Design Checks for HVAC

A BSRIA Guide www.bsria.co.uk

A quality control framework (Second edition)

Revised by Kevin Pennycook

Supported by

BG 4/2007 Design considerations Design data Calculations Systems and equipment

PREFACE

This publication provides practical, easy to follow HVAC design guidance. It is presented in a format that can be readily incorporated into company Quality Assurance (QA) systems and become part of the daily routine of design. It can be used to demonstrate compliance with the relevant requirements of ISO 9001 and BS 7000 Part 4.

There are two major elements of the guidance. The design guidance sheets provide information and guidance on design inputs, outputs and practical watchpoints for 62 key building services design topics, to aid the design process and reduce errors. The design check sheets provide checks that can be used as part of the project quality assurance process to record and demonstrate control of design inputs and outputs.

The guidance and check sheets are detailed and relevant to many design applications, although they cannot be fully comprehensive or exclusive or cover every possible design scenario. Every design project is different and has differing needs. It is the responsibility of the design engineer to consider fully all design requirements. In particular, the design watchpoints are not an exhaustive list of all factors to be considered, so designers should exercise professional judgement to decide which factors are relevant. Diagrams are included for illustrative purposes only and do not necessarily include all required components.

Designers must be aware of their contractual obligations and ensure that these are met. Adherence to this guidance does not preclude or imply compliance with those obligations. Similarly, it is the duty of the designer to ensure compliance with all relevant legislation and regulations. This publication is also relevant to those responsible for the installation, commissioning, operation and maintenance of building services.

This second edition of Design Checks for HVAC is up to date with the requirements of the latest building legislation, standards and codes of practice current in January 2007. The guide also contains new design checks for whole life costing and health and safety. Where possible, design topics have been cross-referenced to the relevant Common Arrangement of Work Sections (CAWS).

It is hoped that design practices and individual designers will be encouraged to further share knowledge and experience by extending and adding to the design watchpoints and disseminating this within their organisations. BSRIA would be pleased to receive any such contributions for incorporation into any future revisions of this publication.

DESIGN CHECKS FOR HVAC © BSRIA BG 4/2007 Design considerations Design data Calculations Systems and equipment

OVERVIEW OF DESIGN CHECK TOPICS AND ADDITIONAL CONTENTS

Design considerations Systems and equipment

1 Design margins 12 30 Radiators 78 2 Future needs 14 31 Natural convectors 80 3 Plant space allowance 16 32 Radiant panels/radiant systems 82 4 Spatial co-ordination 18 33 Underfloor heating 84 5 Zoning 20 34 Perimeter fan Coils 86 6 Ventilation requirements 22 35 Overhead fan coils 88 7 Intake and discharge locations 24 36 Natural ventilation 90 8 Pressurised zones 26 37 Mixed mode ventilation systems 92 9 Sensor locations 28 38 Constant air volume air conditioning systems (CAV) 94 10 Commissioning – piped systems 30 39 Displacement ventilation 96 11 Commissioning – ducted systems 32 40 Chilled beams 98 12 Flushing and chemical cleaning 34 41 Chilled ceilings 100 13 Maintenance 36 42 Variable air volume systems (VAV) 102 14 Whole life costing 38 43 Variable refrigerant flow systems (VRF) 104 15 Health and safety 42 44 Toilet extract 106 45 Kitchen extract 108 46 Pipework 110 47 Ductwork 112 48 Diffusers 114 49 Pumps 116 50 Fans 118 51 Boilers 120 Design data 52 Air handling units (AHUs) 122 53 Humidifiers 124

16 Site location factors 46 54 Chillers 126 17 External design criteria 48 55 Cooling towers 128 18 Internal design criteria 50 56 Heat recovery systems 130 19 Occupancy 52 57 Heat pumps 132 20 Internal gains 54 58 Water side free cooling - direct 134 21 Infiltration 56 59 Water side free cooling - indirect 136 22 Fabric 58 60 Oil storage tanks 138 23 Glazing 60 61 HVAC control systems 140 24 Condensation 62 62 Building management systems (BMS) 142

