Loxford School of Science and Technology
Judit Kimpian, AEDAS R&D
Building type, sector and stage
Non-domestic new build, school, handover, post-construction, in-use monitoring, London.
School, ventilation, energy, biomass, controls, lighting, BREEAM
Timing of this summary
Two years after completion (May 2010)
The 16,063 m2 school designed for 2030 pupils comprises two curving parallel buildings around a series of central landscaped courtyards enclosed at either end by pods. These house the main assembly hall and refectory at one end and a library and learning resource centre at the other. The building has many special uses, including a training kitchen, workshops, reprographics, a drama studio, a kiln and and a learning resources centre.
The building is of flat slab construction with precast concrete panels finished with brick tiles. The east and west facades are shaded by vertical external louvers to reduce overheating and cooling loads. Single-sided corridors face into an internal landscaped courtyard. The designers aimed for BREEAM ‘Excellent'.
The design team aimed for a naturally cross-ventilated building with simple controls. Classrooms along the teaching blocks have openable windows, while motorised vents to plenums above corridors exhaust to the courtyards. Centrally located top-floor rooms have operable rooflights. Carbon dioxide sensors installed in classrooms are designed to prompt users to open windows instead of relying on automatic control by the building management system. Active chilled beam cooling is used in the high ICT density central blocks where it wasn't possible to achieve natural ventilation. Space heating is by radiators supplied by heat from a closed-loop ground-source heat pump.
The school was designed to emit 28.7 kgCO2/m2 per annum. The performance to date has been measured at 66.4 kgCO2/m2 per annum.
The ground-source heating system did not initially work as expected, and suffered breakdowns. There have also been issues relating to the control of the heating system, resulting in excessive energy consumption. The GSHP was installed later than other systems the BMS was not reprogrammed to treat the GSHP as the primary provider of heat.
Further concerns were raised about heating set points and timer settings especially when it comes to the kitchen's settings which may extend the heating hours to be extended elsewhere. It is possible that frost coils are used in favour of heat exchangers, thus not achieving full potential of heat recovery.
Lighting accounts for a significant proportion of the building's energy use and is approximately three times higher than the EPC calculation. The research found that there was no overarching guidance available on site for the lighting control system. Without this the school needs to rely on the supplier's phone instructions to get the lighting system under control.
The AEDAS research team conclude that the specification of lighting systems should include a manual override switch per zone and for the entire building. Adequate commissioning of lighting systems is critical as is the provision of user-friendly manuals and training.
Building management systems
BMS training, aftercare and maintenance was found to be lacking. Some simple instructions were missing, and some electricity sub-meters were either not connected or faulty. Large server rooms on second floor are equipped with local cooling, but the remote connection to the BMS was found not be working.
To date the electrical consumption of the ground-source heat pump has not been possible to establish – the figure reads zero in the BMS and the research team has not been able to locate the relevant electricity meter.
During winter the main entrance was found to be too cold. One reason for this is that a sealed entrance lobby was value engineered at concept stage and a warm air-curtain that was specified instead was not installed.
The research team found that the specification of doors, windows, and openings through building fabric is severely affected by procurement. Last minute changes by subcontractors frequently occur without the approval of the design team. Due to the contractual arrangements the design team is often not in a position to witness and reject work that is not in line with the specification.
More robust specification is recommended and the adoption of Energy Efficiency Measures Register from design to operation. A clear line of responsibility for checking energy efficiency measures and reporting on these and relating risks directly to the client is proposed for future projects.
The plenum vents exhausting classroom air to the courtyards are meant to be triggered both by temperature and CO2 settings. These are rarely high enough in the winter period to be triggered.
Some vents locked in the open position (shown) as their motors had failed due to current-draw problems. This was resolved as a defect.
Lighting in common areas (corridors and stairwells) is controlled with remote switches. There have been some issues with zone controls and difficulties with switching off the lighting.
Evidently lights are on when not needed, and when daylight is adequate to illuminate spaces, as left. The daylight sensors do not override PIRs in either in the classrooms or the common areas.
Classrooms have carbon dioxide sensors that inform teachers when to open the windows. Interviews with the teachers indicated that some don't know that they are meant to close the windows in the winter when the carbon dioxide sensors are showing a yellow light, and that the thermostat should be turned off when the windows are open.