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JOURNAL
OF
CRITICAL REVIEWS
ISSN- 2394-5125
VOL 7, ISSUE 19, 2020
278
A CRITICAL REVIEW OF THERMAL INSULATORS
FROM NATURAL MATERIALS FOR ENERGY
SAVING IN BUILDINGS
Shalom Akhai1, Suneev Anil Bansal2, Sarabjit Singh3
1Department of Mechanical Engineering, CGC Technical Campus, Mohali, India
2Department of Mechanical Engineering, MAIT, Maharaja Agrasen University, HP, India 174103
3Department of Mechanical Engineering, MAIT, Maharaja Agrasen University, HP, India 174103
E.mail: shalomakhai@gmail.com, suneev@gmail.com, sarabjit5464@gmail.com
ABSTRACT: This article offers a brief guide to widely used natural insulation materials and their ranges of
thermal conductivities published by various researchers. The properties of composite or hybrid materials from
these natural insulator materials can be studied to improve their environmental performance, energy efficiency,
and including their costs economics. The thermal characteristics are considered most important in the context of
low values of conductivity. A lot of previous researchers showed that the naturally occurring insulation boards
can be developed from natural resins, fibers, etc. The researchers were able to fabricate insulation panels which
were so good that they could be directly compared to the synthetic boards. In this paper, the authors have
studied a lot of past studies and then have shortlisted the most relevant of those studies. Thus the aim is to
provide a summary of natural insulation materials and their thermal engineering applications by illustrating the
review papers written on various subjects, for readers to link to the latest review papers on such materials and
make contributions to the specific area of interest. Thus the basic explanation of natural insulation material with
compactable values of various properties is stated and included herein.
KEYWORDS: Insulation material, thermal conductivity, energy efficiency.
I. INTRODUCTION
The modern era's problems with energy optimization require modern solutions. The advent of the
construction started with the early man making homes for protection and also some relief from the
surroundings. The early construction material was a mixture of mud and leftover crop remains. This shows
that the natural remains are good insulators. The early man also used sheepskins as clothes. All these
indicate that the early man had the key to thermal insulation. The insulation of a structure is done against
both hot and cold climates. The present conditions of insulation are done to protect ourselves against the
harsh outer conditions. The insulation of almost all structures is becoming so natural that there are
nowadays no buildings or structures which are constructed without the use of insulation. The insulation
panels/boards are thick enough to be concealed in between the wall structures. The insulation panels made
of natural renewable sources are gaining a lot of popularity in today’s world. The chemical coating on the
natural insulation panels should be of a certain quality to prevent the loss of any of its natural properties.
The chemicals should only enhance the insulation properties and in no way diminish its thermal properties.
The use of natural insulators helps in reducing the stress on natural resources. This process can be used to
insulate any type of surfaces but the insulation pads require the addition of certain chemicals for binding
and also for increasing their life. The main base of research should also be focused on the proper chemicals
for insulation, so that the natural insulation materials do not lose their properties, but can increase their life
to as long as possible. The selection of raw material should be something that can be allergic to people and
other pets. The natural insulators should be treated well to prevent the panel from decaying and spreading
any kind of bad odor. Technically the efficiency of any process is defined ratio of thermal energy to the
electricity required by the energy-consuming facility [Tareja P. & Tareja M. (2010)]. For example, energy
efficiency in the building can be optimized by the use of proper insulation material in form of roof tiles;
falls ceiling, etc. while using air conditioners [Braulio-Gonzalo M. &Bovea M. (2017)]. Air conditioners
are used to maintain the thermal quality in buildings [Tanwar N, & Akhai S. (2017)]. They are many
systems made by homogenous material that can reduce transmission of heat to the surroundings and
reduced the heating and cooling load of building thereby reducing energy consumption [Akhai S. et al.