Calculations Additional contents

25 Computer calculations 66 Common Arrangement of Work Sections references 145 26 Heat loss 68 Design checks – Bibliography 146 27 Heat gain 70 References 154 28 Pump and pipe sizing 72 Alphabetical list of design checks 155 29 Fan and duct sizing 74

DESIGN CHECKS FOR HVAC © BSRIA BG 4/2007 Design considerations Design data Calculations Systems and equipment

INTRODUCTION

Aim Intended users The aim of Design Checks for HVAC is to improve the This guidance is intended for practising HVAC design engineers. quality control and performance of the technical design Clients, PII providers and others involved in the design process process within the building services industry by identifying and its outcomes are also potential users as they may request best practice. This should reduce the risk of design errors compliance with this guidance or ask to see evidence that and omissions, improve the overall efficiency of the design reasonable design quality assurance procedures are being followed. process, and provide HVAC services that better meet the The guidance complements the CIBSE Guide B, Heating, needs of the client. Ventilating, Air-conditioning and Refrigeration, and the CIBSE Concise Guide. A comprehensive review of current building services design practice and procedures was carried out in consultation with The check sheets and design inputs and outputs guidance are the industry to identify best practice and current problems intended for use by all design engineers, whether to gather and explore relevant design tools. The result includes: information and complete the sheets or to check or sign off as completed. While the more detailed guidance in the design • A map of the HVAC building services design process watchpoints is obviously directly useful for junior engineers, • Design guidance sheets giving information and guidance experienced engineers will also find it useful when designing a on design inputs, outputs and practical watchpoints for less-familiar system. 62 key design topics, to aid the design process and reduce errors Companies may also use the guidance to support formal design • Design check sheets that can be included in project quality assurance procedures while the check sheets may be quality assurance procedures. photocopied, they are also available, for purchase in electronic format, thus enabling them to be customised for particular projects These provide a formal framework to record and review and kept on specific project files. For further information visit design inputs and encourage designers to consider the www.bsria.co.uk/bookshop. requirements for installation, commissioning, operation and control and subsequent maintenance of their selected Note that the design of HVAC systems involves working in a systems at the design stage. design team with other disciplines. This involves interactive efforts, co-ordination and project programming. This should lead to improvements in both the design process and in the subsequent implementation of that design, and reduce the risk of problems occurring during installation, commissioning or system operation.

This practical easy to follow guidance can be incorporated into company quality assurance systems to become part of the daily routine of design and can be used to demonstrate compliance with the relevant requirements of ISO 9001:20001 and BS 7000 Part 4:19962.

The guidance incorporates practical design watchpoints based on feedback from many practising engineers and others experienced in design. These vary from avoidance of possible errors or misunderstandings that could be made by inexperienced, junior engineers to very practical tips based on experience of installation, commissioning, maintenance and facilities management over many years. Use of the design checks will allow these lessons to be passed on to other engineers, particularly junior engineers, and future projects. This can help improve design quality, reduce risk and increase client confidence.

DESIGN CHECKS FOR HVAC 1 © BSRIA BG 4/2007

DESIGN CONSIDERATIONS

Design considerations Design data Calculations Systems and equipment

1 DESIGN MARGINS

Project title...... Project No...... Design stage......

Engineer...... Revision No ...... Date ......

Checked by...... Approved by ...... Date......

