Schools and education facilities supplement Classroom ventilation
A ‘chilling’ class room dilemma
Natural or mechanical?
It is not a straight choice
when it comes to classroom
ventilation, as Ewen Rose
discovers.
he issue of school ventilation raises stronger
T
feelings in the building services community
than almost any other. The seemingly
intractable challenge of minimising energy
consumption while also ensuring children have the
best possible learning environment is one that has
brought seasoned engineers to their knees time
and again.
Designing services for educational areas also
presents a greater challenge than, say, a conventional
offi ce building. Classrooms generally have to cater for
a wider variety of activities, numbers of occupants and
hours of use.
However, existing design guidance from the former
Department for Education and Skills (DfES) in the
shape of Building Bulletin 101 states that, whatever
method you choose, it should be capable of providing
pupils and teachers with eight litres per second (8l/s)
of ‘fresh’ air and a minimum average of 5l/s per person
per day. The department does not stipulate whether
engineers should use natural, mechanical or ‘hybrid’
systems, but offers its ClassVent tool as an approved
software instrument for calculating airflow rates
and required ventilation capacities in any given
school area.
Legislation, in the shape of the School Premises
Regulations (SPR), states that a minimum of 3l/s must
be provided for ‘the maximum number of persons the
area will accommodate’. That is the legal minimum,
but clearly does not provide an ideal learning
environment.
Freshness
Concentration of carbon dioxide (CO2) is the
measurement by which engineers calculate the
‘freshness’ of the air. Current legislation states that
this should not exceed 5,000 parts per million (ppm)
during the teaching day, yet this is clearly far too high
to provide a healthy environment. Anything above
1,500ppm has been shown in numerous studies to
impair learning.
Most existing school buildings were designed for
natural ventilation so are largely narrow-plan with
openable windows. It has been possible for such >
www.cibsejournal.com February 2010 CIBSE Journal 13
CIBSEfeb10_School_pp12-14,16,18_Ventilation.indd 13 25/1/10 15:39:27
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