Choosing the Right Type of Windows to Improve Energy Efficiency of Buildings

Abstract

During construction or renovation of the building there is a question of choice windows. The modern market offers several kinds of windows: wooden, plastic, aluminum, and combined models. The most common and constantly competing with each other are wooden and plastic windows. This paper discusses the advantages and disadvantages of all types of windows and offers the advice on selecting the type of windows for energy efficiency in buildings.

Full text

Choosing the right type of windows to improve energy efficiency of
buildings
Nikolay Vatin1,a, Olga Gamayunova2,b
1,2St. Petersburg State Polytechnical University, St.Petersburg, 195251, Russia
avatin@mail.ru, bgamayunova@inbox.ru
Keywords: windows, wooden windows, plastic windows, aluminum windows, energy efficiency,
energy saving, energy-saving plastic windows, i-glass, k-glass.
Abstract: During construction or renovation of the building there is a question of choice windows.
The modern market offers several kinds of windows: wooden, plastic, aluminum, and combined
models. The most common and constantly competing with each other are wooden and plastic
windows. This paper discusses the advantages and disadvantages of all types of windows and offers
the advice on selecting the type of windows for energy efficiency in buildings.
Introduction
In recent years, Russia has become increasingly focused on energy saving and energy saving in
construction. In the program of energy saving the windows play an important role, since the current
level of their thermal protection is considerably inferior thermal protection of envelope structures of
buildings (up to 40% of all losses of the building).
According to the data of energy audits, one of the causes of energy losses is a windows in the old
wooden frames, installed in many buildings, which belong mainly to budgetary organizations, such as
kindergartens, schools, etc. [10, 12, 14-20].Obviously, such a windows should be replaced. The right
choice of the type of windows affects not only on energy efficiency, but also on economic efficiency.
Heat loss through the window occur through several channels: loss through window unit and
frames, losses due to heat conduction and convection air flows between the panes, as well as heat loss
through heat radiation.
Obviously, the amount of heat loss through the window unit is directly dependent on the window
construction, materials and manufacturing quality.
With the continuous increase of tariffs for electric and heat energy, improved thermal performance
of windows is one of the most effective ways to address energy efficiency in buildings.
Main types of windows
The main materials for the fabrication of windows in Russia now are wood, aluminum and plastic.
According to various estimates, the share of plastic windows is 60-80% of all windows.
Each of these windows has its advantages and disadvantages (refer with: Table 1), as well as their
own consumers [7]:
 plastic windows is the most economical option glazing industrial, public and residential
buildings;
 aluminum windows gradually starting to be used in residential buildings (such as the glazing
of balconies and loggias), but until recently, their main area of application were industrial and
public facilities;
 modern wooden windows (“euro-windows”) with glass unit belong to the elite segment of
translucent structures and installed mainly in luxury villas and apartments.
Further shall consider in more detail the main characteristics and properties of plastic and wooden
windows. Aluminum windows will not be considered as they are used mainly in industrial buildings
and non-residential premises (for example, for glazing of balconies and loggias)
Applied Mechanics and Materials Vols. 633-634 (2014) pp 972-976 Submitted: 22.07.2014
© (2014) Trans Tech Publications, Switzerland Accepted: 26.07.2014
doi:10.4028/www.scientific.net/AMM.633-634.972
All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP,
www.ttp.net. (ID: 79.175.1.139-13/09/14,00:22:04)

Table 1. Advantages and disadvantages of wooden, plastic and aluminum windows
Type of
windows
Advantages
Disadvantages
Plastic
windows
 Durability, resistance to all forms of
meteorological influences (especially
important in high humidity);
 Sealed seams and joints;
 Does not require additional finishing
(during the lifetime retain original color);
 High levels of thermal and acoustic
insulation;
 Don’t require special care.
 The need for ventilation or use of
devices for ventilation;
 Relatively high requirements to
qualification of installers of windows
and to the technology of manufacture.
Aluminum
windows
 Almost unlimited durability;
 High strength at low specific weight;
 Resistance to corrosion, distortion and
other environmental hazards;
 No need for special care;
 The ability to produce very large
windows and windows of all forms;
 Wide design possibilities.
 Production of aluminum is a very
energy-intensive and expensive
process;
 Ability of electrochemical reactions;
 High thermal conductivity;
 The need for ventilation or use of
devices for ventilation.
Wooden
windows
 High durability of wood at a small
weight;
 Low heat conductivity and sound
conductivity;
 High frost;
 Environmentally friendly;
 Attractive appearance of natural
materials;
 Maintainability.
 The presence in the wood defects
(cracks etc.);
 Can rot and attacked by
microorganisms;
 Need the periodic care (coloring etc);
 Costliness;
 Relatively high requirements to
qualification of installers of windows
and to the technology of manufacture;
 The need for ventilation or use of
devices for ventilation.
Plastic windows
Numerous advantages of plastic windows (ease of operation and maintenance, noise protection,
heat insulation) always attract potential buyers. However, you must know both the positive and
negative aspects that should be considered before deciding the question of replacing conventional
windows with plastic.
Plastic windows can reduce noise inside the rooms. It is very important if your home or office is
located near the roadway, bustling shopping centers, construction sites. Attractive opportunity is to
install a mosquito net for the summer period, which protect not only from insects, but also from dust
and dirt.
But the main advantage of plastic windows is that in that room where they are installed, it becomes
much warmer and the heat stored long time.
Plastic windows do not cause too much hassle to use, do not require sealing in winter, the annual
coloring and repair, unlike wooden, conveniently washed with any suitable for this purpose detergent.
Disadvantages of plastic windows are also evident. Sealed property of modern windows violate
ventilation inside of rooms, and as a consequence is increased relative humidity. In the cold season on
the surface of the glass appears condensate. On the window slopes and walls can be appears mold.
This not only spoils the look of the room, but also dangerous to health.
The main disadvantage of plastic windows is almost complete lack of fresh air into the apartment
(if they are closed).
Applied Mechanics and Materials Vols. 633-634 973

