Schools and education facilities supplement Classroom ventilation
> ventilation provision may be inadequate to remove excess down’. Displacement working with highly engineered
heat without causing discomfort from draughts. All the façade insulation and good air-tightness would also
schools we studied were built between 2004 and 2006 eliminate the need for perimeter heating, according
and were in compliance with BB93, which signifi cantly to Wyatt. The key seems to be a ‘hybrid’ approach that
revised the standard for acoustic performance.’ involves using as much natural ventilation as possible,
They would als0 have complied with BB101. BB93 but supplemented where necessary and given a
refers to acoustics, while BB101 refers to temperature. measure of mechanical control that is still not present
However, Dejan Mumovic, of University College in most schools. This ‘demand-led natural ventilation’
London and CIBSE School Design Group, believes that, could overcome the obstacles facing the BSF design
if designed and used properly, in most cases natural teams as they seek to balance energy, air quality and
“Being slaves
ventilation systems are capable of meeting all Building security issues.
to natural
Bulletin 101 requirements. ‘Natural ventilation should be
ventilation
the default design solution for ventilation of classrooms,’ Noise
remarks Mumovic. But he stresses that because schools ‘Innovative design of natural ventilation systems for
can lead to a
are ‘complex, dynamic, socio-technical systems’ their urban schools has an enemy – noise,’ says Richard
colossal use of
ventilation strategies must be viewed holistically. Arnott, market manager for WindowMaster. ‘Natural
heat energy” –
According to leading design engineer Terry Wyatt, ventilation requires that the windows be open. If the
of Hoare Lea, the root of the problem is this desire windows are open then the noise inside the classroom
Terry Wyatt
to use natural ventilation, come what may, to reduce is potentially greater. More noise means concentration
energy consumption and remove maintance costs and levels will be affected and educational performance
commitment. will suffer.’
‘We must not be slaves to natural ventilation, and He proposes what is, in effect, closely controlled
daylighting, in teaching spaces – this is utterly wrong,’ natural ventilation: ‘To provide a comfortable and
says Wyatt, who is also a main board member of the healthy indoor climate you need precise millimetre
British Council for School Environments. ‘At best it’s by millimetre control of the openings and intelligent
wishful thinking that denies the facts, which include modes of operation suitable for the specifi c building,’
acoustics and human behaviour, leading to stinking explains Arnott. ‘This enables the windows to be
unventilated classrooms or a colossal use of heat energy. opened at the optimum distance to provide noise
In Denmark and Germany, mechanical ventilation insulation and avoid classroom disruption.
is normal and things are very different,’ he adds. ‘I ‘Ventilation also needs to be demand controlled
am absolutely convinced that ventilation must be of in order to lower the carbon-footprint of future
“all fresh-air” and be introduced into a space by the schools.’
“displacement” method. Peter Rogers, chairman of the Building Acoustic
‘And this must not be dependent on actions to Group which is part of the Institute of Acoustics,
arrange it by teachers, it must be automatic, adjusted believes that by taking air from the quiet side
continuously to the amounts commensurate with (unattenuated acoustically) and drawing it through,
prevailing occupancy, incorporate heat recovery with using stack effect, is perhaps the preference for a
integral thermal storage, and able to provide 12l/s per general balanced principle from the acoustician’s
occupant of the space.’ perspective, ‘meaning that our challenge is often to
Teachers should have the ability to open windows in make natural systems work.’
IT suites in schools can bring
spring and autumn, according to Wyatt, but this should Many engineers feel that heat recovery is the most
their own challenges for
also be controlled to ‘when outdoor temperatures are energy efficient method for achieving ventilation
ventilation systems. between, say, 17 to 23 deg C, and in case the system breaks rates. But to work well heat recovery ventilation must >
16 CIBSE Journal February 2010 www.cibsejournal.com
CIBSEfeb10_School_pp12-14,16,18_Ventilation.indd 16 25/1/10 15:41:14
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