Insulating glass, also known as double glazing, multiple glazing, or Climalit (trademark), consists of two or more glass sheets separated by a space that prevents any contact between the glass.
The inner space between the glass sheets is usually filled with dry air or other inert gas, but it is also possible to form a vacuum, thus improving their performance. In any case, the spaces are hermetically sealed to prevent air flow and the entry of pollutants.
There are also insulating glasses with special 'very low emissivity' treatments, a transparent metal coating on the inner surface, which provides 50% more insulation than conventional double glazing.
Insulating glass can be combined with other solar control functions, low emissivity, etc.
Insulating glass properties.
If there is a positive aspect to double glazing compared to other glass models, it is the possibility of creating customised glass according to the performance required. Therefore, this type of glass can incorporate heat, acoustic and safety insulation features.
For example: a product with highly beneficial features can be achieved by combining an insulating glass with a low-emissivity and solar control glass all in the same panel, even adding a laminate or acoustic laminate.
In addition, thanks to its space this glass offers very low thermal transmittance and therefore great thermal insulation, which will provide air conditioning savings of over 50%.
Finally, it must be noted that the gas contained in the space will also greatly influence the properties of the glass.
For example: the main objective of the SF6 is to improve the acoustic insulation by reducing approximately 3 dB. Argon, on the other hand, has a low heat conductivity, lower than that of air, which provides greater thermal insulation (reduction of the U value by more than 0.3 W/m²). On occasions, a mixture of two of these gasses is used to achieve specific properties.
Chamber size and energy transmittance.
The thermal transmittance (U-value) in a glass sheet has an inverse relationship to its thickness. The higher the interlayer profile (and therefore the greater the distance between the glass sheets), the lower the radiation transmission (the U-value decreases).
Please note: in spaces greater than 15-18 mm, the air currents created inside them increase energy transmission, so the generic rule referred to here does not apply.