1. Final Year Project
NAME: IAN PYBURN
I.D NUMBER: 11117133
SUPERVISOR: DR. DAMIEN THOMPSON
COURSE: B.Sc. ENERGY
YEAR: FOURTH YEAR
PROJECT TITLE: USE OF NANOTECHNOLOGY IN ENERGY
EFFICIENT BUILDINGS
DATE: 23rd March 2016

2. i
Acknowledgements:
I would like to thank Damien Thompson my project supervisor for his guidance and wisdom.
I would also like to thank the Department of Physics and Energy in the University of
Limerick for aiding me throughout my studies.

3. ii
Abstract:
In my project I want to synthesis and summarize the effects that nanotechnology can have in
energy efficient buildings. Since nanotechnology can affect all elements of buildings I had to
choose just two aspects of construction I could concentrate my research on within the time
frame. The two areas I chose were cement based materials and windows. While explaining
the manufacturing processes I want to be able to portray which process is the most suitable
for energy efficient buildings. When outlining the outcomes of nanodevices and nanoparticles
being incorporated into windows and concrete I want to highlight the production cost and
environmental risks. I also want to show if these new technologies can be easily integrated
into buildings and whether or not these are appropriate to be mass-manufactured into
buildings.

4. iii
Table of Contents
Chapter 1: Introduction:.............................................................................................................1
Chapter 2: Literature Review:....................................................................................................4
2.1 Nanotechnology Definition:.............................................................................................4
2.2 Nanotechnology, Nanoscale and Terms of Nanotechnology:..........................................4
2.3 Nanoparticles Manufacture:.............................................................................................6
2.4 Science and Properties at the Nanoscale:.........................................................................7
2.5 Importance of Nanotechnology in Energy Efficient Buildings: ......................................8
2.6 Nanotechnology and Sustainable Development ..............................................................9
2.7 The Cost and the Integration of Nanotechnology into the Built Environment: .............10
2.8 Environmental Impact of Nanotechnology:...................................................................11
Chapter 3: Experimental ..........................................................................................................16
Chapter 4: Results, Analysis and Discussion...........................................................................18
4.1 Evaluation of Construction Areas..................................................................................18
4.1.1 Concrete..................................................................................................................18
4.1.2 Thermal Insulation..................................................................................................18
4.1.3 Solar Energy (Photovoltaics) ..................................................................................19
4.1.4 Windows and Glass.................................................................................................20
4.1.5 Evaluation ...............................................................................................................21
4.2 Nanotechnology in Concrete..........................................................................................22
4.2.1 Addition of Nano-Silica (SiO2) to Concrete ...........................................................22
4.2.2 Addition of other nanoparticles to Concrete: (Nano-Al2O3, Nano-Fe2O4, Nano-TiO2,
Nano-ZrO2) ......................................................................................................................29
4.2.3 Reinforcing Concrete with Carbon Nanotubes:......................................................34
4.2.4 Financial Comparisons of Nanomaterials used in Concrete ...................................40
4.3 Nanotechnology in Windows.........................................................................................40
4.3.1 The Use of Nano-TiO2 (Titanium Dioxide) Coatings on Energy Efficient Windows
.........................................................................................................................................40
4.3.2 The Use of Nano-SiO2 (Silica) in Energy Efficient Windows................................49
4.3.3 Smart Windows and Nanotechnology.....................................................................50
Chapter 5: Conclusions............................................................................................................63
References:...............................................................................................................................65

5. iv
List of Figures:
Figure 1 - Nanoscale in comparison to other objects with metric portion scales ...................5
Figure 2 - Biodegradable nanoparticles under an electron microscope..................................5
Figure 3- Deviations of nanotechnology terms and how they are linked with one anothe........6
Figure 4 – Simplification of the top down and bottom up approach . ......................................7
Figure 5 - Kelvin Equation . ......................................................................................................7
Figure 6 – Two graphs of nanomaterials concentration in sediments and in sludge treated
soil............................................................................................................................................13
Figure 7 – The comparison of different thermal insulation techniques...................................19
Figure 8 - Specific surface area of all components in nano-engineered concrete. ................23
Figure 9 – Concentration of materials used in the tests conducted in Building and Materials
36. ............................................................................................................................................25
Figure 10 - Tensile strength of the six mixtures in Building and Materials 36. ......................25
Figure 11 – Mercury intrusion porosimetry test undertaken in Building and Materials 36 ...25
Figure 12 - Cement hydration processes chemical equations .................................................26
Figure 13 - Results from the adiabatic temperature test done in Construction and Building
Materials 36 ............................................................................................................................27
Figure 14 – Mechanical properties tests and the Durability tests results completed for
Procedia Engineering 14 ........................................................................................................33
Figure 15- Difference between single-wall carbon nano-tubes and multi-wall carbon
nanotubes.................................................................................................................................34
Figure 16 - Percentage of CNT that agglomerates .................................................................35
Figure 17 - Compressive strength test in Construction Building Materials 25.......................37
Figure 18 - Mercury intrusion porosimetry test in Construction and Materials 25................38
Figure 19 - Similarities between CNT fibres and asbestos fibres............................................39
Figure 20 - Comparison of prices of nanoparticles from US Research nanomaterials, Inc. ..40
Figure 21 Titanium dioxide oxidation process: Stage 1 ........................................................43
Figure 22 Titanium dioxide oxidation process: Stage 2..........................................................43
Figure 23 Titanium dioxide oxidation process: Stage 3..........................................................44
Figure 24 - BEES life cycle assessment of Nano-TiO2 coating environmental improvement..46
Figure 25 – Increase in CO2 emissions due to Nano-TiO2 oxidation process. .......................46
Figure 26 - Nano scratch test results from Solar Energy 125 ...............................................47
Figure 27- BEES economic and environmental model for Nano-TiO2 coated glass...............48
Figure 28 - Environmental importance versus economic performance from BEES model.....49
Figure 29– Comparison of smart window technologies. .........................................................54
Figure 30 - Operation of a PLDC smart window....................................................................55
Figure 31 - Transparency of silver nanowires used as the transparent electrode. ................56
Figure 32 - Specular transmittance and haze of silver nanowires and ITO electrodes...........57
Figure 33 – Operation of a suspended particles smart window..............................................57
Figure 34 - Operation of an electrochromic smart window ...................................................59
Figure 35 - Visual representation of Nano-Prussian Blue applied to ITO glass.....................59
Figure 36 - Scanning transmission electron microscopy results in Nature 500. ...................61
Figure 37– Operation of the Niobium Oxide and ITO glass composite . ...............................62

6. 1
Chapter 1: Introduction:
Nanotechnology could potentially revolutionise the world we live in today. Nanotechnology
has many applications such as medicine, food production, space exploration, energy
efficiency and electronics. Nanotechnology could make a big impact on the built environment
already around us. To protect our planet and to make sure all living things have a sustainable
future here on earth we have to become more efficient. Miniaturised nanodevices is aiding us
reach our sustainability and our efficiency goals. However the literature of these factors in
manufacturing these devices still can be investigated.
My project is going to be an investigation of the literature on how nanotechnology is affecting
the energy efficiency of new and existing buildings. During my project I will be selecting
certain areas of construction and researching in detail the outcomes of nanotechnology being
incorporated into these areas.
There are a lot of different areas of construction that nanotechnology could improve. For
instance, physical and chemical degradation of building materials is a main reason why
buildings and construction use energy. This can also cause maintenance costs to rise.
Nanotechnology can improve a materials mechanical stability, durability and resistance to
external forces. Another example would be that if a building incorporates renewable energies
to aid energy consumption, such as solar energy. One of the main difficulties with solar
energy is the efficiency, which nanotechnology could greatly aid.
Nanotechnology could have a huge effect globally but there are a lot of factors to be
considered and compared. A lot of different aspects have to be deliberated to see if
nanotechnology can be successful in energy efficient buildings. I have outlined and explained
the factors that have relevance to nanotechnology in energy efficient buildings on the next
page.

7. 2
 Manufacture of Nanodevices and Nanomaterials
I will explain the science behind these devices and materials and take into
consideration that if a certain device’s manufacture is too complex that it may not be
feasible to incorporate into the built environment.
 Positive and Negative Outcomes of Nanotechnology in Energy Efficient Buildings
Nanotechnology can provide buildings with a lot of positive outcomes such as more
mechanically stable materials and more efficient devices.
 Integration of Nanotechnology into the Built Environment
I want to investigate whether or not it is possible to incorporate these new
nanotechnologies into existing buildings and materials.
 Financial & Production Cost of Nanotechnology
I will review the production cost of these materials and devices and the cost of
integrating nanotechnology into existing buildings.
 Human Health Hazards
The potential health risks caused by the manufacture and utilisation of efficient
nanotechnologies have on lab researchers, construction workers and the occupants of
these energy efficient buildings.
 Environmental Impact of Nanotechnology
Considering the possible impact nanotechnology will have on our environment and
outlining potential risks.
 Comparison of Nanotechnology to Alternative Technologies
In some areas of my project I will be comparing nanotechnology to alternative energy
efficient technologies.
 Potential for Mass Manufacture
I want to establish if these nanodevices or nanomaterials are suitable for mass
production and distribution.

8. 3
Ultimately at the end of my project I want to make conclusions on the energy efficient
nanotechnologies I have investigated and decide if they are suitable for mass manufacture. I
want to be able to give my own opinion and whether or not these nanotechnologies are
appropriate for energy efficient buildings.
Implementing energy efficiency in new and existing buildings is vital to reduce our negative
impact on our environment and to make sure earth becomes more sustainable.
Nanotechnology is assisting in a lot of different aspects of green building. Designs of
buildings are becoming more sustainable through nanotechnology. Air and water purification
are possible due to de-polluting nanoparticles. Energy regulation can be improved due to
nanodevices which allows for less energy wastage. Materials can have longer life cycles and
less need for regular inspections due to stronger materials as a result of nanotechnology.
Nanotechnology involves the ability to observe and control molecules at the nanoscale.
Quantum mechanics play a big role in developing nanomaterials and nanodevices. Quantum
mechanics allows the properties of very small objects to behave unpredictability. Molecules at
the nanoscale behave erratically to make materials with improved functions, such as lighter,
stronger, durable etc. Substances that are insulators and cannot carry an electric charge in
bulk form might become semiconductors when reduced to the nanoscale. Melting points can
change due to an increase in surface area. [1] [2]
The use of nanotechnology can hold a lot of promising prospects for energy efficiency.
However all of the factors in implementing this relatively new technology must be considered
which I shall do in this project by a review of the scientific literature.
Nanotechnology could hold the key to our current global problems and the widespread
incorporation of nanotechnology into our buildings could go a long way to making this planet
more sustainable and advanced for the future.

