Comparative Study of Single-glazed and Double-glazed Windows in Terms of Energy Efficiency and Economic Expenses

Abstract

Saving fossil fuels and the use of clean sources of energy lead to reduce in building operating costs, protect the environment and people's health. Windows are the most vulnerable part of building where energy loss occurs. Double-glazed windows are very effective in keeping inside temperature isolated from outside; thereby, saving electrical and thermal energy. The current study estimates the numerical changes in cooling and heating load in case of replacement double-glazed window with single-glazed window and calculates saving level for this replacement. In this context, this paper presents a model of real samples taken in Mashhad climate. To ensure the accuracy of the simulation results, real results were compared with electricity and gas bills. To calculate energy related parameters such as cooling load, heating load, the consumption of gas and electricity, the energy simulation software (Design Builder) was used. The research method was a quantitative analysis based on energy consumption modeling, associated with building windows which comes in four sections. The field study was also used to compare with real electricity and gas bills. As the first stage, samples of the plan were identified, based on the observation of climate models and library studies. Then, simulation parameters such as window materials and internal and external walls were considered. The simulation was performed based software’s parameters and model limitations were determined based on thermal, lighting, climatic and architectural parameters. Finally, the experimental and practical data were used to determine the validity of the model under Mashhad climate conditions. Overall, the results indicated that double-glazed windows could save 50% of entire building loads, 0.2% on power consumption, 16.2% on gas and 12.4% on overall households’ energy consumption.

Full text

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DOI: 10.7596/taksad.v6i3.884
Citation: Forughian, S., & Taheri Shahr Aiini, M. (2017). Comparative Study of Single-glazed and
Double-glazed Windows in Terms of Energy Efficiency and Economic Expenses. Journal of
History Culture and Art Research, 6(3), 879-893. doi:http://dx.doi.org/10.7596/taksad.v6i3.884
Comparative Study of Single-glazed and Double-glazed Windows in
Terms of Energy Efficiency and Economic Expenses
Samaneh Forughian*1, Masoud Taheri Shahr Aiini2
Abstract
Saving fossil fuels and the use of clean sources of energy lead to reduce in building operating costs, protect
the environment and people's health. Windows are the most vulnerable part of building where energy loss
occurs. Double-glazed windows are very effective in keeping inside temperature isolated from outside;
thereby, saving electrical and thermal energy. The current study estimates the numerical changes in cooling
and heating load in case of replacement double-glazed window with single-glazed window and calculates
saving level for this replacement. In this context, this paper presents a model of real samples taken in
Mashhad climate. To ensure the accuracy of the simulation results, real results were compared with
electricity and gas bills. To calculate energy related parameters such as cooling load, heating load, the
consumption of gas and electricity, the energy simulation software (Design Builder) was used. The research
method was a quantitative analysis based on energy consumption modeling, associated with building
windows which comes in four sections. The field study was also used to compare with real electricity and
gas bills. As the first stage, samples of the plan were identified, based on the observation of climate models
and library studies. Then, simulation parameters such as window materials and internal and external walls
were considered. The simulation was performed based software’s parameters and model limitations were
determined based on thermal, lighting, climatic and architectural parameters. Finally, the experimental and
practical data were used to determine the validity of the model under Mashhad climate conditions. Overall,
the results indicated that double-glazed windows could save 50% of entire building loads, 0.2% on power
consumption, 16.2% on gas and 12.4% on overall households’ energy consumption.
Keywords: Builder Design, Single and double-glazed window, Energy saving, Economic saving, Cooling
load, Heating load.
1Corresponding author. M.A. of Architecture engineering, Shahrood University of Technology, Iran. E-mail:
Foroughian_samaneh@yahoo.com
2 Professor, College of Architecture, Shahrood University of Technology, Iran. E-mail: mtaheri87@yahoo.com
Journal of History Culture and Art Research (ISSN: 2147-0626)
Tarih Kültür ve Sanat Araştırmaları Dergisi Vol. 6, No. 3, June 2017
Revue des Recherches en Histoire Culture et Art Copyright © Karabuk University
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Introduction
The issue of non-renewable energy use has become so important in recent years. Given that the
windows are the main part of the building in terms of thermal dissipation, one way to optimize
energy consumption and prevent the completion of fossil energy is to design types of windows that
waste less energy than does the common kind. In energy balance sheets published in 2011 by the
Deputy of Energy in the Ministry of Energy, energy consumption in Iran is 40.6% belonging to
residential and commercial consumption and almost 99% of the energy consumption of these
buildings comes from oil and gas production that is fossil fuel component. In addition, the highest
share of this energy consumption within the building is to provide thermal comfort (Balance Sheet
Energy, 2013). According to figures provided, we can see that if we can make scientific way to
reduce energy loss in buildings, this leads to savings in energy consumption and to reduce
environmental pollution caused by excessive use of fossil fuels and thereby returning on
investment.
Basic Studies
Of the factors affecting energy consumption in buildings, geometry and design of various
components as well as the climatic conditions is concerned the most that this will be possible
through careful analysis of the site. Windows, as one the most important buildings features, play a
key role in saving energy, either in terms of heating and cooling load or in terms of design, which
can reduce energy loss through capturing more sun light. Depending on the size and orientation of
windows, different behaviors are deemed. For simulating windows and their efficiency, different
energy simulation software are used, because windows are the most important part of building in
terms of absorbing solar radiation.
Some energy simulator software:
Considering the main goal of this study which is investigating the effect of windows on optimizing
energy use, four different packages of software were applied. The position of the sun in each region
is generally given as an altitude (elevation) and azimuth (side) angle. Altitude angle is the angular
height of the sun in the sky measured from the horizontal. Azimuth angle is defined as the angle a
horizontal projection of a direct ray from the Sun makes with the true north-south axis. Annual and
daily changes of the angle depend on latitude of the location (Table 1) (Qiyabkoloo, 2010).

