Systems prove their adaptability

Architectural aluminium glazing systems by Kawneer were specified for a landmark office building in the Edinburgh New Town Conservation Area for their ability to meet a diverse range of requirements.

CDA (Comprehensive Design Architects) in conjunction with Hoskins Architects specified three types of Kawneer’s curtain walling and two types of doors for the £42 million redevelopment of 3 to 8 St Andrew Square on a prominent corner of the sensitive World Heritage Site.

The Kawneer AA110 capped and SSG (structurally silicone glazed) curtain walling with a 65mm sightline and a bespoke 80mm wide system, complemented by series 190 heavy-duty and 350 severe-duty commercial entrance doors, have been used on the offices on the second to sixth floors of number 6 and on some elements of the eight retail/restaurant units on the ground, first and basement floors of numbers 3 to 8.

The development comprises 112,000ft2 of Category A office space, now let in its entirety to Standard Life Investments, arranged around a full-height atrium, with roof terraces at the fourth and sixth floors, ground floor reception and double-height entrance on St Andrew Square, parking/bike storage at basement level and welfare facilities at lower ground floor.

Formerly the headquarters of the Scottish Provident Institution, the site had been developed in piecemeal fashion over the years, culminating in a series of interlinked buildings that were no longer fit for purpose. The poor-quality office space, in a prime city centre location, had lain empty for 12 years.

The key aim was to create a sustainable future for the site which had been severely compromised prior to the redevelopment. The brief recognised the importance for the elevations to be of the highest architectural quality, to complement and stand alongside adjacent buildings surrounding the square and beyond and to create economically viable, high-quality Grade A office space.

The building takes advantage of natural daylight and the spectacular views to the castle, over St Andrew Square and to the Forth beyond by framing the views rather than creating vast expanses of glazing. Bronze feature picture windows and the Kawneer curtain walling mullions contrast visually with the background and frame the stunning views.

Specialist sub-contractor Charles Henshaw and Sons was appointed by the client’s team in 2008 for its facade knowledge, and in conjunction with CDA and Gareth Hoskins Architects they addressed critical issues such as live load movement and deflection, resulting in the bespoke 80mm Kawneer system.

After a two-year build by main contractor Bowmer and Kirkland, the site is now transformed, with the nine-storey building clad in stone and glass with bronze feature picture windows and bespoke Aurubis ‘bronze’ metal fins attached to the curtain walling by Kawneer.

CDA project director Gareth Thompson said: “The project required different types of curtain walling, capped and SSG, not to mention the bespoke fin caps. The adaptability of Kawneer’s systems played a critical part in achieving the design and successfully resolving the complexities of the different types of curtain walling.”

The bespoke metal fins attached to the Kawneer curtain walling were fabricated from a proprietary aluminium bronze flat sheet, Aurubis Nordic Royal, an alloy of copper with aluminium and zinc, with a rich golden through-colour.

As they were especially made for the project, extensive research was carried out to establish the best method of forming their tapered profile by folding the flat sheet and achieving a high-quality finish.

Nordic Royal has a natural mill finish that is initially bright, eventually losing some of its sheen as the surface oxidises. Further research was carried out with mock-ups having a variety of grit finishes to speed up the oxidization process and fine-tune the appearance of the bronze patina that will develop over time.

When viewed from straight-on the fins are almost invisible, allowing uninterrupted views in and out. When viewed from an increasing angle the visibility progressively closes up until completely blocked by the fins and the elevations appear solid. The appearance of the building continuously changes as you walk around it and will continue to do so with time as the fins develop a rich patina.