(2016)]. By utilizing such insulation materials to isolate systems from surroundings, thermal comfort levels
can be achieved at a low operational cost [Evin D. &Ucar A. (2019)]. The use of insulation materials
cannot be limited to wool, natural fibers, and other crop leftovers, but new materials can be used studied,
to get good results and develop new insulation structures.
JOURNAL
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CRITICAL REVIEWS
ISSN- 2394-5125
VOL 7, ISSUE 19, 2020
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The authors in this study have not only focused on the previous research done but also tried to prove the
claims of the researchers, by making an insulation board by using banana barks. The panels were made and
then tested for their thermal conductivity value. These panels are lightweight and can be used for a wide
variety of applications. The banana barks are sometimes found in vast quantities left to rot, or just dumped.
This is easy to obtain the raw material. So panels made of these barks can be cheap.
Thermal insulation materials
This review paper compiles all the existing researches based on synthetic insulation materials. A basic
explanation of insulation material with various/approximate ranges values of their thermal conductivities
are included herein from published literature as presented in Table 1. The table has been carefully
researched well by the authors, to have a compilation of the best and the latest sources in the field of
synthetic insulation panels. The latest studies have been arranged in order, to have an idea of the latest
studies. The thermal conductivity of the materials, studied by the researchers is presented in Table 1.
II. LITERATURE SURVEY
Several types of research and studies to investigate efficiencies of material characterized by thermal
performance and structural designs have been proposed. Table 1 compiles the existing researches based on
the use of naturally occurring insulation materials in the area of mechanical and structural engineering. It
demonstrates numerous work studies by researchers in which they used natural materials for thermal
insulation for energy saving in buildings.
Table 1: Natural materials used for thermal insulation in engineering applications.
Source
Material
considered
Thermal
conductivity
Application
sector
Remarks / Comment
Yildiz, G., et
al. (2020)
Petrochemicals
0.051 W/m. K.
Building
insulation
The fabrication of insulating material
from natural and organic sources can
be a bit difficult, but the insulating
sources thereby made have a lot of
environmental advantages.
Mandili, B.,
et al. (2019)
Waste paper
0.061 W/m. K.
Eco-friendly
composite
material/
Recycled waste
paper
The low bulk density of the material
composed is low. The water
absorption is high making it possible
to use this material for making bricks.
Wang, Hao,
et al. (2018)
Plant fibers&
photochromatic
glass
0.023 W/m. K.
Development of
green buildings/
Green
construction
material
Developing insulating construction
materials to decrease the cost of other
wall structures.
Kasperski, J.,
&Grabowska,
B. (2018)
Cellulose
0.54 W/m. K.
Composite
material for
building
insulation
The insulation board can provide high-
quality insulation to roofs and floors.
Cellulose with
fibers
0.041 W/m. K.
The composite
material of
cellulose with
fiber for wall
insulation
The insulation of walls and other
surfaces can be done using this
composite.
Daşdemir,
Ali, et al.
(2017)
Rock wool
0.04 W/m. K.
Insulation
material for
HVAC pipe
insulation
Using plastic to increase the thickness
of insulation material on HVAC pipes
to reduce the cost and expenditure on
heating and cooling expenses.
Aditya, Lisa,
et al. (2017)
Sheep wool
0.038 W/m. K.
Insulation of
HVAC
components
The optimum insulation thickness has
to be determined to save the costs of
the insulation material and for better
insulation of the building as a whole.
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Stone wool
0.035 W/m. K.
Insulation of
HVAC ducts and
components
The insulation thickness should not be
excessive because that could increase
the weight of the equipment.
Cotton wool
0.037 W/m. K.
Insulation and
acoustic lining
The insulation can act as a barrier
against unwanted sounds and
vibrations too.
Kumar et al.
(2016)
Wood
0.039 W/m. K.
Building
insulation and
moisture control
The use of wood and its fibers acts as
good insulation material and prevents
the movement of moisture also
between the insulated structures.
