1. Integrated school design
Integrated
school
design
TM57
The Chartered Institution of Building Services Engineers
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TM57: 2015
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2. Integrated school design
CIBSE TM57: 2015
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4. Foreword
School buildings, and in particular spaces for learning, have environmental requirements that are more
demanding and complex than many other types of buildings. Meeting these, often conflicting, design
requirements is fundamental to the occupants’ sense of well-being and educational attainment. The premise
behind this publication is therefore to consider the individual environmental parameters of successful
learning spaces and identify the conflicts and interactions that exist when providing an holistic design
solution.
In producing this Technical Memorandum the aim has been to provide guidance not only for the building
services engineer but also other members of the design team, such as architects, contractors, client bodies and
users, who have an influence on the design outcomes. Our hope is that simple and clear guidance can help
steer the design team and users towards creating places where our teachers, our children, and our community
can become inspired.
However, this Technical Memorandum alone will not guarantee good school design. A checklist of criteria
does not constitute successful design. School designers must also make the effort to visit existing school
buildings and study exemplar cases to fully experience the results of the design process, both good and bad.
Dejan Mumovic
Co-ordinating editors
John Palmer (AECOM)
Professor Dejan Mumovic (The Bartlett, UCL)
Principal authors
Andrew Bissell (Cundall)
Esfand Burman (UCL/AEDAS)
Richard Daniels (Education Funding Agency)
Dr Mike Entwisle (Buro Happold)
Paul Eslinger (The Wessex Environmental Partnership)
Dr Benjamin Jones (Nottingham University)
Gregory Keeling (Essex County Council)
Professor Maria Kolokotroni (Brunel University)
Professor John Mardaljevic (Loughborough University)
Ian Taylor (Feilden Clegg Bradley Studios)
Dr Andrew Wright (De Montfort University)
Mike Wood (Exeter University)
Contributing authors
Colin Ashford (ConsultEco)
Roderic Bunn (BSRIA)
Emeritus Professor Derek Clements Croome (Reading University)
Lia Chatzidiakou (The Bartlett, UCL)
Amrita Dasgupta (Leicester City Council)
Sung Min Hong (UCL Energy Institute)
Professor Martin Liddament (Monodraught)
Dr Judit Kimpian (AEDAS)
Andrew Parkin (Cundall and Institute of Acoustics)
Greig Paterson (The Bartlett, UCL and AEDAS)
Craig Robertson (UCL Energy Institute)
Joe Williams (The Bartlett, UCL and Feilden Clegg Bradley Studios)
Acknowledgements
The Institution is grateful to Ann Bodkin, Gordon Hudson and Ian Pegg for refereeing the draft prior to
publication.
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5. Permission to reproduce extracts from BS EN 15251: 2007 is granted by BSI. British
Standards can be obtained in pdf or hard copy formats from the BSI online shop: www.
bsigroup.com/shop or by contacting BSI Customer Services for hardcopies only: Tel: +44
(0)20 8996 9001, Email: cservices@bsigroup.com.
Editor
James Parker (BE Knowledge)
CIBSE Editorial Manager
Ken Butcher
CIBSE Head of Knowledge
Nicholas Peake
CIBSE Technical Director
Hywel Davies
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6. Contents
1 Introduction 1
1.1 Aims of this document 1
2 Setting the design process 1
2.1 Introduction 1
2.2 The informed client 2
2.3 Developing a brief 2
2.4 Briefing for ‘performance in use’ 4
2.5 Room data sheets 6
3 Early engineering considerations and design hierarchy 6
3.1 Site evaluation 6
3.2 Integrated design process 6
3.3 Operational design issues 10
3.4 Conflicts 10
4 Acoustic design 10
4.1 Introduction 10
4.2 Methods 11
4.3 Design conflicts 12
4.4 Operational conflicts 13
5 Lighting design 15
5.1 Introduction 15
5.2 Daylight design principles 16
5.3 Daylight design evaluation 18
5.4 Electric lighting design principles 19
5.5 Modelling and visual amenity 19
5.6 Controls 19
5.7 Conflicts 20
6 Ventilation design 20
6.1 Introduction 20
6.2 Methods and strategies 22
6.3 Design conflicts 24
7 Overheating and comfort cooling 26
7.1 Introduction 26
7.2 Passive methods for avoiding overheating 27
7.3 Mechanical cooling 30
7.4 Mitigating the impact of climate change 32
7.5 Design conflicts 32
8 Heating and thermal performance 32
8.1 Introduction 32
8.2 Key design parameters 33
8.3 Fuel selection 35
8.4 Design conflicts 35
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7. 9 Controls 36
9.1 Introduction 36
9.2 Heating control 37
9.3 Lighting control 38
9.4 Windows 38
9.5 Night time cooling 39
9.6 Designing controls for the users 39
9.7 Usable controls 39
9.8 Conflicts 40
10 Energy 42
10.1 Introduction 42
10.2 Energy metrics 42
10.3 Approaches to ‘zero’ carbon design 44
10.4 Energy performance in use 45
11 Methods for post occupancy evaluation 48
11.1 Introduction 48
11.2 Benchmarking 48
11.3 Appraising the design 50
11.4 Investigating a problem 50
11.5 Human factors 50
11.6 Physical performance evaluation 50
11.7 Monitoring plan 53
12 Facilities management 53
12.1 Introduction 53
12.2 Documentation and training 54
12.3 Building optimisation and control 54
12.4 Metering 56
12.5 Monitoring and targeting 56
12.6 Towards energy efficient fm 57
13 Integrated case study 57
13.1 The building context and design process 57
13.2 Acoustic design 59
13.3 Lighting design 59
13.4 Ventilation design 60
13.5 Overheating and thermal comfort 61
13.6 Heating system and controls 62
13.7 Energy performance 63
13.8 Building use studies 63
13.9 Lessons learnt 64
References 64
Appendix: Example building assessment questionnaire 68
Index 70
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8. services engineer in particular will be able to bring their
understanding of all aspects of building design and
performance to influence a more informed design team.
Each chapter of this guide indicates best practice approaches
alongside practical feedback from completed projects to
help identify the key issues that need to be addressed to
create successful learning spaces. Our hope is that simple
and clear guidance can help steer designers, contractors,
and users towards better outcomes will move a long way
towards creating places where our teachers, our children,
and our community can become inspired.
However, this guide alone will not guarantee good school
design. School designers must also make the effort to visit
existing school buildings and study exemplar cases to fully
experience the results of the design process, both good and
bad.
2 Setting the design process
This section describes the key issues that relate to the
establishment of a design and procurement team, and the
brief that they will work to. The need to provide an
integrated design solution requires the whole design team
to know the overall process by which the school is to be
constructed. For the building services design engineer this
requires an understanding of the many factors that relate to
the design process. This includes an awareness of the
various interlocking briefs, namely the master plan,
educational outcomes, capital and revenue costs, and
performance in use standards, together with the roles of the
members of the design team. The potential for the building
services engineer to foster the role of ‘informed client’ is
clear due to the breadth of influence they have over the
design outcomes.
2.1 Introduction
Taking into account the range of activities that take place
within school buildings, it is essential that the design
process should reflect the interactions between occupants,
spatial layout, energy efficiency and the provision of
suitable indoor environmental quality (Mumovic and
Palmer, 2008). The final design should aim to deliver an
integrated solution that minimises conflict between all
aspects of the design, achieves value for money and
incorporates whole life cycle costing in its selection. This
requires a holistic approach to building design and feedback
on real performance that involves collaboration between
the architect, engineer, contractor, client, end user, facilities
management provider and other stakeholders (Pegg, 2007).
1 Introduction
Schools should offer a safe, comfortable, and stimulating
environment for learning and social interaction. New and
refurbished schools should create spaces where discomfort
and functional problems are avoided. The design team,
through spatial, fabric and system design, should aim to
create an environment with optimum conditions as
efficiently as possible.
Spaces for learning, where physical, visual and aural
comfort, enhance communication and thinking, create
inspirational buildings. Uncomfortable conditions will not
enable teachers to work at their best, or children learn as
well as they could. Meeting this standard of adequacy
should be a minimum performance requirement. Design
teamsneedtounderstandthesebasicissues,andconcentrate
on meeting them, whilst also striving for solutions to add
value, and for excellence that will inspire. Poorly designed
spaces can work against educational outcomes, just as good
design and appropriate internal environments can facilitate
good performance.
