Australian Journal of Basic and Applied Sciences, 8(15) Special 2014, Pages: 86-91
AENSI Journals
Australian Journal of Basic and Applied Sciences
ISSN:1991-8178
Journal home page: www.ajbasweb.com
Effectiveness of kapok fibre (Ceibapentandra) as roof insulation for residential buildings
in hot climate
1
Muhd Fadhil Nuruddin, 1NadzhratulHusna Ahmad Puad, 2Azirul Zainal, 1Syed Ahmad Farhan, 3MohdFaris Khamidi
1
Department of Civil Engineering, Faculty of Engineering, UniversitiTeknologi PETRONAS,Bandar Seri Iskandar, 31750 Tronoh,
Perak,Malaysia.
2
Project Management and Delivery Department, Technology and Engineering Division, PETRONAS Holdings Berhad, Level 6,
MenaraDayabumi, Jalan Sultan Hishamuddin, 50050 Kuala Lumpur, Malaysia.
3
School of the Built Environment, Heriot-Watt University Malaysia, Level 2, MenaraPjH, 2 JalanTun Abdul Razak, Precinct 2, 62100
Putrajaya, Malaysia.
ARTICLE INFO
Article history:
Received 15 September 2014
Accepted 5 October 2014
Available online 25 October 2014
Keywords:
Kapok
fibre,
roof
insulation,
residential building, hot climate,
thermal discomfort
ABSTRACT
Background: Occupants in residential buildings experience high levels of thermal
discomfort due to the intense and long hours of solar radiation that causes the indoor
temperature to rise. Absence of insulation in the roof structure of residential buildings
allows more heat to penetrate into the indoor space through the roof. Many building
insulation materials in the market today such as polystyrene, polyurethane and
polyethylene are expensive and not environmentally friendly because they are produced
synthetically and involve numerous processes that emit carbon dioxide to the
environment. Kapok fibre is an organic material that is cheap, environmentally friendly
and easily obtained. Previous researchers have conducted laboratory experiments on
kapok fibre and proved that it has low thermal conductivity. However, there is lack of
research on the performance of kapok fibre as a roof insulation material. This paper
evaluates the effectiveness of kapok fibre as roof insulation for residential buildings in
hot climate. Two scaled-down experimental house models equipped with temperature
data loggers were set up. One house was uninsulated and the other was insulated with
kapok fibre. The thickness of kapok fibre insulation was 5 cm and then increased to 10
cm. Hourly outdoor and indoor temperatures for each house were measured for five hot
days. The highest outdoor-indoor temperature difference was 6.42 °C, which was
obtained by 10-cm kapok fibre insulation at 1000 hours. The results proved that kapok
fibre can reduce indoor temperature of residential buildings. The effectiveness of kapok
fibre insulation can be further validated by conducting experiments in actual houses
with the presence of occupants, appliances and furniture.
© 2014 AENSI Publisher All rights reserved.
ToCite ThisArticle:Nuruddin M.F., Puad, N.H.A., Zainal, A., Farhan, S.A. andKhamidi M.F., Effectiveness of kapok fibre
(ceibapentandra) as roof insulation for residential buildings in hot climate. Aust. J. Basic & Appl. Sci., 8(15): 86-91, 2014
INTRODUCTION
The production of 30% carbon dioxide in 2005 comes from buildings in many developed countries (United
Nations Environment Programme, 2009). McKinsey & Company (2009) stated that greenhouse gases can be
reduced through building insulation. Thermal insulation materials can retard heat from solar radiation from
penetrating into the building. There are many different types of commercialized insulation materials in the
industry. Traditional insulation materials such as mineral wool, cellulose, cork and polyurethane are widely used
because of their high thermal resistance (Jelle, 2011). However, many building insulation materials in the
market are expensive (Al Yacoubyet al., 2011) and some of them are hazardous and not environmentally
friendly. Many of the commercialized products such as expanded polystyrene, cellulose fibre, cork, glass wool
and polyurethane has thermal conductivity ranging between 0.02 to 0.06 W/mK.
Insulation materials can be installed in different parts of the building envelope such as walls, ceiling and
roof. Other than that, insulation materials can also be mixed into the material that is used to construct the
building envelope (Khamidiet al., 2014; Farhanet al., 2012b). Previous research on building insulation focused
more on wall insulation (Farhanet al., 2012a).The effectiveness of installing insulation in the roofing system
must be explored further as most of the heat gain into the building is through the roof(Suehrckeet al., 2008; AlHomoud, 2005).
