Insulated glazing

Insulating glass (MIG ), also referred to as thermal insulation glazing or double glazing, is a composite of at least two panes of glass component for windows and other glazing. There is a cavity that is air sealed and the insulation is used between the panes. Precursors were the double glazing without exclusion of air, the composite window and double glazing the casement windows single or winter window.

In the first decades, since the rise of insulating glass ( 1950s to 1970s) the thermopane brand in the German -speaking area had a large spread. The name thus became - now faded - a synonym for double glazing. As a Product, the terms of climate protection glass or heat-insulated glass may be used.

From 1950 to 1978 dominated by single glazed windows as well as box - and composite windows with two single panes. Permitted by law, the use of single glazing for residential buildings until 1978. As a result of the thermal insulation regulation ( WSchVO ) came in 1978 reinforced insulation glass windows on the market. ( Two-disc ) glazing was typically installed in the period 1975 to 1994. As of 1995, then the coated thermal insulation glass prevailed (Low -E) and windows with triple insulation glazing are since 2005, with particularly strong growth in share since 2009, used ( 2 Low - E coatings ).

Terms like sun protection glass, privacy glass, burglar resistant glass or soundproof glass, thermo windows typically refers to a multi-pane insulating glass with special additional features (even if a single flat glass construction, this may also have.

Mode of action and structure

The glazing is in contrast to other heat-insulating glazing types a standalone system, which has a surrounding frame for functioning - usually a window sash - not required. This is achieved by means of a edge seal, which holds together the individual glass plates at a distance and at the same time seals the space between the panes sealed. In the space between the panes is since many years, not air, but usually the better insulating Argon gas.

To minimize the thermal conduction of an insulating glass pane, of the disc space can be enlarged. However, since gas transfer with increasing volume amounts of heat not only by conduction ( conduction ), but also by airflow ( convection), the thermal insulation is at a certain distance between discs by the trapped gas worse again. In order to prevent this, a further (third) glass panel built into the insulating glass.

Insulating glass has - how many transparent components - the greenhouse effect. Glass panes are more permeable than the emitted thermal radiation from the interior of the room for the incoming solar radiation. The permeability to heat radiation decreases with the number of glass panes and can be further reduced by an evaporated metal layer each glass pane. The achieved positive effect deteriorates at the same time the potential solar heat gain something, as this also decreases the energy transmittance (g- value ). Depending on the heat transfer coefficient (U - value ), the energy transmittance (g- value ) to the solar radiation available ( radiation gain coefficient) of the total heat loss can be calculated with a formula. It is usually at a low sun position, a higher g value (and have a slightly poorer and hence higher U-value ) is better. With a small range of winter sun, the importance of the U- value is far higher than that of the g - value.

The heat losses of an insulating glass pane are determined mainly by the following factors:

• The number and thickness of the gas layer and the type of gas.
• Number of layers of glass and the coating of the glass sheets in order to reduce the losses due to heat radiation (the thickness of the glass sheets has no effect )
• Thermal conductivity of the edge seal and the glass retaining strips. ( Mounting situation at the wafer edge; see below)
• Inclination angle of the insulating glass pane.
• Solar radiation available ( south or north exposure, degree of shading, sunshine hours in the heating season )

Gas filling

In the space between the individual disks - the disk space ( SDRs) - there used to dry air, for years almost only about 10 % better thermal insulation noble gas argon or krypton rarely much more expensive. Krypton with the minimum of heat conduction is only slightly lower, but is achieved at a significantly lower distance plate - an advantage especially when more than one gas layer. Previously (SF6 ) was filled with sound insulation glazing sulfur hexafluoride. It is no longer used due to the very high global warming potential, so that other methods - such as the use of laminated glass - are used.

The gas pressure in the cavity corresponds to the pressure during the production of the insulating glass pane. The height difference between the production site and location may - depending on the disk size - certain values ​​do not exceed, as otherwise there will be an undue burden on the edge seal or even the glass panes. When installing places more than 1000 meters above sea level, special precautions must be taken. One possibility is the subsequent sealing of the disc space at the installation site.

Changes in the gas pressure in the cavity may also result in changes in temperature. The larger the disc space, the smaller the disk formats, and the stiffer ( thicker) the individual panes of glass, the greater the risk that the load on the edge seal reduces its service life. One speaks here of air conditioning load, which can be calculated in specific detection methods. This concerns in particular the triple glazing, because the sum of the disc spaces ( SDR ) is decisive for the air conditioning load. For a standard triple glazing ( SDR = 2 × 12 mm) are considered below 600 mm in the literature as problematic edge lengths. In a SDR of 2 × 18 mm, the minimum length would be already at 900 mm.

