Technical Information for Glass

  • Miscellaneous
  • • Appearance (when viewed from the exterior): the aesthetic appearance of the glass (colour, intensity, reflection) depends on 4 factors:

    - Orientation of the building
    - Surrounding environment
    - Glare
    - Amount of direct sunlight

    The final choice must be made after viewing samples of the proposed glass types in their intended location.

    The overall performance of a window is dependent on the combined effect of frame and glazing components and the air-tightness of the finished window. Ratings maybe improved by decreasing thermal losses.


    Decreasing thermal losses

    -Type of Low-E glass: with its optimised balance of very low emissivity and high solar gain SGG PLANITHERM can improve the energy index for a given window

    -Inert Gas filling: argon gas filling can improve the energy index for a given window compared to an air filled unit

    -Optimised cavity width: the optimum cavity width for an argon filled unit is 15mm (10mm with krypto)

    -Warm edge spacer: Using SGG SWISSPACER can improve the energy index for a given window compared to standard aluminium spacer bars

    -Triple glazing: can further reduce glazing U values

    -Frame type: U values can be reduced with advanced materials and design

    There have three major considerations when we need choose high advanced energy saving glazing: The light Transmittance (TL), the U- value, and Shading Coefficient (SC). 

    The light transmittance is the ratio of the transmitted light flux to the incident light flux. Usually, the higher TL, the more natural day light.

    Heat transmittance through a surface by conduction, convection and radiation is expressed by its U-value.  Usually, the lower the U- value, the lower the heat loss. 

    The solar factor of glazing is the percentage of the total solar radiant heat energy entering the room.  Usually, the lower the SC, the less solar radiant heat energy entering the room through the glass.


    You may need to choose the glass product according to the local building regulations. Normally in the north region of China, it is cold and severe cold area, then the lower U- Value becomes the most important factor for you when choose the glass. For example, the SGG PLANITHERM is most popular in north regions, with higher Light transmittance, and lowest U-Value=1.16 w/m2.k (with 6+16Ar+6). 

    Or in severe cold area, the triple double glazing unit with low-e coating is also one of the best solution for enery saving.

    In certain circumstances, the colours of some materials, when exposed to direct sunlight, can fade.  Materials can change colour when exposed to solar radiation. The most efficient way of preventing fading is to exclude ultra-violet radiation, since despite its low proportion within the electromagnetic spectrum, it is the main contributory factor to the process.

    UV radiation can be virtually eliminated by the use of PVB laminated glass.  A second option is to use a body-tinted glass, which will filter light selectivety. Thirdly, glass with a low solar factor could be used to reduce the thermal effect of the radiation.

    Solar radiant energy entering a room through the glass is absorbed by interior objects and surfaces, which then retransmit the energy as thermal radiation, mainly in the far infra-red band.  The solar energy entering through the glass is trapped in the room, which then tends to heat up and is referred to as the "greenhouse effect".

    Condensation forms very differently depending on whether it is inside or outside the building, due to the thermal bridge effect around the cavity. Surface condention on the internal face always starts in the corners, mainly due to the additional cooling caused by the thermal bridge. The high performance low-E glass, such as SGG PLANITHERM series, or " warm-edge" spacerbars, made of insulating material, such as SGG SWISSPACER, can effectly reduce the risk of condensation at the corners.

  • Noise control
  • The World Health Organisation(WHO) recommends an ambient noise level of below 35dB for a good night's sleep. The acoustic danger threshld has been set at 90 dB. In excess of 105 dB, irreparable hearing loss may occur. The threshold of acoustic pain has been set at 120 dB. Above this, noise becomes unbearable, leading to extreme pain and hearing loss.

    Noise is blame for:

    -11% of accidents in the workplace;

    -15% of lost working days;

    -20% of psychiatric hospitalisation admissions.


    SGG Stapid Silence is a laminated sound-insulated safety glass. It is composed of two or more layers of glass assembled using one or more films of sound-insulated polyvinylbutyral: sound-insulated PVB or PVB silence.

    The acoustic performance of glazing was improved mainly by increasing the thickness and asymmetry of glass panes in double-glazed units. In certain cases laminated safety glass would behave almost like monolithic glass of the same thickness. On average it is possible to improve performance by 1 to 3 dB compared to glass similar in type or thickness and above all to ensure uniform performance across a broader range of frequencies.