Wooden windows
The Russian market of high-quality wooden windows began to emerge in the 1990s in parallel with
the market of plastic windows. Economic crisis in 1998 slowed it development, and due to the
increasing popularity of plastic windows in the 2002-2004 the market of wooden windows showed a
negative trend [7].
Active growth in demand for wood windows in Russia resumed in 2005. However, in 2008, under
the influence of the economic crisis, the positive dynamics again changed to negative: during two
years consumption of wooden windows decreased by 53.5% [7]. Nevertheless, now the market of
wood windows gradually increases and experts hope that in the coming years, this growth will be
more prominent.
The main consumers of the Russian market of wooden windows are apartments, townhouses and
cottages of business and premium class. The overwhelming volume of consumption (over 85%) are in
the individual low-rise buildings.
Advantages and disadvantages of wooden windows are presented above (refer with: Table 1).
Consider the advantages and disadvantages of certain types of wood used for the manufacture of
wooden windows (refer with: Table 2).
Table 2. Advantages and disadvantages of certain types of wood used for the manufacture of wooden
windows
Kind of
wood
Advantages
Disadvantages
Pine
 Low heat conductivity;
 Ease of processing and drying;
 Optimal ratio “price - quality”.
 Lower durability compared with larch;
 Use of chemical compounds that prevent
rotting, which negatively affects the
environmental properties.
Larch
 Resistance to any type of biological
impact;
 Increased strength and fire resistance
compared with pine;
 Lower cost compared with windows
made of oak.
 Difficulty in processing;
 Cracking due to rapid drying in direct
sunlight.
Oak
 Resistance to any type of biological
impact;
 High durability (2.5 times higher than
that of a pine).
 Demand careful processing;
 May crack during drying;
 High cost (2 times higher than the
windows of pine).
Ash
 Resistance to any type of biological
impact;
 High hardness (more than oak);
 Flexibility and elasticity.
 May crack during drying;
 High cost compared with windows made
of pine or larch.
Beech
 High durability (beech is one of the
most durable type of wood);
 Ease of sanding (because less dense
than oak);
 Ease of drying, no cracks.
 Chance of fungal infections of
constructions.
Energy-saving plastic windows
Energy-saving plastic windows - are windows that use energy-efficient k-glass (glass paved) or
i-glass (glass with a soft covering). According to its characteristics i-glass surpasses k-glass.
Differences between the i-glass and k-glass are in production technology and the value of the
coefficient of radiating capacity. Using of window units with I-glass allows not only to reduce energy
costs but also significantly improve indoor comfort.
974 Advanced Materials and Processes IV

During the heating season the energy saving effect of the window construction of medium size
with i-glass equivalent burning liquid fuel (fuel oil, diesel oil) with a total weight of up to 300 kg. The
disadvantage of i-glass compared with k-glass is its reduced abrasion resistance. It is the reason of
certain difficulties during transportation. However given the fact that the energy-saving coating of
i-glass is always inside a sealed, this deficiency does not affect the characteristics of i-glass.
Advantages of energy-saving glasses:
 one-chamber glass with i-glass or k-glass has a larger effect of energy saving than
dual-chamber glass with ordinary glasses;
 one-chamber glass with energy-saving glass lighter than dual-chamber on 10 kg/m2 (for glass
thickness 4 mm), which provides a longer service life casement and reduces the load on the
window fittings;
 one-chamber glass with energy-saving glass has more light transmission than dual-chamber
glass with ordinary glasses;
 at mass production the price of one-chamber glasses with energy-saving glass does not differ
from the price of the two-chamber glasses with ordinary glasses.
Resume
In order to improve energy efficiency in new construction, reconstruction, repair and maintenance
of buildings, priority should be given to the newer types of energy-efficient windows. All of that
without warming of exterior walls should allow get lower power consumption (up to 30%) at a high
return on investment [23-25].
For many years in Russia are very popular plastic windows. However, wooden windows are
environmentally safe but less moisture resistant than the plastic window. But unlike plastic, wooden
windows “breathe”, or in another way through the wood occurs breathability. Therefore, even if the
windows are closed tightly air in rooms with wooden windows will be fresher than in rooms with
plastic windows.
Thus the correct choice of windows is one of the most effective ways to increase energy efficiency
in buildings.
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