Journal of Heat Island Institute International Vol. 9-2 (2014)

Academic Article

Field Investigation on Thermal Environment and Human Thermal
Sensation in Premises Woods in Urban Area
Shoko HASHIDA *1

Yasuhiro SHIMAZAKI *2

Atsumasa YOSHIDA*3*1 Program in Environment and Ecology, Meisei University* Department of Systems Engineering for Sports, Okayama Prefectural University*3 Department of Mechanical Engineering, Osaka Prefecture University
2

Corresponding author: Shoko HASHIDA, shokoh@es.meisei-u.ac.jp
ABSTRACTThe thermal environment parameters of premises woods in an urban area were measured in summer andwinter. These measurements were used to calculate the human thermal load to evaluate thermal comfort in thisregion. The thermal environment parameters in the premises woods were compared with those in an adjacent open
space, and the parameters were examined considering daily and seasonal fluctuations. The results indicate thatpremises woods effectively screen sunlight in both summer and winter and also clearly reduce wind speed during
the day in summer. Thermal neutrality is maintained in the premises woods in summer during the day. The
difference in thermal environment and thermal comfort inside versus outside the premises woods at night wassignificantly smaller than that during the day.
Key Words : Urban homestead tree canopy, Thermal environment, Thermal comfort, Field measurement, Daily and seasonal variation

to maintain them over generations. Thus, the number of

1. Introduction

premises woods is steadily decreasing, and it is feared that soon
Trees planted around a house on a farm are referred to as

no premises woods will be left in Musashino(2). In addition to the“premises woods,” and they are common all over Japan. Theyrole of the premises woods in environmental conservation, inplay numerous roles in mitigating environmental factors: they

suburban areas, they are expected to provide psychologicalshelter buildings from the strong seasonal winds that blow fromcomfort to the local residents and a place of rest andwinter to the beginning of spring, create shade during summer toenvironmental education. There is an increasing need toblock the midday and evening sun, and help keep the air

conserve the premises woods by designating them as publictemperature beneath their canopy constant. They are also

property and protecting them through collaboration between

important in terms of safety, as they are believed to help prevent

residents and local authorities. Figure 1 shows protected trees inthe spread of fire from neighboring structures. In flat areas withthe premises woods, and Fig. 2 shows an example of the use oflittle woodland, the premises woods supply several resources:

the premises woods by local residents. The neighboring elderly

fallen branches can be used as firewood, wood is obtained fromgather in the premises woods every morning and make an effort

the trunks, and fallen leaves are composted. Thus, with their

to promote their health through physical exercises.

variety of functions, premises woods are well integrated into the

The thermal comfort provided by premises woods has been

lives of people living in the plains(1).

demonstrated in several studies. In one study, air temperature

The premises woods that still exist in suburban areas have beenmeasurements were made in the premises woods and in an

attracting attention due to their rich ecology, supported by theadjacent residential area in summer and winter using aprotected, old-growth tree; their role in cleansing the air; andmaximum and minimum thermometer. The study determined

their contribution to environmental regulation by transmittingthat whereas the temperature fluctuates greatly in the residential

cool air to adjacent areas in summer. A number of premisesarea, fluctuations in the premises woods are modest throughout

woods once existed in the Musashino area, a suburb of Tokyo,

the year. Therefore, it is more comfortable inside the premises

but with the appreciation of land prices, it has become difficult

woods(2). Apart from the physical thermal environment, i.e., the- 127 -

temperature, it is important to discuss the thermal mitigation
effect of the premises wood from the viewpoint of humanthermal sensation. The present study investigates the thermal
comfort provide by the premises woods in a suburban area fromthe perspective of human thermal load. To calculate the thermalload, various aspects of the thermal environment in the premises
woods and in the adjacent open space are measured, and theenvironmental thermal easing and the effects on thermal comfort
are examined. On the basis of these measurements, the influenceof seasons is also investigated. This study focuses on thepremises woods that have survived in Nishi-Tokyo-shi (formerly

Fig. 1 Protected trees in the premises woods

known as Hoya-shi), which is located in the central region of theMusashino Plateau in the Tokyo area, an area known for its rapid
loss of green space.
2. Measurement site and method
The studied premises woods are shown in Fig. 3. This woodland
has an area of 1.1 ha and is located 300 m northwest of Hoya
station in Nishi-Tokyo-shi. It is a mixed wood with bothevergreen and deciduous trees. Figure 4 illustrates the layout of
this woodland. It contains protected trees, including a
300-year-old Japanese zelkova and a 100-year-old camphor