Design outputs Notes / Design file cross-reference • Overall design margin strategy, including QA procedures, and design reviews • Clear identification in the design file of any margins used within design calculations, together with a written justification for their use • Clear statement of operating limits of the design for client

Key design checks Notes / Design file cross-reference • Agree margins policy with client as part of a value engineering strategy • At the end of a calculation procedure review all margins used to avoid possible double counting and remove excess margins • At design review stage review again the appropriateness of any design margins used • Assess system part load performance and review the impact of the use of any margins on the system design

Project specific checks and notes Notes / Design file cross-reference

12 DESIGN CHECKS FOR HVAC © BSRIA BG 4/2007 Design considerations Design data Calculations Systems and equipment

1 DESIGN MARGINS

Why consider this? Design outputs Consideration of design margins at design stage is essential for: • Overall design margin strategy, including QA procedures and design reviews • Avoidance of unnecessary oversizing of plant and systems • Clear identification in the design file of any margins used • Good part load performance of plant and systems within design calculations, together with a written • Client future need requirements justification for their use • Equipment and system selection • Clear statement of operating limits of the design for client • Plant space allowance • Avoidance of re-design and extension of programme Key design checks • Agree margins policy with client as part of a value Design information engineering strategy • Client brief including future needs requirements and any • At the end of a calculation procedure review all margins specific requirements for system or plant duplication or used to avoid possible double counting and remove excess critical systems margins • Details of building and space use to determine the level of • At design review stage review again the appropriateness of system reliability required any design margins used • Building construction details such as heavyweight or • Assess system part load performance and review the impact lightweight of the use of any margins on the system design

See also: Future needs

DESIGN WATCHPOINTS

General watchpoints 11. To optimise part load performance consider installing two or three smaller boilers instead of one larger boiler. Each will then run at full load more 1. Clearly identify and justify the use of all margins added during the design frequently, increasing efficiency. This must be balanced against the increased process in the design file. costs. 2. Reduce the need for margins where possible. Provide the client with a 12. Margins added to pipework and ductwork distribution systems to account clear statement of operating limits of the design to ensure client is aware for future needs can result in low initial operating fluid velocities. For air of, and satisfied with, the anticipated real performance of the system. Make systems this can affect the performance of grilles and diffusers and make explicit any risk of under-performance and get client agreement. Some commissioning and system control difficult. clients are now accepting designs where design conditions are exceeded by an agreed amount, such as 1-20C for short periods of time. 13. Where grilles and diffusers are selected on a greater air volume to allow for future needs, they are likely to underperform, resulting in poor room 3. Clarify with the client the level of system reliability required. Critical air distribution and possible occupant discomfort. The lower air volume systems and services will require a different level of safety provided by gives reduced face velocity and reduced throw. redundancy, or installed plant margins, to non-critical ones. 14. Check that suitable controls have been provided to cope with the margins 4. At the end of a calculation procedure review all margins used to avoid applied. In ductwork systems low air velocities due to oversizing may make possible double counting and remove excess margins. air sensing and subsequent control difficult. 5. At design review stage review again the appropriateness of any design 15. Do not assume that control systems can make an oversized design operate margins used. efficiently and effectively to meet building and occupant needs. Controls 6. Design margins can be added for legitimate operational reasons and these cannot cure bad design. Part load performance should always be assessed. should be clearly identified, for example in heating systems, a pre-heat 16. Avoid oversizing chillers as this can cause cycling and excessive starts. margin may be required to provide rapid heat-up in the mornings to avoid Consider selection of chillers with more stages, the addition of extra the plant having to run all night. system capacity or widening the control band to increase the switching 7. Margins are sometimes added to allow for design or installation differential. uncertainties and missing design information. Uncertainties or assumptions should be clearly flagged and reviewed when correct information is Economics available. Reduce uncertainties in design as much as possible by clarifying 17. Agree margins policy with client as part of a value engineering strategy. the brief, agreeing acceptable airtightness standards, and having equipment performance tested. 18. Sizing systems and equipment initially for anticipated future expansion can result in lower operating efficiencies and increased running costs. Allow 8. Avoid unnecessary use of margins. Excessive use can result in system space for future plant items or, where additional capacity is required, select oversizing and inefficient plant operation with plant running at a fraction of systems to maximise energy efficiency and optimise part load performance, rated load for much of the time. This may result in hunting and cycling for example by the use of modular or multiple plant systems. under low load conditions, reduced efficiency, excessive wear through continual stop/start operation and increased risk of failure. 19. Where a known margin is to be applied to a system to cater for future expansion, consider selecting plant and equipment that can provide a 9. Assess the impact of the use of margins on system design and system part variable supply, such as variable speed pumps and fans. This will allow load performance. optimum efficiency in both cases, and the increased capital cost should be Installation, operation and control recovered through increased energy efficiency. 20. Applying margins to a system can lead to increased installation costs as well 10. For good part load operation consider using boilers with fully modulating as increased capital costs. burners, not just on/off or two stage firing as the output can be more accurately controlled to the system load at any time, giving good operating 21. Consider the life cycle cost implications imposed by enhanced controls, and efficiency at part load. plant selection.