9. 4
Chapter 2: Literature Review:
2.1 Nanotechnology Definition:
“Nanotechnology is the branch of technology that deals with dimensions and tolerances of
less than 100 nanometers, especially the manipulation of individual atoms and molecules.”
[3]
2.2 Nanoscale and Terms of Nanotechnology:
Nanotechnology is the precise atomically technology done on the nanoscale. Atoms are being
manipulated at the nanoscale to give nanomaterials and nanodevices new desirable properties.
All technology at the nanoscale is known as nanotechnology and there are many deviations of
this atomically precise technology (nanotube, nanomaterial, nanoparticles, nanosensors, etc.).
The nanoscale is between 1 nanometer and 100 nanometers (nanometer = 10-9
meters). 1
nanometer is a billionth of a meter. Regular laboratory microscopes cannot even see atoms at
the nanoscale. To see what is going on at this extremely small scale we have to use high
powered microscopes. To put the nanoscale into a relatable context 1 nanometer is how much
your fingernail grows every second. The nanoscale is where properties of a certain material
can change substantially. In the macro and micro scale property changes happen because of
bulk or volume changes. However between 1 nm and 100nm the quantum effects have an
extreme effect on any materials property. [2] [4]

10. 5
Figure 1 - shows how small the nanoscale actually is in comparison to other objects. It
also has the relative comparison of other metric portion scales such as the mesoscale and
the microscale.
Observation of particles at the nanoscale is done by high powered microscopes. In 2014 the
Nobel Peace Prize in Chemistry was awarded to Eric Betzig, William Moerner and Stefan
Hell for fluorescent microscopy. This greatly advanced the techniques used in observing
objects at the nanoscale. [2] [5]
Figure 2 - shows biodegradable nanoparticles. This image was captured using an electron
microscope in the Justin Hanes Lab at John Hopkins University. With the 500nm scale
bar, the image shows the scale at which high powered microscopes can observe.
All technology at the nanoscale is known as nanotechnology and there are many deviations of
this atomically precise technology. All of these terms have the prefix Nano (e.g.
Nanoparticle). This prefix means “one billionth” and describes the scale at which at which
this technology is completed on a certain area. [2] [6]

11. 6
Figure 3- shows the deviations of nanotechnology terms and how they are connected with
one another.
2.3 Nanoparticles Manufacture:
Particles of matter are made into nanoparticles by two different processes. These are:
 Bottom Up approach
Small particles (smaller than the nanoscale) atomically assemble due to self-attraction
or due to an external force. These particles keep assembling until it is part of a larger
system which is a nanomaterial.
 Top Down approach
Larger particles (larger than the nanoscale) have finer and finer tools or chemical
processes used upon them until a nanoparticle is created. These particles then can
form together to create a nanomaterial.
To visualise this, the brick and building example is used. For the Bottom Up approach,
imagine bricks constructing together until a building is formed. For the Top Down approach
imagine a building being unconstructed by smaller and smaller tools until finally only a brick
is left. [7]
Bottom Up approach
Top Down approach

12. 7
Figure 4 – shows the simplification of the top down and bottom up approach using a brick
and building example.
2.4 Science and Properties at the Nanoscale:
Nanotechnology is ultra-precision engineering and because of this the properties of these
atoms can change drastically. At the nanoscale scientists can change the mechanical, chemical
and biological properties of a given substance through quantum mechanics. Before
nanotechnology these changes at an atomic level were not possible. I have outlined a few
property changes that happen at the nanoscale that are relevant to energy efficient buildings.
Mechanical Properties:
Interatomic spacing between nanoparticles gives the nanoparticles a very high tensile
strength. The Griffith Theory state that lg (the Griffith length) is part of the nanoscale (1nm-
100nm). Therefore molecules of a material that are below this length have a very high tensile
strength. If an object is the same size as the Griffith length it supposedly has the strength of a
perfect crystal. This can give a system that incorporates nanoparticles extra tensile strength
and a higher resistance to external forces. [2]
Chemical Properties:
At the nanoscale, atoms are more chemically reactive compared to bulkier atoms. This is
because smaller atoms have free valences which mean these atoms have better bonding
possibilities. Nanoparticles are also more soluble than regular atoms. According to the Kelvin
equation the vapour pressure increases when the radius decreases. Since nanoparticles have
such small radiuses there vapour pressure increases and then therefore there solubility
increases.
𝑙𝑛
𝑃
𝑃0
=
2𝛾𝑉𝑚
𝑟𝑅𝑇
Figure 5 - shows the Kelvin Equation where P is the actual vapour pressure and r is the
radius and you can see as r diminishes the actual vapour pressure will increase.
[8]

13. 8
Electrical Properties:
Quantum dots are nanoparticles smaller than the Bohr’s radius rb. In these particles the
electrons energy levels are greatly increased. The tighter the confinement (such as in
nanomaterials) the energy levels increase even more. This greatly increases the emissions of
light from electrical transitions. It shows how nanotechnology can improve lighting in
buildings. [2]
Casimir Effect at the Nanoscale:
The Casimir effect or force arises due to the change of the spectrum of zero-point oscillations
of the electromagnetic field by material boundaries. This concept is shown in
nanoelectromechanical devices. It involves the stiction of particles. It is the driving force in
closely spaced elements. This Casimir effect is important as this gives nanoparticles in
materials the ability to become more durable. [2] [9]
2.5 Importance of Nanotechnology in Energy Efficient Buildings:
The importance of nanotechnology in our constructed environment cannot be understated.
The precise methods behind this technology can lead to new devices being developed and
positively modify existing devices which all leads to a more sustainable future.
Nanotechnology have many benefits including making devices and materials more durable,
efficient and better conductors of heat. There is more to nanotechnology than just improving
already existing materials. Scientists have now developed new materials and devices that can
hugely benefit our society. New devices that incorporate nanotechnology can have dual
functions making our environment more efficient. These technologies include insulators that
are also conductors and opaque substances that now have variable transparency properties.
But why is it important to integrate this new technology into an already built environment and
into new planned buildings? Nationally it is very important for Ireland to push forward

14. 9
nanotechnology into our environment. The EU has produced requirements for each member
state (including Ireland) to improve its sustainability. The requirements for each country were
the following:
 A 20% reduction in greenhouse gas emissions by 2020
 A 20% average energy efficiency by 2020
 20% of the EU’s energy consumption to be from renewable sources by 2020
If Ireland does not meet these requirements we will be penalised by the EU. Ireland will have
to adopt new strategies and techniques to meet its efficiency targets. Incorporating
nanotechnology into construction could benefit Ireland greatly. [10]
Not only can nanotechnology improve efficiency but it could also make you money. For
example, New York City’s Empire State Building was retrofitted with smart technologies to
reduce and monitor energy efficiency. These technologies included smart sensors, air
purification controls and LED’s. This refurbishment had many positive outcomes but the
main one was that after the first year the Empire State Building had recorded savings of up to
$2.4 million dollars. Nanotechnology is at the forefront of new smart technologies and could
potentially make a company more profitable. [11]
2.6 Nanotechnology and Sustainable Development
The introduction of nanotechnology into green buildings is producing a lot of positive aspects
for sustainable development. Sustainable development aims to reduce carbon emissions from
our buildings and reducing environmental threats to future generations. According to the
United Nations Environmental Programme in 2007 buildings consumed between 30% - 40%
of the world’s electricity. This figure is rightly assumed to be higher nowadays with the
developing world constantly building for a better quality of life. [12]
This isn’t even considering the environmental impact buildings have on our sustainable
development such as waste from buildings and maintenance costs to preserve our buildings.
With the introduction of nanotechnology buildings will become more efficient by reducing
energy consumption, conservation of natural resources and produce less pollution. However

15. 10
the point must be made of what other issues can be brought up by introducing nanotechnology
into green buildings. Environmental risks, societal issues, financial costs and resistance to
change can all harm our sustainable development. In this project I will investigate whether or
not the nanotechnologies I discuss will generate any of these problems or will
nanotechnology’s impact on sustainable development will be all positive.
Global warming is the biggest threat to this planet’s sustainable development and
nanotechnology can go a long reducing our carbon emissions but in this project I would like
to see if the methods involved in producing these nanotechnologies are causing more carbon
emissions than conventional technologies.
If nanotechnology is incorporated into buildings it will have an impact on the occupants of
that building. Not only will adapting to modern methods of energy efficiency change people’s
habits but improved nanostructured materials require less maintenance and cleaning. This is
due to the unique properties that nanomaterials can impose onto the built environment. In this
project I will observe and speculate how the people utilise energy efficient buildings. [13]
2.7 The Cost and the Integration of Nanotechnology into the Built
Environment:
By the end of the year 2015, products incorporated with nanotechnology are predicted to be
worth $1 Trillion globally and millions of jobs are also going to be affected. Nanotechnology
across all applications is going to cause huge economic growth. But the challenge remains to
be seen whether integrating efficient nanotechnologies into construction is cost effective.
Integration of nanotechnology into existing building materials and processes is a vital element
of my project. The term nanoarchitecture is being already coined as engineering construction
materials with nanotechnology. As nanotechnology can improve our building materials,
architecture will also improve. For example carbon nanotubes can reinforce most materials
used in construction. Because of carbon nanotubes excellent molecular composition and
carbon’s high bonding strength it can be incorporated into a lot of different construction
materials allowing for these materials to become more efficient and have a longer service life.

