CASE STUDY | LSE NATURAL VENTILATION TREADING LIGHTLY In response to the London School of Economics zero carbon aspirations, RSHP and ChapmanBDSP have come up with a natural ventilation solution for a 13-storey tower in central London. Andy Pearson discovered how they rose to the challenge A natural ventilation solution was never in question, says Lucy Vereenooghe, operations director at engineering consultancy ChapmanBDSP. Shes talking about the building services design for the Centre Buildings Redevelopment at the London School of Economics and Political Science (LSE), where ChapmanBDSP has been working with architect Rogers Stirk Harbour + Partners (RSHP) on a scheme that will form the heart of the Schools Aldwych campus. RSHP and its design team won an international design competition for the 78m project in 2013, with a predominantly naturally ventilated scheme in response to the brief that called for a Breeam Outstanding building with an aspiration to be zero carbon. Opting for natural ventilation was ambitious; getting a solution to work in central London required total commitment. RSHPs design for the 19,000m2 scheme comprises a 13-storey tower block and the adjoining six-storey Houghton Block, plus a new public square, all enclosed by LSEs existing buildings. An atrium space separates Houghton Block from the tower, and houses a feature staircase that forms a dramatic circulation route between floors. The staircase continues PROJECT TEAM Client: LSE Architect: Rogers Stirk Harbour + Partners Building services and environmental consultant: ChapmanBDSP Structural consultant: AKT II Main contractor: Mace MEP contractor: Dornans Cost consultant: Deloitte Soft Landings and clients sustainability adviser: Max Fordham diagonally upwards through the tower as a series of double-height spaces, its route clearly visible in the faade. To facilitate the cross-flow of ventilation air and provide thermal mass, the buildings have reinforced concrete floor plates that are just 16m deep. We worked with RSHP from day one on developing the buildings form, to enable the scheme to be primarily naturally ventilated in response to LSEs zero carbon aspiration, says Vereenooghe. In addition to its form, spaces within the building have been organised to facilitate the natural ventilation solution. The design is vertically zoned, with highly serviced facilities such as the cafe, auditorium and large lecture theatres situated at the lower levels. General teaching spaces are on the first and second floors, from where there is access to a terraced garden. Above the second floor are the academic departments, a mix of open-plan and cellular accommodation. The occupancy densities, pollution, dust and environmental noise mean comfort conditions on the lower floors have to be maintained using mechanical systems, says Vereenooghe. From Level 3 to Level 12, however, comfort conditions in all of the academic spaces are maintained by natural ventilation alone. There is noplan B no mixed-mode option available because theres no riser space and no available chilled water, Vereenooghe adds. The client and the architect were totally committed to achieving this solution. The starting point for developing a naturally ventilated solution is thefaade. LSEs tower is orientated such that the main areas of faade faceeast and west; its lower floors are shaded by the surrounding buildings, while the upper floors are subjected to longer hours of uninterrupted solar radiation. In response, these faades incorporate vertical fins of varying depths to shade the glazing from the oblique sunlight. Through parametric modelling, the fins have been sized to allow the more sheltered lower floors to achieve the necessary daylight levels. Solar shading was a big part of minimising the risk of overheating, says Vereenooghe. 30 June 2019 www.cibsejournal.com CIBSE Jun19 pp30-33 LSE.indd 30 24/05/2019 18:57