Why are windows still made of glass?

Which glass for my windows?

Modern windows are expected to have a U-value of at least 1.40 (stipulation of the new OIB guideline 6) or less. Danger! In order to achieve funding, better values ​​are almost always required. It is irrelevant whether this value is achieved with 2- or 3-pane glazing. However, it is essential that the windows remain permanently free of condensate.


One can expect from a passive house window that it is “energy-active” even in the cold season. This means that it lets more energy into the house during the bright hours of sunshine than it gives off again in the dark of the night.

In addition to the U-value (heat transfer coefficient), the G-value is also of interest. It denotes the energy permeability value and measures the energy flow from the outside to the inside in percent. The higher the G-value, the higher the heat gain through the window. Modern thermal insulation glazing has a G-value of about 0.6 to 0.65, which means that 60 to 65% of the solar heat is made available to the room behind it. The following is an overview of the common types of window glass:

Float glass / flat glass

refers to a single disc, the name comes from the manufacturing process. Glass made in the normal process (cast or rolled sheet glass) has fluctuations in the material thickness and must be polished and ground. "Float" glass, on the other hand, is manufactured using a floating process. Use for large discs and thermocouples.

insulating glass

consists of at least two individual panes and a different space between panes. It is not the thickness of the glass but the space between the panes and any gas filling that regulate the U-value, i.e. the thermal insulation capacity.

Triple insulating glass

Prefabricated glazing elements consisting of several panes with layers of air between them. They are connected to one another airtight.

4-fold glazing

Windows with quadruple thin glass technology, which achieve a Ug value of 0.3 W / m2K, are not only ideal for passive houses. In combination with highly heat-insulating wood-aluminum window designs, such windows achieve values ​​of just 0.59 W / m2K.

Soundproof insulating glass

The sound insulation depends on the weight per unit area of ​​the built-in component. The thickness of the outer and inner pane must be different. With heavy gas filling, the sound insulation values ​​can usually be improved by 3 to 5 dB. However, this gas filling hardly improves the U-value.

Sun protection insulating glass

offers a separate sun protection layer, usually inside the glazing element as a vapor-deposited metal layer. Sun protection works through absorption or reflection of the infrared components of sunlight.

Single pane safety glass ESG

Tempering the glass by thermal treatment results in stronger glass. Crumbled into small pieces if broken.

Laminated safety glass VSG

Splinter-binding glass, less risk of injury. Two or more float panes or high-strength glasses placed one above the other are connected by one or more highly elastic foils.

Fire protection glass

can be used in fire resistance class G for the passage of fire and fire gas. Furthermore, as fire protection glass of fire resistance class F (fire-retardant), these glasses must not only be smoke and room tight, but also prevent the source of fire from being transmitted through heat radiation. It needs thermal insulation.