The Importance of Knowing Material Compatibility and Suitability for Double-Glazed Windows

The compatibility of materials used in double-glazed windows is crucial to ensure their overall effectiveness and longevity. One critical aspect of material compatibility is the relationship between the glazing silicone and secondary sealants used in the window.

Over the years we have helped many customers identify why DGUs have failed. Most of the time the failure has been caused by very simple mistakes during installation. DGUs cannot be installed with just any type of glazing silicone, as the secondary sealants used can have detrimental reactions to incompatible silicone and setting blocks.

The glazing silicone is used to seal the perimeter of the glass in the window frame and provides an additional layer of protection against water and air infiltration. The secondary sealant, on the other hand, is used to give strength to the unit and seal the space between the two panes of glass providing an additional barrier against moisture.

If there is an incompatibility between the glazing silicone or setting block and secondary sealant, it can lead to several issues. For example, incompatibility with the secondary sealant can lead to unit failure, decrease in energy efficiency and structural integrity of the window, and quite often lead to the softening and dissolution of PIB causing it to leak into the unit.

Unfortunately, many silicones used to glaze traditional monolithic glazing are not compatible with secondary sealants.

It is essential to ensure that the glazing silicone and secondary sealants used in the double-glazed window are compatible with each other. This can be achieved by selecting products from reputable manufacturers and suppliers who carry out regular tests of their products with other materials. It is also important to follow the manufacturer's recommended installation procedures and ensure that the installer is qualified and experienced in the installation of double-glazed windows.

There are several inferior products available in the silicone and secondary sealant market that haven’t been tested for compatibility or approved for AS 4666. These products are produced with inferior or reduced amounts of raw material to lower cost, often leading to machinery blockage, increased fluctuation of viscosity and dramatically reduced performance which all increase the risk of failed units returning to haunt all involved. This is a risk that should be avoided at all costs.

The suitability of secondary sealants for different applications is also very important to consider as certain products are much better suited for different applications. For example, silicone as a secondary sealant is the only choice for structural or exposed units that aren’t encased in frames but is the lowest-performing secondary sealant when it comes to moisture vapour transmission (MVT) and gas retention. Silicone as a secondary sealant will do the least to help reduce the chance of moisture entering the unit. For those applications polysulphide or hotmelt is the better choice performance and cost wise.

Speak to your supplier about what is the best all round or specific solution for you and your customers.