In modern windows, it depends on the edge

For decades, insulating glass windows have ensured a considerable saving of heating energy. With the steadily increasing demands on thermal insulation, these are also optimized down to the last detail.

The construction of a multi-pane insulating glass has its energetic weakness at the edge. In this case, a circumferential spacer ensures the desired interspace space and connects the individual disks to an insulating glass unit. Together with an additional insulation, this frame ensures a permanent seal and thus also prevents the escape of noble gases with which the disc intersperses are filled.

Since the advent of the insulating glass windows until the 1990s, this spacer has mainly been made of aluminum, a material that is light and weather-resistant but also has good heat conduction. As a result, the disk edge cooled down strongly at low outside temperatures and reduced the efficiency of the thermal insulation as a thermal bridge.

Today, stainless steel, plastics, silicone foam and thermoplastic materials are used in the spacer systems. The plastic polypropylene, which is known for its low thermal conductivity, is often used as a base material for the spacer. As a result of these thermal improvements in the insulating glass pane, the inner edge of the room does not cool down so much and is called a “warm edge”.

Warm edge is particularly worthwhile in triple glazing

The effectiveness of a thermal insulation is, of course, always determined by the surface which it insulates. Thus, a three-pane glass is generally 32 millimeters thick and the surface of the edge is one-third larger than a double-glass pane with 24 millimeters. The importance of the warm edge in triple glazing is correspondingly higher.