Schools Energy performance
School test
Post-occupancy evaluations of five similar academies
highlight the difficulties in implementing energy efficiency
measures in secondary schools – and the need for continuing
assessment, writes Ian Pegg
A
ccurate feedback on the true performance in at least some of the classrooms. In one academy
of buildings, with full data on energy this was coupled with an automatic night-cooling
consumption, is key to delivering energy strategy.
efficiency. In order to calculate the true effects In an attempt to avoid cooling, cross-ventilation was
of any design changes we must first be able to estimate applied in four of the academies. This worked well
energy consumption accurately. But, while modelling and with clerestory vents on the first floor of one building
estimating carbon emissions of buildings is a simple task, although, when coupled to a central atrium, some
producing accurate data can be enormously difficult – acoustic problems did arise.
energy use is affected by the actions of many stakeholders Mechanical ventilation was deployed only when road
in a building, from the design team to the contractors noise was too great to enable openings in the façade. In
through to the end-users. some cases this was done by using standard constant-
Assessing the performance data from the operations volume air handling units serving a number of zones
of new school buildings can be particularly challenging. with tempered air.
But the data can also provide some valuable lessons for In an attempt to save fan power, one building used
designers. A post-occupancy-evaluation (POE) study a single air handling unit and concrete ductwork to
by global multidisciplinary engineering consultancy serve 17 classrooms. Each classroom had a damper
Buro Happold, of five new academy schools built in controlled on room occupancy. The speed of the fan
Britain during 2002-05, offers some useful insights. was determined by the number of classrooms in use.
The measurements were carried out over 14 months All five buildings used full-height circulation or atrium
between September 2005 and December 2006. They zones. Two of the schools had a significant need for
provided monthly energy data and looked at issues such mechanical cooling; in one academy, fan coil units
as overheating in summer and winter ventilation rates. were used for internal zones.
The academies – one each in Bristol, Liverpool and
Nottingham, and two in London – had more or less Logging
the same requirements and operated with similar One of the academies specialises in information and
constraints and budgets. This makes it much easier to communications technology (ICT) and provides one
compare the findings and determine what causes the laptop per student. It was recognised that the criteria in
differences in performance. Building Bulletin 87 could not be achieved passively, so
The initial challenges faced by the designers involved chilled beams were installed. Combined with natural
with these schools can be summarised thus: ventilation on the north façade of the school, this
• How can ventilation and acoustics be managed in approach enabled higher cold-water flow temperatures
classrooms? and free-cooling for most of the summer.
Designers
• How was mechanical cooling to be avoided, while There was a concern that the school would use the
panels for comfort cooling rather than peak lopping,
need to argue
still allowing each student to have their own PC in
classrooms? but the data logging has shown this not to be the case.
that the energy
• How complex can a school get before maintenance The logging involved applying loggers to different
benefits may
budgets become unmanageable? and electricity circuits, split between HVAC, lighting and
small power. On-off loggers were also applied to light to
justify higher
• How can an academy have greater functionality, with
better environmental conditions, and still have low identify overuse and temperature logging was carried
capital costs
carbon dioxide emissions? out during summer and winter months.
and a different
The five buildings in the study used a variety of Figure 1 shows the energy consumption for
electricity and gas for all five academies, compared
approach to
approaches to tackle these issues. Some techniques
were common – all the schools had high thermal mass with Department for Education energy benchmarks. >
design
www.cibsejournal.com November 2009 CIBSE Journal 39
CIBSEnov09 pp38-41 poe.indd 39 22/10/09 17:12:28
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