only approximately 1 °C. The air temperatures

Relative
Relativehumidity
humidity(c)in the wild plant area and the main house area were expected tobe higher than those in other areas, based on the relationshipFig. 9 Environmental elements within the premises woods andbetween LAI values and solar radiation. In the wild plant area,from the rooftop of an adjacent building

the ground was primarily covered with grass and the groundsurface temperature decreased. The main house area was36

some variation between areas due to spatial variations in groundsurface moisture. The values of absolute humidity in the mainhouse area and the forest area were lower than those in otherareas. In the forest area, the ground surface was covered withleaf litter.
The participants’ thermal sensation indicated that there werecooler temperatures in the premises woods than in the park

Air temperature [℃]surrounded by the other cool areas. Relative humidity showed3432302826(Figure 11). The participants felt more comfortable and healing

DaytimeNightForest

Forestin the premises woods than they did in the park. For allYard
Wild Bamboo
Bamboo Yard
Wildplantgrove
plant grove

categories except for V (Vigor), the reference area provided the(a)Relative humidity [％]100Premises wood/Roof [％]

120
10080

DaytimeNight60
40900
InfraredInfraredradiation
radiation

WindWind
speed
speed

DaytimeNight80
7060
5020Solar
Solarradiation
radiation

MainMainhousehouse

ForestWild Bamboo Yardplant grove

Mainhouse(b)
Fig. 10 Air temperature and relative humidity within premises

(a)

woods

- 119 -3.03

Premises wood

Premises wood
ParkPark
Premises Wood

2.5
2.5

Familiar/Unfamiliar
Calm/Restless

2.02
Score
Score[‐]

Park

Relaxed/Strained
Secure/Anxious

1.5
1.5

Brisk/Gloomy
Sense・Space

1.01

Silent/Noisy
Beautiful/Ugly

0.5
0.5

Orderly/Disorderly00

sensation
Thermal comfort
ComfortSensation

Open/Close
Spatial/Planar

Healing

thermal sensation

healing sensation

Natural/Artificial
Brightness
Livedin feelFig. 11 Thermal sensation, comfort, and healing within thepremises woods and park

Score

2520Light/Dark
Vitality/Nonvitality
01234567Fig. 13 SD classification of scenic impressions in the premises

Premises wood

15
105woods and park

Parkcollection. Human-participant experiments were conducted todetermine the psychological effects of premises woods and the0-5

impressions that study participants had of these woods. The-10

the day than did the adjacent open space. Participants’ daytime-15

thermal comfort was higher in the premises woods than in the-20

premises woods had less sunlight and lower wind speeds during

T-A

D A-HVFadjacent open space. Differences in air temperature between theC TMD

land-use types in the premises woods were small. The spatialFig. 12 POMS categories of mental state in the premises woods

distribution of humidity was related to ground surface cover.

and park

Values representing participants’ thermal comfort, healing, andmental state were higher in the premises woods than those inparticipants with a more pleasant experience than did thegreen park.

premises woods (Figure 12). Positive aspects of the premises
woods were seen in the average values of TMD because of theAcknowledgments

significant difference in V between the premises woods and thereference area. However, the significant difference in TMD wasThis study was financially supported by the Ministry of

not recognized because of the large deviation.

Education, Culture, Sports, Science, and Technology under its

Through factor analysis, SD items were classified into ‘sense

Grants-in-Aid for Scientific Research Planning (Grant Numberand space’, ‘brightness’, and ‘feeling of life’ factors (Figure 13).

17H00802, Lead Researcher: A. Yoshida). The members of the‘Sense and space’ factors were better in the premises woods thanTokyo Yashiki-rin Network and ‘Clover’, an environmental

those in the reference area. Because canopy cover blocked muchconservation volunteer group at Meisei University, offeredof the sky in the premises woods, ‘brightness’ scored low in thisgenerous help with data collection.

area. As a whole, the greenery of the premises woods provided a
psychologically relaxing effect, confirming that premises woods

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