1 Application of for Predicting Indoor Airflow and Thermal Comfort.
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Thermal comfort and Indoor Air Quality at Green Building in
Malaysia
Y.H. Yau*
Department of Mechanical Engineering
University of Malaya, Kuala Lumpur
Email: [email protected]
L.C. Ding
Department of Mechanical Engineering
University of Malaya, Kuala Lumpur
Email: [email protected]
B.T. Chew
Department of Mechanical Engineering
University of Malaya, Kuala Lumpur
Email: [email protected]
Abstract - A thermal comfort assessment and indoor air quality evaluation was conducted in
Suruhanjaya Tenaga (Energy Commission) office building located in Putrajaya, Malaysia. This
field study involves the physical measurements and subjective assessment through
questionnaire distributed to every occupant in selected floor of the building. The
environmental parameters, which had been measured in this study, include indoor air
temperature, relative humidity, air velocity and air contaminants are compared to Malaysia
Standard. Key question for this study is to answer the doubt on “whether a green building
incorporated with various energy-saving design features able to provide good thermal comfort
and good indoor air quality to the occupants, locally in Malaysia”. Outcomes of this study
indicate that the indoor parameters show a good agreement with criteria specified in standards.
The neutral temperature found from linear regression of actual mean vote and operative
temperature is 23° C, which imply a thermally comfort condition inside the office.
Keywords: green building, thermal comfort, indoor air quality, air-conditioning, tropical
climates, thermal satisfaction
1. INTRODUCTION
The satisfaction with the thermal environment
is regarded as thermal comfort. The subjective
nature of comfort perception requires
considerations on ample of parameters, physically,
physiologically and psychologically (ASHRAE,
2009a). Hensen (1991) argued that thermal comfort
is a condition where there is no driving impulse to
adjust the environment. Hence, there is no absolute
standard in dealing with thermal comfort. In order
to examine the comfort level of occupants, adaptive
method and heat balance method are two methods
that is usually used. Former method is developed
based on six factors affecting thermal comfort
which are environment factor (temperature, relative
humidity, air velocity and mean radiant temperature)
and personal factors (activity level and clothing
insulation). All of the factors mentioned are taken
into account on heat balance method and it had
been developed by Fanger (1970). Through series
of testing in controllable climate chamber,
predicted mean vote (PMV) had been introduced to
estimate the mean response of occupants in terms
of thermal comfort. Inasmuch of the energy crisis
on oil price in 1970’s, adaptive comfort theory was
proposed. The essence of this method is on the field
surveys to assess the comfort level. In most of the
cases, it depends strongly on both behavior and
expectation of the occupants (Noël et al., 2010).
This method require researcher to collect the
thermal response of the occupants and measure the
thermal environment, simultaneously. As surveyed
by Hwang et al.(2009), when dealing with the
tradeoff between energy-saving and occupants’
thermal comfort, attaining energy-saving via
sacrificing occupants’ comfort is hard to implement
(Hwang et al., 2009). Meanwhile, there are
arguments on whether green buildings prevail in
providing indoor air quality and thermal comfort
than conventional office building. However, there
were doubts on the ability of green building
providing good thermal comfort since the energy
consumption is utilized minimally (Heerwagen et
al., 2009, Karyono, 2000, Paul et al., 2008).
Regardless of the validity on the argument, this
preliminary study is aimed to include a survey on
occupants’ thermal comfort in Suruhanjaya Tenaga
(Energy Commission), which is a green building
located in Putrajaya, Malaysia.
In line with thermal comfort, Malaysia
Standard, MS 1525: 2007 (Code of Practice on
Energy Efficiency and Use of Renewable for Non-
Residential Building) have established acceptable
indoor conditions for comfort cooling in non-
residential building (Department of Standards
Malaysia, 2007). The recommendations have been
widely applied by every the researchers and
engineers to study and design a suitable air
conditioning system in Malaysia.
