CASE STUDY | ST JOHNS COLLEGE, OXFORD, LIBRARY AND STUDY CENTRE in this task by incorporating elements of the BSRIA Soft Landings framework, including a commitment to aftercare and building optimisation, post-handover. As a result, the colleges facilities management team, the main contractor, the M&E contractor, and the BMS and controls engineer have worked together, with Max Fordham, to minimise its energy use. We worked collaboratively with the contractors team, the facilities managers and librarians to optimise the buildings performance throughout the first year, says McNeil. Optimising the ventilation system, in particular, has been tricky because of Covid-19. This is partly because occupancy numbers have been lower than expected. The college acknowledged the impact of Covid on the process and retained the consultants for another year. Now, we should be able to get a better picture of how the ventilation system works when the library is closer to full capacity, says McNeil. As part of the aftercare reviews, BMS data is scrutinised to understand how well the building is maintaining internal conditions. Outputs show the first-floor spaces are significantly warmer than those on the ground floor because of higher solar gains and less thermal mass. That said, the temperature on the first floor has only gone above 28C three times, so overheating does not appear to be a problem, says McNeil. In the ground-floor reading room, the temperature has not risen above 24C all summer. In winter, space temperatures are maintained between 19C and 21C in the main library, which students have SPACE TO REFLECT The series of planes that form the buildings west-facing wall feature sculptural stonework by artist Susanna Heron. The addition of a water-lled pool beneath the faade enables light to be reected upwards onto the carvings and into the reading room in a series of moving patterns, capturing the movement of the water. The architect wanted to exploit this effect, so Max Fordham developed a 3D modelling technique to accurately predict the caustic reection and refraction patterns from sunlight hitting the surface of the pool and from lighting submerged in the pool. The results were validated by testing at the artists studio. found acceptable. Feedback indicated that some other rooms were struggling to reach temperature set points in cold weather. In response, it was decided to increase the heating system weather compensation curve, to raise the set point of the buffer vessel, which would slightly increase the flow temperature of the circuit feeding the underfloor and trench heaters (which had been lowered to save energy). This was done gradually, because any increase in supply temperature will decrease the efficiency of the heat pumps. The rooms are now up to temperature and the increased flow temperature is in line with that of the original design. The controls have been centralised at the reception desk touchscreen. This allows the librarian to shut down the upper floors at quiet times to avoid heating and lighting spaces unnecessarily. We explained that, in order for the building to get near to carbon neutral, the college would have to consider some of these more intrusive measures, says McNeil. In 2012, when Max Fordham designed this project, there were very few precedents for carbon-neutral schemes; now, there are many more. So, if the Max Fordham team were to design the scheme today what would they do differently? If I was doing it now, I would go for insulated shutters on the glazed rooflights, so when its dark and cold the shutters would close to further reduce heat losses, says Rushford. He would also investigate a mixed-mode solution, which would save energy, but would also undoubtedly increase the complexity of the building and so may not be appropriate considering the additional embodied energy it would require. The schemes 2020-21 measured energy use intensity (EUI) of 65kWh.m-2 per year shows that the building meets the RIBA 2020 and 2025 interim EUI targets, and comes close to the RIBA 2030 and London Energy Transformation Initiative target for schools a great achievement considering the buildings servicing strategy was designed in 2013. CJ Few precedents for carbonneutral schemes existed when the building was designed in 2012 Rooights ood the reading rooms with natural light 24 April 2022 www.cibsejournal.com CIBSE Apr 22 pp20-22, 24 St Johns College.indd 24 25/03/2022 15:39