or
I. R
n
ace,
UK
Article history:
Received 29 January 2008
Received in revised form 26 June 2008
Accepted 27 June 2008
committing to a £45 billion (app. 90 billion US dollars) pro-
gramme of rebuilding and refurbishing secondary schools in
England and Wales called Building Schools for the Future (BSF).
To underpin the BSF programme the former Department for
Education and Skills (DfES) has published design guidance –
2
5000 ppm during the teaching day.
3. At any occupied time the occupants should be able to reduce
the concentration of CO2 to 1000 ppm.
4. Purpose provided ventilation in naturally ventilated buildings
should provide an external air supply to all teaching and
learning spaces with (a) a minimum of 3 l/s per person,
(b) a minimum daily average of 5 l/s per person and (c) a capa-
bility of achieving a minimum of 8 l/s per person at any time.
5. Purpose provided ventilation in mechanically ventilated
Contents lists availab
E
ls
Building and Environment 44 (2009) 1466–1477* Corresponding author. Tel.: þ44 (0) 20 7679 8235; fax: þ44 (0) 20 7916 1887.1. Background
In the UK, school buildings to date have been built in a series of
waves [1]:
1. The first wave commenced after the introduction of the 1870
Education Act; this resulted in a huge investment in school
buildings – the ‘Victorian school building stock’.
2. The second wave followed the 1944 Education Act; most of the
school buildings in this wavewere built in the 1940s and 1950s.
3. The most recent wave of school building started in 2006 and is
expected to continue till 2020 due to the UK Government
Building Bulletin 101 ‘Ventilation in School Buildings’ (BB101) [2].
This performance standard document is cited as a means of
demonstrating compliance with the new Building Regulations Part
F (Ventilation) in England and Wales [3]. In BB101 CO2 concentra-
tion has been chosen as the key performance indicator for the
assessment of indoor air quality and ventilation in schools. The
recommended ventilation performance standard can be summar-
ised as follows:
1. The average concentration of CO2 should not exceed 1500 ppm
during occupied hours.
2. The maximum concentration of CO should not exceedKeywords:
Indoor air quality
Thermal comfort
Acoustics
Schools
Operational performance
ClassroomE-mail address: d.mumovic@ucl.ac.uk (D. Mumovi
0360-1323/$ – see front matter  2008 Elsevier Ltd.
doi:10.1016/j.buildenv.2008.06.014Previous studies have found that classrooms are often inadequately ventilated, with the resultant
increased risk of negative impacts on the pupils. This paper describes a series of field measurements that
investigated the indoor air quality, thermal comfort and acoustic performance of nine recently built
secondary schools in England. The most significant conclusion is that the complex interaction between
ventilation, thermal comfort and acoustics presents considerable challenges for designers. The study
showed that while the acoustic standards are demanding it was possible to achieve natural ventilation
designs that met the criteria for indoor ambient noise levels when external noise levels were not
excessive. Most classrooms in the sample met the requirement of limiting the daily average CO2
concentration to below 1500 ppm but just a few met the need to readily provide 8 l/s per person of fresh
air under the easy control of the occupants. It would seem that the basic requirement of 1500 ppm of CO2
is achieved as a consequence of the window areas being just sufficient to provide the minimum of 3 l/s
per person at low and intermittent occupancy. Thermal comfort in the monitored classrooms was mostly
acceptable but temperatures tended to be much higher in practice than the design assumed.
 2008 Elsevier Ltd. All rights reserved.a r t i c l e i n f o a b s t r a c tWinter indoor air quality, thermal comf
built secondary schools in England
D. Mumovic a,*, J. Palmer b, M. Davies a, M. Orme b,
R. Critchlow d, H.A. Medina a, G. Pilmoor c, C. Pearso
a The Bartlett School of Graduate Studies, University College London, 1-19 Torrington Pl
b Faber Maunsell, 94-96 Newhall Street, B3 1PB Birmingham, UK
cBSRIA, Old Bracknell Lane, RG12 7AH Bracknell, UK
d Sound Research Laboratories, Holbrook House, Little Waldingfield, CO10 0TH Sudbury,
Building and
journal homepage: www.ec).
All rights reserved.t and acoustic performance of newly
idley a, T. Oreszczyn a, C. Judd c,
c, P. Way d
WC1E 6BT London, UK
le at ScienceDirect
nvironment
evier .com/locate /bui ldenvbuildings should provide external air supply to all teaching and

Envlearning spaces with a minimum of 5 l/s per person at all times,
and a capability of achieving a minimum of 8 l/s per person at
any time.
The importance of maintaining adequate indoor air quality in
schools is recognised as being a contributing factor to the learning
performance of pupils [4–6]. Recently, a study based on both
a subjective questionnaire survey and objective test scores
concluded that learning performance improved with a decrease in
the percentage of pupils dissatisfied with the indoor air environ-
ment [7]. Another study, based on five independent experiments
carried out in mechanically ventilated classrooms, concluded that
improving classroom conditions should be an urgent educational
priority [8]. The study showed that doubling the ventilation rate to
10 l/s per person would improve school performance by 14.5%
while reducing the temperature by 1 C would improve it by 3.5%.