    No, it will however reduce the amount of noise that both enters and leaves your home by approximately 3-4dB over standard double-glazing, which is an audible difference. The noise reduction gained will be dependent upon the quality of your window frames and the type and level of noise you are trying to cut out. Click on the link to listen to our acoustic glass, SGG STADIP SILENCE web module, demonstrating the effectiveness of acoustic glass: 


  • Safety & Security
  • Laminated glass has the same strength as ordinary glass but it consists of two pieces of glass containing a sandwich of plastic interlayer. If the glass does get broken this interlayer holds the whole piece in place so there is no hole left in the window for an intruder to get in through for example or large free shards that can cut.

    It should be used in low level glazing, glazing in and around doors, overhead and in large areas of glazing to prevent injury following accidental glass breakage.

    Toughened glass is upto five times as strong as ordinary glass which means that it has to be hit much harder in order to break, also when it does break it is into lots of small pieces which are much less dangerous. Laminated glass has the same strength as ordinary glass but it consists of two pieces of glass with a sandwich of plastic interlayer. If the glass does get broken this interlayer holds the whole piece in place so there is no hole left in the window for an intruder to get in through for example or large free shards.

  • Solar control
  • Solar control glass is typically used to prevent excess heat build up in areas where large amounts of glass are used. For example glass roofs, south-facing elevations. The choice of product is then dependent on the level of performance and appearance requirements, e.g. very reflective, coloured , neutral etc.

    The solar factor (or g-value) measures the percentage of heat that passes through the glass. The lower the solar factor the higher the solar protection and therefore the higher the performance of the solar control glass.

    A solar control glass is a glass with a special coating designed to reduce the amount of heat entering a building. It reflects and absorbs heat as well as filtering light for reduced glare.Using a solar control glass can reduce the need for air-conditioning and blinds. There are many types of solar control glass offering different aesthetic options; tinted, reflective and neutral.

    There are three major considerations regarding solar control glazing:

    - the reduction of solar energy heat gain to achieve the lowest possible solar factor

    -the control of heat transfer from the outside to the interior by means of the lowest U-value possible

    -to achieve a good level of natural daylight through the highest light transmittance value possible

    Saint Gobain Glass offers a comprehensive range of solar control glasses, providing varying performance and appearance options for individual applications.

  • Thermal insulation
  • Government Building Regulations require us to save energy, to help protect the environment. Using low-E glass is the most efficient way of doing this with glazing. This also provides benefits to you as a property owner as money can be saved on heating bills as heat loss is reduced by a massive 75% compared to single glazing and at least 40% compared to traditional double glazing. Rooms are also more comfortable as cold spots near windows and drafts are reduced. Finally unsightly condensation on the inside of the glass is reduced beacuse the temperature of the interior pane is kept closer to room temperature.

    Low-E is designed to reflect heat back into a room, therforere reducing heat loss. By using a low-E glass in your windows your home will be better insulated, thus reducing your requirement for additonal heating.

    Due to the enhanced thermal properties of a double-glazed unit comprising a low-E glass, the outer pane of glass does not get warmed by heat escaping from inside the building through the glass. This results in the outer pane being kept cooler in comparison to a less thermally efficient insulating unit. Certain climatic conditions or high humidity levels, without rain can lead to the formation of condensation on the external surface of the outer pane. It is also possible that due to shelter from nearby trees or buildings, external condensation will appear on some windows but not others. This phenomenon is due to localised atmospheric conditions and is in no way an indication of a defective unit. Indeed this can be seen as a positive indication of performance.

    Ideally SGG PLANITHERM should always be positioned on face 3 of the double-glazed unit. However, if necessary it can be positioned on face 2 as long as it is facing the cavity and thus protected from the external atmosphere.

    A low-E glass is a glass with a special coating designed to reflect heat back into the room, thus reducing heat loss. The extent to which low-E glass reduces heat loss is measured by the U-value, the lower the U-value the better the thermal insulation. You are required to have a low-E glass in your windows to comply with the latest Building Regulations. These new regulations have been introduced to reduce CO2 emissions associated with heating.