Fig. 2 Use of the premises woods by the local residents(2)tree . Moso bamboos are also cultivated. Four kinds ofevergreen needle-leaved trees including cedars and Japanesecypress, fifteen kinds of evergreen broad-leaved trees including
shira kasa oaks and ring-cupped oaks, and twenty-five kinds ofN

deciduous broad-leaved trees such as Japanese zelkovas andsawtooth oaks are present here. The total number of trees in thepremises woods is 336. Many are taller than 20 m, and theirlowest branches may be at a height of 2 m or more. As Fig. 4
shows, the measurements were made at a site more than 20 m

Hoya station

away from the edge of the wood and covered by the tree canopy.
Its leaf area index was 5.47 in summer and 1.96 in winter. Mostof the ground surface was covered by fallen leaves, and somewas covered by undergrowth. The measurements of the adjacent

200 m

open space were collected in an asphalt parking lot. The sky

Fig. 3 Map of the premises woods and its neighborhood

factor of the premises woods was 18.4% and 46.0% in summer(retrieved from Google Maps)

and winter, respectively, whereas that of the adjacent parking lot
was more than 90%. Figures 5 and 6 show the premises woods
in summer and winter, respectively. Figures 7 and 8 show how
the measurements were made in the premises woods and theparking lot, respectively.
A parking lot has one of the most severe thermal environments.
The variation in the thermal environment and biometeorology
within urban areas was made clear mostly by the comparison of
the measured data between the premises woods and the parking
lot. The overall thermal environment and biometeorology of thebuilt-up area are assumed to have intermediate characteristics
between those of the premises woods and the parking lot. Except- 128 -

Fig. 4 Plan of the premises woods

around Hoya Station, the houses in the built-up area are low-risebuildings. There is a park with an area of 0.3 ha between thepremises woods and Hoya Station. The major ground cover in
the area is lawn.
Measurements were made in summer and winter. The summer
measurements were made on August 10 and 11, 2013, whichcorresponded with the tropical and extremely hot weather.
Winter measurements were made on February 6 and 7, 2014,
when the minimum temperature did not exceed 0°C. The
following quantities were measured: air temperature, relative
humidity, wind speed, global irradiance, globe temperature, andsurface temperature. With the exception of surface temperature,

Fig. 5 The premises woods in summer

measurements were made at a height of 1.2 m above the ground.
The temperature and humidity sensors were stored in a whiteradiation shield that permitted air passage. Measurements weremade at 10-min intervals. An infrared camera captured images insix directions (north, south, east, west, above, and below) every
2 h during the day and every 4 h during the night in summer.
The configuration factors of the representative material wereobtained with fish-eye lenses (orthographic projection), and theradiation temperatures determined from the infrared camera
images were used to calculate the average temperature of theinfrared radiation. During nighttime in winter, the averagetemperature of the infrared radiation was obtained from theFig. 6 The premises woods in winterglobe temperature, air temperature, and wind speed(3). Surface
solar reflectance was measured separately. The solar reflectancesof the premises woods and the parking lot were 30.8% and14.6% in summer and 23.5% and 8.5% in winter, respectively.
The asphalt of the parking lot was repaired before the wintermeasurement period and that measurement was made when theasphalt was still in an unused state and free of dirt.
This study employs human thermal load as a thermal comfort
index. Human thermal sensation has attracted attention as anevaluation criterion for the assessment of thermal environment.
Thermal feeling is a mixed sensation, and in general it isdetermined by six dominant factors: air temperature, humidity,
radiant temperature, wind speed, metabolism, and clothing.

Fig. 7 Taking measurements in the premises woods

Therefore, it is advisable to include as many of these factors as
possible for a thermal index. The human thermal load is in itself
the heat flux under given condition based on the human energybalance equation. The human thermal load is considered to be an
accurate indicator of thermal feeling because it contains all sixof the above-mentioned factors. In fact, a previous study
determined that human thermal sensation can be obtained using
human thermal load in outdoor environments. Human thermalload refers to the thermal load on the human body and is
calculated from the energy balance of the whole body in heat
flux. Human thermal load and thermal comfort are sufficiently
correlated(4). In an experiment involving human subjects, humanthermal load is calculated using environmental data (air- 129 -

Fig. 8 Taking measurements in the parking lot

60

temperature, humidity, wind speed, global irradiation, solar

Air temperature
Summerparking
forestGlobe temperatureparking
forestreflectance, and the average temperature of the infrared