Palumbo et
al., (2015)
The crop
remains and
extract
0.050 W/m. K.
Building
insulation
The insulation of buildings can be
done by using the natural crop remains
from harvested crops and the remains.
This has been used as part of
construction material since time
immemorial and therefore the use of
such crop leftover can be used for
insulation.
Kayfeci,
(2014)
Rock wool
0.039 W/m. K.
Heating pipe
insulation
The insulation of a heating pipe is
required to prevent the waste of energy
in the form of heat loss. This
insulation can be applied especially for
district cooling techniques.
(Zach et al.,
2013)
Mineral wool
with fibers
0.036 W/m. K
Building
insulation
Natural insulation is a better way to
prevent additional stress on the
ecology, but that requires hydrophobic
treatment to prolong its life.
Bektas Ekici,
Aytac
Gulten, and
Aksoy (2012)
Coal
0.038 W/m.K.
Building
insulation
The insulation of buildings is
necessary to avoid the loss of thermal
comfort and also reduce the quantity
of energy consumed to provide
comfortable conditions for the
inhabitants.
(Korjenic et
al., 2011)
Hemp fibers
0.0458 W/m.
K.
Insulating walls
Natural material can act as good
insulators, but there is a requirement
for a chemical treatment to increase
their lifetime.
Bozsaky,
D..(2010)
Cork, reed flax
0.027 W/m. K.
Organic
materials/
Insulation of
buildings
Propagating people to use materials
like hay, sheep wool for insulating
would be difficult because of their
short lifecycle and inflammable
properties.
The above table shows only the most relevant studies related to natural insulation materials. The
researchers have studied each of the insulation boards widely, and the thermal conductivity of the material
used by them was also tested. The thermal conductivity of the materials was also found to be at par with
the synthetic insulation boards.
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Figure 1: Banana barks after drying and compaction process
III. OVERVIEW
The current research did not only study the past studies alone, but the authors tried to test the accuracy of
the claims. For this reason, the authors made an insulation panel using banana bark. This can be considered
to be a crop residue. The harvested banana tree is generally left to decay, and there is not much use for it.
The bark was peeled and then dried naturally. After drying for a week, the banana bark was pressed and
compacted. This was then tested for its thermal insulation, which showed quite good results. The results
showed that the thermal conductivity was 0.031 W/m. K. The addition of binding chemical and the decay
protection would make this natural leftover material a very good natural insulating material.
The banana barks are quite found in abundance, especially in countries like India and other countries
having a coastline. This is a harmless product and mostly non-allergic to everyone. There is the least odor
from this product. The use of this product should be widely appreciated and people should be made more
aware of the advantages of using this product as an insulation material. This not only reduces the use of
synthetic materials that are harmful to the environment but also helps in the proper disposal of the waste
remains. This product is the light weight after drying and can be transported easily. The use of banana
barks for the insulation materials is a very good example of what all materials can be used for making
insulation panels.
IV. CONCLUSION
This brief overview discussed the most popular natural insulation materials and the spectrum of their
thermal conductivity as the heat gain or loss may be reduced if the insulation is appropriate. The natural
insulator is although cheaply available and in large quantities but it is difficult to convince people into
using such natural insulation materials because they have a very short life cycle and have to be replaced
every short while. The research is mainly to mix the natural insulation boards with some kind of chemicals
to increase their life cycle. This makes the insulation materials last not only for a long time but helps in
lowering the stress on the ecology. The natural insulators also have additional qualities of reducing the
moisture transited between the structures, noise absorption, and noise cancellations. A lot of research
going on in this direction of development of sustainable material and technologies so daily new product s
are coming up with a comparative analysis of properties but still there is a deficiency of data regarding
composite materials from various admixtures. Care should be taken that some natural fibers can be allergic
to certain people and some pets, but can be prevented by the use of some chemicals. It is necessary to do
show a disclaimer when using natural fiber, to act as a caution.