Edge seal

The edge seal has the task to hold the glass at a distance mechanically and to prevent gas filling escapes and penetrate instead of their ambient air and humidity.

At the beginning of the technical development of the dual - insulating glass is soldered type a metallic spacer between the two panes. Another method has been to fuse the glass edge and crimping at the same time to weld in this manner, the individual glass panes. Welded these glasses were known under the brand names Gado and Sedo.

For decades, a 1959 developed by Alfred Arnold in two stages glued edge joint is common. A 10 to 20 mm wide profile aluminum, stainless steel or plastic - the spacer - is coated on both sides with a sticky layer of butyl rubber. It combines the slices after heavy pressing together and represents at the same time the first seal level dar. After filling the space between the panes with gas, the gap between the periphery of the spacer and the projecting glass edge is provided with a second permanent elastic sealing layer of polyurethane or special polysulfides. With facade elements that are exposed at this point, UV light, silicon is used, which is, however, permeable to gas.

The edge seal ensures the efficiency of the insulating glass pane only for a certain period of time, since the diffusion of gases through a bonded edge seal is not completely avoidable. As a result, the thermal insulation value continuously degraded by the filling gas escaping - the default is a maximum of one percent loss of gas per year - and ambient air humidity and a penetrate. In the literature, a service life of 20 to 30 years is known. Thus, the penetration of moisture is not obtained as a condensation between the panes, in the spacer, a desiccant material from the family of silica gels or molecular sieves (zeolites) is introduced. When the drying agent has been consumed, fogging the inner surface of the disc. This is called "blind plate ".

The edge seal deteriorate the insulation of an insulated plate. The heat transfer coefficient ( g = glazing ) in insulating glass Ug - value as specified, and does not consider the effects of the edge seal. A dual pane glazing of 1 m × 1 m with a conventional aluminum spacer (Psi - value: 0.068 W / m • K) and would have a U-value of 1.2 W/m2K with the inclusion of the effect of the edge seal a U- value by: (1 m2 × 1.2 m × 0.068 W/m2K 4 W / m • K ) / 1 m2 = 1.5 W/m2K

The impairment of the thermal insulation value at the wafer edge leads at low outdoor temperatures even for attack of water condensate on the inner edge of the disk space. ( Since older window units often have a high permeability of joints, the condensate is dried by invading cold air and is not noticeable. ) The use of a thermally improved edge seal - the Warm Edge with Psi- values ​​of 0.03 W / m • K to 0, 05 W / m • K - enters the condensate depending on the Psi value and room humidity on only at lower outdoor temperatures.

Wavelength selective coating ("Low - E")

Body handed over radiation in the infrared heat energy. This is known as emissivity. Many polished metals exhibit a significantly lower emissivity than glass. The low-E coating ( low emissivity from the English word ) is applied to glass, thin metal or metal oxide layer to decrease the emissivity. The coated glass is also called low-E glass or glass - LE. In the thermos glass, this effect is used for a long time. The coating of Low-E glass has to be very consistent for the incoming solar radiation, resulting in a high total energy transmittance and no shifts of the visible light spectrum as with some sunglasses results.

The principle of most by sputtering or pyrolytic coating ( with higher demands on the mechanical strength ) the applied low-emissivity coating is not bonded to the insulating glass pane. The U-value is reduced even with a single glazing. Wherein the insulating low-E coating is typically applied on the room side to the disc space between the panes through. The type of coating among others the total solar energy transmittance, the light transmittance LT (percentage of the continuous radiation range of 380-780 nm), the light reflectance ( percentage of externally reflected radiation range of 380-780 nm), the UV transmittance (percentage affected portion of the continuous radiation range of 280-380 nm ) and color rendering index Ra. One can thus produce functional glasses such as solar control glass or mirrored glass.

The metal coating attenuates as a side effect radio waves. In the frequency range of modern mobile phones have an attenuation of up to 30 dB is reached; corresponding to a shielding of up to 99.9 %.

Variants

For many years, there is next to conventional insulating glass also special versions, such as sound insulation, sun protection or insulating safety. The technical difference between these and the common insulation is primarily in the respective building: Through specially coated glasses and different gas fillings can be significant advantages, for example in terms of sound insulation, achieve.