16. 11
Nanotechnology can also give windows and walls variable transparency. Variable
transparency means that windows and walls can adapt to the climate outside a building. This
is done by changing the window or wall from translucent to transparent as the time of day and
weather changes outside the building. This smart glass can change the amount of wavelengths
of light to enter a building. This variance in the light transmission can be undertaken when
heat, light or voltage is applied. This is just one of the many ways that nanotechnology can
reduce a building’s energy costs and therefore why nanotechnology is becoming an integral
part of architecture. [14]
At first glance, replacing old methods of energy conservation looks like a costly exercise but
once the payback region is in the near future integrating Nanotechnology into our buildings is
a profitable choice. For example the SEAI have estimated the cost of replacing all the
insulation in a semi – detached house to a more energy efficient insulation (such as insulation
engineered with nanotechnology). In a typical house half of the heat energy is lost through the
walls. They say the average cost to replace the insulation in a semi-detached house in Ireland
is €550 - €700. However the annual savings on energy bills is €100 - €160 making the
payback period between 4 – 7 years. Although every house will be different this still portrays
the idea that integrating nanotechnology into people’s homes may seem costly at first but in
the long run it can potentially payoff. [15]
2.8 Environmental Impact of Nanotechnology:
Although many consider nanotechnology to be the way of the future there is still going to be
an environmental impact and health hazards have to be considered. The long-term effects of
exposure to Nanotechnology have yet to be recorded. Research in nanomaterials and
nanodevices are becoming more common however this poses the threat of researchers being
exposed to harmful substances. In this project I try to highlight how nanotechnology is good
for our environment and for construction. However, nanotechnology and the processes
involved in manufacturing nanodevices may not be advantageous for all aspects of our
environment.

17. 12
Nanomaterials are being created with some fantastic physical and chemical properties but the
increase in the demand for these materials is potentially putting our environment at risk.
Nanoparticles being discharged from these new materials will eventually come in contact
with living organisms in our environment. These particles are also virtually undetectable as
they are on the nanoscale, so it is hard to track the progress of nanoparticles as it comes in
contact with our surrounding environment. Some nanoparticles toxicity is still a subject of
debate. According to the 2013 International Symposium on Environmental Science and
Technology, nanoparticles might cause different reactions in macro-interfacial processes
when entering into the mediums of environment, and then causing water contamination. [16]
Nanoparticles entering our soil could be a very serious problem aswell. With relation to a
building’s sustainability if the soil is contaminated around it could lead to problems in
foundations, load bearing walls and maintenance costs. In the Environmental Science Journal
in 2009 it illustrated a relevant study of engineered nanomaterials concentration in sediments,
sludge and soils. Nano -Titanium Dioxide (TiO2), Nano – Zinc Oxide (ZnO), Silver -
Nanoparticle (Ag), Carbon Nano-Tubes (C) and Fullerenes (C60) are graphed shown in figure
4. All these materials are used in our buildings and have many other applications. In this
study they predict that concentrations of these nanomaterials are showing a consistent
increase. This shows an increase in the use of nanomaterials worldwide and that nanoparticles
with unknown risks are in the environment. Of course some of these particles are not toxic to
our environment but if another engineered nanoparticle was produced that had a high toxicity
level these graphs show how easy it would be for those particles to be discharged in our
environment. [17]

18. 13
Figure 6 – shows two graphs of nanomaterials concentration in sediments and in sludge
treated soil in Europe and USA. The concentration of these materials in our environment is
increasing. In both cases carbon nano-tubes and fullerene show only a very slight increase.
Titanium dioxide shows a large increase in both graphs.
[17]
Human health can also be put at risk when dealing with Nanotechnology. Nanoparticles come
under the range of inhaled ultrafine particles (UFP’s) which causes damage to people. For
example Titanium dioxide (TiO2) can cause apoptosis of liver cells if inhaled in high enough
amounts. For nanotechnology to be successful in energy efficient buildings the required

19. 14
amount of research and tests must be completed. This can cause dangers to lab attendants who
may potentially be working with ultrafine nanoparticles that can become lodged in the lungs
and other organs. Because of this the EU have made integrated nanotechnology risk
regulation and management a vital concern. [18] [19]
In this section I have talked about the adverse effects nanotechnology can have in our
environment. However nanotechnology could produce a lot of potential benefits to our
environment. Nanoparticles can be used to convert pollutants to less harmful chemicals. For
example nanostructured silica can be used to remove cadmium from an exhaust combustion
environment. Smart technologies and nano-sensors can be used to detect chemical and
biological contaminants in the air.
Nanotechnology’s most vital environmental benefit in relation to this project is addressing the
issue of our environment’s sustainability. Nanodevices produce smarter ways to monitor and
reduce energy costs. Nanomaterials can reduce every building’s energy demand by using
more durable and efficient materials. The environmental benefits for the buildings that use
this technology include some of the following:
 More effective temperature control meaning a building’s energy consumption is
reduced.
 Nanoparticles can have better electrical transmission and less dissipation. This can
reduce the energy wasted from a building.
 Quantum dots (nanoparticles in semiconductor’s) could also make solar cells more
efficient which would benefit a building that uses solar energy panels.
 Nanoparticles in paint results in thinner coats to get the same desired effect. This
would reduce a building’s maintenance cost and save materials.
 Nanotechnology in filtration may enable more energy efficient ways of water
purification in the built environment.

20. 15
Nanotechnology being incorporated into our buildings has a lot of potential effects. Use of
nanotechnology is continuing to increase in construction due to a wide range of benefits but
there potentially can be some adverse effects. During the course of this project I will be
discussing in detail both the negative and positive effects that nanotechnology has on our
environment. [19]

21. 16
Chapter 3: Experimental
My final year project is solely research based. The materials I will be using are
scientific research papers along with nanotechnology based books and accredited
websites. Since nanotechnology is an ever-changing field of study it is important that
I only used recent literature and the majority of my citations are from the year 2010
onwards. Nanotechnology is a very broad subject and can affect a lot of different
areas in an energy efficient building. In my preliminary research phase I realised that I
could only concentrate on a few of these areas if I wanted a substantial review of the
scientific literature. The areas in modern construction that nanotechnology could have
an effect on were the following from my initial research:
 Thermal Insulation
 Paints
 Adhesives
 Lighting and LED’s
 Solar Energy (Photovoltaics)
 Roofing
 Drywall
 Plastic
 Wood
 Concrete
 Steel
 Energy Storage
 Smart Grid Technology
 Windows and Glass

22. 17
I then tapered this list into four viable options to do more research. Those four areas
were Concrete, Thermal Insulation, Solar Energy and Windows. I then continue to do
basic research into all four of these areas and decide on two of these areas to do
detailed analysis for the rest of my project. In my results section I will explain the
reasoning on why I chose these areas to concentrate my project on. I will portray
scientific data in my project to emphasise an objective but this data was not carried
out by me. All scientific data shown in this project is labelled clearly to show the
institute that undertook this research. In my project I synthesis and summarize the
arguments for incorporating nanotechnology into the built environment and in my
conclusions I give my own opinions on whether or not nanotechnology can thrive in
energy efficient buildings.

23. 18
Chapter 4: Results, Analysis and Discussion
4.1 Evaluation of Construction Areas
In this section of my project I will explain how nanotechnology could affect each of these
construction areas and why these aspects of the built environment are so important regarding
energy efficiency.
4.1.1 Concrete
Concrete is the most used manmade material on earth. The cement industry is one of the
most energy consuming industries in the world as the annual global manufacture of concrete
and concrete materials is over 2.6 billion tonnes. The CO2 emissions from this industry are
also extremely high. The concrete industry produces 5% of the world manmade C02
emissions. A lot of research has been conducted to reduce the effects the cement industry has
on greenhouse gases by improving concrete’s sustainability. Nanotechnology integrated into
concrete materials can make the cement industry more efficient and reduce its harmful
effects. By improving the strength and pore structure of concrete it makes concrete more
dependable and has the potential to make buildings more energy efficient. Nanoparticles
added to the cement mixture can provide the concrete with desirable properties that can make
concrete more durable and help protect the environment. Theses additives include SiO2 (the
most commonly used concrete additive) and TiO2 (an additive that de-pollutes the
environment). Carbon nanotubes can also re-enforce concrete to make it more durable and
increase the compressive strength. [20] [21]
4.1.2 Thermal Insulation
All traditional Insulation is being replaced by high tech insulation techniques but there is still
a lot of room for improvement. A modern thermal insulation technique can conserve a lot of
energy in a building. This is where nanotechnology can greatly aid thermal insulation. At the
moment there are four different types of new modern building insulation which are vacuum
insulation materials, gas filled materials, aerogels and nano-insulated materials. For example
graphene insulation made with carbon nanotubes has desirable values of thermal conductivity.
Nanoparticles dense agglomeration leads to less thermal losses such as with silica

24. 19
nanospheres. Nanotechnology can also give thermal insulation a dual functionality by making
insulators to also have the property of being a semiconductor. However there are many
different thermal insulation techniques all with their own unique properties. In the table below
I have compiled a list of the main thermal insulation used in buildings today with their
conductivity values.
Thermal Insulation Thermal Conductivity
mW/(mK)
Method of Thermal
Insulation
Mineral Wool 30 - 40 Traditional
Expanded Polystyrene 30 - 40 Traditional
Cellulose 40 – 50 Traditional
Polyurethane 20 - 30 Traditional
Aerogel 13 -14 Modern
Vacuum Insulation Materials Less than 4 Modern
Gas Insulation Materials Less than 4 Modern
Nano-Insulated Materials Less than 4 Modern
Figure 7 – shows the comparison of different thermal insulation techniques with
corresponding conductivity values.
As can be seen in Figure 7, there is a lot of alternative methods to nanostructured thermal
insulation. Nanostructured thermal insulation also has a very high cost of production. The
pore structure of nano-insulated materials also can create problems and more research into
this area is needed for mass manufacture. [22] [23] [24]
4.1.3 Solar Energy (Photovoltaics)
Solar energy is a plentiful renewable energy and countless researchers are spending time and
money on how to make solar cells more efficient. Solar energy can also radically reduce a
building’s energy consumption by having solar panels installed. But problems can arise from
the efficiency of these solar cells. Photovoltaic technology is technology used to convert
sunlight into electrical current. Nanostructured devices and materials can greatly enhance the
efficiency of these photovoltaic devices. As mentioned throughout this project nanoparticles

