WHY SEALED UNITS FAIL?
Sealed units are designed to trap dry air as a thermal barrier between the two panes of glass. This dry air (or inert gas such as Argon) provides insulation for your home.
However, when the sun heats the unit during the day, the air inside expands creating positive pressure which pushes outward on the seal. When the unit cools at night, the air contracts, creating negative pressure which pulls inward on the seal.
This daily cycle of expansion and contraction — known as solar pumping — gradually weakens the edge seal over months and years.
What Happens When the Seal Opens
Eventually, the seal opens under the constant pressure cycling. The unit then acts as a pump, pumping in cool damp air each time it contracts. The desiccant material in the spacer bar, designed to absorb small amounts of moisture, eventually becomes fully saturated.
Once saturated, the moisture has nowhere to go and begins to condense on the inner glass surfaces when the temperature drops. This is the mist, fog, or condensation you see between the panes.
THE REPAIR
The repair is remarkably simple. Two 4mm holes are drilled through the inner pane using diamond-coated drill bits — one at the bottom corner and one at the top. Drying pellets are applied through the bottom hole, absorbing all the trapped moisture over several days.
Once clear, small one-way vents are inserted into both holes. These convert the sealed unit into a pressure-equalised unit, meaning it can breathe without trapping moisture.
Will the Repair Last?
The repair will last the lifetime of the unit. Once pressure-equalised, the unit no longer builds up internal pressure from solar pumping. The repair carries a 20-year guarantee.