School design has always had its own challenges; teaching
spaces need to be flexible and education methods change
with time. Carbon and energy targets have become more
demanding, and internal environmental performance
standards have increased. Therefore, changes in design
practice, to a more holistic approach, are needed to help
create schools which are more usable, more comfortable,
and easier to operate by their users and offer opportunities
for the educational challenges of the coming decades.
The premise behind this publication is therefore to focus
on the environmental parameters of successful learning
spaces and identify the conflict between the individual
design parameters that need our greatest attention.
However, it must be emphasised that performance in use,
rather than design intention, is the best test of success, and
issues relating to design, building operation, handover
procedures, and the complexity of BMS systems are found to
have significant impacts on outcomes. Therefore, all
stakeholders should be aware that over emphasis on reduced
costs, reduced floor areas and design standardisation,
delivered within ever-shortened procurement processes,
increases the need for clear design guidance and for
feedback to inform best practice.
1.1 Aims of this document
The aim of this Technical Memorandum is to provide
guidance not only for the building services engineer but
also other members of the design team, such as architects,
client bodies and users, who have an influence on the
design outcomes. By doing this it is intended that the
Integrated school design
1
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9. 2 Integrated school design
Poor environmental solutions can be the result of designers
not working together as a team. This can result in elements
of the design being overlooked or overemphasised, and
insufficient attention being paid to the needs of the users of
the school. Head teachers and governors are responsible for
their school’s academic results and so need to be aware of
design issues. A poor internal environment can affect the
performance of both the teaching staff and students, as
discussed in several journal articles (Dockrell and Shield,
2006; Dunn et al., 1985; Parnell and Procter, 2011). In
addition, poor design or inadequate contractual require
ments for the construction of new buildings can result in
increased operational costs, reducing the budget available
for teaching. Therefore, it is important to establish the
educational brief and future needs at the early planning
stage.
Teaching and learning spaces pose a great challenge to
designers and engineers as the environmental needs are
more complex than with most rooms. The challenge is not
just to deal with high heat gains, due to operating at full or
nearly full capacity most of the time with high internal heat
gains from equipment, but also the intermittent occupancy
as pupils move between spaces. Although complex,
achieving the balance between the provision of indoor
environmental quality, energy use and operating costs is
just one of many socio-technical engineering challenges in
school buildings, as discussed in several papers (Dasgupta
et al., 2012; Demanuele et al., 2010).
For school buildings, the integrated approach to design,
rather than the linear process where the architect presents
the engineers with a box to heat, ventilate and light, is even
more important to achieve good learning environments. In
a collaborative design team the architect can often benefit
from the engineer setting out basic environmental design
principles such as preferred orientation, massing, and
ventilation mode before they have started planning the
school. During the early feasibility stage of a project it is
necessary to establish good communication channels
between the client team, the design team and the future
users of the building. This allows all parties to agree the
proposals and ensure they will deliver the required
standards of performance; for example, that the proposals
are in line with a school development plan. Lack of clarity
and agreement in the procurement processes and contrac
tual requirements can result in undesirable environmental
outcomes. There are many different procurement routes to
appoint consultants and/or contractors, as well as different
contract types. Each type has different risks that need to be
explained and understood by the client so they can make
the most appropriate selection.
A survey of CIBSE professionals identified the important
issues to the energy efficient provision of good indoor
environmental quality in school buildings (Prodromou et
al.,2009).Thepractitionerssurveyedfrequentlyemphasised
the challenges they face in attempting to implement notions
of design quality. These include:
—
— Design guidelines are often misinterpreted,
imposing rigid constraints on designs often leading
to carbon intensive solutions in order to avoid
litigation.
—
— Regulatory requirements developed in isolation
with no consultation with other building specialists
represent a driving force in ever increasing
unregulated energy consumption.
2.2 The informed client
A key requirement of a successful school design process is
the need for an informed client. An informed client is a
client who is aware of the relationship between aspects of
design and the likely outcome for the teaching environment
in the proposed school (Figure 1). They are not necessarily
skilled in design but are able to ask informed questions
concerning how design options will be used to meet the
educational process and operational needs of the school; or
vice-versa, how an educational need will be met, or
compromised, by proposed design solutions. They can also
act as a bridge between the design/construction team and
the users, assisting with briefing the users in how to get the
best from their buildings. This specialist role will review
design solutions with the end user, as well as sharing their
own technical experience and knowledge with the design
team and contractor.
‘Informed clients are not necessarily skilled
in design but are able to ask questions
concerning how a teaching need will be
met, or compromised, by proposed design
solutions.’
The design team should recognise the need for an informed
client role and establish the mechanism by which this is
achieved in their procurement and design process. The
Commission for Architecture and the Built Environment
(CABE) developed a document entitled Successful school
design: Questions to ask (CABE, 2009). This provides a series
of questions that need to be asked during the development
of a design from the earliest site considerations through to
strategies for internal environmental conditions. It provides
an ideal source of questions for an informed client and is
also a valuable checklist for designers.
Figure 1 How do proposed design solutions affect teaching and learning
in schools?
2.3 Developing a brief
The following factors all have an impact on the design of a
successful school building during the early design stage.
Whilst many are not under the direct control of the services
designer, they can have an impact on design issues that lead
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10. 3
to reduced performance of the school. They can also lead to
the need for services to remedy inadequacies of the basic
design decisions. For example, requiring comfort cooling
to address an over-glazed lightweight structure. Therefore
services design engineers should try to exert influence over
matters that have implications for the internal environ
mental conditions.
2.3.1 Understanding and defining the
need: master planning
Producing a strategic masterplan, or school development
plan, should be the first task for any school anticipating the
need for building work, both new-build and improvements
to the existing estate. Therefore, before considering any
building work at a school there is a need to review the
overall premises needs. This may include new construction
work and/or reusing existing spaces differently. From this
review, a development plan can be produced that will reflect
the long-term building needs of the school’s education and
community objectives. This allows a school to decide the
extent of new construction required, and whether existing
accommodation can be cost effectively refurbished or
remodelled.
The choice of whether to build new, or refurbish and
remodel buildings, should be based on a thorough survey of
the existing buildings, coupled with a whole life value
options analysis. Issues to consider are the condition and
the remaining life of the building and its systems, and the
suitability of the building for its intended use. This should
include an appraisal of the annual maintenance and
running costs, compared to the available funding. This
consequently may require the input of a facilities
management specialist.
Asset management plans (AMPs) are suitable tools for
assessing the condition of school building stock. School
AMPs look at the sufficiency, suitability and condition of
the existing buildings to allow prioritisation of funding
depending on the AMP priorities. Therefore an AMP is an
ideal starting point for any school development.
Additionally, refurbishment and remodelling provide a
good opportunity to improve the energy efficiency of
buildings. Part L2B of the Building Regulations requires
the thermal performance of buildings to be upgraded when
refurbishment or extension takes place.
2.3.2 Educational requirements
The educational setting in which schools operate is
frequently changing. For example, the last ten years have
seen electronic white boards and data projectors installed
in nearly every classroom. Now ICT (information and
communications technology) is the norm. Changes to the
curricula may mean, for example, that class and group sizes
change, or the range of abilities found within a class result
in smaller groups working together in a classroom.
Consequently, buildings need to be able to adapt and so a
degree of flexibility is required in the design solutions
developed. The procurement team, including all advisors,
must clearly understand these aspects of a school building.
‘Early design issues all have an impact on
the design of a successful school building.
Services engineers should try to exert
influence over design issues that may lead to
reduced performance of the school.’
2.3.3 A series of interlocking briefs
As the stakeholders and design team work from the initial
identification of needs, an appropriate brief can be
developed. The brief for a school should normally include
a series of interlocking briefs. These may not be applicable
in all cases but can be considered as follows:
(1) Overarching brief: This brief governs the develop
ment of the other briefs and should clearly identify
the sustainability and energy efficiency vision for
the local authority and/or school. It identifies the
preferred site location, defines local constraints,
states the number of pupils now and in the future,
the size of the building, required facilities in
timetabled and non-timetabled areas, playground
and sports areas etc. The brief should cover site
security and access control, and identify the
required structural life and maintenance schedules.
