The idea of lighting the atrium had been proposed more than a year ago by Mindseye Lighting Consultants from London. The impetus to develop and implement the concept came from the 150th anniversary of the Bank which would fall on 3 March 2015.
Illumination Physics was already engaged on a major project for the HSBC headquarters - the design replacement of all external lighting and the creation of three large media walls, all of which would be used during the nine month long 150th celebrations and beyond.
The atrium is eleven stories high. Mounted at the top are a bank of giant mirrors designed to reflect natural light being captured by the computer controlled 'Sunscoop', a massive articulated reflector mounted on the exterior of the South façade. Sadly the proliferation of new skyscrapers has rendered this remarkable device largely ineffective today but if you are lucky enough to be present on a day when the light strikes the Sunscoop, you will witness these magical mirrors come to life just briefly.
Creating an internally illuminated light box on the chamfered floor edges proved problematic for structural reasons. Indirect grazing light produced obvious aberrations because of the slight differences between the metal panels. Mock-ups and testing found that a direct view LED strip with a 100% diffused lens would produce the best result. The clean lines emphasise and support the architecture and add spectacle and drama to the space. Previously the upper levels of the atrium were regarded as too dark and the addition of the line of light on each of the five floors which bound the atrium corrected that impression.
Illumination Physics developed a custom version of the popular 'IP Bar rectilinear', an architectural light strip with a unique rectangular profile. This shape is in keeping with the rectangular profile of the chamfers where a round profile would be discordant. IP Bar is a fully programmable RGB linear product designed to display graphic content with ten pixels per metre.
The installation process called for a new product to be created - the 'IP Bar Rail'. A mounting rail was required to hold the IP Bar as the soffit cladding needed to be removable for access to the fire extinguisher system. It was necessary to attach the rail to the stanchions of the balustrade to provide both structural integrity and a method for concealing the power and data cables. The rail and light fixtures were finished in an identical colour and texture as the existing balustrade metalwork.
The Cathedral Wall was the most challenging of the three features to illuminate. The wall is composed of two vertical layers of glass forming a cavity approximately one metre apart. Between the two layers and the elaborately designed supporting structure are layers of louvered working platforms and a cat ladder system to connect them. All of this has been designed in the finest detail as it is visible from outside the building in Bank Street. The aim was to illuminate the inner glass layer from within the cavity whilst keeping the light fixtures and cables invisible.
(Jim Evans)