Temperature (℃)

radiation), representative skin temperatures from seven points on
the body, metabolism, mechanical workload, and the amount ofclothing worn. When only environmental data are obtained, as inthis study, the skin temperature is calculated using a human body
model

that

predicts

physiologicalresponses

based

on

environmental data and conditions such as metabolism,
mechanical workload, and the amount of clothing; this skintemperature is then used to calculate human thermal load. Here,

50
40
30
9

skin temperature was calculated using the 65MN model(5). This

12

18

model considers the human body as a tube and evaluates four0Time (h)612layers at 16 sites and central blood; it further evaluates heatFig. 9 Daily variations in air temperature and globe temperature

conduction between the layers at each site, radiation from thein summer

external environment, convection heat transfer, and perspiration
evaporation on the superficial skin layer. This study simulates an

Air temperature
Winterparking
forestGlobe temperatureparking
forest20
Temperature (℃)

individual 172 cm tall, weighing 53 kg, and stationary in astanding position. The metabolism is set at 80 W/m2, and themechanical workload at 0 W/m2; the amount of clothing was set
at 0.3 clo in summer and 1.3 clo in winter; the surface infrared
radiation was set at 1.0. Thermal comfort was predicted based onhuman thermal load(6).
3. Measured results and discussion

10
0

-10
9

Figures 9 and 10 show the air temperature and globe temperature

12

18

0
Time (h)612measurements in summer and winter, respectively. The results

Fig. 10 Daily variations in air temperature and globe temperature

revealed that the premises woods had a significant cooling effectin winterduring the day in summer but were not very effective at night.
The cooling effect of the premises woods during the day inwinter was smaller than that in summer, and there was hardly
any difference in air temperature at night. The globe temperaturein the premises woods exhibited little discrepancy from the airtemperatures during both day and night. The nighttime globe
temperature in the premises woods was higher than that in theadjacent space due to radiative cooling, especially in winter. In
summer, an almost uniform temperature field was observed in
the premises woods. The temperature difference between theambient air and the green canopy formed by tree leaves was
small throughout the day. The trunk surface temperature of thetrees was lower than the other surface temperatures in thedaytime as shown in Fig. 11. In winter, there were few
differences among the air temperature and the surface
temperatures of the green leaves, tree trunks and the groundcovered with dead leaves in the premises woods.
Figure 12 displays the irradiation measurements for solar
radiation. In both summer and winter, the premises woods
exhibited a high sunlight screening effect, which was considered
to have a significant influence on the premises woods globe

Fig. 11 Thermal image collected in the premises woods

temperature and daytime air temperature. The transmittance ofduring daytime in summer- 130 -

ultraviolet radiation in the premises woods was also less than 2%

comfort in the premises woods in winter did not indicate aand 10% in summer and winter, respectively. Figure 13 shows

windbreak effect of the woods and the reduction in the sunlightthe relative humidity measurements. The relative humidity in thescreening effect was small; thus, no environmental easing effects

premises woods was higher than in the parking lot during thewere observed in winter.

day in summer, but there was hardly any difference between the

It is essential to consider the following factors in future studies.

two during the night. In winter, there was no difference between

In this study, measurements were made at only one site in thethe two sites during either day or night. This was attributed topremises woods. To examine how spatial representative thisthe amount of moisture on the surface and the wind speed, as

result is, it will necessary to obtain measurements from a few

discussed in the following paragraph. Figures 14 and 15 show

more sites there. Furthermore, in this study, measurements wererespectively. In summer, the wind speed during the day was
lower in the premises woods than that in the parking lot, butthere was hardly any difference between the two sites during thenight in summer or at any time in winter. In summer, a southerly
wind blew during the day and a northerly wind blew during thenight according to AMeDAS (Automated Meteorological Data
Acquisition System) data from Nerima, the station locatednearest to this site. In winter, a northerly wind blew all day.

Relative humidity (%)

the wind speed measurements for summer and winter,

When a northerly wind blows, it is suggested that the wind speed

80

parking
forest70

Summer60
Winter50
40

parking
forest30
9observed at the parking lot is lower because a wind blocking

1218

effect is observed for the premises woods. Furthermore in winter,

0Time (h)6the measurement of wind speed in the premises woods wasFig. 13 Daily variations in relative humidity

thought to be affected by the fact that their measurementin summer and winterlocation was near the northern edge of the premises woods,

4

Figures 16 and 17 show the human thermal load and thermal
comfort values calculated from the measurements for summer
and winter, respectively. Thermal comfort in summer and winterwas affected by a difference in thermal load; it was higher in theparking lot than in the premises woods during the day, and there

Wind speed (m/s)

which contained many deciduous trees with a lower leaf areaindex.