The brief should establish the key performance
indicators (KPI) defining the success of the design
solution.
(2)
Educational brief: This brief identifies features that
will ensure that the building does not detrimentally
affect the educational process. Best practice is to
define these requirements as ‘performance in use’
rather than ‘design compliance’. Where appropriate,
sanctions should be in place for failure to achieve
the required performance. This brief should also
include any aspirations for the buildings to
demonstrate sustainable development and must
highlight the educational key performance
indicators (E-KPI) defining the success of the design
solution.
(3)
Technical brief: The brief that details the internal
environment required for each space, together with
the fixtures and fittings to be installed. This brief is
often extended to include furniture and portable
equipment. It is the brief that underpins the
solutions developed in response to the KPIs and
E-KPIs established as a part of the overarching and
education brief.
(4) Operational brief: This brief defines the client
requirements related to facilities management tasks
such as grounds maintenance, cleaning, building
maintenance, and energy usage.
(5)
Community brief: This brief covers the needs of
users other than the normal school occupants,
particularly out-of-hours use for local community
groups. Community use is ever changing in nature.
Care must be taken to allow for sections of the
building to be segregated from the rest for
community use. This approach helps with security
and limits energy consumption. For example, limit
the community use to a space easily accessible from
the main entrance and cluster it within a zone. This
will prevent the whole building from being lit and
heated when only a few rooms are being used.
Setting the design process
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11. 4 Integrated school design
now want to see a move from design compliance to proof of
performance in use as the measure of success of a project.
The term ‘performance in use’ describes the assessment of
the building, and its services, by the measurement of
specified parameters under the designed conditions of
occupancy. For example, if the brief requires that the
concentration of carbon dioxide in a classroom should
remain below 1500 ppm at any time of the day. The specified
parameters should be measurable to allow compliance to be
tested.
Performance in use standards must be evaluated in the
school under the conditions specified in the design brief,
and therefore used in developing the design. Such design
conditions would need to indicate:
—
— the definition of the day (occupied period or total
school day)
—
— the occupancy levels in the classroom
—
— agreed assumptions concerning user behaviour
—
— the location of measurement of the carbon dioxide
(for example, at seated head height in the centre of
the room and not adjacent to the ventilation inlets),
and
—
— the state of any ventilation system (windows in
suitable positions for the prevailing climatic
conditions).
With these design assumptions the measurement of the
performance in use parameter will then indicate either,
satisfactory performance, or a potential design failure.
However, if, for example, ventilation is limited by window
opening restrictors, or lack of awareness of the occupants of
how to boost fan speeds, then it may be an operational issue
rather than design failure.
The practical implication of this is that at the detail design
stage attention must be given not only to the theoretical
performance, but also how to ensure that the occupants can
use the building as the designer intended. Therefore
designers and builders must work together, and account for
occupant behaviour, when designing the building.
An examination of the effectiveness of the building can be
carried out as part of a wider post occupancy evaluation
(POE). See sections 11 and 13 for more details. This can
prove that the design intention has been met, by using low
cost equipment that ideally gives results immediately.
To help ensure that a building is designed to the needs of
users and that occupants know how to operate the building,
particular attention should be paid to:
—
— effective briefing
—
— the commissioning processes
—
— end user training
—
— control specification
—
— handover procedure
—
— maintainability.
Regardless of the use of ‘design compliance’ or ‘performance
in use’ assessment criteria, the client should always
explicitly define the technical detail of their design
requirements. This reduces the opportunity for project
2.3.4 Cost issues: defining essentials and
desirables
All the technical aspects of the brief, as indicated above,
need to be considered within the budget for the school
development. To ensure that the key outcomes are always
delivered, it is important to differentiate at the briefing
stage between the essentials and desirables. This will
involve skilful discussions between all stakeholders. Cost
tends to be the overriding factor driving projects and there
is a risk than short-term capital savings will lead to poorer
environmental conditions, longer-term expense, and
greater energy use/carbon emissions. This is where the
informed client/advisor’s role is important for highlighting
the implications of all decisions.
2.3.5 Capital and revenue implications
The capital cost of a design option and associated running
costs should always be quantified and agreed with the
client. Educational buildings need to be affordable to
operate and maintain. It is essential for designers of schools
to consider how affordable their design will be for the end
user. The competition between building operation and
educational support budgets should not lead to poorer
teaching resources.
‘The capital cost of a design option and
associated running costs should always be
quantified and agreed with the client.’
Many cost planning issues are related to whole-life costs. A
sensitivity analysis should be carried out looking at future
costs. This will allow the client to have a better
understanding of the impact of higher or lower than
expected costs.
2.4 Briefing for ‘performance in
use’
Typically, building specification, design, fit-out,
commissioning and final handover, are based on design
compliance. The assumption being that, if the design, as
‘signed off’, complied with design standards, good practice
and Building Regulations then the client receives the
building they expected. The problem with this approach is
that design compliance does not necessarily meet the
client’s expectations of the school building once occupied
and in use. This has been assessed and reported on in
academia (Pegg, 2007; Dasgupta et al., 2012).
Some design failures are a result of design options that
appear satisfactory at the design stage, when meeting
traditional design standards, but fail to deliver the required
standards when the building is in use. A school design that
shows adequate performance when subject to computer
simulation at the design stage may depend on assumptions
that are not reflected in the real building in use. This
disparity between design intentions and final outcomes has
led to many of the problems cited in reports on the design
quality of schools (Pegg, 2007; Clements-Croome et al.,
2010). Consequently, a growing number of informed clients,
together with the Education Funding Agency (EFA, 2014a),
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12. 5
Setting the design process
Table 1 Examples of performance in use parameters (not necessarily as in any given specification)
Parameter Definition
Summertime overheating The building is said to overheat if two of the following three conditions apply:
—
— The number of hours (He) the measured operative temperature exceeds the acceptable operative
temperature by X °C or more is not more than either 40 hours or 3% of the total occupied hour.
—
— The sum of the weighted exceedance is more than Y degree hours.
—
— The temperature exceeds the appropriate value of Tmax by Z °C or more at any time.
In addition, for mechanically ventilated buildings, during the required period there must be no
more than 200 hours in a year when the internal air temperature exceeds A ºC.
Winter overheating The heating system shall not put heat into any treated space for a period of time exceeding a
specified duration that causes the air temperature in the middle of the room at 1 m above floor level
to exceed a specified temperature.
Space temperature sensing All sensors used to monitor heating or cooling energy in treated spaces must be in the middle of the
room, at 1 m above floor level, at all times.
Carbon dioxide CO2 CO2 level in any occupied space must not exceed a stated concentration at any time when occupied.
Lighting energy in daylight hours When the overhead sky luminance is higher than a predetermined value, daylight must displace at
least a fixed percentage of the building’s artificial lighting energy during normal occupied hours.
This is easily measured now that lighting circuits must be separately metered. The energy use with
all lights on at night is easily determined, which is the 100% reference. This requires daylight design
to manage glare to avoid ‘blinds-down, lights-on’.
Lighting energy efficiency Maximum lighting energy in any occupied space larger than 8 m², and not requiring lighting for
accurate colour assessment, shall not exceed a maximum value in W/m² per 100 lux.
Mechanical cooling in occupied spaces Mechanical cooling shall not be used to cool any treated space with an ict load below X W/m² when
the outside air temperature is below a specified threshold value.
Fan power Total specific fan power to ventilate treated spaces, flow and return, must not exceed a given value in
W/L·s–1 at any time.
Ambient noise level Only applies to rooms that are normally occupied for more than one hour a day.
Noise measured at least 1 m from any fixed equipment, shall not exceed a specified value during
normal occupation.
managers, designers and contractors to interpret client
requirements incorrectly, and possibly disadvantage the
client. Many of these issues can be dealt with by robust
briefing processes, and adopting suitable procedures such
as Soft Landings (Bunn, 2014) and post occupancy
evaluations. Enthusiastic trained occupants in the school
can also help to give advice on day-to-day operation.