25. 20
have a high surface area to volume ratio. This makes nanoparticles an ideal conductor for
solar collection. By having more conducting surfaces available to sunlight it can greatly
increase the efficiency of these solar devices. Nanostructured materials can also release more
electrons when hit by a photon of light. These nanostructured materials (e.g. lead-selenide)
can improve the photovoltaic process in solar cells. Solar energy being incorporated into
buildings can be costly to set up but there will be a payback period due to the savings on
energy consumption. Since new houses built in Ireland have to have a renewable energy
requirement, solar energy is becoming increasingly popular. Although nanotechnology has
been shown to improve the efficiency of solar cells, solar energy can still be inefficient
especially in a country like Ireland where the amount of sunlight varies. There are countless
research articles on solar energy not just with nanotechnology but with other methods of
improvements as well. [25]
4.1.4 Windows and Glass
A nanofabricated smart window is a huge asset to have in an energy efficient building
currently. Nanodevices that can act as sensors and regulate the transparency of windows can
improve the energy efficiency of any building. Smart windows are windows that can change
their optical properties as the outside environment changes. Silver nanowires and other
nanowire based electrodes are being incorporated into the design of a lot of smart windows as
they have a low cost of production and they enhance the optical performance of these
windows. Self-cleaning glass is another desirable outcome due to nanotechnology. This not
only improves a building’s environmental impact but it also reduces maintenance costs and
purifies the air in buildings. This self-cleaning glass is due to the addition of a layer of
nanoparticles (usually NanoTiO2) on the glass. Nanostructured coatings added to windows
can give a window a lot of desirable functions and properties. With these nanostructured
coatings windows can become a better thermal insulator, more resistant to external
environmental forces and have a higher visible light transmittance. Because of the advantages
that nanostructured windows exhibit all new buildings being constructed are including the

26. 21
design of these smart windows. The cost of integration into existing buildings may still be an
important factor to be researched. [25] [26] [27]
4.1.5 Evaluation
Concrete needs to be more sustainable in our modern world to reduce the threat of global
warming. Concrete is incorporated into every home, office and city in the world in one shape
or another and I am interested to see whether or not nanotechnology can make a significant
contribution to improving the concrete industry. This is why I am choosing concrete as one of
the areas to do in depth analysis.
Thermal insulation is a factor of buildings that is currently being revolutionised. High quality
insulation can significantly reduce buildings energy consumption. However nanotechnology
is just one of the many methods being used to do this. Likewise nanotechnology being
incorporated in thermal insulation techniques needs a lot more research before being available
for mass production.
Efficiency has long been a problem for solar energy and nanotechnology is doing a lot to
improve it. But solar energy is a location dependent renewable energy. Solar energy can still
have a big impact in colder climates but for the integration of solar nanotechnologies into all
buildings might not be the most suitable solution. Furthermore, solar energy is a huge field of
research with a lot of work already being undertaken and discussing the potential outcomes.
The potential for windows and glass in buildings to have more functionality could be crucial
in an energy efficient building. By making a window a better heat insulator, more sustainable
and by making it have a variable transparency can reduce a buildings heating, cooling,
lighting and maintenance costs. There are a lot of different methods on how windows can
improve the energy efficiency of a building and nanotechnology can aid all of these methods.
That is why I have chosen to do more intense research into nanostructured energy efficient
windows.

27. 22
4.2 Nanotechnology in Concrete
In this section of experimental work I review the literature on nanostructured concrete and
how this can have an impact on energy efficient buildings.
4.2.1 Addition of Nano-Silica (SiO2) to Concrete
SiO2 = Silicon Dioxide or Silica
4.2.1.1 Manufacture, Synthesis and Dispersion of Nano-Silica Concrete:
Silica is one of the most abundant materials on earth. It is usually found in sand, quartz and in
various living organisms. Silica used as an aggregate in concrete can be obtained from a lot of
different sources. Silica fume an industrial solid waste can be recycled to be used in
nanostructured concrete which can help make the manufacture process more efficient for
production companies. It was estimated in 2016 that the global yield of silica fume is between
1 and 1.5 million tonnes. Because of the abundance of silica fume from smelting processes
from other industries the recycling methods to obtain silica is a very sustainable method of
retrieving nanoparticles and gives Nano-SiO2 an advantage compared to alternative concrete
enhancing techniques. The content of silica can be up to 85-99% if obtained from the by-
product silica fume. The dimensions of these atomic silica particles occur as almost perfect
spheres with diameters of 20nm to 500nm. This can make silica an ideal candidate to improve
concrete’s performance. The amorphous phase of silica is used rather than the mesoporous
phase. Bothe phases can be used for concrete but the mesoporous phase has a longer reaction
time during synthesis. Therefore, the amorphous phase of silica is more widely used due to
the shorter manufacturing process. The synthesis procedure involves using
cetyltrimethylammonium bromide as the template for the silica source while ethyl acetate as a
catalyst. The silica is usually extracted in a pressure steam sterilizer and then goes through a
filtration process before the catalyst ethyl acetate is added for the reaction. Then a calcination
process would remove the template to leave the nanoparticles to be added to concrete during
the production phase.
Nano-SiO2 particles have a high surface area to volume ratio which allows for a lot of
chemical reactivity at the nanoscale which gives concrete and cement based materials unique

28. 23
properties. Silica also has highly reactive pozzolanic properties which are appropriate for
cement based materials.
Figure 8 - shows the specific surface area of all components in nano-engineered concrete.
Nano-SiO2 particles have the highest surface area although they have the smallest particle
size.
The concentration levels of Nano-SiO2 particles in cement can range from anywhere between
(0.25% - 20%). Although concentration levels of Nano-SiO2 higher than 30% are utilised for
special applications such as marine equipment. There are two main forms of Nano-SiO2 that
can be added to concrete. They are dry compacted grains and colloidal suspension. Dry nano-
silica requires a special preparation procedure before mixing. This is to make sure that Nano-
SiO2 particles are evenly dispersed throughout the cement base. While colloidal suspension is
stabilized by a dispersive agent, it is the better option of the two forms of Nano-SiO2 for
energy efficiency purposes. The biggest issue with addition of nanoparticles to concrete is the
dispersion of those particles evenly throughout the cement mixture. Non-effective dispersion
of Nano-SiO2 particles can cause aggregation in the concrete mixture. This would reduce the
benefits of Nano-SiO2 particles being added. Non-effective dispersion can also produce
unreacted portions of the material which potentially could lead to a concentration of stresses
in one area of the material. These stresses could then lead to faults in the concrete which
would make them unsuitable for mass-manufacture. To overcome this problem mechanisms
in the production stage are introduced to evenly disperse the Nano-SiO2 particles although this
increases production. [20] [28] [29]

29. 24
4.2.1.2 Mechanical Stability and Sustainability of Nano-Silica Concrete
Greater durability, strength and workability have been shown in concretes that incorporate
Nano-SiO2. This can make concrete a more efficient material because of less maintenance and
a longer service life. The increase in strength can also reduce faults due to external forces.
However pure silica has shown a higher strength than concrete that uses silica nanoparticles
from the by-product silica fume. Concentration of 10% Nano-SiO2 with dispersing agents
was observed to increase the compressive strength of cement as much as 26%, compared to
only a 10% increase with the addition of 15% silica fume. Although the extraction of pure
silica would increase production costs and it would be less efficient as silica from silica fume
would be recycled.
Even with a lower concentration of Nano-SiO2 in concrete still produces positive outcomes.
Even a 0.25% Nano-SiO2 concentration in concrete has shown to improve the compressive
strength by 10% and flexural strength by 25%. The reason why strength is increased when
Nano-SiO2 is used as an additive is because of the nano-sized pore structure of these
nanoparticles increases the number of molecules in concrete. These molecules are also more
compact. The strength of the concrete is proportional to the amount of Nano-SiO2
incorporated. [20]
In Construction and Building Materials 36 (2012), they did a series of tests with colloidal
Nano-SiO2 concrete. The Nano-SiO2 used was in a colloidal form of an aqueous solution
with 50% SiO2 content. The average nanoparticle size of the silica was 35 nm, the specific
gravity was 1.36 and the pH was 9.5. Mixtures B-0, B-1, B-2 are also mixed with fly ash
another reusable material. Mixtures A-0, B-0 has 0% Nano-SiO2 concentration. Mixtures A-
1, B-1 have 3% Nano-SiO2 concentration. Mixtures A-2, B-2 has 6% Nano-SiO2
concentration. The cement used was Type II/VI Portland cement.

30. 25
Figure 9 - shows the amount of materials used in the tests conducted. Mixtures A-0, B-0
has 0% Nano-SiO2 concentration. Mixtures A-1, B-1 have 3% Nano-SiO2 concentration.
Mixtures A-2, B-2 has 6% Nano-SiO2 concentration. A-0 and B-0 were the control in these
tests and contained no Nano-SiO2.
Two of the tests they undertook have a lot of relevance to energy efficient buildings. These
were the tests on tensile strength and the test on the concrete porosity. Tensile strength can
show the concrete’s durability and therefore its sustainability. Concrete porosity shows the
materials resistance to external forces. A splitting tensile strength test was carried out to find
the tensile strength. A mercury intrusion porosimetry test was carried out to show the
concrete’s porosity.
Figure 10 - shows the tensile strength of the six mixtures. All mixtures that contained
Nano-SiO2 performed better than the control mixtures A-0 and B-0. A-2 the mixture
containing 6% Nano-SiO2 concentration performed the best overall. It is shown in the
mixtures without fly ash that tensile strength is proportional to the amount of Nano-SiO2
in the concrete.
Figure 11 – shows the mercury intrusion porosimetry test. The percentage of small pores is
very relevant to energy efficient buildings. A higher percentage of small pores, means the
mixture has a better microstructure and is more resistant to external forces. This improves
the sustainability of the mixture. In all the mixtures shown above the mixtures containing
Nano-SiO2 in the concrete had a higher percentage of small pores (<0.1µm is approaching
the nanoscale).

