Why Sealed Units Fail — and the Early Warning Signs

A well-made sealed unit in a well-drained frame routinely lasts twenty to thirty years. The same unit sitting in water can fail inside five. Most premature failures are preventable — and most give warning first.

What actually kills the seal

• Thermal pumping: daily flexing that slowly works at the seals — unavoidable, but quality seals resist it for decades
• Standing water: blocked frame drainage leaves the unit edge soaking; secondary seals are not designed for immersion
• UV exposure on the edge seal: a concern in frameless and structural applications where the seal sees direct sun
• Incompatible glazing compounds: some older sealants attack modern edge seals

The early warning signs

Before visible mist, look for: a faint dusty bloom inside the glass at the bottom edge; intermittent morning fog that clears by noon (moisture is in but not yet saturated); and a rainbow-oil sheen near the spacer. Any of these means the unit is breathing and the desiccant is on borrowed time.

Five-minute annual check

Clear the frame drainage slots with a thin plastic strip, check gaskets sit home, and confirm the beads have not opened at the corners. That routine alone pushes most units to the far end of their life expectancy.

When failure comes anyway

Replacement into existing frames is quick and lets you upgrade the spec at the same time — measure up with the measuring guide and price the swap in the quote calculator. Our units carry a 5-year warranty as standard.