Introduction The site occupies an area of 0.17ha and the existing building extends to 6,014m2 of gross external area, made up of Basement, Lower Ground, Ground and 3 upper floors. The project comprised a 1970’s office building situated in the heart of the Clerkenwell Conservation Area. The building itself had developed something of an iconic status within the immediate locale, unusual for a building of this age, and was locally listed. The client brief asked for complete refurbishment and reconfiguration of the entire site - creating more flexible and sustainable office accommodation whilst significantly improving the environmental performance of the building. The brief also required the creation of a new entrance arrangement together with the enhancement of the public piazza. Background The topography of the area has resulted in a change of level across the site equivalent to two stories. This situation had been exploited by the original architects, YRM, to place 50% of the buildings floor space below what was perceived to be ground level on Britton Street. As a result the principal floor plate is actually located below the public entrance piazza but on a level with the public park to the south. This situation was further exploited by placing all the servicing elements on the floor below this, effectively basement, but which was itself on grade with Turnmill Street to the west. Our concept looks to return the building to its original iconic form and regenerate the site in a manner which will enable the building to function in a sustainable manner into the 21st Century. Given the importance of the site within the immediate public realm the proposal seeks not only to be sympathetic to, but to enhance, the context. There were a number of key interrelated factors which required thorough before the final development approach could be determined. These were: Solar Performance Historic data showed that the upper floors of the building suffered from chronic overheating and extreme glare. This was due to a number of factors, not least of which was the extent of the expanses of unprotected south and west facing glazing. Detailed modelling by our sustainability consultants, Cundall, confirmed what the historic data had indicated, that the peak summer temperatures would be extreme. Furthermore this modelling indicated that without a significant reconfiguration the existing buildings cooling system would continue to not be able to cope with these extremes Systems Performance As mentioned above the cooling system installed within the original development had never functioned to an acceptable level. The system was a chilled beam arrangement, originally ahead of its time, which perhaps had not been fully understood at the time of the original installation. The original supplier, Frenge, was found to hold test data and further modelling and investigation by Cundals discovered a major flaw in the original installation, which resulted in a serious underperformance of the system. This flaw related in the lack of a dedicated return air path within the plasterboard ceilings, an issue which was easily rectified through design development and detailing. The modelling also determined that if the issues resulting from excessive insolation could be addressed then it would be possible to augment and extend the existing chilled beam system to enable a well tempered environment to be delivered. Thermal Performance The building cladding had long since reached the end of its useful life. In addition to the building suffering excessively from solar gain on the upper parts the black brick cladding to the plinth forming the lower floors was found to be poorly insulated, resulting in summer overheating and heat loss in winter. Our proposal sought to address these issues in a manner which would proactively assist the other building systems to provide acceptable performance levels. Again using the dynamic thermal model the performance of a new external solar shading system was developed which was then incorporated into an upgraded insulated cladding system. The lower floors were also upgraded through the incorporation of an externally applied insulated render system. Internal Environmental Standards The lower floors of the building were deep in plan and as a result suffered from poor levels of natural light. In looking to redefine the public piazza and entrance arrangement a new stand-alone pavilion was designed which not only provides a new entrance and reception to the building but also formed the location for a large atrium rising between ground, lower ground and basement levels. This greatly increases the levels of natural light available within this portion of the development. A large and dramatic helical stair was also placed within the atrium, accessed via glass bridges, which sought to encourage occupants to walk between the ground and lower floors, rather than use the lifts. The external design of the pavilion compliments the existing office building, which sits adjacent. Full frameless glazing creates the appearance of the piazza continuing into the interior of the pavilion, with matching floor finishes continuing inside and out. In order to avoid undermining the clarity of the original building however the pavilion was clad in a mirror polished finish. Sustainability Measures The design team determined that the building itself and its environmental systems are fundamentally sound and as such were recycled. The strategy put forward sought to address the capacity, energy requirements and over heating issues by: - Replacing the exterior cladding with new, insulated, panels. - Incorporating a sympathetically designed external shading system to reduce overheating in the internal spaces to reduce overheating in the internal spaces. - Overhauling, extending and improving the functionality of the existing chilled beam system. - Replacing external flat surfaces with new, insulated, membranes and finishes. - Incorporating facilities for recycling of waste material into the design. - Encouraging the use of alternative methods of transport by providing secure cycle storage and changing facilities - Incorporation of dual flush lavatories. - Incorporation new water meters and major leak detection system - Incorporation of self closing taps with spray nozzles. - Incorporation of movement sensitive lighting throughout the development. EPC The various systemic upgrades and initives have resulted in the building improving its EPC asset rating from a D rating of 97 to a C rating of 60. BREEAM The various systemic upgrades and initiaves have resulted in the development achieving a BREEAM rating of Very Good, achieving a score of 58%.