1 Exchange Square is the redevelopment of a 1990s postmodern office building designed to meet the highest sustainability criteria.

BREEAM Outstanding anticipated
WELL Platinum anticipated
NABERS 4.5* anticipated

The block is being dramatically transformed and extended while retaining 90% of the existing structure and a substantial amount of the original facade. The enlarged building will offer 42,000sqm of office space over 13 floors, 1500sqm of retail, and a new public pavilion.

The building is to increase in height and extended to the west, where the floor plates will be suspended from a steel exoskeleton penetrating the facade. The facade panelisation and installation strategy has been led by this challenge and the resulting thermal movement of the structure.

The design seeks to retain the existing stone cladding mounted on steel ‘mega panels’ on the street elevation. The stone cladding will be removed and cleaned, but internally the insulation is to be enhanced to meet current standards. Windows mounted into the mega panels are to be replaced and upgraded to triple glazing. The additional weight on the mega panels has required careful review of record drawings, site measurements and detailed structural analysis.

We have carried out embodied carbon calculations at all stages of the design to steer options towards low-carbon solutions. By retaining the existing stone facades on the east and north elevations, a saving of nearly 50% is achieved compared to full replacement.

The facade has opening windows as part of a mixed-mode ventilation strategy, while solar shading and glazing ratios have been carefully managed on the west elevation to mitigate heat gain.

London, UK


Fletcher Priest Architects