Expert knowledge

Insulating glazing

Insulating glazing is the short term for multi-pane insulating glass. It refers to a complex glazing unit in which a hermetically sealed interior is created between at least two panes of glass, the so-called space between the panes (SDR) or air space (LZR). This is usually 8 to 16mm wide. The panes themselves are only held together by the edge seal. Insulating glazing is to be regarded as an independent system. A circumferential frame is not absolutely necessary.

Image: Double insulating glazing (simplified) - baukobox

More about insulating glazing Insulating glazing

can be produced with different numbers of glass panes. Depending on the number, they are divided into 2-fold and 3-fold insulating glazing. Triple insulating glazing is becoming increasingly popular due to ever higher energy-saving regulations.

Depending on the requirements for certain properties such as static requirements, float glass, heat-strengthened glass (TVG), toughened safety glass (ESG) or laminated and laminated safety glass (VSG ☛) made of ESG can be used for the production of insulating glazing as panes laminated safety glass (LSG).

Air is a poor conductor of heat. Insulating glazing takes advantage of this property by creating a thermal insulating layer in the air space enclosed between the panes. Energy loss is thus significantly reduced compared to single glazing. Since the room-side pane has no direct contact with the outside air, it does not cool down as much and thus reduces the lowering of the room temperature.

The panes of insulating glazing are only held together by the edge bond. This has the task of permanently connecting the panes and forming a vapour-tight barrier. Post-diffusion of water vapour into the space between the panes must be prevented over the entire service life. Deformations of the glass must be elastically compensated for by the edge seal. It must be resistant to chemical influences and UV radiation. The spacer filled with a desiccant determines the width of the space between the panes. It is glued with polyisobutylene. This bonding prevents the diffusion of water vapor and gas. The spacer itself is usually made of aluminium, galvanised steel, stainless steel or various plastic composite mixtures. The cavity outside the spacer is filled to the edge of the pane with a secondary sealant made of polysulfide, polyurethane, a silicone base, hot melt or a hot melt adhesive. The secondary sealant connects the panes and hermetically seals the space between the panes.

Different coatings are recommended for the different areas of insulating glazing, or different coatings are possible. The following position designations are used for this purpose:

  • Position 1: Outside of the window
  • Position
  • 2: Inside of the outer window (facing the SDR
  • ) Position 3: Outside of the inner window (facing the SDR)
  • Position 4: Inside of the window Positions

1 and 2:

  • Sun protection coatings (reflecting solar radiation)

Position 3:

  • Thermal insulation coatings
  • Solar control coatings
Notes on planning

Heat transfer coefficient (U-value) Insulating glazing: < 1.0 W/(m²K) // Comparison Single glazing: approx. 4.8 W/(m²K)

Heat transfer coefficient (U-value) Triple insulating glazing, coated: 0.5 W/(m²K)

The minimum value of the thermal resistance is achieved at a pane distance of 15 mm.

The U-value of an insulating glazing depends on various factors: size,

space
  • between the panes
  • ,
  • type of filling gas,
  • coating
  • , but also: installation situation! (The values given by the manufacturers usually refer to vertical installation.)

Depending on the outside temperature and pressure, a pressure difference to the outside atmosphere is generated in the hermetically sealed space between the panes and the insulating glazing curves outwards or compresses inwards. This effect and the difference in height must be taken into account as a separate load case for insulating glass. Special conditions such as internal sun protection and unheated buildings due to possible surcharges and discounts must also be taken into account.

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