Why double glazed sealed units fail

17 Oct , 2016


The purpose of a double glazed sealed unit is to create a thermal barrier between the two panes of glass. A thermal barrier is created by trapping still dry air in the unit, as still dry air is a very poor conductor of heat.

The sealed unit is under pressure and expands and contracts daily when it is heated by the sun and then cools. One day a seal on the unit will open under pressure and reseal when the unit cools. The unit now acts as a pump pumping out dry air and breathing in cool damp air.

Eventually when the desiccants in the spacer bar are saturated you will see condensation in the unit.


We solve this problem by drilling two 4mm holes in the glass with our diamond coated drills (supplied) and then you apply our drying pellets through the bottom hole. When the desiccants have completely dried you plug the two holes. That is the repair complete.


The repair will last forever! The unit is no longer a sealed unit but rather is now a pressure equalised unit. In the centre of the plug is a tiny hole so the unit will never again expand under pressure. The unit will once again hold still dry air to create the thermal barrier.

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