September 12th, 2021. The durability of the edge seal is decisive for the service life of an insulating glass unit. This is not only a question of how carefully the components of the edge bond (spacer, desiccant, primary and secondary sealant) are processed in the manufacture of the insulating glass. The quality and suitability of the materials used also play a critical role.

The requirements for spacers are diverse and demanding: The profiles must be UV and temperature resistant, withstand the mechanical loads of insulating glass such as climatic and wind loads, be compatible with the other materials of the edge seal and offer a suitable adhesion surface for primary and secondary sealants. Above all, however, together with the primary sealant (butyl) the spacer must form a continuous sealing level from glass to glass all around the unit, because the inert gas filling enclosed in the space between the panes should not be lost over time. In addition, no water vapor must penetrate through the edge seal, otherwise the unit would become “blind”.

Apart from a type test according to EN 1279 Part 2 (long-term test method for moisture penetration) and Part 3 (long-term test method for gas leakage rate), there are currently no normative specifications for proving the suitability of a spacer system. That is why the Warm Edge Working Group of the BF Bundesverband Flachglas has been dealing with the criteria for the usability of spacers for several years. Several sub-projects such as the verification of the linear thermal expansion for spacers of categories B and C, the fogging test at elevated temperatures for categories B to E as well as the bond strength of the profile construction for categories B and C have already been completed (an explanation of the spacer categories can be found in this post). For these sub-projects, suitable measurement methods were first developed. All systems for which BF data sheets with representative Psi values ​​are already available were then tested using the newly developed procedures. Further sub-projects are currently planned or in preparation.

Based on these sub-projects, when today a BF data sheet with representative Psi values ​​is requested for a newly developed spacer system, extensive technical documentation must be submitted, which is deposited with the BF Bundesverband Flachglas (German Federal Flat Glass Association). This is to ensure that only those systems receive a data sheet that can be proven to work in practice.

On this subject, in cooperation with the warm edge working group, ift Rosenheim has developed the ift guideline VE-17, in which the test methods for the usability of spacers are presented in detail. The ift guideline can be ordered from ift Rosenheim here.