CASE STUDY | LSBU HUB The two-storey library is at the heart of the building The system has been designed as constant temperature, variable flow, incorporating 2-port motorised pressure independent control valves (PICVs). Domestic hot water is provided via plate heat exchangers and associated buffer vessels. The ventilation system consists of around 20 variable speed-controlled AHUs across the buildings with demand-controlled ventilation using variable air volume boxes as the primary strategy for the system. The AHUs for the classrooms, library and sports hall provide tempered air into the space, with space heating/cooling via FCUs and trench heating. There are radiators in circulation spaces, WCs and sports changing areas. The AHUs in the basement use the cycle parking area (converted from the car park) as part of an exhaust air plenum to avoid additional ductwork in an area with low floor-to-ceiling heights. As a principle, MEP systems were integrated into existing services zones, although additional horizontal and vertical routes were required, resulting in extensive use of prepared service openings within the existing waffle concrete structure. All building services systems are designed to be compatible with estate-wide systems and maintenance strategies, using LSBU design guidelines and liaison with the estates team to agree and ratify manufacturer selections and systems choices. Life-cycle assessment A detailed life-cycle assessment (LCA) was conducted to evaluate the embodied carbon intensity of the retained structure 34 April 2023 www.cibsejournal.com BDP carried out acoustic modelling of the waffle ceiling renovation. The model was created in One Click LCA, based on the projects bill of quantities and specification documents. To measure the benefit of retaining the structure, a new building equivalent scenario was modelled using One Click LCAs Carbon Designer tool. Results showed that the retained structure model presented an overall 39% saving compared with the new equivalent model. The largest carbon emissions for the retained structure model were associated with the new building services (MEP), comprising 38% of the embodied carbon emissions, followed by the superstructure (faade, upper floors, roof and stairs, 21%), internal finishes (13%) and external walls (12%). The embodied carbon savings from reusing the existing structure means total embodied energy is half the 2030 RIBA target benchmark. The majority of the risers were re-used, despite room layouts and functions changing significantly. Building services in areas of the LSBU Hub that had been recently refurbished were retained where practical, including kitchen ventilation hoods, ventilation grilles, lighting, ductwork and electrical distribution. The refurbishment has created bright, well-ventilated, and comfortable spaces. A simple, but innovative and environmentally conscious approach has been executed, from large-scale interventions through to smaller-scale solutions. CJ LAURA SMITH is the engineering director, BDP CUT THE WAFFLE The acoustics were designed to new-build standards where designs permitted, considering sound insulation, external noise ingress, building services noise and room acoustics. A key part of the acoustic design was controlling external noise ingress, with the site being located off the busy London Road. The new faade provided the opportunity to incorporate the necessary acoustic performance requirements, to ensure internal spaces were adequately protected from external noise, particularly the main open-plan library spaces. With a mechanically ventilated building, it was important to ensure noise from building services was controlled so internal noise levels were suited to the room use. Detailed calculation and modelling of the retained structural waffle slab was carried out to inform airborne sound insulation, and to make enhancements to achieve the criteria. Extensive acoustic modelling of the open-plan library areas and lecture theatres was carried out to advise on room acoustics and comfort, specifically, the location, quantum and performance of acoustic finishes.