PASSIVHAUS CASE STUDY BUSHBURY HILL PRIMARY SCHOOL
predominantly from linear fluorescent lamps. These are switched on and off manually; presence detection ensures lights will turn off when rooms are empty. The team also worked closely with the ICT consultant to ensure low energy use equipment was selected for the school. One area of unexpected energy consumption that was a particular challenge was in the sprinkler room. Wolverhampton City Council has a policy that all buildings have sprinklers fitted for life safety. Bushbury Hill’s sprinkler water-storage tank and diesel pump are located in a standalone building situated near the perimeter of the site. ‘The amount of energy needed just to
classrooms while enabling the boilers to run in full condensing mode. The heating circuit
The Passivhaus solution is a handsome timber and brick-clad school where the building works had to ensure a comfortable learning environment without expensive energy saving add-ons
has a high temperature differential, typically 50°C flow 30°C return, to keep flow rates to a minimum. All heating pipework is highly insulated to prevent uncontrolled heat loss. A separate, dedicated supply and extract
MEASURED PERFORMANCE
Thermal energy: 15kWh/m2 Hot water: 12kWh/m2 Lighting: 14kWh/m2
Sprinklers: 17kWh/m2 (gas) (gas) (Electric)
Power and plant: 14kWh/m2 (electric) Kitchen: 7kWh/m2
(electric) (electric)
system is used to ventilate the kitchen. Because unregulated energy use is included in a Passivhaus design, it was important to minimise the kitchen’s energy consumption. School kitchens typically use gas-fired cooking appliances. However, for this project the caterers were persuaded to use electric induction cooking, which means there are no combustion gases to be removed and waste heat from around the pans is minimised (see box: Turning off the gas).’The caterers were not too keen on the idea at first, but it has turned out to be a huge success both in terms of energy use and comfort for the catering staff,’ explains Hines. In addition to reducing energy consumption in the kitchen, the designers also set about minimising lighting and ICT loads. The form of the building ensures that most spaces have high residual light levels to minimise the need for artificial lighting. When light is needed it is supplied
34 CIBSE Journal May 2013
frost protect the sprinkler system caught us out,’ admits Jarvis. He says that on subsequent schemes, fabric insulation for the sprinkler room will be improved and that improvements to Bushbury Hill, too, are being considered. When the building was handed over to the teaching staff in October 2011, the architect and contractor spent time explaining the principles behind the design and how to operate the building to its new occupants. They also issued staff with this information in a booklet. However, some users have struggled to understand the control strategy. ‘We’re trying to use the same design team to address the issues of over-complication for the users,’ explains Jarvis Equally importantly in ensuring the
success of the scheme is the design team’s access to the building’s sophisticated Trend BMS system. This enables them to continue to monitor the building in use throughout the year. The team is still tweaking systems to optimise performance; the controls, for
example, had to be reconfigured after the 2012 spring heatwave led to some spaces becoming uncomfortably warm because of the high solar gain from the low-angled sun. Teething problems aside, this highly successful design received full Passivhaus accreditation. More importantly from the council’s perspective, the low energy solution has resulted in minimal energy bills, cushioning them from the impact of future energy price hikes. Not bad for a school that cost £1,768/m2
to build. If further endorsement were needed for
this award-winning, low-energy, low-cost school, the client has engaged the same team to work on its next school project – and this time the client has specified a Passivhaus solution. ‘This solution has the making of a potential low energy model for school buildings,’ says Jarvis. CJ
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