‘The term 'performance in use' describes the
assessment of the building, and its services,
by the measurement of specified parameters
under the designed conditions of occupancy.
However, the conditions under which the
criteria must be met must also be adequately
specified for the designer to be able to design
for this performance in use standard.’
Table 1 gives examples of performance in use parameters
that could be defined within the client requirements. The
actual values for the performance in use requirements
should be decided with the agreement of all interested
parties. Output specifications often set values for many of
these parameters.
In the pursuit of satisfactory performance in use a good
engineering design requires early discussions with the end
user. A means of ensuring this is holding ‘charrettes’ —
periods of discussion and collaboration of the design team
and end user/client representatives. The ideal time to run
charrettes is at the initial stages of a project. These should
be conducted in nontechnical language, to understand the
needs of the end user, and to explore potential solutions. A
design charrette held during RIBA stage 2 (concept design)
is essential as it can address the following issues:
—
— Sets quantifiable metrics to verify compliance with
client objectives.
—
— Helps all design team members understand the
implications of the agreed project objectives, for
their individual profession and across professions.
—
— Sets project strategies for consideration of potential
design solutions, including cost and time
constraints. The object is to avoid surprises later in
the design and construction processes.
—
— Reviews grants and funding available to the project,
and takes a decision on the value to the project of
attempting to access such funding.
—
— Identifies outline solutions for key design issues.
—
— Identifies the phasing of decisions. (e.g. decisions
on heat sources are only made when daily/seasonal/
peak load profiles are defined).
—
— Identifies the need and available budgets for
external specialist input, such as comprehensive
thermal and daylight modelling to optimise
summer overheating, window sizing, acoustics,
ventilation and space heating requirements.
In designing for performance in use a key aim of the
designer is to optimise the performance across all the
desired outcomes rather than maximise individual aspects.
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13. 6 Integrated school design
3.1 Site evaluation
During the site evaluation and selection process, it is
important that engineering considerations, and any
constraints imposed by the site, are fully evaluated and
understood (CIBSE, 2006a). These will all influence, to
varying degrees, the strategies adopted for acoustics,
lighting, heating, ventilation, controls, fire, security and
environmental matters. Of these, the primary concerns are
the acoustic, daylighting and ventilation strategies. When
considering these, note should be taken of the surrounding
noise and pollution levels (e.g. traffic and aircraft), the
microclimate, and any significant obstructions to daylight.
At this stage it is possible to either eliminate or reduce
factors that can impinge on the final design options. For
example, locating the building as far as possible from
sources of noise and pollution; and orienting it to optimise
daylight, whilst avoiding excessive solar gain (Figure 2).
Other factors can also influence the site evaluation such as
access for vehicles, especially if using biomass fuel, and
planning limitations.
An integrated approach, wherein no particular design
aspect takes precedence, but all factors are given suitable
weight, will deliver the better overall outcome. Attempts to
maximise a specific parameter may conflict with other
critical issues that affect the quality of the internal
environment.
‘In realising the design aspirations a key
aim of the designers is to optimise the
performance across all the desired outcomes
rather than maximise individual aspects.’
2.5 Room data sheets
From the environmental perspective there are 16 basic
types of space in a school. Each type is fitted out differently
and has slight variations in services, fittings and furniture
depending on the end use. The space types commonly
found are:
(1) basic teaching spaces
(2) practical spaces
(3) multipurpose halls
(4) sports halls
(5) kitchens
(6) changing rooms and showers
(7) toilets
(8) drama, movement and activity studios
(9) dining and social areas
(10) performance spaces
(11) music rooms
(12) libraries
(13) learning resource areas
(14) offices
(15) server rooms, and
(16) storage areas.
Room data sheets are one way of ensuring that the
conditions required of all the various spaces are specified
unambiguously. Although a room data sheet will be needed
for nearly every room type, the environmental requirements
will be based on a fewer types of space.
3 Early engineering
considerations and
design hierarchy
This section outlines an iterative and progressive approach
to the design process. References are made to the sections
dealing with the various design strategies. Conflicts that
arise because of competing design solutions are also
described.
Figure 2 Microclimate analysis
N
Sun
Wind
Noise
3.2 Integrated design process
After the acoustic challenges of the site have been addressed,
described in detail in section 4, the development of
strategies for the daylighting, ventilation, thermal comfort
and energy follow. Figure 3 shows the process route for the
development of these strategies.
The provision of daylight is the first priority (SLL, 2011).
This determines the orientation of the building on the site,
and the distribution and size of glazed areas. In most
situations this aspect of the school is the ‘building block’
for the design on which other design decisions rest. This
includes the development of ventilation and thermal
comfort strategies. Section 5 deals with daylighting
strategies in more detail.
Having established a basic approach for the daylight, the
ventilation strategy should be developed next. Natural
ventilation should be a default option (CIBSE, 2005).
Windows will often be the default source of ventilation,
although other methods should be considered. Chapter 6
deals with ventilation strategies in more detail.
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14. 7
quality and thermal comfort during the summer, this would
then provide the starting point for development of the low
and zero carbon energy strategy.
A balanced design is achieved by checking if the current
design is likely to meet the required criteria, or if that is not
the case, by investigating alternative strategies that may be
able to do so. This can be achieved most successfully from
an early stage in the design of the building. This makes it
possible to follow a structured approach using appropriate
design tools in a logical order. An iterative process should
be used until a satisfactory design strategy has been
achieved.
Table 2, shows some key factors that need to be considered
during the design process. The CABE document Successful
school design: Questions to ask (CABE, 2009) provides a
checklist of issues that need to be addressed at all stages of
With the daylighting and ventilation strategies proposed
the thermal comfort of the space is the next concern (BSI,
2005). Here the interplay of ventilation (daytime and night-
time) with the thermal mass of the fabric is a key factor in a
successful design. At this stage an iterative design process
may be required as the degree of thermal mass in the fabric
may need more or less ventilation, affecting the ventilation
strategy. Chapter 7 deals with methods of limiting
overheating and avoiding the use of mechanical cooling.
