Thermal comfort and Indoor Air Quality at Green Building in

Malaysia

Y.H. Yau*

Department of Mechanical Engineering

University of Malaya, Kuala Lumpur

Email: yhyau@um.edu.my1

L.C. Ding

Department of Mechanical Engineering

University of Malaya, Kuala Lumpur

Email: lcding@um.edu.my

B.T. Chew

Department of Mechanical Engineering

University of Malaya, Kuala Lumpur

Email: chewbeeteng@um.edu.my

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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study of 4373 office workers. Annals of

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Department of Standards Malaysia (2007)

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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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Indonesia. Building and Environment, 35, 77-90.

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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 <yhyau@um.edu.my>