12

3

parking
forest2

Summer1

were smaller daily fluctuations in the premises woods. Thermal
comfort in the premises woods in summer was almost neutral.

0
9

The difference in thermal load and thermal comfort between the

1218

two sites during the night was small. Thermal load and thermal

0Time (h)612Fig. 14 Daily variations in wind speed in summer

Summer Winterparking
forest2

Solar radiation (W/m )800

Wind speed (m/s)

600

4

400
200
0
9

12

18

0
Time (h)612Fig. 12 Daily variations in global irradiationin summer and winter3

parking
forestWinter0Time (h)

6

2
1
0

9 12

18

Fig. 15 Daily variations in wind speed in winter- 131 -

12

4

300
200

3
2
1

100
0
9

0

significant during daytime in summer when the leaf area index

Thermal sensation

human thermal load Summer
parking
forestthermal sensation
parking
forest

-1
12

18

0
Time (h)6

was high. The difference between the thermal environments ofthe premises woods and the adjacent open space during the night
was small. Human thermal load in the premises woods during
the day in summer was significantly lower than that in theadjacent open space, and thermal neutrality was almost
achieved.
Acknowledgement

12

This study was financially supported by the Ministry ofFig. 16 Daily variations in human thermal load and

Education, Culture, Sports, Science and Technology under its

thermal comfort in summer

Grants-in-Aid for Scientific Research Planning (Grant Number

100
human thermal load
parking
forestthermal sensation
parking
forest0-100

Winter

1
0
-1
-2

-200
-300

23501076, Lead Researcher: S. Hashida and Grant Number

2

-3
9 12

18

0
Time (h)626281057, Lead Researcher: A. Yoshida). The members of the

Thermal sensation

2

Human thermal load (W/m )2

Human thermal load (W/m )effect of the premises woods on wind speed reduction was

400

-4
12

Tokyo Yashiki-rin Network and Mr. S. Kamio and Mr. M.
Nagahama from “Clover,” an environmental conservation
volunteer group at Meisei University offered generous help in
acquiring measurements; we would like to acknowledge their
help and thank them.
References(1) M. Okada, Studies on the Evaluation of Forest Landscapeson Flat Rural Areas for Using on the Role and Functions ofFig. 17 Daily variations in human thermal load andPremises Forest, Memoirs of the Research Faculty ofthermal comfort in winter

Agriculture, Hokkaido University 25, 203-282 (2003)(2) A group to record ‘yashiki-rin’ in Nishi-Tokyo-shi, The

made only over short periods of time, and therefore further

eco-system that co-exists with human life: Yashiki-rin – Theefforts should include obtaining longer-term measurements

Takahashis’ yashiki-rin in the 1990s and now in 2007,

spanning approximately a month and statistically analyzing them.

Hagiwara Kikaku (2007)

It is also necessary to develop a questionnaire survey on(3) T. Kinouchi, A Study on Thermal lndices for the Outdoor

premises woods focused on psychological factors such as moodand impression. Additionally, in future work we aim to propose a

Environment, Tenki 48, 661-671 (2001)(4) Y. Shimazaki, A. Yoshida, S. Kinoshita, Proposal on Thermal

design for premises woods from the viewpoint of controlling the

Comfortthermal environment based on this study.

Transactions of the Japan Society of Refrigerating and Air

Index

Based

on

Human

ThermalLoad,

Conditioning Engineers 26, 113-120 (2009)(5) S. Tanabe, K. Kobayashi, J. Nakano, Y. Ozeki, M. Konishi,

4. Conclusion

Evaluation of Thermal Comfort using Combined Multi-nodeMeasurements of thermal environmental parameters under the

Thermoregulation (65MN) and Radiation Models andtree canopy and in a nearby open space were made in summer

Computational

and winter to investigate the thermal comfort generated by the

Fluid

Dynamics(CFD),

Energyand

Buildings 34, 637-646 (2002)

premises woods in an urban area with reference to the human(6) Y. Shimazaki, A. Yoshida, R. Suzuki, T. Kawabata, D. Imai,thermal load. The premises woods effectively filtered out

and S. Kinoshita, Application of Human Thermal Load into

sunlight in summer and winter, and the daytime temperature in

Unsteady Condition for Improvement of Outdoor Thermal

the premises woods was lower than that in the adjacent open

Comfort, Building and Environment 46, 1716-1724 (2011)

space. The premises woods consisted of almost homogeneousradiation fields, and the difference between the average infrared(Received Dec. 27, 2014, Accepted Jan. 17, 2015)

radiation temperature and the air temperature was small. The- 132 -