View From Within: Glazing

Glass is a modern and convenient material for the construction and furnishing of premises. Modern technologies allow for the creation of complex and strong designs. Glass facades today carry out the role of insulation, ventilation systems, protection from noise, wind and even fire. Alexander Skvortsov, head of the group of companies AGC Flat Glass Russia, explains the popularity of recent architectural trends among developers: the borders between the "private world" of a building and the environment are erased, the simple and concise external shape of the building is more welcoming. In the opinion of Alexei Lyashko, head of the department of material-technological support of STiS group, the increased requirements in the construction of buildings were an incitement for the development of new directions in the glass industry, such as glass with coverings, hardened and safety glass.

According to Skvortsov, glass designs should meet to two main requirements - multifunctionality and safety. Glass should keep in the heat in winter and protect the internal premises from overheating in summer. It is also important that it protects from traumas and in case of fires, limits thermal radiation.

Spiders for glass

Clear glass facade systems vary in design. There are two main schemes: one with the use of metal structures and the fixture of glass on the perimeter and one with spatial constructions and separate glass fastenings. Aluminium and steel may be used with both designs. The first is used mainly in profile systems, and the second in spatial. The classical system - so-called nogging – is most widely used. Such a facade looks like a glass surface divided by horizontal and vertical lines of decorative covers.

Another popular technology is the structural system of glazing which started to be used in the 1960s. It has the same metal skeleton, but the only difference is in the way the glass is installed using silicone sealant. Due to the complete absence of visible exterior fixing elements you get a continuous glass wall. The lifetime of such facades is not limited because the glass and silicone sealant are in contact with the aggressive environment. The structural system can also be used for roof glazing.

The top evolution of glass has become cartridge façade systems. Theses are as simple and economical as they are technological. A nogging frame rack is filled with factory-made cartridges. Although the block system is 30-40% more expensive than rack nogging, it has significant advantages in terms of installation as ready blocks are simply secured. There are no complex assembly works that require high qualifications and a lot of management. Plus the speed of installation is 3-4 times quicker. Moreover, high quality of the façade is guaranteed, which is difficult to achieve with the construction of skyscrapers.

As an alternative way of glazing facades in the second half of the twentieth century more complex systems with spatially developed frames started developing. Modern materials and the newest design procedures are used. These systems got their name from the English word “planar.” The planar glazing system involves the joining of glass panels (unary glass or double-glazed windows), which are fixed with special spider-connecters ("spiders").

The scope for their use is quite wide: walls, roofs, porches, the protective surroundings of a building, double facades, etc. Designs vary from simple partitions to intricate interlacings of beams, cores, guys, etc. Such glazing allows to create as transparent designs as possible. Planar glazing allows to air the premises at any time of the year and protect the main facade of the building from the external environment. But such glazing demands high quality work at all stages, from the manufacturing of the glass to installation and finishing operations, which for Russia can appear an absolute obstacle.

A real problem for glassed premises is overheating. In the 1970s a system of ventilated facades was developed to regulate a microclimate - from the premises along the main facade an additional glass wall is established.

The interglass space is included in the ventilation system of the premises, thus there is an exchange of air layers. If you add to that effective sun protection from infrared beams, comfort will be provided all year round.

In the 1980s the Double Skin system was developed in Germany. These facades have all the advantages of ventilated facades to create a favorable microclimate with the necessary light exposure, temperature and humidity modes, movement of air, etc. When correctly designed, they relieve the necessity to use traditional systems of heating, ventilation and air-conditioning. Unlike previous systems the glass screen is located on the outside and carries out the functions of a weather protection cover.

In the gap between the two facades the air circulates horizontally due to the difference in temperatures and vertically due to the difference in pressure. And the building cools naturally. This system is also effective, for example, on busy highways or in places where there is strong wind.

What’s underneath?

As a foundation for transparent designs (facades, show-windows, doors, winter gardens, light lanterns, stairs and floors) stainless steel is used. Such designs are capable of maintaining high static loadings (2.8 times more than the same made from aluminium). Accordingly, there is the opportunity to create a greater distance, to increase the isolation of a premises, and install large-sized windows and doors. Steel profile systems possess low heat conductivity and therefore they can be used in complex climate conditions. Temperature expansion of a steel structure is approximately 2 times less than aluminium, which allows to reduce the assembly gap.

The wide use of aluminium is explained by the fact that it is a light, strong and non-corrosive material, does not contain the impurities of heavy metals, does not emit harmful substances under ultra-violet rays and keeps maintains its operating capacity in any climatic conditions and temperatures from -80 °С to +100 °С. After processing the surface of aluminium products they become protected against harmful influences caused by rain, snow, and also smog. The majority of "cold" and "warm" frontal profile systems are made from aluminium. The structures, as a rule, are made from three-componential alloy: aluminium, magnesium, silicon. However aluminium is undesirable for use in harsh climatic conditions due to its higher heat conductivity in comparison with steel structures.

To keep the heat

A lack of glass panels results in low heat insulation. The active loss of heat through a window is caused by the heat conductivity of a material, convection (moving of microscopic particles of the environment - gas, liquid - that carry the weight or heat) and infrared radiation. To reduce the loss of energy caused by infrared radiation, when glazing buildings energy saving glass Planibel TopN+, a special transparent covering consisting of several layers of oxides of metals, is used on one side of the glass.

Also to help reduce heat loss a single-chamber double-glazed window with special energy saving covering is used. In comparison with the usual two-chamber double-glazed windows it improves energy saving and keeps heat in a premises provided it is (the distance between glass in a double-glazed window) no less than 15 mm from the framework.