Figure 3 presents an overview of the recommended iterative
approach for new school buildings. Although each of the
key environmental design issues must be addressed with
respect to their own design requirements and solutions,
they are interrelated. Therefore and integrated design
approach is needed to provide an optimum solution. Once
a satisfactory strategy has been investigated and agreed for
all passive design aspects, including acoustics, indoor air
Early engineering considerations and design hierarchy
Daylight
3
1
2
4
5
6
Ventilation
9
7
8
Thermal comfort
D
A B
C
12
11
10
Low and zero carbon energy
Key
A: Daylight
1. Size/orientation/position
2. Type of glazing
3. Solar shading
B: Ventilation
4. Simple natural ventilation
5. Complex natural ventilation
6. Mechanical (assisted) ventilation
C: Thermal comfort
7. Thermal mass
8. Night cooling
9. Base gains
D: Low and zero carbon energy
10. Energy efficiency
11. Low carbon technology
12. Renewables
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15. 8 Integrated school design
Table 2 Iterative and progressive nature of holistic school building design
Step Design path Factors Advice
1 Site Local noise
Microclimate
Solar access
Orient to avoid local noise intrusion — this will help with natural
ventilation design check with possible impact of solar gain
The main impact of orientation on most sites is to avoid large areas of
glazing on east and west elevations, but ensure that south elevations have
good shading
2 Form Plan depth Set building geometry to limit plan depth, maximise ceiling height, and
keep window head high — essential for daylighting and natural ventilation
3 Fabric Thermal mass Medium to heavy thermal mass — helps to reduce risk of overheating
4 Daylight
strategy
Local environment Set window locations and areas to provide glare free daylight
5 Overheating
risk
Heat gains from sun and
occupancy
Assess overheating risks — model interaction of thermal mass, ventilation
strategy and incidental gains (check with low energy design of appliances
step 7) for day and night cooling — back to step 3 for window areas and
solar shading options
6 Ventilation Natural ventilation preferred
option
Develop ventilation design — provide ventilation for adequate winter
indoor air quality with minimum ventilation heat loss and avoiding
summertime overheating — back to step 3 for openable areas of windows
Ensure that ventilation is available at all times and that secure night
ventilation is available
7 Iteration
point
Continue to iterate between steps 3 4, 5 and 6 to provide optimal solution
for all parameters
8 Low energy
design
Minimise carbon emission Lighting, heating, domestic hot water, ventilation and non-regulated uses
such as ict equipment as required (note impact on incidental gains under
step 5)
9 Renewables Carbon limitation Limited budgets but ideal for educational purposes
10 Operation Occupants influence most
aspects of the performance
of the building
Soft Landings approach to commissioning and handover — note this has to
be established in earlier client briefings
Table 3 Design guidance for acoustic performance (Isanska-Cwiek et al, 2008) (DFES, 2003)
Site location Conflicts Guidance
Avoidance of noisy sites: locate the building away from
sources of noise
Orientation of building: place the school on the site to
provide self-shading from noise sources
May reduce daylight, solar gain and sunlight access Sections 4, 5 and 6
Noise barriers: provide appropriate barriers to prevent
noise impinging on facades
May reduce solar heat gain and sunlight access
Building envelope:
—
Heavyweight construction gives good isolation from
external noise sources
Slow thermal response to heating system Section 8
—
Limited penetrations prevent noise entering the
school through opens in the envelope
Compromised natural ventilation Section 6
Glazing areas Small areas may reduce daylight availability Section 5
Services:
—
Mechanical ventilation: locate air handling plant to
reduce noise impact, reduce supply duct velocities
Limits maximum flow rate required for controlling
overheating
Section 7
—
Mechanical cooling: location of plant Unavoidable local noise source Section 4
—
Motorised dampers: avoid noisy actuators Control of natural ventilation openings Section 6
Internal surfaces:
—
Sound absorbent materials: control reverberation
times with suitable surface finishes
Reduced exposed thermal mass compromises control of
overheating
Section 7
Acoustic separation between internal spaces Air flow paths for natural ventilation
Geometry:
—
Room size and geometry: shaped ceiling may cause
unwanted reflections
Ceiling design for ventilation or daylight Sections 4, 5 and 6
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16. 9
Early engineering considerations and design hierarchy
Table 5 Design guidance for ventilation performance (DfES, 2006; CIBSE, 2013)
Site location Conflicts Guidance
Exposed site aids wind driven ventilation Control of draughts
Building envelope:
—
Façade requires suitable area required for ventilation
penetrations
Increase noise ingress BB 93
Glazing areas: Security of openings CIBSE AM10
—
Double aspect design: for cross ventilation and
daylight
Services:
—
Automatic vent actuators External noise
Internal noise
BB 93
—
Mixed mode fans Internal noise
—
Earth tube supply Draughts at low level
Geometry:
—
High ceilings narrow plan Narrow plan
Ceiling design for ventilation or daylight
BB101 and CIBSE AM10
Safety:
—
Control of fire spread Risk of fire spread See BB 100
Table 4 Design guidance for light/lighting performance (DfES, 1999; SLL, 2011)
Site location Conflicts Guidance
Orientation: south facing increases daylight Overheating: increased solar gains; may allow noise source
into space
Sections 5 and 7
Building envelope:
—
Increased glazing allows more daylight Overheating: increased solar gains; high proportion of
glazing can lead to glare problems; blinds might affect
ventilation design performance
Sections 5 and 7
Internal surfaces:
—
Colour of materials: prevent glare; allow to
maintain constant lux levels
Perception of space Section 5
Geometry:
—
Services areas: usually no daylight due to
architectural design
Increase in energy use for artificial lighting Sections 5, 10 and 13
Table 6 Design guidance for thermal comfort (DfES, 1999; CIBSE, 2013)
Building envelope Conflicts Guidance
Façade requires suitable area required for ventilation
penetrations
Increase noise ingress
Security of openings
Glazing areas for daylight Large glazed areas may increase solar heat gains
Double aspect design: for cross ventilation and daylight
Services:
—
Automatic vent actuators Limits maximum flow rate required for controlling
overheating
Section 7
—
Mixed mode fans Unavoidable local noise source Section 4
—
Earth tube supply Control of natural ventilation openings Section 6
Geometry:
—
High ceilings narrow plan Narrow plan
Ceiling design for ventilation or daylight
BB101 and CIBSE AM10
Safety:
—
Control of fire spread Risk of fire spread See BB 100
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17. 10 Integrated school design
essential for successful education, imperative for learning
of all pupils and critical for those with special hearing
requirements. However, it is often the case that the acoustic
requirements are not considered until relatively late in the
design process. Early consideration of acoustics is essential,
since this can avoid expensive remedial works. However,
without basic knowledge of acoustics, the design team may
not have the know-how to inform their decisions. This
section is intended to guide non-acousticians towards the
principles of good acoustic design so that their design
strategies can be evaluated holistically.
4.1 Introduction
It is of paramount importance for designers to understand
that the choices they make from the early stages will affect
the cost and ease in which a good acoustic environment can
be delivered. The position and layout of the building are
key decisions affecting acoustics, see Figure 4. For example,
placing classrooms on sides of the building not exposed to
transportation noise can reduce the need for high perfor
mance acoustic glazing.
Acoustic performance requirements are determined by the
type of activities carried out during the occupied hours in a
particularspace.Inordertoproduceasuitableenvironment,
the acoustic design needs to be considered alongside other
requirements, such as natural ventilation and access to
thermal mass, in addition to the requirements of the pupils
that use the space. Designing for acoustics is the best
starting point for a good iterative design process involving
all aspects of environmental design. See Table 7.
A key aim in the design of schools is to provide an acoustic
environment that facilitates and enhances learning. It has
been shown that increased indoor noise levels can be linked
to a reduction in academic achievement (Shield and
Dockrell, 2008; Xie et al., 2011). Poor acoustic environ
ments have even been linked to pupils having less positive
relationships with their peers and teachers (Overbaugh,
2011). Pupils with special hearing requirements are
particularly vulnerable, and are affected disproportionately
by poor acoustics. It is important to understand that pupils
with special hearing requirements do not just include those
with auditory problems, but also include pupils:
—
— with speech and language difficulties
—
— whose first language is not English
the development of the school. It highlights the role of the
site and community context for the school through the
form and massing of the building to the strategies for
daylight, ventilation and energy. This hierarchical
approach, followed by an integrated and iterative process,
will aid the design team in ensuring that all issues are
addressed and potential conflicts avoided.
A detailed design process protocol and urban school site
template was developed by Partnerships for Schools
(Partnership for Schools, 2009). When following this design
procedure is advisable to relate this to the RIBA work
stages (RIBA, 2013).
3.3 Operational design issues
Good design does not automatically result in a school that
operates as the designer intended. There are many matters
that come between the design conception and the operation
of the school.
The Soft Landings framework, published by BSRIA (Bunn,
2014), is a useful tool to help deliver successful outcomes, to
maintain the ‘golden thread’ throughout the life of a project
and deliver the clients requirements. This involves the
design team continuing to be involved with the building
post-handover to make sure that the building operators are
able to run the building as it was intended. The framework
also encourages feedback from the end users of the building
to be collated and shared with the original designers, to
help improve future designs.
3.4 Conflicts
Tables 3 to 6 above indicate how conflicts arise from
competing design aspirations. The tables are neither
comprehensive nor exhaustive in their treatment of the
potential for conflicts, but indicate some of the major areas
of concern. These have been observed in schools. However,
the designer can resolve these conflicts by integrated design
solutions that work optimally together, rather than
consideration of the design parameters in isolation.
4 Acoustic design
Acoustic design is directly linked with architectural design
and surface material selection. Good acoustic design is
Traffic noise
and vibration
Plantroom noise
and vibration
Ductborne noise fan
Aircraft noise
Weather
and rain noise
Playground
noise Noise via
open windows
Noisy
corridors Breakout/break in
of ductborne noise
Noise through
doors and walls
Ductborne noise
Plumbing
noise Figure 4 Potential noise sources
affecting schools (DfES, 2003)
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18. 11
—
— with visual impairments
—
— with fluctuating conductive deafness
—
— with attention deficit hyperactivity disorders
(ADHD)
—
— with central auditory processing difficulties.