Table 1: The recommended indoor condition
of MS: 1525: 2007.
Recommended dry bulb
temperature
23oC - 26
oC
Recommended relative humidity
( RH)
55% - 70%
Recommended air movement 0.15 m/s to
0.5 m/s
Minimum dry bulb temperature 22oC
Maximum air movement 0.7 m/s
Despite of providing thermal comfort, a good
air-conditioning system should able to provide
good indoor air quality (IAQ). The implication of
unacceptable IAQ is the increasing prevalence of
health complaints caused by sick building
syndrome (SBS) by the occupants inside office
(Burge et al., 1987). The IAQ requirements may
vary from place to place. In Malaysia, according to
Code of Practice on Indoor Air Quality published
by Department of Occupational Safety and Health
(DOSH), Ministry of Human Resource, Malaysia
2005 (DOSH, 2005) , The table below shows the
maximum allowable limits of each indoor air
contaminants are shown in Table 2.
Table 2: The maximum limits of indoor air
contaminants.(DOSH 2005)
Indoor Air
Contaminants
Eight-hour time
weighted average
airborne concentration
ppm 1mg/m
3
Carbon dioxide, CO2
Carbon monoxide, CO
Formaldehyde, HCOH
Respirable Particulates
Total volatile organic
10002
10
0.1
3
0.15
compounds , TVOC 1Concentration at 25°C, 1 atmospheric pressure 2 Maximum ceiling limit
Carbon dioxide is the most common contaminant in
indoor environment. The concentration of carbon
dioxide is strongly related with occupant density as
well as the type of activity carried out. Common
effect of staying in a space with high concentration
of carbon monoxide is feeling headache, sleepy and
drowsy. When we compare with carbon dioxide,
the maximum threshold for the concentration of
carbon monoxide should be reduced 100 times
lower than carbon dioxide. Carbon monoxide
concentration level up to 15ppm is harmful since it
could inhibit the transportation of oxygen in human
body. The adverse effect of human exposure to
high concentration of carbon monoxide is
headaches, dizziness, vomiting, and loss of
consciousness (ASHRAE, 2009b). The dust with
size below 4μm is considered respirable by human.
Hence, total concentration of respirable particulate
should be kept below 0.15mg/m3, in order to avoid
any health effect to occupants.
2. METHODOLOGY
A field measurement was conducted at
Suruhanjaya Tenaga office building located at
Putrajaya, Malaysia, (30 km to the south of Kuala
Lumpur), surrounded by hot and humid climate
throughout the year. The Suruhanjaya Tenaga
building consists of eight floors, recently has been
awarded for Malaysia Platinum Green Building
Index (GBI). A nickname of “Diamond Building”
was given to this building due to its diamond shape
facade.
Figure 1: Façade of Suruhanjaya Tenaga (Energy
Commission), Putrajaya.
The air in Suruhanjaya Tenaga is air
conditioned by variable air volume (VAV) system.
The measurement was taken at sixth floor of the
office building. Two unit departments are located in
this floor, known as Administration & Facility
Management Unit (Zone A) and Promotion &
Communication, External Relations & IT Units
(Zone B). There are 10 measurement stations
selected as shown in Figure 2 and Figure 3.
Figure 2: The layout of zone A with 5 measurement
stations.
Figure 3: The layout of zone B with 5 measurement
stations.
The measurements of physical parameters include
indoor air temperature, relative humidity, air
velocity, concentration of CO2 and CO, and dusts.
The subjective responses of 25 occupants were
collected through a thermal comfort survey
questionnaire. The measuring devices used in field
were globe temperature meter, indoor air quality
meter Alnor CF930, air velocity meter Alnor model
AVM 440, TSI DustTrak II Handheld Aerosol
Monitor. Outdoor air condition corresponds to the
study was 25.5°C, 89% RH.
3. RESULTS AND DISCUSSION
a) Dry Bulb Temperature
Figure 4: Graph of average temperature of each
station at zone A.