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Mashhad Climatic Data:
To achieve accurate results from simulation software for the investigated building, Mashhad
climatic data was used as apw file format. This file format has been approved by Design Builder
manufacture and is available online (Design Builder, 2010).
Background of the research
A copious amount of studies has been done on energy saving solutions, most of which were in the
field of sustainable design. Studies differ from the most general issues of sustainable design to
providing the most partial solutions to save energy and reduce fossil fuel consumption and replacing
it with sustainable solar energy. These include the impact of green roofs design and etc. But given
the importance of energy loss by windows and on the other hand their vital role in receiving sun
light, this construction element which seems of no importance is the main concern of discussion in
terms of saving energy. To measure the amount and type of saving and achieve savings figures
there are different mathematical selected and compared, among which Design Builder software was
selected as the most appropriate software. Design Builder was used to calculate and simulate
windows. The results were presented as graphs.
The effect of climate on architecture:
To launch a climate-compatible project, paying attention to regional climate and climate-compatible
materials to gain better establishment, using methods and technique software have great importance
(Tommerup & Svendsen, 2005). For this purpose, two typical residential buildings were examined
and the results were represented in graphical form. (Krarti et al., 2005) has also dealt with the need
to provide a way to estimate the energy saving. He also analyzed four geometry of buildings with
different coverings and expressed a close connection between window and their frame in energy-
savings (Krarti et al., 2005). In addition to these methods provided, there are packages of software
that enable us to investigate energy efficiency and the efficacy of windows and canopies in terms of
type, material, number of chamber, direction, and etc. Among which Design Builder is the most
completed software. Several studies in this field have been performed to measure how to reduce
energy consumption in buildings, such as control of air conditioning, sunlight, glass coating,
orientation and etc (Florides et al., 2002). Orientation plays a major role in saving energy. In a
study, six cities from six different climates of Iran (hot, humid, cold, mountainous, warm, and dry)
were selected and optimal orientation for each city was examined. The results indicated that,
southern direction was appropriate for cold, cold and mountainous, hot and humid and mild and wet

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climates, and the northern direction was more suitable for hot and dry and mountainous climates
(Akbar Azimi Hosseini, 2011).
A number of detailed reviews have been conducted on windows and their overall behavior (when
opened or closed) such as their impact on thermal comfort of residents (Rijal et al., 2007), energy
consumption by letting the daylight enter into living or working places, which helps to reduce
energy consumption by 50-80% (Bodar t& De Herde ,2001; Pyonchanihm et al., 2008) and finally
the effect of chamber number on reducing energy consumption in buildings. In a study, different
types of glass and their walls and also difference air type used between the walls were studied. The
studied windows included single-glazed windows, 3 mm double glazed with 13 mm air, 3 mm
double glazed windows with 13 mm Oregon, double glazed windows coated with light controller
with 13 mm air and finally double glazed windows coated with light controller with 13 mm Oregon.
Finally, the best type was also introduced (Barjastehbaf et al., 2012).
In another study, eight types of double-glazed windows were compared including 6 mm clear
windows on both side filled with 12 mm air, 6 mm clear windows on one side and on the other side
6 mm clear window coated with light controller filled with 12 mm air, 6 mm blue window on one
side and 6 mm transparent window on the other side filled with 12 mm air (yalcin et al., 2012).
Another research was done on eight types of windows oriented towards four main geographical
directions and ultimately the most appropriate direction for each type of window was determined
(Hassouneh et al., 2010). Furthermore, the impact of window fittings on saving energy was studied.
The results indicated that by choosing the best fitting we can save energy up to 12% (Rayment et
al., 1985). Moreover, studies have shown that for a specific climate, energy loss from the pop-up
windows is directly related to the percentage surface but not to the direction of windows. However,
in terms of solar energy absorption, windows opening towards south do better than those opening
towards south (Hussain Zadeh et al., 2013). In addition, the influence of smart glasses to increase
energy efficiency was noted. Smart windows are made in such a way that turns dark and light as sun
light increases and decreases, respectively and as such causes thermal comfort of residents
(Heydari, 2013). Another form of windows includes windows which have ability to rotate 180
degrees during the years. These windows absorb a considerable amount of heat in summer and by
rotating it out in the winter, rays pass through. The amount and type of impact of these windows
have been compared for different climates (Feuermann & Novoplansky, 1997). As mentioned
above, a variety of researches have been done on various parameters in different types of windows.
In the current study, the main goal was to gain a numerical number equals to power and gas
consumption and calculate the monetary cost of family in case of using single-and double-glazed