Corresponding Author: Dr. Muhd Fadhil Nuruddin, Department of Civil Engineering, Faculty of Engineering,
UniversitiTeknologi PETRONAS, Bandar Seri Iskandar, 31750 Tronoh, Perak, Malaysia.
E-mail: fadhilnuruddin@petronas.com.my
87
Muhd Fadhil Nuruddin et al, 2014
Australian Journal of Basic and Applied Sciences, 8(15) Special 2014, Pages: 86-91
Kapok fibre is an organic material extracted from kapok trees and it has a low thermal conductivity (0.034
to 0.035 W/mK) (Louppeet al., 2008). Kapok fibre has a low density and is seven times less dense compared to
cotton because it contains unicellular fibres (Chaiarrekijet al., 2011; Manohar et al., 2006). Kapok fibre shows
better performance in thermal properties compared to other natural fibres and allows it to challenge other
synthetic fibres (Voumbo, 2010). However, Nuruddinet al.(2014) reports that based on previous literature, there
is presently no research that explores the adoption of kapokfibre as a roof insulation material.
Herein, this paper determines the effectiveness of kapok fibre as an insulation roofing material in residential
buildings in hot climate. Also, the effect of thickness on its insulation effectiveness is also determined.
Experimentation:
Measurements of outdoor and indoor temperatures were conducted using two scaled-down experimental
house models equipped with temperature data loggers. The house models were built with reference to the
minimum dimensions of a room as mentioned in Uniform Building By-Laws (UBBL) 1984 (Legal Research
Board, 2012a; Legal Research Board, 2012b) Dark grey coloured roof tiles were employed to allow maximum
absorption of heat from solar radiation. Table 1 presents the insulations installed in the house model variations.
Table 1: Insulations installed in the house model variations
House Model
Insulation
A
Uninsulated (Figure 1)
B
5-cm kapok fibre (Figure 2)
C
10-cm kapok fibre (Figure 2)
D
Radiant barrier (Figure 3)
Fig. 1: Top view of attic of uninsulated house model
Fig. 2: Top view of attic of insulated house model
88
Muhd Fadhil Nuruddin et al, 2014
Australian Journal of Basic and Applied Sciences, 8(15) Special 2014, Pages: 86-91
Fig. 3: Top view of attic of radiant barrier house model
Kapok fibre used in this study was obtained from Bota, Perak. Impurities were removed from the kapok
fibre before it was placed in the model. Brown paper was selected as the ceiling board material to hold the
kapok fibre in place because it is very thin and will not influence the indoor temperature. Radiant barrier used in
this study was obtained from a local manufacturer. The radiant barrier is a pure aluminium foil bonded to a layer
of woven fabric.
Indoor and outdoor temperatures were recorded simultaneously for all models using temperature data
loggers with built-in thermometers. Hourly temperatures were taken for five hot days. The climate of Malaysia
is hot throughout the year and therefore, five hot days is sufficient. Then, hourly outdoor-indoor temperature
differences were calculated.
RESULTS AND DISCUSSION
40
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1600
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0800
1300
1800
2300
0400
0900
Temperature for
uninsulated house model
(Model A) (°C)
Figure 4 shows the indoor and outdoor temperature profiles of Model A. In general, daily outdoor
temperatures peak in between 1000 to 1600 hours due to the position of the sun that leads to maximum solar
radiation. The highest outdoor-indoor temperature difference recorded was 4.82°C, which was obtained at 1100
hours in Day 4.
Hours
Indoor
Outdoor
Fig. 4: Indoor and outdoor temperature profiles for uninsulated house model (Model A)
Figure 5 shows the indoor and outdoor temperature profiles for Model B. The highest outdoor-indoor
temperature difference recorded was 5.26 °C, which was obtained at 1000 hours in Day 3. The outdoor-indoor
temperature difference for Model A at this time was 4.63 °C, which is 0.63 °C lower compared to Model B.
Therefore, Model B is effective in retarding heat into the house model.
