Dual Seal Glazing Units
Standard sealed units are constructed from two sheets of glass held apart by a hollow aluminium bar with the sealant filling the cavity to the edge of the unit. The "Dual Seal" system takes this approach one step further by applying a fine layer of a butyl sealant to the sides of the spacer bar. This has two important advantages.
- By using sealants with differing properties the likelyhood of a breakdown of the unit (and subsequent water penetration) is reduced. Butyl has very high resistance to water penetration (it is often used as a pond liner!). One study found the average life of a dual sealed unit to be twice that of a standard unit.
- The film of butyl forms a partial thermal break between the aluminium and the glass and reduces heat loss around the edge of the unit
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