What is the typical lifespan of a sealed unit?

As a general guide, a good-quality double-glazed sealed unit will typically last in the region of 15–25 years before the perimeter seal begins to deteriorate, though this varies with the quality of manufacture, the installation, and the conditions it’s exposed to. Units in south-facing or weather-exposed positions, or where frame drainage is poor and water is allowed to pool against the seal, can fail sooner; well-installed units in sheltered positions often last longer. Modern units with quality spacer bars and dual-seal construction — the type SevenDay supplies — are built to give a long service life.