Muhd Fadhil Nuruddin et al, 2014
Australian Journal of Basic and Applied Sciences, 8(15) Special 2014, Pages: 86-91
45
40
35
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25
20
0900
1400
1900
0000
0500
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1500
2000
0100
0600
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1600
2100
0200
0700
1200
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2200
0300
0800
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1800
2300
0400
0900
Temperature for 5-cm
kapok fibre insulated house
model (Model B) (°C)
89
Hours
Indoor
Outdoor
Fig. 5: Indoor and outdoor temperature profiles for 5-cm kapok fibre insulated house model (Model B)
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Temperature for 10-cm
kapok fibre insulated house
model (Model C) (°C)
Figure 6 shows indoor and outdoor temperature profiles for Model C. The highest outdoor-indoor
temperature difference recorded was 8.4°C, which was obtained at 1000 hours in Day 3. Model B recorded a
5.26 °C difference during this time. This proves that the outdoor-indoor temperature difference for Model C is
3.14°C higher than Model B. Therefore, Model C provides better thermal performance than Model B. In
addition, the outdoor-indoor temperature difference for Model A is 4.63 °C, which is 3.77 °C lower than Model
C.
Hours
Indoor
Outdoor
Fig. 6: Indoor and outdoor temperature profiles for 10-cm kapok fibre insulated house model (Model C)
Figure 7 shows indoor and outdoor temperature profiles for Model D. The highest outdoor-indoor
temperature difference recorded is 7.05°C, which was obtained at 1100 hours in Day 4. Model C recorded a 2.79
°C difference during this time. This proves that the outdoor-indoor temperature difference for Model D insulated
house model is 4.26°C higher than Model C. Therefore, Model D provides better thermal performance than
Model C. In addition, the outdoor-indoor temperature differences for Model A and Model B are 4.82 and 2.79
°C, which are 2.23 and 2.11 °C lower than Model D respectively. Table 2compares the outdoor-indoor
temperature differencesof all house models from 1000 to 1400 hours. The highest average temperature
difference is 5.09 °C, which was obtained by Model C.
Muhd Fadhil Nuruddin et al, 2014
Australian Journal of Basic and Applied Sciences, 8(15) Special 2014, Pages: 86-91
45
40
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25
20
0900
1400
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0500
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1500
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0100
0600
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1600
2100
0200
0700
1200
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0800
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2300
0400
0900
Temperature for 10-cm
kapok fibre insulated
house model (Model D)
(°C)
90
Hours
Indoor
Outdoor
Fig. 7: Indoor and outdoor temperature profiles for radiant barrier insulated house model (Model D)
Table 2: Outdoor-indoor temperature differences of insulated and uninsulated house models
Outdoor-Indoor Temperature Difference (°C)
Time (hours)
Model A
Model B
Model C
1000
3.60
4.61
6.42
1100
3.98
4.29
5.11
1200
2.79
3.28
4.56
1300
2.86
2.33
5.18
1400
2.21
2.71
4.19
Average
2.72
3.44
5.09
Model D
5.45
5.13
5.23
3.61
4.06
4.69
Analysis of Variance (ANOVA):
Analysis of variance (ANOVA) was used to determine the significant differences between uninsulated and
insulated house model. A one-way analysis was performed to compare the means of subgroups. The analysis
included standard deviations, variances and 95% of confidence interval means. The results are considered
significant when the P-value is lower than 0.05. However, it is considered marginally significant if the P-value
is lower than 0.1. The ANOVA results are shown in Table 3. Results showed a marginally significant preference
for Model A (M = 3.087, SD = 1.137, p = 0.089) and Model B (M = 3.446, SD = 1.539, p = 0.068). The
outdoor-indoor temperature difference for Model A is marginally significant at 1100 and 1400 (p = 0.084).
However, there are no statistically significant differences for Model C (M = 5.090, SD = 1.579, p = 0.221) and
Model D (M = 4.697, SD = 1.395, p = 0.139).
Table 3: Results of ANOVA on insulated and uninsulated house models
House Model
Mean (M)
Standard Deviation (SD)
Model A
3.087
1.137
Model B
3.446
1.539
Model C
5.090
1.579
Model D
4.697
1.395
P-Value (p)
0.089
0.068
0.221
0.139
Conclusion:
Findings suggest that kapok fibre is effective as a roof insulation material in residential buildings in hot
climate. In addition, thicker kapok fibre improves its effectiveness. The highest outdoor-indoor temperature
difference was 5.09 °C for 10-cm kapok fibre insulated house model, which is 2.37°C higher than the
uninsulated house model. For future research, it is recommended that higher thicknesses of kapok fibre are used
for evaluation. Also, the evaluation can be conducted in actual houses with the presence of occupants,
appliances and furniture.
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