TM57-b

Integrated school design

Integrated school design TM

57

The Chartered Institution of Building Services Engineers222 Balham High Road, London SW12 9BS+44 (0)20 8675 5211www.cibse.org

TM57: 2015

9 7 8 1 9 0 6 8 4 6 5 2 7

ISBN 978-1-906846-52-7


CIBSE TM57: 2015

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Note from the publisherThis publication is primarily intended to provide guidance to those responsible for the design, installation, commissioning, operation and maintenance of building services. It is not intended to be exhaustive or definitive and it will be necessary for users of the guidance given to exercise their own professional judgement when deciding whether to abide by or depart from it.

Any commercial products depicted or described within this publication are included for the purposes of illustration only and their inclusion does not constitute endorsement or recommendation by the Institution.

The rights of publication or translation are reserved.

No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means without the prior permission of the Institution.

April 2015 The Chartered Institution of Building Services Engineers, London

Registered charity number 278104

ISBN 978-1-906846-52-7 (printed book)ISBN 978-1-906846-53-4 (PDF)

This document is based on the best knowledge available at the time of publication. However no responsibility of any kind for any injury, death, loss, damage or delay however caused resulting from the use of these recommendations can be accepted by the Chartered Institution of Building Services Engineers, the authors or others involved in its publication. In adopting these recommendations for use each adopter by doing so agrees to accept full responsibility for any personal injury, death, loss, damage or delay arising out of or in connection with their use by or on behalf of such adopter irrespective of the cause or reason therefore and agrees to defend, indemnify and hold harmless the Chartered Institution of Building Services Engineers, the authors and others involved in their publication from any and all liability arising out of or in connection with such use as aforesaid and irrespective of any negligence on the part of those indemnified.

Typesetting and layout by James Parker (BE Knowledge) for CIBSE Publications

Printed in Great Britain by Page Bros. (Norwich) Ltd., Norwich, Norfolk NR6 6SA

Cover photograph: Oasis Academy Hadley, Enfield, United Kingdom. Architect: John McAslan & Partners, 2013. VIEW Pictures Ltd/Alamy

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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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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: [email protected].

EditorJames Parker (BE Knowledge)

CIBSE Editorial ManagerKen Butcher

CIBSE Head of KnowledgeNicholas Peake

CIBSE Technical DirectorHywel Davies

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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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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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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 IntroductionSchools 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 teams need to understand these basic issues, and concentrate 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


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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 schools 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). The practitioners surveyed frequently emphasised 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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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 schools 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.

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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 1 500 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/advisors 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 clients 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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5Setting 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 C.

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 buildings 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 m, and not requiring lighting for accurate colour assessment, shall not exceed a maximum value in W/m 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/m 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/Ls1 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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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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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

12

4

5

6

Ventilation

9

7

8

Thermal comfort

D

A B

C

12

1110

Low and zero carbon energy

Key

A: Daylight

1. Size/orientation/position2. Type of glazing3. Solar shading

B: Ventilation

4. Simple natural ventilation5. Complex natural ventilation6. Mechanical (assisted) ventilation

C: Thermal comfort

7. Thermal mass8. Night cooling9. Base gains

D: Low and zero carbon energy

10. Energy efficiency11. Low carbon technology12. Renewables

Figure 3 The design process for new school buildings, showing how the individual aspects are interrelated

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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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9Early engineering considerations and design hierarchy

Table 5 Design guidance for ventilation performance (DfES, 2006; CIBSE, 2013)


Exposed site aids wind driven ventilation Control of draughts

Building envelope:

Faade 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)


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

Faade 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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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 particular space. In order to produce a suitable environment, 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 designAcoustic design is directly linked with architectural design and surface material selection. Good acoustic design is

Traffic noiseand vibration

Plantroom noiseand vibration

Ductborne noise fan

Aircraft noise

Weatherand rain noise

Playgroundnoise Noise via

open windows

Noisycorridors Breakout/break in

of ductborne noise

Noise throughdoors and walls

Ductborne noise

Plumbing noise Figure 4 Potential noise sources

affecting schools (DfES, 2003)

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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 schools 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 rooms 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 chosen to minimise the need for expensive high performance internal partitions, see Figure 5. The higher the performance

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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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

Otherclassroom

Musicclassroom

Grouproom

Grouproom

Grouproom

Grouproom

Grouproom

Grouproom

Grouproom

Grouproom

Store

Store

Store

Store

Store

Intrumentstore

StoreStore

Musicclassroom

Staffbase

Ensembleroom

Recording/controlroom

Corridorcreatesacoustic

separation

Easyaccess to supportspaces

Stores provideacousticbuffer

Acoustic separationfor esumble room and

group rooms

To otherdepartments

Figure 5 Using buffer zones to minimise the need for expensive high performance sound attenuating walls (DfES, 2003)

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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 1030 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-

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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/m)

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 faade, 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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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 designNatural 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 lossLess heat loss

Figure 9 Daylight design is a balance between daylight, solar gains and electric lighting

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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 daylighting is rather more involved than simply maximising 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 faade and too bright adjacent to the faade. 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 altitudesun during midday

shaded by overhang

Classrooms

Classrooms

North

South

EastWest

Overhang

Axis

Figure 10 Preferred orientation

North

South

EastWest

Classroom

s

Classroom

s

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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windows, multiple aspect windows, light wells and similarly articulated structures/forms (Figure 15).

However, to be effective these structures/forms have to be incorporated into the design with due consideration of a number of key factors. Foremost amongst these are facade orientation and prevailing climate. For example, overhangs on the south f

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