There is also a huge scope for the development of insulation panels from crop leftovers or remains because
they contribute to a huge part of the waste generated. The burning of such waste can be dangerous. So
using such waste materials for making insulation panels will also help in their proper disposal. The boards
can be made by mixing them with proper binding materials and using other chemicals to increase their life
cycle.
The study shows that there is a wide scope of development in the field of insulation using natural
materials. There needs to be a wide awareness among users to educate them about the benefits of using
natural insulation panels.
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V. FUTURE SCOPE
The paper had presented some of the work by some researchers in the field of making insulating material
from natural sources. This was found to be successful, even though there were some drawbacks. It should
be stated here that more research needs to be done in this area, to improve the life cycle of the natural
insulating material and also making people aware of the environmental advantages of using th ese natural
insulators. Research also needs to be done in the area of the coating of natural insulation materials to
prevent the spread of allergy, but the chemical should not affect its properties of thermal insulation. The
life cycle of the insulation board should also be improved to as long as possible. The insulation board
should also be free from any kind of odors, and also prevent any kind of allergic reactions to any of the
occupants.
A lot of studies are required for the chemical coating mixture in the insulation board, to increase the life of
the insulation board, and also prevent the spread of allergy. The chemical should improve the binding
ability of the panel, the chemical should also prevent the decay of the material and the spread of unwanted
odor and it must also be preferred that waste materials like fly ash which otherwise pose environmental
threats or disposal issues are utilized as admixture. The research should also be focused on the ratio in
which the chemicals should be mixed with the fibers or the natural materials to get the best results. Studies
can be also done to prepare the construction raw materials like bricks, plaster in such a way, that the
insulation materials can be inscribed in them, and thereby get products that have high thermal resistance.
Such products will be cost-effective, and also reduce the space occupied by the insulation panel. People
have to be made aware of the benefits of such products also, to build a greener and ec o-friendly
environment.
VI. REFERENCES
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[2] Akhai, S., Singh, V. P., & John, S. (2016). Investigating Indoor Air Quality for the Split-Type Air
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[3] Bektas Ekici, B., Aytac Gulten, A., & Aksoy, U. T. (2012). A study on the optimum insulation
thicknesses of various types of external walls with respect to different materials, fuels and climate
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[4] Bozsaky, D. The development of thermal insulation materials from the beginnings to the
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[5] Braulio-Gonzalo, M., & Bovea, M. D. (2017). Environmental and cost performance of building
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Journal of Refrigeration, 92, 94-105.
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Authors Profile
Dr. Shalom Akhai is currently employed as Associate Professor at CGC Technical
Campus, Punjab. He has industrial experience as an engineer in Bhushan Power &
Steel Ltd. He was formerly working at PEC University of Technology at a faculty
position for educating UG and PG courses. He is author of several books in
Mechanical Engineering and guiding ME and Ph.D. candidates in their research
work. His academic articles have been published in various National and
International journals, and he is also the editorial board member in various journals
of repute. He has also served as a team member in several design patents.
Er. Sarabjit Singh has more than 10 years of diverse experience in industry and
academia. He held key positions in various engineering institutions of repute. His
research interest is in the field of manufacturing, materials, polymer/metal
composite materials, automobiles etc. Presently, he is perusing his Ph.D. in
Mechanical Engineering at Maharaja Agrasen University. He has published
research papers and also served as a guide for various award-winning projects.
Dr. Suneev Anil Bansal has more than 15 years of diverse experience in the
industry, research laboratory, and academia. He served key positions in key
projects like automobile development at Hero Motor Corp., fighter aircraft
development at DRDO, and Nanomaterials & manufacturing development at
various Universities. His research interest is in the field of
Micro/nanomanufacturing, materials, 2D materials, graphene, polymer/metal
composite materials, sensing, etc. Presently, he is an assistant professor (& head
Nano/micro-manufacturing and materials research group), Maharaja Agrasen
University. He has published more than 20 research papers, 1 patent, and served as
a subject expert for several journals.