31. 26
As shown in Figure 10, the tensile strength can be increased with the incorporation of Nano-
SiO2 which can make the material more durable. The inclusion of fly ash can also improve the
percentage of small pores along with Nano- SiO2. Not only helps the material’s resistance to
external forces but it causes the production phase to become more energy efficient as more
recyclable materials are used to improve performance.
The porosity of the material shows how resistant the material can be to external forces which
can cause the degradation of concrete. Generally the percentage of small pores increase with
the addition of Nano-SiO2.
[21]
Nano-SiO2 as an additive in concrete can protect from disintegration and chemical leaching
both problems that arises from excess calcium hydroxide CH. Too much calcium hydroxide is
produced as by – product of the cement hydration process. This is shown in the cement
hydration chemical equations:
2𝐶3 𝑆 + 6𝐻 → 𝐶3 𝑆2 𝐻3 + 3𝐶𝐻
2𝐶2 𝑆 + 4𝐻 → 𝐶3 𝑆2 𝐻3 + 𝐶𝐻
Figure 12 - shows the cement hydration processes chemical equations where C = CaO, S =
SiO2, H = H2O. The C-S-H product is the strength phase of concrete while CH is a by-
product.
Calcium hydroxide has no desirable properties in cement and can be easily leached. This
leaves cement based materials open to chemical deterioration. With the addition of Nano-
SiO2, the extra SiO2 will react with the excess CH (calcium hydroxide). This reaction will
create more C-S-H which is the strength phase of concrete. The extra C-S-H will replace the
excess CH. This will ultimately improve the pore structure and reduce the risk of chemical
deterioration. This is known as pozzolanic reaction where you take a by-product with poor
cement qualities and chemically turn it into a product with good cement qualities. If Nano-
SiO2 is used as an additive to concrete it would improve the durability material as chemical
deterioration is not as big a factor and therefore the material is more efficient. Only very few

32. 27
concrete additives can create this reaction which shows how Nano- SiO2 can be pivotal to
improving concrete’s sustainability. [30]
4.2.1.3 Efficiency of Nano- SiO2 Concrete
Another desirable outcome of Nano-SiO2 in concrete is a quick setting time. A quick setting
time reduces a building’s maintenance cost by allowing more time for construction workers.
By having a quicker setting time it also improves concrete’s early compression strength which
would reduce early faults and degradation. The incorporation of 2% Nano-SiO2 into cement
based materials reduced initial setting time by 95 minutes and a final setting time by 105 min.
It also increased early compression strengths of the concrete. The compression strength test in
this case was done after 7 days. [21]
Using the same mixtures found in Construction and Building Materials 36 (2012) and in
section 4.2.1.2 of this project an adiabatic temperature test was carried out. The results of
these can be seen in Figure 13.
Figure 13 - shows the results from the adiabatic temperature test done in Construction and
Building Materials 36 (2012). Generally the concretes that incorporated nano silica had
higher peak temperatures along with shorter times.
The results of the adiabatic temperature test show that Nano-SiO2 concrete had a faster rate
of hydration. This faster rate of hydration is not because of the pozzolanic reactions as it was
too early in the hydration process for these to occur. This shows that Nano-SiO2 speeds up the
kinetics of hydration because of silica’s particle size. This shows that Nano-SiO2 concrete is a
more efficient and timely concrete for construction workers to use. Ultimately Nano-SiO2

33. 28
concrete can save construction time, reduce the construction worker’s hours and save costs
for a building. [21]
4.2.1.4 Environmental Impact of Nano-SiO2
Silica incorporated into concrete had a lot of positive outcomes for the environment as it
utilises eco-friendly processes like recycling and it also can make concrete more sustainable.
However, ultra-fine particle inhalation of silica dust can cause some very serious lung
problems. Exposure over a period of time allows these nanoparticles to be lodged in the lungs.
The three main lung diseases caused by silica dust are bronchitis, lung cancer and silicosis.
Silicosis is a serious occupational lung disease that in 2013 killed 46,300 people globally.
[31]
There are three stages of silicosis which are the following:
 Chronic Silicosis
This occurs after 10 or more years of exposure. This stage is the most common type
of Silicosis.
 Accelerated Silicosis
This occurs after exposures to higher levels of silica dust but it only takes between 5-
10 years of exposure. A lot of factors can contribute to the acceleration of silicosis
such as smoking cigarettes.
 Acute Silicosis
This can occur after only months after exposure to very high levels of silica dust.
[32]
Construction workers and nanotechnology researchers are the people most at risk when comes
to lung disease’s caused by ultra-fine Nano-SiO2 particles. It takes only 10 years of exposure
to get this disease which is the exact same amount of exposure time that it takes for the
dangerous building material Asbestos to give you the disease Mesothelioma. [33]
To overcome the health risks involved with Nano-SiO2 particles protective masks should be
worn when altering materials containing silica dust. Of course if the proper precautions are
taken these lung diseases are not a problem but they are something to be aware of. Also

34. 29
potential harmful by-products in the manufacture phase could also be an issue as of yet not a
lot of research has been done into this area.
4.2.1.5 Integration and Financial Cost of Nano-SiO2 Concrete
Nano SiO2 concrete can save a construction company a lot of money due to the reusable
materials involved. The synthesis of the nanoparticles does put the production costs slightly
higher though. For a silica fume percentage in between 30 to 40 of total cement plus silica
fume in the concrete mix, the savings in the overall cost of concrete mix is about 15%.
Furthermore due to the quicker setting times less man hours have to put in to the construction
of the building which can save on construction costs. The integration of Nano SiO2 concrete
into cement based structures already constructed in the buildings is a lot more complicated.
For future buildings Nano SiO2 should be incorporated however unless there is a fault in
existing concrete the incorporation into existing structures has to rely on coatings which can
create their own problems due to the use of adhesives and the lack of dimensional freedom.
However these coating are available but will increase maintenance costs in energy efficient
buildings. Silica powders are also available currently for the integration into concrete
mixtures however these also increase building costs and could cause dispersion problems.
[34] [35]
4.2.2 Addition of other nanoparticles to Concrete: (Nano-Al2O3, Nano-Fe2O4, Nano-TiO2,
Nano-ZrO2)
Al2O3= Aluminium Oxide
Fe3O4= Iron (II,III) Oxide or Ferric Oxide
TiO2= Titanium Dioxide
ZrO2= Zirconium Dioxide
4.2.2.1 Manufacture, Synthesis and Dispersion:
Currently there is a lack of research done on the effects of other nanoparticles additives
instead of Nano-SiO2. For these nanoparticles they are synthesized using a catalyst and a
template but the chemical processes differ for each type of nanoparticle and is not specified.

35. 30
But the synthesis of any nanoparticle is going to amplify the production costs. Just like Nano-
SiO2 particles these other nanoparticles are added to the cement during the production phase.
The concentration levels of these nanoparticles in concrete vary, depending on the application
of the cement being used. Again, the biggest issue with addition of nanoparticles to concrete
is the dispersion of those particles evenly throughout the cement mixture. Non-effective
dispersion of these nanoparticles will cause faults in the mixture. This can reduce the benefits
of adding these nanoparticles. Non-effective dispersion can also produce unreacted portions
of the material which potentially could lead to a concentration of stresses in one area of the
material. However dispersive agents added to the mixture can solve the dispersion problems
but this will cause the manufacture cost to rise. [20]
4.2.2.2 The Advantages of other nanoparticles in Buildings:
Although Nano-SiO2 is the popular choice for a performance enhancing additive other
nanoparticles have a lot of unique abilities that are specific for a certain building. For Nano-
Al2O3 particles being added to cement based materials has been shown to increase the
modulus of elasticity making it a desirable concrete for problematic construction structures
and complex buildings. Nano-Al2O3 concrete can improve the elastic modulus but this limits
the compressive strength. Usually in most concrete the amount of nanoparticles is
proportional to the strength of the material but not in this case with Nano-Al2O3 concrete.
Similarly Nano-Al2O3 particles like Nano-SiO2 particles can cause pozzolanic reactions in the
cement which improves the pore structure and reduces the risk of chemical deterioration.
Aluminium has good cement qualities and is one of the few materials that can cause these
types of reactions. [20]
For Nano-Fe3O4 particles have been shown to have self-sensing properties. Nano-Fe3O4
concrete can sense its own compressive strength. This can be a very valuable asset for energy
efficient buildings as Nano-Fe3O4 concrete regulates its own structural health and does not
need external sensors added to the mixture. Nano-Fe3O4 concrete can easily save a buildings
maintenance cost and can help regulate a buildings energy efficiency.

36. 31
Nano-TiO2 particles incorporated into concrete have provided concrete with the function of
being self-cleaning. This type of concrete is also beneficial to the ecosystem as it can remove
pollutants from the environment. Photo-catalytic degradation of contaminants in the air is
done by TiO2 particles. This happens because free radicals generated by TiO2 oxidise polluted
organic matter. Concrete containing TiO2 particles are extremely useful in industrial buildings
as it can purify the surrounding environment. I explain the oxidisation process caused by
titanium dioxide further in this project. Nano-TiO2 concrete is a valuable market product as it
can be sold as an environmentally friendly concrete. Industries want to use this
nanostructured concrete as not only is it beneficial to a company’s sustainability but it also
has excellent physical properties such as good flexural strength and abrasion resistance.
Titanium dioxide itself has a low toxicity level. However carbonation can cause aging in
cement based materials. When this happens in Nano-TiO2 concrete it could potentially lose its
catalytic efficiency. Titanium dioxide is also a carcinogen that can cause lung inflammation
with a concentration of 8.8 mg/m3
. [20]
Nano- ZrO2 particles have a very low value of thermal conductivity meaning concrete that
uses ZrO2 have a higher resistance to large temperatures. This would be a desirable concrete
for buildings that deal with high temperatures. [36]
4.2.2.3 Mechanical Stability and Sustainability
In Procedia Engineering 14 (2011) a series of tests were conducted on the four different types
of nanoparticles reviewed in this section (Nano-Al2O3, Nano-Fe3O4, Nano-TiO2 and Nano-
ZrO2). The aims of these tests were to evaluate and compare the durability and mechanical
properties of concrete samples structured with these nanoparticles. Durability and stress tests
are important to energy efficient buildings as it can indicate a concrete’s resistance to external
forces. Therefore the concrete’s sustainability can be observed. The range of the size of
particles in these tests was 10-25nm. The density of each mixture was 580Kg/m3
. The
concrete mixtures were as follows:
 Control Concrete Sample = 100% (Cement + Metakaolin)

37. 32
 Nano-Al2O3 Concrete Sample = 98.5% (Cement + Metakaolin) + 1.5% (Nano-Al2O3
Particles)
 Nano-Fe3O4 Concrete Sample = 98.5% (Cement + Metakaolin) + 1.5% (Nano-Fe2O4
Particles)
 Nano-TiO2 Concrete Sample = 98.5% (Cement + Metakaolin) + 1.5% (Nano-TiO2
Particles)
 Nano-ZrO2 Concrete Sample = 98.5% (Cement + Metakaolin) + 1.5% (Nano-ZrO2
Particles)
To observe the mechanical properties a compression test and indirect tensile strength test was
carried out. To observe the durability a chloride penetration test and water absorption test was
carried out.
 Compression Test
Samples were tested with a hydraulic press with a 300 KN capacity. The loading rate
was 0.3 MPa/s. The higher the value in this test is the most desirable outcome. Units
of this test are Mega Pascals (MPa).
 Indirect Tensile Strength Test
This test was conducted three times for each sample. The average was then taken.
The higher the value in this test is the most desirable outcome. Units of this test are
Mega Pascals (MPa).
 Chloride Penetration Test
Chloride penetration test were done by seeing how many coulombs passed through
each sample. The lower the value in this test is the most desirable outcome. Units of
this test are coulombs.
 Water Absorption Test
This test was done by seeing the percentage of water in the samples after a period of
time. The lower the value in this test is the most desirable outcome. The test results in
this section are measured by the percentage of water left in the sample.

