Unitised curtain walling from leading architectural aluminium systems supplier Kawneer met a host of criteria for the Grade A office building that tops architects BDP’s £120 million masterplan for the heart of Glasgow’s international financial services district.

Installed by glazed façade contractor Charles Henshaw, the Kawneer unitised AA®201 system met at least a trio of BDP’s requirements – for programme issues as the use of scaffolding was negated, for low air permeability, and for meeting BDP’s design intent for a frameless, structurally silicone glazed (SSG) facade.

The £26 million Capella tower was the last – and tallest - of six buildings designed by BDP for Glasgow’s 420,000ft² mixed-use Atlantic Quay development on the site of a former tobacco warehouse district dating from the city’s sea trade with the colonies and the New World.

Capella is surrounded on three sides by suspended concrete slabs over basement car parking that would not take the load of scaffolding required to construct a traditional stick curtain walling system to 11 storeys, while cantilevering the scaffold from upper floors would have extended the construction programme.

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But as the pre-glazed AA®201 unitised panels can be installed from within the building without the need for scaffolding, this method of installation not only reduced construction time and costs but also the safety risks associated with erecting and working from scaffolding.

BDP architect director Bruce Kennedy said: “The requirement was for large floor to floor panels of curtain walling without face caps. The Kawneer unitised system was able to provide these large single units, with a gasketed SSG system and slim internal mullions/transoms that give excellent sightlines. Every aspect of the required aesthetic appearance was met by the system.

“The performance requirements were informed by the need for good thermal properties combined with robust air-tightness. The building was air pressure tested and more than met the requirement, while the thermal properties of the curtain walling framing resulted in glazed units that met the performance criteria.”

Steel framed with a slip-form concrete core and composite slab upper floors and roof, the building utilised Kawneer’s unitised curtain walling on levels one to nine and the glazing system was installed on the lower floors while the upper floor slabs were still under construction by main contractor Balfour Beatty.

Mr Kennedy said: “This sequential sealing of the building allowed follow-on internal trades to progress independently of the ongoing construction, cutting significant time from the construction programme and allowing the building to be completed within the required construction period, saving cost that would have resulted from extended site works.”

Designed for Wilson Bowden Developments and later sold to BA Pension Fund, the brief to BDP was for a speculative office building capable of sub-division into separate tenancies on each floor and into two separate tenancies per floor, with basement car parking and retail space at ground level.

(GK)