Pupils can also experience temporary hearing problems
(such as glue ear) and even reduced hearing due the
symptoms of a common cold. It is therefore important to
recognise that there is a large proportion of pupils with
special speech and hearing requirements taught in
mainstream schools. Therefore it is important to design
acoustic environments that serve their needs.
A school’s acoustic environment consists of external sounds
penetrating the building envelope, internal sounds that
depend on type of learning activities and selection of
teaching equipment, and HVAC system design. There are
many areas where building performance targets can interact
and early consideration of these issues within the design
process is essential. Characterisation of the acoustic
properties of different school spaces tends to be focused on
the role the space plays in performance of the task being
performed within. For example, many noise ingress
problems encountered in naturally ventilated classrooms
could have been solved by an improved building layout or
orientation of ventilation openings away from traffic.
The choice of acoustic materials is also an important
consideration in an holistic design process. Selection of
materials should not only be based on their acoustic
properties, but should include a consideration of the life
cycle performance of the product, as well as their impacts
on energy use, health and well-being.
There are a large number of variables that can be used to
describe the acoustic environment of a school. Common
criteria that are used to describe the internal acoustic
environment include:
—
— reverberation times
—
— sound insulation between spaces (impact and
airborne)
—
— background and ambient noise levels
—
— speech intelligibility.
The acoustic conditions in schools are controlled by Part E
of the Building Regulations (NBS, 2010) and by the School
Premises (England) Regulations 2012 (TSO, 2012).
Requirement E4 from Part E of Schedule 1 to the Building
Regulations 2010 states:
‘Each room or other space in a school building shall be designed
and constructed in such a way that it has the acoustic conditions
and the insulation against disturbance by noise appropriate to its
intended use.’
The School Premises Regulations contain similar
statements to those in requirement E4 of the Building
Regulations, and apply to both new and existing school
buildings. To comply with the School Premises Regulations
open plan teaching and learning spaces will need to provide
an adequate Speech Transmission Index. Operational noise
levels (i.e. of equipment) in teaching and learning spaces
will also need to be suitable for the activities taking place.
Different rooms will have different requirements and the
room’s function should be considered when setting any
standard. Generally speaking, the more critical the listening
activity, the lower the reverberation time and ambient noise
levels should be in order to avoid distraction. The room
should be well isolated from those around it, particularly
when activities in adjacent rooms are likely to be loud (e.g.
music suites, kitchens and sports halls etc.).
4.2 Methods
It is important to recognise that having poor sound
insulation, excessive reverberation or high levels of ambient
noise could significantly degrade the learning environment.
Having a good level of sound insulation between classrooms
may be of no benefit if the room is so reverberant that is it
impossible to communicate. It is also important to recognise
that acoustic targets cannot be set without consideration of
other factors. For example, it might be possible to achieve a
good level of sound isolation between classrooms and
corridors at the expense of good ventilation. It is therefore
essential to consider acoustic targets alongside those of
ventilation and thermal performance. For example,
reverberation affects ambient noise levels and the perceived
sound isolation. However, acoustic absorbers can block
access to the thermal mass of a building by covering up too
much of the structure. Table 7 illustrates the complexity of
acoustic target setting and demonstrates the interrelation
between acoustic design targets and those related to
ventilation and thermal performance. It can be seen that
the reverberation affects the ambient noise levels, which in
turn is affected by a wide variety of other factors, and so in
turn affect other design requirements.
The layout of rooms within the building should also be
chosentominimisetheneedforexpensivehighperformance
internalpartitions,seeFigure5.Thehighertheperformance
Acoustic design
Table 7 Matrix for holistic target setting for acoustic targets
Reverberation Ambient
noise
Sound isolation
(internal to
internal)
Reverberation†
Ambient noise† •
Sound isolation†
(internal to internal)
• •
Room function • • •
Internal to internal
ventilation
• •
External to internal
ventilation
• •
Access to thermal
mass
• •
Mechanical
ventilation plant
noise
•
Efficiency of
mechanical
ventilation
•
Doors (size and
density)
• •
Windows •
Note: Acoustic requirements marked †; targets that will affect one
another are indicated by •
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19. 12 Integrated school design
requirement of a partition, the more difficult it is to meet
targets due to the increased reliance on detailing and
workmanship, in addition to the problem of flanking
transmission. Once the basic layout has been chosen, the
design can then be refined further. If the design team has
not already engaged the services of an acoustic specialist, it
is advisable that one is appointed to examine these early
stage designs first before proceeding further.
As a rule of thumb, opening windows and vents are deemed
to satisfy the acoustic requirement if external noise level at
the window position is no more than 13 dB (for single sided
ventilation) or 18 dB (for cross-ventilation) above the
internal ambient noise level (IANL). However, this only
applies when the IANL inside the room, with the windows
closed, does not exceed the IANL design requirement and
concentrations of carbon dioxide are within limits below.
Additionally, it should be noted that this only applies where
windows are top or bottom hung with 100 mm maximum
opening. For side hung glazing, the attenuation against
external noise will depend on the hinge side in relation to
the noise source. For other types of glazing, such as
horizontal/vertical sliding (sash) or in-line sliding, noise
ingress may be significantly greater than top or bottom
hung glazing. For these, and other types of opening,
calculations will be required to demonstrate than IANLs
will be met. At higher external noise levels mechanical
ventilation or sound attenuated natural ventilation is
required to meet the IANL with mechanical ventilation
operating to provide 1000 ppm and natural ventilation
operating to provide 1500 ppm in all teaching spaces (EFA,
2014b).
It is recommended that during unusually hot weather a
means is provided for the teacher to increase the air velocity
in the room to improve comfort, for example, by opening
windows, switching on local fans (such as punkah fans) or
boosting the mechanical ventilation. Under these
conditions higher noise can be considered to be acceptable.
Related British Standards include BS EN 15251:2007 (BSI,
2007), BS EN ISO 3382:2000 (BSI, 2000), BS EN 60804:
2001 (BSI, 2001) and BS EN 60268-16:2011 (BSI, 2011b).
4.3 Design conflicts
4.3.1 Natural ventilation and acoustics
It is often necessary to provide cross ventilation, by
ventilators, through partition walls. Sound insulation
between spaces can be compromised by crosstalk via
ventilation ducts. Naturally ventilated systems pose a
particular problem due to the low pressure drop needed for
sufficient airflow.
The use of indirect natural ventilation routes (e.g. from one
classroom through a circulation area to another classroom)
is often compromised by noise generation in the circulation
area. Guidance is available in a BRE report, A prototype
ventilator for cross ventilation in schools: Sound insulation and
airflow measurements (Hopkins, 2004). This project
developed different configurations of a prototype ventilator
intended for cross flow ventilation in schools. The design
of the ventilators was based on sound insulation and airflow
tests. Eight of the prototype ventilator configurations tested
had sufficiently high airborne sound insulation to satisfy
the performance standards of Building Bulletin 93 (DfES,
2003). In addition, the airflow tests indicated that although
the equivalent areas are reduced, due to the presence of
sound absorptive material inside the ventilator, the values
were high enough to allow cross ventilation. This study
provides evidence of the possibility of designing suitable
acoustic ventilators for this application.
Ductwork on a route through a number of rooms will
usually require crosstalk attenuators in series. This may be
impractical and can be particularly limiting for the economy
of layout in natural ventilation systems.
4.3.2 MVHR and acoustics
Mechanical ventilation with heat recovery (MVHR) can be
an efficient option for ventilating a school, especially in
winter when opening windows and ventilators can lead to
cold draughts. The noise generated from these systems
should be carefully considered. Acoustically attenuating
louvres can be used at ventilation openings to reduce noise.
However, since these louvres generally have an increased
pressure drop associated with them, they will increase the
Other
classroom
Music
classroom
Group
room
Group
room
Group
room
Group
room
Group
room
Group
room
Group
room
Group
room
Store
Store
Store
Store
Store
Intrument
store
Store
Store
Music
classroom
Staff
base
Ensemble
room
Recording/
control
room
Corridor
creates
acoustic
separation
Easy
access to
support
spaces
Stores
provide
acoustic
buffer
Acoustic separation
for esumble room and
group rooms
To other
departments
Figure 5 Using buffer zones to minimise the need for expensive high
performance sound attenuating walls (DfES, 2003)
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20. 13
crate grilles can be used to provide sound absorption
whilst maintaining air circulation between the
body of the room and the underside of the soffit.
