Insulating glazing: deformations and stresses

If certain rules are not observed, the deformations and stresses in the components of an insulating glass unit caused by natural stresses can adversely affect the normal life expectancy of the unit, which is to be expected of a quality product.

To assess these deformations and stresses, we need to know about the environment in which the glazing is manufactured, installed and even transported: ambient temperature, sunlight, atmospheric pressure (difference in altitude between manufacturing and installation sites).

In all cases, we take into account the most demanding parameters that the glazing is likely to encounter over the course of its life.

The calculation method consists of successively calculating: the environmental conditions of the glazing, the spectrophotometric characteristics of the glass, the temperatures of the glass and the gas spaces, the pressures outside and inside the insulating glass unit, and the internal pressures in the gas spaces. We then deduce the deflections and stresses in the glass and the reactions in the joints.

This method applies to factory-sealed double- and triple-glazed units for use in vertical or sloped windows and light facade elements.

It does not apply to insulating glass units (IGUs) manufactured on site, or to "breathable" glazing units for which a communication device enables the pressures of the gas blades to be balanced with external ambient pressures.

The results of the calculations presented here can be compared with the quality criteria imposed by the standards and certification bodies whose aim is to guarantee the durability of these products.

Properly installed, insulating glass units are covered by a ten-year warranty provided by most manufacturers. In practice, life expectancy can exceed thirty years.