38. 33
Figure 14 – This shows the mechanical properties tests and the durability tests results
completed for Procedia Engineering 14 (2011). The control sample contained no
nanoparticles and had lesser test results.
Nano-ZrO2 incorporated into a concrete sample was shown to be the most durable as it had
the lowest water absorption and chloride penetration. Nano-ZrO2 concrete would therefore be
an advantageous concrete to use in an energy efficient building as it can protect from
chemical deterioration. But out of all the concretes tested on Nano-Al2O3 concrete was the
most desirable as it had the best mechanical properties and relatively low water and chloride
penetration levels. In all the samples mentioned above it was more advantageous to
incorporate nanoparticles into concrete for these tests rather than not incorporate
nanoparticles. These tests did not include Nano-SiO2 which shows that there are viable
alternative nanoparticles that can be added to concrete to cover a wide range of applications
and improve the energy efficiency. [37]
Concrete Test Control
Concrete
Sample
Nano-Al2O3
Concrete
Sample
Nano-Fe2O4
Concrete
Sample
Nano-TiO2
Concrete
Sample
Nano-ZrO2
Concrete
Sample
Compression
Test 92.3 MPa 143 MPa 119 MPa 113.3 MPa 110.9 MPa
Indirect Tensile
Strength Test 5.57 MPa 7.1 MPa 7.22 MPa 6.57 MPa 6.29 MPa
Chloride
Penetration
Test
48 coulombs 14 coulombs 38 coulombs 32 coulombs 13 coulombs
Water
Absorption
Test
0.5% 0.124% 0.122% 0.133% 0.092%

39. 34
4.2.3 Reinforcing Concrete with Carbon Nanotubes:
Carbon Nanotubes = Allotrope of Carbon
CNT = Carbon Nanotube
4.2.3.1 Manufacture and Synthesis of CNT Concrete
A buckyball or C60 (60 atoms of carbon) was discovered to have incredible material
properties. These allotropes of carbon were formed into cylindrical tubes to what we call
today carbon nanotubes. Carbon nanotubes are fullerenes which have exceptional structural
properties. Carbon nanotubes are precisely structured graphene cylindrical materials with high
aspect ratios and surface areas. An aspect ratio is the ratio of the width and height of particles.
A carbon nanofiber that incorporates graphene and made into a cylindrical shape is a carbon
nanotube. There are two different types of carbon nanotubes being incorporated into concrete:
 Single-wall carbon nano-tubes
These are single graphene cylinders incorporated into a material.
 Multi-wall carbon nanotubes
These are multiple concentric graphene cylinders arranged around a hollow core.
Figure 15- shows the difference between single-wall carbon nano-tubes (left) and multi-
wall carbon nanotubes (right). Both produce positive effects when added to concrete.
The concentration level of these nanotubes within the cement material varies depending on
the materials function but it is usually between (1 -20%) These exposed surfaces allow for
chemical and physical interaction to give concrete more desirable properties.

40. 35
The synthesis of carbon nanotubes can be done in a number of different ways. Carbon arc-
discharge, laser ablation, high pressure carbon monoxide and chemical vapour deposition are
the main techniques used for CNT production. The cheapest method of synthesis is the
chemical vapour deposition however the carbon arc-discharge is proven to be the best quality
CNT technique. All techniques are acceptable for reinforcing concrete and they can be added
to cement based materials during the production phase. [20] [38]
4.2.3.2 Dispersion of CNT’s through Concrete
The proper dispersion of CNT’s into cement paste is the main problem with CNT integrated
concrete. The dispersion problems come from high hydrophobicity due to CNT’s strong sense
of self attraction. A lot of research has gone into the dispersion of CNT’s as they have a large
agglomeration tendency which can lead to faults in the concrete which would make CNT
concrete unsuitable for mass manufacture. The addition of a surfactant may be able to
produce a homogenous CNT dispersion. The surfactant used in Cement and Concrete
Research 73 2015 was Pluronic F-127. Pluoronic F-127 was chosen because it had low
toxicity levels and results were unclear from previous research. This dispersing agent was
added to cement mortar mixes to see if it could fix CNT’s agglomeration problems. It was
also compared to the commonly used dispersing agent sodium dodecylbenzene sulfonate as a
control.
Figure 16 - shows the percentage of CNT that agglomerates calculated from microscope
images. MWNT stands for multi wall nano tube, SWNT stands for single wall nano tube
and SDBS stands for sodium dodecylbenzene sulfonate which was used as a control in this

41. 36
experiment. The difference between the addition between 3% Pluronic and 5% pluronic
makes a considerable difference to the area of CNT that agglomerates.
These tests show that 3% pluronic added to CNT concrete does not have a big effect on the
agglomeration tendency of the nanotubes. But the addition of 5% pluronic can significantly
reduce the agglomeration caused in the cement based material making CNT strengthened
concrete more suitable for mass production. However the use of the admixture Pluronic F-127
at 5% or more will drive up production costs. Pluronic F-127 is currently selling at €15.30 per
gram. Considering that you would need 5% of the CNT aqueous suspension to significantly
prevent agglomeration a manufacturer would have to spend €76.50 on Pluronic F-127 per
kilogram of concrete which is unreasonable for production. However this does show that the
addition of a surfactant could make CNT concrete more efficient. [39] [40]
4.2.3.3 Compressive Strength and Porosimetry of CNT Concrete
Carbon nanotubes reinforcements can give concrete some very unique properties. The
addition of carbon nanotubes have shown to greatly increase the pore structure of concrete
and making the material more durable. Even a concentration level of 0.5% and 1% of CNT‘s
acted as a filler for the pore structure and help protect the material from calcium leaching and
reinforces the C-S-H concrete strength phase. This makes the material more efficient as not
only is the strength increased but less CNT’s are used in production. [38]
In Construction Building Materials 2011, compressive strength tests were undertaken to
monitor the compressive strength of carbon nanotubes into 6%nano-metakaolin concrete.

42. 37
Figure 17 - shows the compressive strength test in Construction Building Materials 2011.
CNT’s were incorporated into concrete containing 6% nano-metakaolin. The CNT’s
concentration levels as a percentage are shown on the X-axis. The control concrete
contained no nano-metakaolin or CNT’s.
This test showed interesting results. As you can see the addition of CNT’s to nanostructured
concrete does increase the compressive strength until a limit where the compressive strength
starts to decrease again. Compared to the control concrete it is a lot more desirable to add
CNT’s to improve strength but only at small concentrations levels. CNT’s increased the
compressive strength because of the interaction with the hydration product which prevents
micro-crack formation. However as the concentration levels go higher than 0.02% the
compressive strength starts to decrease. This is due to the CNT’s, being formed around
cement grains leading to only a partial hydration of some areas causing a weak bond. This
does result in micro-cracks in the material. The positive aspect to take out of these results is
that for concrete to have the highest functionality only a small concentration of CNT’s is
needed. This can reduce production costs as only a small amount of CNT’s is required for an
efficient concrete to be manufactured. The negative of this of course CNT’s do not have the
same tensile strength as nanoparticles added to concrete due to the potential of micro-crack
formation. Depending on the application of the concrete CNT reinforced concrete may not be
suitable.
(28)

43. 38
Figure 18 - shows the mercury intrusion porosimetry test conducted on CNT concrete with
concentration levels of 0.5% amnd 1%. PC stands Portland cement and was used as the
control for this test. CNT’s improves the total porosity of concrete.
As the porosity decrease in these tests show how CNT’s can improve the sustainability of
concrete by reducing chemical degradation caused by moisture and external forces. Faults are
less likely to occur when the total porosity percentage is low which will make CNT concrete
more efficient. [41]
4.2.3.4 Structural Health Monitoring of CNT Concrete
Structural health monitoring could be an integral part of energy efficient buildings in the
future as assessment of structures can be done on condition based maintenance rather than
prevention based or breakdown based maintenance. Structural health monitoring is done
through analysis from information from sensing systems situated in the building themselves.
Structural health monitoring systems could reduce the financial costs of buildings by reducing
repairs and by implementing more efficient methods of inspection of building materials.
When cement based materials that incorporate multi walled CNT’s undergo mechanical
deformation, the distance between CNT’s change. This distance change of the CNT’s,
changes the tunnelling effect of CNTs which distorts their electrical conductivity. The
variation in electrical conductivity corresponds to a change in the electrical resistivity which
can be measured through an electrical resistance measurement system. Due to dielectric
effects this variation in internal resistance can only attributed to a mechanical deformation in
the material. Data tests on the measurement system show the system monitoring the structural
fatigue is very accurate with minimal error. CNT’s dispersion problems again are the only
hindrance to this concrete material being mass produced. The admixtures and the ultrasonic
examination required to make sure that the CNT’s are well dispersed can cause the
manufacture cost to rise significantly. Structural health monitoring concrete would be an

44. 39
important asset in new energy efficient buildings but the cost of this technology might impede
the integration of this type of concrete into the built environment. [42]
4.2.3.5 Environmental Impact of CNT’s
There is a lot of debate among researchers whether or not CNT’s can harm the health of
humans. CNT’s structure, size, surface chemistry, charge and agglomeration tendencies have
caused inaccurate data for medical researchers determining the potential health hazards. Some
reports have shown that in the right circumstances, CNT’s can intersect membrane barriers
and cause damage to organs. In rodent studies, CNT’s caused inflammatory problems and
epitheloid granulomas of the lungs. Another worrying issue is the fibre shape of CNT’s which
is very similar to the fibre shape of the deadly construction material asbestos. The fearful
aspect of this is that profound use of CNTs may cause the disease mesothelioma just like
asbestos. Of course there is no preliminary result to prove this however it is a precaution we
should be aware of due to the soaring popularity of CNTs in a wide range of applications. At
one stage in our history, researchers across the globe thought that asbestos was the new
revolutionary construction material with very little risk which is exactly the same opinion we
have about CNT materials currently. [38]
Figure 19 - shows the similarities between CNTfibres (left) and asbestos fibres (right).