Exposing the perimeter of the ceiling and a strip
across the centre of the room has been shown to be
effective. Here the airflow across the soffit is subject
to negligible degradation with over one-half of the
soffit exposed.
—
— Provide suspended acoustic absorbers: Acoustically
absorbent rafts (horizontal) or baffles (vertical) can
provide very a highly efficient method of sound
absorption. This is due to their greater surface area
compared to a traditional ceiling (both sides of the
element are exposed and accessible to incident
sound). Rafts can also be accommodated with
lighting, or in multi-service arrangements
containing other elements such as PIRs, smoke
detection etc. Care should be taken to see that any
sprinkler heads can operate efficiently with
suspended absorbers.
—
— Provide sound absorptive wall panelling: This can
be used to supplement absorption provided on the
ceiling, the area of which may have been reduced to
retain access to the thermal mass of the soffit.
Spreading the sound absorption across several
surfaces can be beneficial to the acoustic
performance of the room.
—
— Provide floating floors to control impact sound
originating from above: The isolation of structure-
borne sound is an important aspect of acoustic
design. Typically, impact sound is controlled either
at the floor surface (e.g. by a soft floor covering,
resilient layer or floating floor construction), by
means of an isolated ceiling (such as a sound
attenuating plasterboard ceiling on resilient
hangers), or by a combination of the two. For
buildings that have an exposed concrete soffit (to
provide access to thermal mass) the best option is to
control impact sound at the floor surface. Carpet or
a resilient vinyl can reduce impact sound
experienced in the room by up to 20 dB, whereas a
floating floor can provide a further improvement in
performance. Controlling impact noise at source
also helps to avoid flanking transmission through
the structure to other nonadjacent rooms.
4.4 Operational conflicts
It is important to understand that acoustic requirements
are intended to enhance the usability of a building, not to
impose unnecessary restrictions. However, some oper
ational requirements, such as providing folding partitions
for increasing the flexibility of a space, can have a negative
impact on the acoustic environment and the design
solutions that provide for these requirements need to be
thought out carefully.
4.4.1 Access, flexibility and sound
insulation
Doors and demountable partitions are often provided to
directly link teaching spaces to improve the flexibility of
the accommodation. They can also be provided to meet
specific requirements such as trolley access between
preparatory rooms and laboratories. However, doors and
load on the ventilation system, reducing the efficiency.
Moving the plant for MHVR to a location further away from
inlet and extract vents has the potential to minimise the
need for acoustic attenuators. The building services
engineer should work closely with an acoustician to provide
a ventilation solution that minimises the energy use of the
system while maintaining suitable levels of ambient noise
in teaching areas.
4.3.3 Natural ventilation and noise ingress
In developing a successful natural ventilation arrangement,
attenuation of external noise can be a limiting factor. The
best way to avoid problems with noise ingress problems
begins with the planning of the form of the building. Where
the building is located in a very noisy environment, the
building should be constructed so that it screens noise from
locations where openings will be needed. There will often
be limits to what can be achieved in this way, but it remains
the single most effective means of reducing noise ingress
for naturally ventilated buildings. It is also important to
locate window openings away from other noise sources,
such as air exhausts.
Where external noise (or in the case of noise leaving a
building, internal noise) levels are still too high, the
viability of attenuation without excessive pressure drop
should be checked first. Naturally ventilated double facades
can provide up to 20 dB when using a staggered air flow
path and sound absorbing material in the reveals. However,
staggered airflow paths need to be carefully designed so
that they do not introduce a flanking sound path.
Arrangements suitable for modest attenuation at openings
include:
—
— local acoustic lining for small openings
—
— double glazing with staggered air openings
—
— labyrinth air paths with lining (performance in use
is variable and dependant on the dimensions)
—
— lined extract ductwork/hoods/split duct ventilators.
For these, the usual practical limits on pressure drop are in
the range 10–30 Pa, and should be checked for the specific
situation. It should also be noted that the solutions may
only offer modest attenuation, and the level of sound
attenuation will be dependent on the spectrum of the
external noise.
‘Traffic noise contains high levels of low
frequency noise the mitigation of which
requires careful consideration.’
4.3.4 Access to thermal mass
Exposing thermal mass to help provide thermal comfort is
often perceived to conflict with acoustic requirements.
This includes the provision of sound-absorptive surfaces to
control reverberation and requirements for airborne and
impact sound insulation vertically between spaces. The
conflict can be overcome in a number of ways:
—
— Provide a partial suspended ceiling: Acoustic tile-
in-grid ceilings incorporating areas of open egg-
Acoustic design
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21. 14 Integrated school design
folding partitions can be weak points for sound insulation,
with high specification doors and folding partitions often
failing to meet their expected performance. Furthermore,
the performance of folding partitions in particularly are
likely to degrade with time as seals wear and the building
settles. Due to the need for maintenance, doors and folding
partitions that directly link teaching spaces should be
discussed with the school to ensure that they are not
specified unnecessarily.
4.4.2 Open plan design versus usability
Open plan design is often proposed as a flexible alternative
to separate teaching spaces, making more effective use of
space and allowing different groups to interact. However,
there is a substantial body of evidence that open plan
designs result in unsuitable acoustic spaces (TES, 2008). In
addition to open plan teaching areas, there has also been a
trend towards the provision of multipurpose resource areas,
containing libraries and ICT facilities. The acoustic impact
of these design choices need to be considered carefully,
with both the school and the client being made aware of the
potential difficulties introduced by an open plan design.
All of these areas need to be designed so that effective
communication, without disturbance from neighbouring
zones, is possible in any individual teaching zone. Since
these spaces often double as circulation spaces, the timing
of lessons should also be considered to avoid disturbances
to pupils working in each area. The design of open plan
areas should also be verified using an acoustic computer
model so that the potential limitations of the space can be
understood.
‘In theory, open plan design is often proposed
as a flexible alternative to separate teaching
spaces, making more effective use of space
and allowing different groups to interact. In
practice, open plan designs can create poor
acoustic environments.’
Exciting and visually appealing architectural design can
sometimes lead to poor acoustic performance. Glass curtain
walling, for example, generally offers relatively low levels of
sound insulation to multistorey open plan, although
visually attractive offers poor acoustic separation between
teaching areas. The functionality of such designs should be
understood and critically appraised by the end user.
4.4.3 Disabled access versus sound
insulation
Disabled access often requires minimum door sizes, and
maximum opening forces for manually operated doors, and
minimum dimensions for door lobbies. However, since
doors (and particularly large double-leaf doors) are a weak
point for sound insulation their specification and location
should be carefully considered. The sound insulation of
doors can be improved by providing acoustic seals to the
perimeter and threshold. However, the need to compress
these seals when closing the door can pose a problem when
automatic door closure devices are provided. The force
required to fully close the door must then be overcome
when the door is opened; ‘swing free’ type door closers may
need to be specified.
Case study 1: Bideford College, Devon
(naturally ventilated)
This replacement secondary school in North Devon was designed
with careful attention to acoustic and environmental design
criteria. Cross flow ventilation was provided to the classrooms.
A metal raft acoustic absorption system was used in the
classrooms, which reduced the reverberation time to below 0.8
seconds while maintaining access to the thermal mass above.
Airborne sound isolation was enhanced by sound attenuating
ceilings in the workshops (the lower occupancy in these areas
made access to thermal mass less critical). Soft floor coverings or
high performance resilient rubber floorings were also provided
to reduce impact sound.
Exposure of the partition head created challenges since the floor
slabs were poured on to profiled liner trays, and remedial works
were required to fit mineral wool infill wedges to reduce sound
transmission between spaces.
Figure 6 Acoustic rafts allow access to thermal mass
Art room
Workshop
Void
100 mm general
purpose insulation
Lay-in-grid ceiling tiles
Metal liner
Poured concrete slab (320 kg/m²)
Acoustic rubber flooring
(∆L - 16 dB approx.)
approx 4 mm
Figure 7 Floor cross-section with acoustic rubber flooring
Ventilation ducts were provided from the rear of the classrooms
through the corridor to the external façade, to allow cross
ventilation.