In addition, an ongoing study on ventilation rates in schools aims to
determine the effect of indoor air quality on pupils’ performance by
monitoring nine schools in Southern England [9]. The preliminary
results of this study based on eight different primary school
buildings strengthen the evidence that improved ventilation has
beneficial effects on pupils’ learning performance and that without
intervention the existing ventilation rates remain below the
minimum recommended levels [10]. The provision of adequate
ventilation is likely to become more difficult with the introduction
of carbon reduction strategies in school buildings (i.e. increased
airtightness).
However, indoor air quality alone is not sufficient to provide
a good learning environment. Thermal comfort and acoustic
performance are also vital aspects of the internal conditions and
have been previously defined by Building Bulletin 87 ‘Guidelines
for Environmental Design in Schools’ [11]. In 2003 the DfES
produced, ‘A Design Guide, Building Bulletin 93’ (BB93) [12] that
significantly revised the standards for acoustic performance in
classrooms. The revised standards of BB93 are considered to be
very difficult to achieve in a naturally ventilated school and
a significant proportion of the design profession considered that
natural ventilation designs were not compatible with the acoustic
standards and thus were proposing only mechanically ventilated
designs. Therefore, when BB101, was published in 2006 it
provided further guidance to facilitate the use of natural venti-
lation. The objective was to provide suitable indoor ambient noise
levels (a) for clear communication of speech between teacher and
student, and (b) for study activities. The definitive guidance is as
follows [2]:
1. If the design uses aminimum fresh air supply rate that is equal or
greater than 3 l/s per person, the indoor ambient noise levels
with this ventilation rate should not exceed the upper limit for
the indoor ambient noise of 35 dB LAeq,30min in classrooms,
tutorial rooms, seminar rooms, and language laboratories.
2. When the design capability supply rate of 8 l/s per person is
provided by natural ventilation, the design should achieve the
BB93 performance standards for the indoor ambient noise
levels when they have been increased by 5 dB LAeq,30min.
This means that a natural ventilation strategy which meets the
BB93 indoor ambient noise level requirements should be possible
because there is flexibility for lower noise levels during occupied
periods at a ventilation rate of 3 l/s per person and higher
permissible levels at a higher ventilation rate of 8 l/s per person. In
addition, but at the discretion of the teacher, when the classroom is
occupied higher noise levels may be acceptable when rates of
ventilation higher than 8 l/s per person are required – for example
D. Mumovic et al. / Building andduring overheating on hot summer days when it may be necessary
to open all the windows [2].The present project aimed to measure the ventilation rates in
secondary schools built to comply with BB93 and to assess the
balance between indoor air quality, thermal comfort and acoustic
performance of the design. The main focus of the project was to
concentrate on the performance of naturally ventilated schools, but
it also took the opportunity to monitor examples of mechanically
and hybrid ventilated schools, gathering information on the
ventilation, acoustic and thermal performance of these designs.
2. Methodology
A monitoring approach was developed to investigate the key
performance parameters assessing if the design provided adequate
indoor air quality, thermal comfort and acoustic performance in
winter.
2.1. Schools
Nine schools were monitored during 2006 and 2007, all of
which were secondary schools built in compliance with BB93. The
first school acted as a pilot study to develop the monitoring
methodology, which was then followed in the remaining eight
schools. A total of 16 classrooms were monitored in the main
sample and two in the pilot study. The sample was geographically
spread across England from the south-east and south-west to the
north-west.
The sample classrooms used a range of ventilation strategies.
The breakdown was as follows:
 single sided ventilation (4)
 cross-ventilation (4)
 single sided and stack ventilation (5)
 mixed mode (2)
 full mechanical ventilation (3)
Some schools had more than one ventilation strategy and in
these schools the impact of different strategies was investigated.
Table 1 contains the following technical details for all monitored
schools/classrooms: (1) classroom identification, (2) location of
the school building, i.e. urban, suburban, and rural, (3) mode of
ventilation, i.e. natural ventilation (NV), mixed mode (MM), and
mechanical ventilation (MV), (4) classroom volume [m3], (5) type
of ventilation, (6) type of windows, (7) maximum openable area
[m2], (8) type of heating, and (9) various comments related to its
operation and design. A typical newly built classroom is shown
in Fig. 1.
2.2. Ventilation
The monitoring was carried out for a week during the heating
season in two representative classrooms in each school.
In order to indicate the overall indoor air quality and provide
a means of inferring the ventilation rate based on the number of
occupants, levels of CO2 were monitored at 5-min intervals
throughout the occupied day, in locations close to the occupied
zone at seated head height. Two Quest Technologies infra-red gas
monitors (AQ5001Pro) (accuracy: 3% in the range: 0–20,000 ppm)
were used for the indoor measurements. The Quest Technologies
monitors included thermistor sensors measuring ambient
temperature (accuracy: 0.5 C) and capacitive sensors measuring
relative humidity (accuracy: 3%). In addition, outdoor CO2 was
measured using a Telaire 7001 infra-red gas monitor (accuracy:
50 ppm or 5% of the reading, whichever is greater). Ventilation
ironment 44 (2009) 1466–1477 1467rates were estimated over suitable intervals using Eq. (1), a form of
‘continuity equation’ [13,14].