45. 40
4.2.4 Financial Comparisons of Nanomaterials used in Concrete
Figure 20 - shows the comparison of different prices of nanoparticles from US Research
nanomaterials, Inc.
The financial comparison table shows Silica, Titanium Dioxide and Aluminium Oxide used as
nanoparticles in concrete are good value for money for mass-manufacture. Zirconium Dioxide
and Iron (II, III) Oxide are more expensive although these particles are used for unique
applications. [4]
* Multi walled carbon nanotubes are hard to relate to nanoparticles in terms of euro per gram
as less carbon nanotubes are needed for desirable outcomes in concrete. Also nanoparticles
can be distributed in powder form and carbon nanotubes cannot.
4.3 Nanotechnology in Windows
In this section of experimental work I review the literature on nanostructured windows and
how this can have an impact on energy efficient buildings.
4.3.1 The Use of Nano-TiO2 (Titanium Dioxide) Coatings on Energy Efficient Windows
4.3.1.1 Manufacture and Solvo-Thermal Synthesis of Nano-TiO2 Coatings:
Nano-TiO2 particles are very commonly used due to environmentally beneficial properties
and the ease of application of these particles. Titanium Dioxide can be produced from two
natural materials ilmenite and rutile. The production process uses only electricity a clean
Nanomaterial Price per gram (€/g) Purity (%) COLOUR
Nano-Al2O3=
Aluminium Oxide
€1.04/g 99% White
Nano-Fe3O4= Iron
(II, III) Oxide or
Ferric Oxide
€1.73/g 98% Dark Brown
Nano-SiO2 = Silicon
Dioxide or Silica
€1.26/g 99.5% White
Nano- TiO2=
Titanium Dioxide
€1.22/g 99.9% White
Nano- ZrO2=
Zirconium Dioxide
€2.84/g 99% White
*Multi-walled
Carbon Nano-
Tubes
€3.42/g 95% Black

46. 41
energy resource. This minimises the carbon footprint of the manufacturing process and is
beneficial to the environment. The synthesis of titanium dioxide can be done in a lot of
different of ways but usually for the purposes of nanotechnology, TiO2 is synthesized using
any one of the following methods:
 Sol–Gel Method,
 Hydrothermal Method,
 Solvo-Thermal Method,
 Chemical Vapour Deposition,
 Physical Vapour Deposition
 Laser Pyrolysis.
There are a lot of different methods for the synthesis and it depends on the application of the
TiO2. Some industrial companies create their own manufacturing processes to suit their own
objectives. Titanium dioxide is then purified into crystals used for application. Anatase due to
its stronger environmental purification properties is usually the crystal form of Titanium
Dioxide used for energy efficient windows. The synthesis of nano-sized titanium dioxide
particles by the Solvo thermal method is the most appropriate for use on windows. This
method is used for energy efficient windows because of the simplicity of applying the
particles to the window and because the thermal treatment enhances the environmental
purification properties. The processes involved in the synthesis using the Solvo – Thermal
Method are listed in order from first to last:
Solvo – Thermal Method
1. Aqua Solution Mixing:
Firstly mix Titanium Tetra Chloride (TiCl4) with a Hydrochloric acid (HCl) using a
magnetic stirrer for at least four hours
2. Neutralisation:

47. 42
The acidic solution of Titanium Tetra Chloride (TiCl4) and Hydrochloric acid (HCl)
is neutralised to a pH of 7.5. This is done by adding Ammonium Hydroxide (NH4OH)
which is a base slowly until a pH of 7.5 is realised while the solution is still stirring.
3. Decantation:
The mixtures are separated using filtration and the precipitate is removed. The
precipitate and deionized water is used to separate the chloride from the titanium
while the mechanical stirrer provides the energy source to the solution.
4. Peroxidation:
Hydrogen peroxide is then added to the solution and it is stirred for a further seven
hours. The result is the first layer Nano-TiO2 particles sprayed onto the window. This
first layer is mixed with water.
5. Thermal Treatment:
The thermal treatment is used to enhance the photocatalytic properties of the next
layer of particles. This is done in a boiler at 100o
C.
The Nano-TiO2 coating is applied during the manufacture phase by spraying a layer of
particles onto the glass. The Nano-TiO2 particles are suspended in aqueous solution for the
coating. The concentration of Nano-TiO2 particles ranges from 0.5% to 10% by volume. The
concentration varies depending on the application of the material. The nanoparticles sizes are
between 1nm and 100nm long. [26]
4.3.1.2 Environmental Benefits of Nano-TiO2 Coated Windows:
As mentioned before in this project a very desirable property associated with Nano-TiO2
particles is their self- cleaning function. Nano-TiO2 particles are a photo catalyst that can
oxidise pollutants and make materials more hydrophilic. Nano-TiO2 windows self-cleaning
process is shown from stages 1 - 3:

48. 43
Stage 1:
Figure 21
UV light from the sun interacts with the Nano-TiO2 particles to release an electron. Only a
small amount of energy is needed for this reaction so this process will still work in dull
weather. Electrons then interact with water molecules producing a Hydroxyl radical.
Stage 2:
Figure 22
Hydroxyl radicals then can break the bonds of carbon based dirt into carbon dioxide and
water. This is the oxidation process provided by titanium dioxide.

49. 44
Stage 3
Figure 23
The hydroxyl radicals also make the window hydrophilic. Hydrophilic means it has a
tendency towards water. Therefore from rain or water molecules in the air the window can be
cleaned. The same process is applied to self-cleaning Nano-TiO2 concrete mentioned earlier
in this project.
Environmental purification is crucial to energy efficiency. With new environmental
regulations being enforced for businesses and new domestic homes, buildings energy
efficiency will be affected by what method of environmental protection that building uses.
Self-cleaning Nano-TiO2 windows can reduce the energy usage and maintenance costs of an
energy efficient building. It will save the occupants of that building time and money as
valuable human resources are not being utilised for cleaning windows and there is no need to
hire a windows cleaning service. These windows help purify the air indoors similarly which
means less resources can be used for air purification.
The self-cleaning attribute of Nano-TiO2 coated concrete is an extremely useful property for a
material to have. Unfortunately there are a few drawbacks to integrating self-cleaning glass
into a building. The chemical process that removes dirt from a window is a slow process as it
takes time for the hydroxyl radicals to break down the dirt. In weather with low levels of
humidity it takes longer for the glass to be cleaned. Furthermore for buildings located by the

50. 45
coast have salt composites wash up onto the windows which are unable to be chemically
broken down by the hydroxyl radicals. [43]
Pollution is an ever present problem in our modern world. The general public are starting to
realise the potential negative impacts on our environment but with the increasing global
population, pollution is emerging as a huge global threat. The environmental benefits of using
Nano-TiO2 windows in an energy efficient building are very significant. In the long run by
incorporating Nano-TiO2 coatings into buildings will considerably reduce pollution and
ultimately improve sustainability. Acidification and eutrophication is the chemical leaching
of nutrients into our environment. These chemical reactions both have negative and positive
effects on our environment. The leaching of enriched nutrients into our environment can
improve the growth of ecosystems. However the release of harmful substances can
contaminate soil, water, and livestock and deplete human health. Chemical leaching can also
cause structural faults in buildings. Smog formation is another type of pollution that can harm
our environment and cause human health hazards. In Construction and Building Materials 40
(2013) the BEES life cycle assessment was undertaken to quantify the environmental benefits
that Nano-TiO2 windows can cause. In Figure 24 not only can you see that Nano-TiO2
coatings reduce the potential harmful impacts of eutrophication, acidification and smog
formation but it improves the indoor air quality and oxidises undesirable pollutants. This will
lead to a more sanitised building but will also improve the sustainability of our environment.
[26]

51. 46
Figure 24 - shows the BEES life cycle assessment of Nano-TiO2 coatings environmental
improvements.
Nano-TiO2 coated glass in windows produces more CO2 than regular uncoated windows. This
is because of titanium dioxide’s oxidation process when removing organic dirt which
produces carbon dioxide. The difference is very slight and the positive environmental factors
caused by Nano-TiO2 windows should outweigh this minor disadvantage. However since
carbon dioxide being released into our atmosphere causes global warming it is an aspect
worth mentioning.
Figure 25 – shows the slight increase in CO2 emissions in the coated glass due to Nano-
TiO2 oxidation process.
[26]

52. 47
4.3.1.3 Efficiency of Nano-TiO2 Coated Windows
Through nano-scratch tests the mechanical properties of a window can be seen. Through
observations by high powered microscopes the indentations shows the thickness of the
coatings is proportional to the surface roughness which can reduce the fractures caused by
external forces. Due to the dense agglomeration of the nanoparticles the Nano-TiO2 coating
after the mechanical fracture showed good adherence, stability and mechanical resistance.
Figure 26 - shows the titanium dioxide coating before (a) and after (b) the nano scratch
test. The density of the nanoparticles supporting the mechanical fracture can be observed
in image b. These tests were conducted in Solar Energy 125 (2016).
[44]
Coatings on windows can harm the windows optical transmittance if the right coating is not
selected. A window coating must have appropriate wavelengths, optical constants and thermal
coefficients to maximise transmittance. The anti-reflective properties of Nano-TiO2 windows
are a beneficial attribute in relation to energy efficient windows due to the transmittance of
light loss through the titanium coating is less than 1%. This shows that Nano-TiO2 coatings
can still be used for variable optical transmittance which is a technology that utilises natural
sunlight as a method of reducing energy consumption. In section 4.3.3 I discuss these
properties in more detail but in this section I want to clarify that Nano-TiO2 coatings do not
impede smart windows technology and improves optical transmittance. Although coatings do
have some negatives when applied to windows for energy efficient purposes. Constructional
constraints are an issue for windows incorporating sustainable like Nano-TiO2 coatings.
Dimensional freedom of the window is restrained with alterations of the window suppressed
due to the coating. Also the use of necessary additional materials such as glues and thin films
can increase costs. [44] [45]