The weight of a double-glazed window decreases due to the use of two, instead of three glass sheets and the weight of the whole structure, accordingly, decreases. As a result: there is less material consumption and the service life is longer. According to Skvortsov, the total cost of a single-chamber design with the use of energy saving glass is several times cheaper than the traditional glazing system. In the central part of Russia where the temperature in the winter usually does not fall below -30 °С, it is enough to install a single-chamber double-glazed window with energy saving glass, and will be cheaper than the usual two-chamber. At a building site in Siberia the two-chamber design with energy saving glass will save money on electricity. Such glass works by the principle of a thermos, keeping the warm indoors. It is important that the energy saving glass does not make contact with the environment otherwise, due to high humidity, corrosion of the covering will begin. Therefore Planibel TopN+ should always be installed with the covering on the inside of the chamber of a double-glazed window. During installation of the glass it is necessary to protect it from cement dust, rusty smudges and spots from welding or grinding works.

Energy saving glass is used in the construction of both residential buildings, and commercial real estate premises. For example, the single-chamber double-glazed window with energy saving glass is used in the facades of Moscow-City, Di Fronte de la Casa office complex on Bolshaya Gruzinskaya, Dukat-3 business center, IKEA, etc. Energy saving glass is also used for premises in which there are a lot of plants: show-windows of flower shops, winter gardens, greenhouses, etc.

An alternative to energy saving glass in some cases may be low emission sheets, which is applied to cover the glass. For example, if it is impossible to replace window systems in a large industrial complex, then the glass is covered with a thin metal layer. The most suitable materials are gold, silver and aluminium.

Low emission sheets reflect 20% - 70 % of the heat in a premises. They make glass safe (if a window smashes there will be no shards), stop the leak of information from a premises by optical, electron-optical and radio-frequency channels and protect people from the influence of external electromagnetic fields created by powerful radio and tele-transferring devices. However, the sheets may exfoliate and are not absolutely transparent.

Fragile protection

The glazing of frontal facades of modern shopping centers and airports have high requirements in regards to sun protection, energy saving and sound insulation. Moreover, it is important to achieve the absence of optical distortions, to protect the building from illegal penetrations and provide complete safety for people who are both inside, and outside. For example, to achieve a high degree of sun protection, energy saving and sound insulation, in the internal glazing of an office center on Bolshaya Gruzinskaya Startobel TopN multi-layered low emission glass possessing high characteristics on energy saving and resistance to heat transfer, was used. Stoposol Supersilver Clear sun-protection glass with a reflective covering was also used.

For good safety of people a multi-layered glass is ideal: its sheets are divided among themselves by one or several layers. At impact such glass does not smash into shards, but remain in the aperture.

To solve the problem of optical distortion the use of external multi-layered glass helps. "In stained-glass windows of many office buildings trees and clouds are reflected in a deformed view,” says Sezgin Sipakhi, project manager of Rasen Construction. “"Creased" facades have been a signature of Moscow for a long time. The use of multi-layered glass avoids optical distortions which usually arise after thermal processing."

A special type of fireproof glass is used inside buildings. At temperatures of nearly 120 °С intermediate layers of polymer start to extend and grow turbid. Glass becomes rigid and a non-transparent shield constrains the distribution of fire. Fireproof glass has limits of fire resistance - from 15 to 120 minutes. For external glazing such material can be used with a special sheet for protection against ultraviolet rays (an ultra-violet filter). The glass can withstand temperatures of up to 1,000 °С. Choosing the limit of fire resistance is defined by the requirements of regulative documents. These days the most demanded are those with a fire resistance limit of 45 minutes. According to statistics, modern buildings burn out in 40 minutes and it is pointless installing protective elements that withstand fire longer than the building. Moreover, the more fire resistant the glass, the higher the cost price of construction.

Fireproof glass possesses high heat insulation, avoiding the danger of ignition of combustible materials. Its use also helps to avoid evacuation panic as people do not see the flames or feel the heat. Such glass is used at schools, hospitals, hotels, restaurants, shops, shopping centers, airports, etc.

According to European standards fireproof glass should be transparent and not cause optical distortions. The main advantage of this design, from the point of view of aesthetics, is look of "air". Glass in such designs can reach the sizes of 1.4 х 2.7m with a minimal thickness metal frame. It is also quick to use in construction.

How the light was caught

In 2005, employee of AGC Flat Glass Europe Hugh Lefevre had an idea to place light-emitting diodes inside the laminated glass. Development of the project took two years but the result was worth it: glass as a usual material has turned into the main ornament of an interior or facade of a building. The design at first sight is simple: light-emitting diodes are located inside multi-layered glass. The main layer, the so-called leading layer, is the source of power supplies for the light-emitting diodes. On the edges of the glass a conductor with current is delivered. As a result it is possible to avoid electricity cables in the glass. A power supply of 24 watts is sufficient for the light-emitting diode to work, but if necessary it is possible to increase it up to 100 W. As a result the light will be bright. For example, goods placed on show windows made of such material do not require illumination to draw the attention of buyers.

Not only monochrome light-emitting diodes are used, but also multi-coloured ones, capable of changing shades. But developers of the technology have not yet learned how to operate separate light-emitting diodes. To switch the lights on and off and to change their color is only possible on the panel. The service life of any light-emitting diode glass product is more than 50,000 hours, i.e. if it is continuously working for 8 hours per day it will not need replacing for 17 years.

The use of such glass for facades in housing, office buildings or industrial enterprises opens up new unlimited possibilities for the construction business. During the day Glassiled, transparent glass, allows for natural light to pass through a building. And at night it turns into a dynamic source of artificial light, drawing attention and inhaling life into the city’s look.