Figure 5: Graph of average temperature of each
station at zone B.
.
In general, the results in Figure 4 and 5 show
that the dry bulb temperatures measured at every
station in both zone A and B are within the range of
design temperature suggested by Malaysia
Standard. The average temperature at station 1 in
zone A is found to be the highest as compared to
the other stations. While in zone B, the highest
temperature measured is found at station 3. This
may due to the number of occupants is higher at
station 1 and station 3 in zone A and B respectively.
In addition, those locations may have considerably
number of miscellaneous equipment such as
computers, fluorescent lamps, and printers. As a
result, the heat gain in the two stations is the larger
and hence the temperature is higher.
b) Relative Humidity, RH
Figure 6: Graph of relative humidity at each station
in zone A.
Figure 7: Graph of relative humidity at each station
in zone B.
From Figure 6 and 7, the average relative
humidity measured for each station in both zone A
and B are within the range of design relative
humidity according to MS 1525: 2007. The average
relative humidity at station 4 for both zones is
slightly higher than other stations. This is probably
due to the location of the station is close to the
return air grille where moisture tends to be higher.
Table 7: Thermal comfort parameters of each point at zone A.
Station Globe
Temperature,°C
Air
Temperature,°C
Air Velocity,
m/s
Mean Radiant
Temperature(MRT) ,°C
Operative
Temperature,°C
Thermal
Vote
1 24.5 23.3 0.05 25.13 24.21 -0.25
2 24.3 23.0 0.04 24.91 23.95 -1
3 24.2 22.7 0.03 24.81 23.75 0
4 23.9 22.8 0.07 24.58 23.69 Nil
5 23.8 22.9 0.06 24.32 23.61 Nil
Table 8: Thermal comfort parameters of each point at zone B.
Station Globe
Temperature,°C
Air
Temperature,°C
Air
Velocity,
m/s
Mean Radiant
Temperature(MRT) ,°C
Operative
Temperature,°C
Thermal
Vote
1 23.3 22.8 0.01 23.42 23.11 0
2 23.4 22.6 0.04 23.78 23.19 0.5
3 23.4 22.9 0.01 23.52 23.21 0.25
4 23.4 22.3 0.04 23.92 23.11 0
5 23.3 22.7 0.07 23.68 23.19 -1
Figure 8: Graph of actual mean vote against operative temperature.
From Table 7 and 8, there are no occupants at
station 4 and 5 and hence they are not taken into
consideration in evaluating the thermal comfort
level. Operative temperature is the temperature that
would result in the same heat loss from an
unclothed, reclining human body in a hypothetical
environment where both wall and air temperatures
are equal with air movement of 0.076 m/s. For low
air velocity (<0.2m/s), the equation of calculating
operative temperature is shown in equation (1).
(1)
The mean radiant temperature, tmrt was calculated
from equation (2).
(2)
where is the globe temperature, is
ambient air temperature and V is the air velocity.
Actual mean vote of the remaining eight stations is
plotted as shown in Figure 8. The average comfort
vote of indoor occupants is approximately -0.19,
which implies that the condition is neutral
according to ASHRAE thermal sensation scale
(ASHRAE, 2009a). In addition, the operative
temperature, or commonly known as neutral
temperature that obtained the most votes from
occupants is 23.0 °C. The neutral temperature is
found by performing linear regression of actual
mean vote and operative temperature. Noted that,
the operative temperature calculated from
measuring parameters is 23.5°C and it is close to
the neutral temperature. It is concluded that the
thermal comfort condition is found acceptable to
the indoor occupants.
Table 9: The clothing insulation and activity level
of each station at zone A.
Station Operative
Temperature,°C
Clothing
insulation
(clo)
Activity level
(met)
1 24.21 0.57 1.23
2 23.95 0.44 1.70
3 23.75 0.46 1.23
4 23.69 Nil Nil
5 23.61 Nil Nil
Table 10: The clothing insulation and activity level
of each station at zone B.