Glazing

As a rule, insulating glass is installed in a frame so that the disc touches the supporting frame at any point directly and through glazing blocks, a minimum distance ( " glass air " ) of 5 mm between the edge of the insulating glass pane and the frame ( Glasfalzgrund ) is complied with. The Glasfalzgrund is to ventilate the outside air consistently to permit a steam pressure equalization, and to derive penetrating leachate. In Germany, the most important standards for the installation of insulating glass panes, DIN 18545 and DIN 18361. An obligation to comply with these standards is not.

If glazing installed in a glass facade and the disc glued joints throughout with a sealant, this is referred to as structural glazing.

Significant glazing systems to IG:

View

State of the art (2012 ) have triple glazing with a U-value of about 0.6 W / m² K to 0.8 W / m² K and thermally improved edge seal ( warm edge ). Maximum possible is currently a Ug value of 0.4 W / m² K, in which case the energy transfer ratio is low and the question of cost is also in the room. [ Rough rule of thumb: A reduction of the U- value of 0.1 W / m² K saves approximately 1.1 liters of heating oil per square meter and heating season, if the heating degree is 3600 (average Germany for existing buildings ) and the oil heater has 75 % efficiency ]

Possible further developments - some already available - for example, thinner inner plates for weight reduction ( a standard triple glazing with 4 mm glass weighs 30 kg / m² ), integrated photovoltaic elements, or electrically variable light and radiation transmittance ( smart glass). At the edge seal development goes to the all-plastic system that facilitates fully automatic manufacture of insulating glass.

The thermo-technical progress of insulating change the design of windows. True ( glass dividing ) sprouts and other small-scale division into several glass panels are increasingly problematic, as the poorer thermal insulation values ​​at the wafer edge (Psi - value ) the more carry weight, the better the thermal insulation values ​​( U-value) are the discs. Reducing air conditioning load, the service life ( see above), resulting in the triple glazing particularly for relatively large-sized disks. Thus, when the window Uf values ​​(f = frame ) of the frame with the Ug values ​​of the glass to keep pace, the overall depth (thickness ) was increased significantly the frame and additionally heat-insulating inserts are inserted into the chambers of the frame material. In this way, Uf values ​​between 0.9 W / m K and 1.2 W / m² K can be achieved.

Vacuum - insulated glass (VIG ) was first established in 1989 in the University of Sydney. 1996 Nippon Sheet Glass began under the brand name Spacia commercial production. Currently (2013 ) strikes a Ug value of 0.7 W / m² K. In about 0.2 mm wide space between the panes ( SDR ) many small legs are fitted grid pattern to stabilize against the external pressure. In one corner of the pane is a visible evacuation valve. The seal at the wafer edge by means of a soldered metal strip. The resulting relatively poor insulation at the wafer edge ( = high Psi- value ) represents a significant thermal bridge and favors the accumulation of condensation on the edges. So far, these discs are mostly used for special applications, for example in listed windows where often there is no space available for standard insulation available. A commercial production in Europe is not known until today ( 2013).

Quality Assurance

The Quality Association for insulating glass eV ( GMI eV ) headquartered in Troisdorf is a quality community in terms of the principles of quality mark RAL German Institute for Quality Assurance and Certification eV ( RAL eV ). The association has no political agenda and has no commercial business. All officers shall perform their activities in an honorary capacity.

The quality assurance of the RAL Quality Assurance Association provides additional about the product standard DIN EN 1279 additional demands on the insulating glass as well as on the quality and characteristics of the precursors. This is to improve the usability and durability of insulating glass. In addition, ensure narrow tolerances of the radiation- physical properties, the emissivity and the Gasfüllgrads reliable function values ​​that are regularly reviewed by an independent monitoring body. The applicable quality and test for obtaining the RAL quality mark Insulating glass units (RAL -GZ 520) were published by RAL German Institute for Quality Assurance and Certification in June 2008.

The association, which includes more than 100 companies in the glass industry has to secure the purpose of the quality of insulating glass (MIG ) and to give the insulating glass quality mark for insulating glass. In addition, the GMI has a duty to ensure that quality mark comply with the Articles of Association. It requires the user to only those products whose quality is guaranteed to identify and acts out that brand awareness and reputation of the quality label be strengthened in public.

Prerequisite for carrying the quality label by the manufacturer of insulating glass is a particular third-party monitoring of its production by an independent test institute.