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windows. In this study, after obtaining the quantity of monetary savings, this value was compared
to the cost of purchasing and installing double-glazed windows, and the results were presented.
Review model
Considering the aim of this study which was to evaluate the effect of window on energy exchange,
computations were done on an actual sample building. This model was a residential building in a 5-
story apartment on the third floor with an area of 105 square meters having two bedrooms (Figure
1). The residential unit had skylights facing north and south directions and had neighborhood from
up, down, east and west so no heat exchange was occurred in this directions (Figure 2). The
materials of the walls and the ceiling are described in this study, the only variable in the building
was windows’ type. The windows’ information in two cases of single-glazed (Figure 4) and double-
glazed (Figure 5).
Results and discussion
At first, the cooling and heating load parameters were studied alone to calculate the total amount of
saving for the loads (heating and cooling), (Table 2).
According to the percentage formula of saving:
Savings percentage= the basic Mode-Strategy mode
Basic Mode
The saving percentage in the total load when double-glazed windows were used, was found to be
49.9%. So far, only the load required for heating and cooling is considered. However, consumption
of equipment is effective in electricity and gas consumption too. Here, we have calculated the
annual total energy consumption saving percentage for the family in which, in addition to cooling
and heating load, fuel consumption and lighting equipment has also been taken into account.
Initially, the model was evaluated by single-glazed window and electricity and gas consumption
was estimated in terms of kilowatt-hours (Table 3). These data were obtained during 12 months
(kWh). The following, data are presented in graphical form for better understanding (Figure 6),
(Figure 7).
As can clearly be seen from the Table 3, installing of double-glazed windows is more effective in
gas consumption than electricity consumption, especially in January. The effect of double-glazed

884
windows on cooling load saving was negligible. In the following, annual electricity and gas
consumption are presented and in the end total electricity and gas consumption are summed in kWh,
and finally the total amount of consumption in both modes, using single-glazed the annual saving in
electricity consumption and gas consumption was 0.2% and 16.2%, respectively. In case of double-
glazed windows, the amount of annual saving in total energy consumption could increase by
windows and double glazed windows, are compared (Table 4).
The main issues in energy saving strategies are prices and initial costs which are imposed to
employers. In the table below the amount of electricity and gas has been converted in to Iranian
Rials (Table 5- Table 6), (Figure 8), (Figure 9). Annual monetary value of electricity and gas saving
are 16,924 and 72,222 Rials, respectively.
As a result, the percentage of annual monetary for electricity and gas saving was 0.7% and 10.3%,
respectively. The total amount of saving was equal to 89146.3 Rials and the total annual saving in
case of double-glazed windows increased by 2.9%. As found in this study, using double-glazed
windows in this building in Mashhad climate could lead 12.4 and 2.9%saving in terms of energy
and household economy, respectively. The reason why energy saving percentage is higher than that
of economy saving is that gas is much cheaper than electricity in Iran. So far, only electricity and
gas costs were compared. Therefore, more precise calculations can be performed when the
purchasing and installing costs for double-glazed windows are calculated too. So considering the
high initial cost for purchasing double-glazed windows, which saves 89,146 Rials per year, we need
to calculate back period of initial costs to find that whether using this windows are economical.
According to the dimensions of the doors and windows in this sample residential unit, the
purchasing and installing cost for double-glazed windows was calculated as IRR 31130374. The
initial purchasing and installing costs for double-glazed windows is very low compared to the
annual monetary saving.
Conclusion
Considering the shortage of fossil fuels, if we consider design criteria based on energy saving
strategies, installing double-glazed windows would be definitely reasonable as these windows save
up to 50% in total load of the building it means having more fossil fuels for longer years. However,
it cannot be ignored that these windows are not really compatible with family economy.

