CASE STUDY | CRANMER ROAD STUDENT RESIDENCE with Passivhaus comfort criteria. Both buildings feature continuous mechanical ventilation from packaged mechanical ventilation with heat recovery (MVHR) units incorporating summer bypass. The Villa Building uses a cascade system of air transfer, similar to that in a domestic house: two MVHR units on the top floor supply fresh air to the bedrooms; this spills into the corridors and, from there, to the kitchens, shower rooms and toilets, from where it is extracted. The Stephen Taylor Building is based on a series of single MVHR units serving MONITORING PERFORMANCE Energy use was reviewed later in the year and the total EUI had risen to 71 kWhm-2 per year in response to some of the students overriding radiator controls. The radiators have built-in thermostats that were pre-set at 20C. These are fitted with a child-proof lock. As it turned out, these locks were not proof against determined undergraduates, who were reportedly turning the thermostats up to 26C in some instances. As a consequence, annual energy figures are currently higher than those predicted by PHPP. We provided the college with user guides to discourage students from tampering with the radiators, explains Still. On subsequent projects, Max Fordham has refined this concept by providing local controls that limit temperature setpoint adjustment to a range of plus/minus 2C. Monitoring also showed the students were using more domestic hot water (DHW) than the PHPP assumption, which was based on a five-minute shower duration. Clearly, Kings College students are cleaner than most and were taking seven- to eight-minute showers. We learned that the PHPP assumptions for domestic hot water usage are lower than usage by the UK student population, laughs Still. This has been fed back to the students, and into energy modelling on future projects, where it will influence system choice and energy usage predictions. The two buildings provide 59 student rooms clusters of four en suite bedrooms. In addition, two separate MVHR units serve the two pairs of kitchens. The ethos behind the scheme was to keep things as simple as possible from a ventilation point of view, so there is no interlock with the windows if someone wants to open a window to increase ventilation, they can, Still explains. On both buildings, extract is from the toilets, kitchen and bathrooms so, if we turned off the vent when someone opened a window, the shower rooms would, for example, start to get humid. A single MVHR unit with summer bypass serves the campus common room in the Stephen Taylor Building. Still describes this room as a special case because of its predicted intensive occupancy. Here, the MVHR unit incorporates a mini air source heat pump to automatically heat or cool the ventilation air. While you could keep the common room comfortable for most conditions, there were enough hours where it was going to get uncomfortably warm that we put in active cooling, explains Still. Ventilation rates are increased further in summer, with windows opened by automatic actuators. The common room also incorporates underfloor electric heating to keep walls clear of panel radiators. The buildings 100-year service life means items such as the MVHR units are designed to be accessible for service and to enable their replacement over the design life of the building. Still says the ductwork is less easy to replace, but it is still possible. A view from a kitchen in the Stephen Taylor Building TM46, long-term accommodation TM46, university campus DEC typical benchmark CIBSE Guide F Good Practice (education, residential, self catering/flats) HEEPI study: best electric powered HEEPI study: best fossil fuel powered Westfield Student Village, Queen Mary: Feilden House 2014 Westfield Student Village, Queen Mary: Feilden House 2009 Westfield Student Village, Queen Mary: Feilden House 2008 Westfield Student Village, Queen Mary: Poole House Solsbury Court, University of Bath Marlborough Court, Univeristy of Bath Bath Campus, Woodland Court Girton College, Cambridge LETI CEDG: office LETI CEDG: residential RIBA 2030 Climate Challenge: non-domestic Cranmer Road 0 50 100 150 200 250 300 350 400 450 500 Annual energy use intensity kWh/(m2.a) Figure 1: The annual energy use intensity of Cranmer Road compared to benchmarks and other accommodation projects 24 October 2023 www.cibsejournal.com