BUILDING PERFORMANCE 2 SCHOOLS
Loxford School in Ilford, Essex, was the only naturally ventilated school in the study. It received a BREEAM Excellent rating
G-values often get worse when more cost- effective glazing systems are selected during construction. Even with good attention to airtight
construction and robust detailing actual airtightness can fall short of expectations. Entrance lobbies, which create a buffer zone to the outside, can easily fall prey to cost cutting under the guise of ‘value engineering’. Doors to the outside can be left open, so the schools end up heating the outdoors instead of the corridors. When wintertime temperature controls are not responsive enough teachers and pupils often leave windows open to lower temperatures. This means that much of the effort that went into creating an air-tight building fabric is compromised by large cavities left by open doors and windows. Many might argue that this is an ‘occupant-related impact’ no designer can be responsible for, yet, a deeper understanding of what prompts occupants to leave openings ajar might alter the perception of ‘value’ during cost- engineering. Night purge is another common challenge.
In the case of automated high-level openings, cheaper actuators are frequently chosen – and these can jam. In other cases the infrared security sensors were found to be triggered by insects or even air movement. After a few incidents like this the automated night- time ventilation gets turned off. Setting the sensitivity of the sensors correctly and turning them away from windows and air ducts are being tested as part of the current study.
Appliance and equipment loads Even if fabric and system assumptions were more realistic, compliance calculations don’t include the energy loads of appliances
42 CIBSE Journal March 2012
– which is a major source of energy use and heat gain in contemporary school buildings. Special equipment such as training kitchens, furnaces, workshop equipment, reprographics, and server rooms are also omitted from these calculations, as are external lights and sports floodlights. When a building is intensively used it tends to have more equipment in it. If this is well managed through automated shut-off schemes and user engagement, the extra consumption is relatively small. If, however, these schemes are not in place, electricity consumption can ‘go through the roof’.
Commissioning, controls and management Lighting controls are other casual offenders. All the buildings Aedas have studied, including the POEs done outside the BPE programme, had issues with controls. Lighting is often not hooked up to the BMS and commonly only one small remote control is provided to manipulate lighting across a whole building. Daylight sensors have a tendency to escape commissioning. In reality these should override PIRs, yet this could not be demonstrated in the buildings studied. Timer settings for PIR-controlled lights are often set up to be too long (ie, beyond 20 minutes) so that the lights never get a chance to dim between classes. When it comes to the control of heating, cooling and ventilation, the biggest culprits are building management systems (BMS) and commissioning. The frustration with BMS in schools is so great that Roundtable participants wanted to design them out altogether. Finding a building with a well- run system, where main and sub-meters are
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Photo courtesy of Aedas
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