The building was provided with Sedum roofs, which deadens
any rain impact noise at source.
A limited amount of folding partitions were provided to improve
the flexibility of teaching accommodation. Testing of the folding
partitions showed that they performed worse than expected.
Nevertheless, the limited provision of such systems means that
the impact on the management of lessons within the school was
kept to a minimum.
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22. 15
4.4.4 Reverberation time versus use of
space
The optimum reverberation of a space can vary depending
on its use (BSI, 2000). Typical examples of such spaces
include multipurpose halls, which may be used for sports,
dining, assemblies and musical performance. In general it
is expedient to design to the lowest reverberation
requirements for the range of uses being considered. This is
because excessive reverberation is more likely to cause
problems than a space that is acoustically dead. Dining and
sports uses will also benefit from low reverberation times
since ambient noise levels will be suppressed. However,
musical performance spaces may require some form of
adjustable reverberation control (e.g. in the form of
absorptive panelling that can be concealed), since
excessively ‘dead’ spaces can sometimes be problematic for
music.
5 Lighting design
Natural daylight is the best source of illumination, and
there is evidence to suggest that it results in improved
academic achievement. It may also have significant long-
term health and wellbeing benefits for the occupants.
Consequently, providing natural light, for as much of the
occupied period as possible, should be the default design
objective. However, it must be considered from the earliest
stages of design in order to avoid glare and excess solar heat
gains. Excess of either of these will result in blinds/shades
being deployed, negating the daylight potential of the
space, see Figure 9. This section is intended to guide
professionals without expertise in lighting towards the
principles of good daylighting and electrical lighting so
that their design strategies can be evaluated holistically.
5.1 Introduction
Daylight should be the principal source of illumination for
all teaching spaces so that electric lighting during daylight
hours is only used when absolutely necessary, i.e at times of
low daylight availability, dawn/dusk or heavily overcast sky
conditions. Daylight is dynamic and variable. It is strongly
favoured by building occupants provided that it does not
result in undue visual and/or thermal discomfort. Adequate
access to daylight can have a positive impact on mood and
concentration (Reinhart and Weissman, 2002).
After designing for acoustic considerations, daylight is the
next starting point for a good iterative design process
involving all aspects of environmental design. See Table 2.
The daily cycle of day and night plays a major role in
regulating and maintaining biochemical, physiological,
and behavioural processes in human beings. These
processes work in a cycle, known as the circadian rhythm,
meaning literally ‘approximately one day’. The circadian
rhythm is produced from within the body, and is commonly
referred to as the ‘body clock’. However, the cycle can be
adjusted to synchronise, or entrained, to the environment
by external cues, the primary one being daylight. Therefore,
it is important that occupants of buildings are given access
to high levels of daylight, particularly in the morning, to
assist the entrainment of circadian rhythms (Monk et al.,
2007).
Similarly, seasonal affective disorder occurs in the winter
when there is little daylight. This disorder has symptoms
that include depression, lack of energy, drowsiness,
increased appetite and weight gain. It is believed that the
disorder can be prevented, or its symptoms reduced, by
exposure to daylight (Edwards and Torcellini, 2002).
Recent research has identified that where there is limited
or no access to daylight then the colour and intensity shift,
recreated by electric lighting, can stimulate the circadian
rhythm. There is clearly an energy penalty associated with
this approach compared to using natural light.
Current teaching practice relies heavily on the use of
projection onto a screen. Considering the position of the
Lighting design
Case study 2: Brook Green Centre for Learning,
Plymouth (naturally ventilated)
Brook Green Centre for Learning is a school for pupils with
educational and behavioural difficulties. The design of the
building mixes heavyweight construction on the ground floor
(for thermal stability) with lightweight construction on the
upper floor. The building is naturally ventilated and has a space
efficient and compact layout.
Access to thermal mass is provided by incorporating egg crate
grilles around the perimeter of the acoustic tile-in-grid ceiling.
These rooms were shown to have a reverberation time of less
than 0.8 seconds.
Figure 8 Egg-crate tiles at perimeter
Cross flow ventilation was provided using a combination of
windows and rooflights. When the windows towards the
centre of the rooms are opened, both the ventilation and sound
insulation criteria could be achieved concurrently.
artificial lighting
Less glazing More glazing
Daylight
Solar gains
More heat loss
Less heat loss
Figure 9 Daylight design is a balance between daylight, solar gains and
electric lighting
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23. 16 Integrated school design
screen in relation to sources of daylight early in the design
process can deliver a solution that avoids the blinds being
closed whilst the projector is in use. It is advised that high
intensity output projectors are used. These can project an
image of sufficient brightness so as not to be overwhelmed
by ambient daylight in all but the brightest of conditions. It
is preferable that any existing low output projectors are
replaced rather than have the daylight provision
compromised for want of a relatively inexpensive item of
equipment.
SLL Lighting Guide LG5: Lighting for education (SLL,
2011) provides an introduction to lighting of educational
buildings. It describes the key requirements for lighting in
schools, deals with designing for daylight, and how to use
electric lighting in conjunction with available daylight. It
reiterates significant aspects of the guidance given in the
previously published Building Bulletin 90: Lighting Design
for Schools (DfES, 1999) and Standard specifications, layouts
and dimensions: Lighting systems in schools (DCSF, 2007) gives
further information on all aspects of electric lighting
including suitable lamps and luminaires.
5.2 Daylight design principles
The need for good daylight can influence many design
parameters for the school. If the initial form and geometry
of the building are not considered from this perspective,
then effective daylighting will not be possible. The designer
needs to appreciate from the outset that providing effective
daylightingisrathermoreinvolvedthansimplymaximising
predictive measures such as the daylight factor. For
example, it is not only the area of glazing that is important
but the degree to which the window receives light directly
from the sky. External obstructions that prevent a view of
the sky by the window will significantly limit the daylight
in the room. The external obstructions may be nearby
buildings or even overhangs provided for solar protection.
Ideally, at least 80% of the working plane should have a
view of the sky. See Figures 10 and 11 for the influence of
orientation and building form on daylight availability. The
main windows type and daylight distribution systems are
given in Figure 12. Note that this is also significant for
solar access and avoidance of overheating, refer to section 7.
Room depths of more than 7.5 m will require ceiling and
window head heights of more than 2.7 m and/or daylight
from more than one facade. A single sided approach will
not usually provide the required standards for rooms
greater than 7 m deep, and multi-aspect daylight is to be
preferred even for shallower spaces. Hence the layout of the
school teaching areas should avoid deep floor plates unless
rooflights can be used to introduce daylight to the heart of
the building.
High level glazing normally has a direct view of the sky and
can deliver more daylight deep into the space. Clerestory
windows can be an ideal design feature providing daylight
with minimal glare and limited solar heat gain, see Figures
13 and 14. They can also provide a draught free means of
ventilation. The inability of clerestory windows to provide
a view can be used to advantage where external activities
may prove distracting to the occupants. Where clerestory
windows and other glazed areas are used to provide
borrowed light it should be remembered that the amount of
light borrowed is often very limited and mainly results in
an increased perception of daylight rather than significant
levels of useful illumination.
The most effective designs will be those where the
architectural form and associated shading system serves to
temper the luminous environment. That is, providing
adequate levels of daylight throughout the space whilst
simultaneously shading from undue levels of direct sun
(Figure 14). If the fixed architectural form and associated
shading systems do not offer effective solar shading and
light distribution, then the space will likely be too dark
furthest from the façade and too bright adjacent to the
façade. This scenario typically leads to lights on and blinds
closed. Part of the solution is to ensure blinds are selected
that admit and redistribute some daylight even when
lowered (Figure 16).
The fixed form structures that can be most effective in
producing a well tempered daylit space include: overhangs,
light shelves, deep window reveals, high-level glazing, roof
High altitude
sun during midday
shaded by overhang
Classrooms
Classrooms
North
South
East
West
Overhang
Axis
Figure 10 Preferred orientation
North
South
East
West
Classrooms
Classrooms
Axis
Low altitude sun
enters classrooms
in the afternoon
Low altitude sun
enters classrooms
in the morning
Figure 11 Problematic orientation
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