53. 48
4.3.1.4 Financial Cost and Integration of Nano-TiO2 Windows
The production cost increases when Nano-TiO2 coatings are applied to energy efficient
windows due to the chemical fabrication before the particles are ready to be applied to the
glass. Even applying the coating through spraying adds an extra stage to the manufacturing
process which increases cost. The Building for Environmental and Economic Sustainability
(BEES) model was employed in Construction and Building Materials 40 (2013) to give an
environmental and economic score to both Nano-TiO2 coated windows and to normal
residential windows.
`
Figure 27- shows the BEES model for Nano-TiO2 coated glass and uncoated glass. An
economic and environmental score is assigned to both types of glass.
As shown above the environmental performance is considerably less than that of an uncoated
window which is beneficial for the environment. However the economic performance was
higher than an uncoated window showing that the extra production costs make Nano-TiO2
coated windows the more costly option. Different companies and industries have different
opinions on whether or not the economic performance of a building is more crucial than the
environmental performance of the building. The BEES life cycle can also portray the different
weighted factors involved when deciding during the construction of a building which is more
important. The BEES model has produced an economic vs. environmental profile for titanium
coated windows. This can aid the integration of Nano-TiO2 coated windows as one can
deliberate on whether or not this type of window suits the objective of one’s building.

54. 49
Figure 28 - shows the environmental importance versus the economic performance of
titanium dioxide coatings produced by the BEES model.
[46]
As the coatings are applied during the manufacture phase of the glass replacing windows in
an existing building can be very costly to the owner. According to a quote from Munster
Joinery, it would cost anywhere from €800 to €5000 for a normal residential house. There are
a lot advantages to replacing windows but the cost of the windows themselves and the cost of
replacement is a significant disadvantage for Nano-TiO2 coated windows. Applying the
coatings after the window is constructed into the building would not work which causes
difficulties when trying to implement this technology into the already built environment. [47]
Titanium dioxide is a carcinogen but it would require a large concentration to be inhaled over
a number of years for cancer to develop. Titanium Dioxide itself has a low level of toxicity
and human health hazards would be kept to a minimum if a building was to integrate Nano-
TiO2 windows. [20]
4.3.2 The Use of Nano-SiO2 (Silica) in Energy Efficient Windows
After the synthesis of Silicon Dioxide to nanoparticles there was two distinct ways of
applying these particles to glass for energy efficiency purposes.
The first involves using Silica as a coating on the outside of the window. The Nano-SiO2
particles are suspended in an aqueous solution in the coating. Along with desirable optical
properties the biggest impact from using Nano-SiO2 as a window coating is the heat
insulation properties. However due to the popularity of Nano-TiO2 coatings the use of silicon
as a coating is limited and not as much scientific literature is available. [48]

55. 50
The second way is to inlay SiO2 nanoparticles into the glass itself during the manufacture of
the glass. The Inlay Silica energy saving glass uses two dimensional periodic nanostructures
to improve the energy conservation properties of the glass. This potentially can give glass
better optical properties and improve the transparency factors involved in making windows
more efficient. To investigate the outcomes of using Nano-SiO2 structures for energy
efficiency purposes in Energy and Buildings 86 (2015), rectangular silica nanostructures were
added to metallic substrates and a series transmission tests were undertaken. The results were
seen as very positive for transmittance values of the glass. By not using coatings and inlaying
the nanostructures into the glass material itself it reduces the complications that come about
applying the coatings. The unavailability of materials with the appropriate optical constants,
dimensional constraints and the use of by products and glues are all problems associated with
using energy efficient coatings on windows. Using inlaid nanostructures can remedy some of
these complications however more research must be undertaken before this method of energy-
efficient glass production can be used for mass manufacture. The integration of inlay
nanostructures into existing windows would not be viable. [45]
4.3.3 Smart Windows and Nanotechnology
4.3.3.1 Importance of Smart Windows and Types of Smart Windows
Windows that allow for the variance of solar radiation into a building can transform the way
windows are constructed forevermore. These windows that can regulate the amount of
sunlight allowed into a building can save energy costs on heating, cooling and lighting. These
smart windows can also work in conjunction with energy efficient window coatings to
provide a very high performing window. The costs of integration of these windows at the
moment are high but the potential energy efficiency could be critical to meeting our energy
efficiency targets. Scientists even believe that there is the capability of combining solar
technologies with these windows so that the excess sunlight can be stored and be re-
introduced to the building further improving energy efficiency. With the global population
growing even higher and a higher demand for natural resources, the integration of smart
windows into new and existing buildings could improve our energy efficiency in the built

56. 51
environment substantially. There are a lot of issues still surrounding the implementation of
smart windows. Some materials used currently in smart windows are inefficient and costly.
There are also drawbacks in the functionality of these windows such as the ability to allow
natural sunlight into a building for lighting purposes while preventing the heat from that
sunlight from entering the building. This is where nanotechnology can potentially be utilised
to drastically improve the problems of smart windows and make them a viable energy
efficient option. [49]
There are many different technologies that can fabricate smart glass. The different types of
smart windows include:
 Thermotropic Windows:
Thermotropic varies transmittance and light as the external environment
changes. These kinds of windows are sensitive to the variation in external
temperature. As the external heat changes a change in the windows specularity
occurs resulting in the diffusion of light into a building. There are two types of
thermotropic windows used currently. These are hydrogels (used mainly for
colder climates) and thermotropic polymers (used mainly for warmer climates).
These windows can provide enhanced visual light even when natural sunlight is
diminished. However this can lead to optical comfort problems such as glare.
 Photochromics or Photochromatics Windows:
Photochromic windows change from translucent to transparent when ultraviolet
light hits the window. They can control optical transmittance which reduces
glare and unwanted sunlight. However due to this reaction being slow to
respond and due to the complexities involved with heat gain from the ultra-
violet light, photochromic windows are inefficient and have limited applications
such as skylights.

57. 52
 Polymer Dispersed Liquid Crystals Windows:
Liquid crystal smart windows are electrically responsive windows in which the
transparency varies as the electrical current is switched “on” and “off”. Energy
consumption is not directly altered with this technology however they improve
a building’s lighting privacy and improve solar heat gain. These windows are in
widespread use due to their architectural comfort properties. Nanotechnology
can potentially improve the inefficient and costly life cycle of these windows.
 Suspended Particle Windows:
Suspended particles device smart windows are electrochromics that change
transparency when an electrical current is applied. They are an alternative to
liquid crystals with similar disadvantages, but their optical transmittance is far
greater and easier to regulate.
 Electrochromic Windows:
Electrochromic smart windows are able to vary optical and thermal
transmittance of natural sunlight when voltage is applied. They are controlled
by an electrical switch. This is the most common type of smart window used
today due to its thermal and optical transmittance properties. Nanotechnologies
can also have their biggest impact in these types of smart windows.
 Thermochromic Windows:
Thermochromic windows also operate due to the input of heat to change the
transmittance of the windows. However due to being controlled by natural heat
rather than electricity the reaction is slow and optical variance is hindered in
this type of window. Thermochromics switch from transmissive to reflective
and due to this it can cause visual light problems in buildings.
[50]

58. 53
All these smart glass technologies can improve the energy efficiency of a building but I
wanted to investigate which of these different technologies can incorporate nanotechnology.
Nanotechnology can significantly improve sustainability and manufacture costs but I wanted
to see which technologies could be enhanced with nanotechnology. The technologies I
mention that cannot incorporate nanotechnology still might one day but currently there is no
scientific literature that emphasises the point. Energy efficient coatings can give a smart
window extra energy efficiency properties but I wanted to see which of these technologies
can realistically incorporate these coatings. Nanostructured coatings are a viable energy-
saving solution for windows and I observed which smart window technologies can integrate
efficient coatings. I also investigated the application of these windows to observe which
smart glass technologies had a limited application and which of these technologies can be
manufactured into general buildings. The results are shown in Figure 29.
Smart Window
Technology
Energy
Source
Application The potential to
incorporate
Nanotechnology
Effective with
Energy Efficient
Coatings
Thermotropic
Windows
Heat Overhanging
Shelved windows
to reduce glare
No No
Photochromic
or
Photochromatic
Windows
Ultra -
Violet
Radiation
Skylights No Yes
Polymer
Dispersed
Liquid Crystals
Windows
Voltage All Windows
(Used for
architectural
preference also)
Yes Yes

59. 54
Figure 29– shows the comparison of smart window technologies.
Thermotropic and photochromic technologies have no scientific literature that can be found
on whether or not nanotechnology can improve the properties of these kinds of windows.
Even though photochromic windows can benefit from an energy efficient coating (such as a
nanostructured coating) the limited application reduces its potential for mass manufacture in
energy efficient buildings. Electrochromic, polymer dispersed liquid crystal, suspended
particles technologies can all incorporate an energy efficient coating (such as a
nanostructured coating) and nanotechnology has also been shown to improve manufacture
costs, life cycle, transmittance and the sustainability of windows in energy efficient
buildings. Thermochromic smart windows can have nanotechnology improve its
functionality however because of its unreliable energy source widespread use of this
technology might be inappropriate. Its application is limited due to the climate, specific
orientation and because of the high positioning requirement on buildings. These reasons
show that thermochromic smart windows are unsuitable for mass manufacture and
integration into buildings. I also portrayed the energy source needed to operate each
technology. Thermotropic, photochromic and thermochromic do not need electricity to
operate as their energy source is extracted from natural sunlight making these technologies
very eco-friendly. However electrochromic, polymer dispersed liquid crystal and suspended
Suspended
Particle
Windows
Current All Windows Yes Yes
Electrochromic
Windows
Voltage or
Current
All Windows Yes Yes
Thermochromic
Windows
Heat Upper Windows
to maximise heat
absorption
Yes No