3k glass

Insulating glass (also known as thermal glass, bay window, 2k glass, 3k glass, selective glass in insulating glass…)
Insulating glass (thermal glass) is usually 2 or 3 panes (2k glass 3k glass). An insulating glass element is made by joining 2 or 3 panes of glass together to form a hermetically sealed element. There is usually an aluminium spacer between the panes, which separates the panes at a certain distance from each other. Insulating glass usually also has a selective glass and argon gas to improve the U-value.

If you are buying a new insulating glass to replace an old one, we recommend that you remove the window sills and measure the exact dimensions of the insulating glass, as well as the total thickness of the insulating glass.
Thermal insulation value (U-value)
The number of layers of glass, the width of the space between the panes and the type of glass affect the U-value of the insulating glass. The lower the U-value (watts/square metre*temperature difference inside vs outside in Kelvin), the less heat is transmitted through the glass. For example, by selecting selective glass (Glass Thicknesses menu) and argon gas for the glass, the U-value is lowered.

You can see the U-value of the selected glass in the additional information below the glass options.
What is selective glass?
Selective glass is normal glass coated with a very thin, and nowadays almost colourless, metallic alloy. This metal alloy reflects the heat radiation from the inside back into the room, but allows the slightly different wavelengths of solar heat radiation from the window to penetrate well inside. The coating of the selective glass is always turned inside the insulating glass, thus protecting the coating. Modern selective coatings are virtually colourless and do little to change the colour of the insulating glass. Almost all new insulating glass has selective glass and argon gas between the panes.

All insulating glass can also be tempered:

If you want more security, you can select the tempering of the glass from the menu above. After tempering, the glass is about 3-5 times more durable than untempered glass (excluding the edge of the glass), and when broken, tempered glass shatters into small “vacuum cleanable” crumbs, so there is little risk of cutting if the glass breaks. Tempered glass is also more resistant to temperature differences in different parts of the glass (200 kelvin difference inside the glass, maximum operating temperature 300C – untempered 40 kelvin). By selecting tempering, all 2 or 3 panes of the insulating glass are tempered. (Note! Insulating glass maximum operating temperature +65C, the mass may start to break down at higher temperatures)

Laminated glass can also be used in insulating glass to increase safety:

Laminated glass usually has two panes of glass bonded together with a PVB or EVA laminating film. If the glass breaks, the membranes still hold the two panes together, which means that laminated glass rarely causes an accident if it breaks. This is why laminated glass is classified as safety glass. The maximum operating temperature for laminated glass is +90C. (Note! Insulating glass maximum operating temperature +65C, the mass may start to break down at higher temperatures)


Applications include: windows and doors in buildings, thermal insulation of terraces, etc.

In all glass construction, take into account building regulations and their requirements for the durability of glass. Also remember to take into account the dimensions of the glass to allow for sufficient clearance. For insulating glass, the black mass area of the glass must be protected from the sun’s UV rays (usually the black edge area of the glass is covered by e.g. fixing strips). The black mass area is about 8-13mm wide, depending on the type and size of the glass.

You can also calculate the weight of the glass by entering the glass data in the fields. The glass weight calculator does not take into account the reduction in mass due to the shape of the glass, but always calculates the weight of the glass in the rectangular area. The glass weight counter is indicative. The weight of the glass can vary between different production batches due to the thickness tolerance of the glass.

If you have any questions, don’t hesitate to contact us – we’re happy to help!

In all glass construction, take into account building regulations and their requirements for the load/durability of glass.

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