Station Operative
Temperature,°C
Clothing
insulation
(clo)
Activity
level (met)
1 23.11 0.33 1.10
2 23.19 0.41 1.10
3 23.21 0.76 1.40
4 23.11 0.49 1.10
5 23.19 0.47 1.23
Note: 1 clo = 0.16 °Cm2/W and 1 met = 58W/m2
Figure 9: Graph of relative humidity against
operative temperature.
In view of the effect of relative humidity against
operative temperature in Figure 9, there is a weak
correlation (of 0.08). Hence, it implies the control
system is able to maintain a control of humidity
regardless of the temperature. From the survey, 20
respondents (80% of total respondents) feel neutral
on the humidity level.
Figure 10: Graph of clothing level against operative
temperature.
The clothing insulation of indoor occupants is
deviate not much from 0.35 clo to 0.6 clo for
summer as specified in ASHRAE recommendation.
From Figure 10, the correlation between clothing
insulation and operative temperature is 0.108.
Figure 11: Graph of activity level against operative
temperature.
However, from the graph of activity level against
operative temperature in Figure 11, higher
correlation which coresspond to 0.500 were found
in comparison with insulation level. It indicates that
there is a dependent relationship established
between both parameters. Hence, the indoor
occupants will increase their activity level to
achieve the thermal comfort level. In other words,
the indoor occupants may take several movement
adaptation such as typing, walking rather than
seating only to maintain their comfort level.
Table 11: The CO2 concentration of each station at
zone A.
Station CO2 (ppm) CO (ppm)
1 891 1.1
2 879 1.0
3 889 0.9
4 880 0.9
5 789 0.9
Table 12: The CO2 concentration of each station at
zone B.
Station CO2 (ppm) CO (ppm)
1 737 1.0
2 719 0.9
3 701 1.0
4 725 1.1
5 758 1.1
According to Code of Practice of Indoor Air
Quality by Ministry of Human Resources, Malaysia,
the allowable average airborne concentration of
carbon dioxide is 1000 ppm within a building. This
field study indicates that concentration of carbon
dioxide in zone A is ranged between 789 to 891
ppm, while concentration of carbon dioxide in
corporate department is between 701 to 758 ppm as
shown in Table 11 &12. The concentration of
carbon dioxide in both departments comply with
standard. This is due to the number of office
workers inside office building is at minimum. In
addition, the high effectiveness of ventilation
system inside office building successfully reduce
the concentration of carbon dioxide. Maximum
threshold for carbon monoxide concentration is
10ppm as stated in Code of Practice of Indoor Air
Quality by Ministry of Human Resources, Malaysia.
The CO concentration in zone A and B are ranged
between 0.9 ppm to 1.1 ppm. Both CO
concentrations in the office are ranged well below
the maximum limit. The CO existed in the office
space is mainly come from outdoor supply air; it is
produced by incomplete oxidation of carbon in
combustion from vehicles since the office is located
beside the junction traffic area.
Table 13: The weight of dust particle of each
station at zone A.
Station Dust Particle (mg/m³)
Minimum Maximum Average
1 0.012 0.144 0.023
2 0.012 0.03 0.018
3 0.012 0.03 0.017
4 0.018 0.042 0.026
5 0.016 0.037 0.024
Table 14: The weight of dust particle of each
station at zone B.
Station Dust Particle (mg/m³)
Minimum Maximum Average
1 0.016 0.041 0.02
2 0.015 0.027 0.018
3 0.014 0.032 0.02
4 0.022 0.037 0.027
5 0.022 0.061 0.031
The Code of Practice of Indoor Air Quality by
Ministry of Human Resources, Malaysia, stated
that the particulates concentration must not exceed
0.15 mg/m³. From measurements as shown in Table
13 & 14, the average concentration of dust particle
is 0.022 mg/ m³ and 0.023 mg/ m³ in zone A and B
respectively. Both of the average weight of dust
particle are all far below the limit specified in
Malaysia standard. This implies that the indoor
environment quality in the office is healthy and
clean. The reason may due to the office building is
being scheduled for cleaning service and
maintenance of air conditioning system.