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References
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different climates. Journal of Environmental Science and Technology. 1(2): 78-92.
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consumption of buildings in our climate. Journal of Energy Conservation. (61):71-82.
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Appendix
Table1. Climate data table (The Ministry of Roads and Urban Development Meteorological
Organization)
Minimum
daily
temperature
Maximum
daily
temperature
Daily
temperature
average
Relative
humidity
average
Maximum
relative
humidity
average
Minimum
relative
humidity
average
Monthly
raining
Total
monthly
sunny
hours
Number
of
cloudy
days
Number
of
snowy
days
9.2 22.6 15.7 49% 69% 30% 168.9 3122.7 52 15
Table 2. Total load of electricity and gas (kw/h)
single-glazed window kilowatt-hours double glazed window kilowatt-hours
Total load of electricity 549
Total load of
electricity
543
Total load of gas 3562 Total load of gas 1765
Total 4111 total 2308
amount of saving is equal to 1803 kWh
Table 3. Electricity and gas consumption in (kw/h)
Marc
h
April
Ma
y
Jun
e
July
August
Septe
mber
Oct
obe
r
Nov
emb
er
Decemb
er
Janua
ry
February
Electricit 244 285 344 387 386 345 260 238 238 238 238 233

887
single-
glazed
window
y
Gas
809 651 630 630 630 630 634 834 1284 1711 1568 1111
double
glazed
window
Electricit
y
244 289 343 380 378 349 262 238 238 238 238 233
Gas 695 631 630 630 630 630 630 668 929 1240 1146 866
Table 4. Total consumption of electricity and gas in kilowatt-hours
single-glazed window kilowatt-hours double glazed window kilowatt-hours
Total consumption of
electricity
3437
Total consumption of
electricity
3430
Total consumption of gas 11122
Total consumption of
gas
9325
Total 14559 total 12755
amount of saving is equal to 1804 kWh
Table 5. Electricity and gas consumption using one -glazed window
Gaz Heating equipment total Rial
March 179 630 809 31589.52
April 21 630 651 70932

888
May 0 630 630 68310
June 0 630 630 68310
July 0 630 630 68310
August 0 630 630 68310
September 4 630 634 68809.43
October 204 630 834 32565.71
November 654 630 1284 50137.14
December 1081 630 1711 66810.48
January 938 630 1568 61226.67
February 481 630 1111 43381.9
Electricity cooling Lighting equipment total Rial
March 0 161 83 244 133612
April 41 161 83 285 175555
May 100 161 83 344 271904
June 143 161 83 387 351067
July 142 161 83 386 349226
August 101 161 83 345 273745
September 22 155 83 260 149980
October 0 155 83 238 127474
November 0 155 83 238 127474
December 0 155 83 238 127474
January 0 155 83 238 127474
February 0 150 83 233 122359

889
Table 6. Electricity and gas consumption with the use of the double-glazed windows
Gaz Heating equipment total Rial
March 65 630 695 27138.1
April 1 630 631 68434.9
May 0 630 630 68310
June 0 630 630 68310
July 0 630 630 68310
August 0 630 630 68310
September 0 630 630 68310
October 38 630 668 26083.8
November 299 630 929 36275.2
December 610 630 1240 48419
January 516 630 1146 44748.6
February 236 630 866 33815.2
Electricity cooling Lighting equipment total Rial
March 0 161 83 244 133612
April 45 161 83 289 179647
May 99 161 83 343 270063
June 136 161 83 380 338180
July 134 161 83 378 334498
August 105 161 83 349 281109
September 24 155 83 262 152026

890
October 0 155 83 238 127474
November 0 155 83 238 127474
December 0 155 83 238 127474
January 0 155 83 238 127474
February 0 150 83 233 122359
(Fig 1). Review model
(Fig 2). Review model

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(Fig 3). The materials of the walls and the ceiling
(Fig 4). Single-glazed
(Fig 5). Double-glazed

892
(Fig 6). The amount of gas consumption in both Double- and single-glazed window.
(Fig 7). The amount of electricity consumption in both Double- and single-glazed window
(Fig 8). Rials gas consumption in two states of single-glazed and Double-glazed windows
0
500
1000
1500
2000
0 5 10 15
kw/h
A-L
one-glazed
window
Double-
glazed
window
0
50
100
150
200
250
300
350
400
450
0 5 10 15
kw/h
A-L
single-
glazed
window
Double-
glazed
window
0
10000
20000
30000
40000
50000
60000
70000
80000
0 5 10 15
kw/h
A-L
one -glazed
window
double-glazed
windows

893
(Fig 9). Rials electricity consumption in two states of single-glazed and Double-glazed
windows
0
50000
100000
150000
200000
250000
300000
350000
400000
0 5 10 15
kw/h
A-L
one-glazed
windows
double-glazed
windows