Table 15: The air movement of each station at zone
A.
Station Air movement (m/s)
1 0.05
2 0.04
3 0.03
4 0.07
5 0.06
Table 16: The air movement of each station at zone
B.
Station Air movement (m/s)
1 0.01
2 0.04
3 0.01
4 0.04
5 0.07
The air movements were measured 1.1m above the
floor. From Table 15 &16, the air move with 0.03 –
0.07m/s with an average of 0.05m/s, while in the
zone B, the air movements obtained are between
0.01-0.07m/s with an average of 0.034m/s. These
air movements, however, are too low compared
with ASHRAE standard upper limit 0.25m/s. This
is probably due to the low number of air change or
low air volume flow rate from the air handling unit.
4. RECOMMENDATIONS
The results show that the design and construction
of this green building has achieved the goals of
sustainability in terms of energy efficiency and
thermal comfort of building occupants. It is
emphasized that the indoor environmental
condition of zone A and zone B are found
acceptable and within the allowable limits as
specified in standards. Building sustainbiltity is
usually measured in energy management aspect.
Although the cooling load and corresponding
electricity consumption cannot be computed due to
lack of building envelope parameters, the measured
physical parameters are sufficient to represent the
capability of VAV system to deliver a thermally
comfortable condition to the occupants. In other
words, the air conditioning system has successfully
meet the instantaneous cooling load in the building.
This implies no additional energy is being wasted.
In addition, the energy saving potential of this
building can be achieved through the design and
construction which is based on the sustainable
concept. The innovative energy saving measures
utilized in this building are the bioclimatic building
technique, solar panel and so forth. Therefore, this
study should be enhanced by including those factor
mentioned above in order to explain the building
sustainbility in a holistic way.
5. CONCLUSION
In general, the thermal comfort and indoor air
quality paramaters measured in sixth floor of
Suruhanjaya Tenaga office building are found good,
that is within the suggested allowable limits by
standards. The neutral temperature, 23oC found
from field studies show good agreement with the
measured indoor temperature. It indicates, despite
of guaranteeing energy-saving features, providing a
good thermal comfort is achiveable in a green
building in Malaysia.
ACKNOWLEDGMENT
The authors would like to acknowledge Mdm.
Hamidah Abdul Rashid, Head of Administration
and Facilities Management Suruhanjaya Tenaga for
granting permission to conduct fieldwork
measurement.
In addition, special thanks are extended to Mr.
Lim Chun Seong, Mr. Kok Jing Shun, Mr. Chin
Kok Hoe and Mr. Kiew Yau Fee for their help in
fieldwork measurement.
REFERENCES
ASHRAE. (2009a) Fundamental, Chapter 9:
Thermal comfort. Atlanta, GA: ASHRAE.
ASHRAE. (2009b) Fundamental, Chapter 11:
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Department of Standards Malaysia (2007)
Malaysian standard 1525: Code of practice on
energy efficiency and use of renewable energy for
non-residential buildings (1st revision).
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http://www.dosh.gov.my/doshV2/phocadownload/
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AUTHOR BIOGRAPHIES
Associate Professor Ir. Dr. Yau Yat Huang is an
Associate Professor at the Department of
Mechanical Engineering, Faculty of Engineering,
University of Malaya. Dr. Yau obtained his Ph.D.
in Mechanical Engineering in 2005 from the
University of Canterbury, Christchurch, New
Zealand. He was a prestigious NZAID (New
Zealand Agency of International Development)
PhD scholar from 2001-2004 at the University of
Canterbury, Christchurch, New Zealand. Dr. Yau
has been practicing as a M&E engineer for the past
fifteen years. In addition, he is a registered
mechanical professional engineer in Malaysia. He
can be reach via <[email protected]>