DESIGN CHECKS FOR HVAC 13 © BSRIA BG 4/2007 A guide to HVAC Building Services Calculations Second edition

BSRIA Guide 30/2007 Supported by the DTI

BG 30-2007coverfnt.p65 1 01/06/2007, 11:12 Heating loads Cooling loads Water flow Air flow Acoustics

ACKNOWLEDGEMENTS

The first edition of this publication was produced by BSRIA as part of a contract placed by the Department of Trade & Industry and funded by the DTI, BSRIA membership and industry partners.

BSRIA would like to thank the following sponsors for their contributions to the first edition Guide:

Department of Trade and Industry CIBSE (Chartered Institution of Building Services Engineers) ACE (Association of Consulting Engineers) ESTTL (Engineering Services Training Trust Limited) HVCA (Heating and Ventilating Contractors Association) Bovis Crown House Engineering FaberMaunsell Hoare Lea N G Bailey South Bank University Troup Bywaters & Anders W S Atkins

The research project was undertaken under the guidance of a project steering group drawn from industry representatives and BSRIA staff. The steering group contributors were:

Fulcrum Consulting Andrew Ford, representing DTI Independent chair Bryan Franklin CIBSE Hywel Davies ACE Jeremy Croxson Bovis Jean-Louis Auguste Crown House Engineering Susan Hone-Brookes ESTTL Tony Barton FaberMaunsell Quinten Babcock Ant Wilson Hoare Lea Graham Cossons Les Mackenzie Terry Wyatt HVCA Derrick Newson Bob Towse N G Bailey Ken Sargeant Roland Edkins South Bank University Martin Ratcliffe Troup Bywaters & Anders David Arnold (representing CIBSE) W S Atkins Adrian Defalco Steve Platt

The first edition of this guide was authored by Gay Lawrence Race and Sally Mitchell. This second edition of the Guide to HVAC Building Services Calculations has been extensively revised and added to by Kevin Pennycook, David Churcher and David Bleicher from BSRIA.

The authors have sought to incorporate the views of the steering group, but final editorial control of this document rested with BSRIA.

All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means electronic or mechanical including photocopying, recording or otherwise without prior written permission of the publisher. ©BSRIA 70186 June 2007 ISBN 978-0-86022-657-4 Printed by ImageData Group

GUIDE TO HVAC BUILDING SERVICES CALCULATIONS © BSRIA BG 30/2007 Heating loads Cooling loads Water flow Air flow Acoustics

PREFACE

This publication provides practical, easy to follow methodologies for a range of calculations used in the design of heating ventilating and air conditioning building services systems.

The calculation sheets are presented in five sections covering:

• Heating loads and plant • Cooling loads and plant • Water flow distribution systems • Air flow distribution systems • Acoustics for building services

The calculation sheets provide practical guidance including design watchpoints, design tips and rules of thumb, and are intended to aid the design process and reduce errors. The guidance is based primarily on data and procedures contained within the CIBSE Guides, together with other sources such as Building Regulations, with clear cross-referencing provided to data sources.

This publication is intended primarily to help junior design engineers, working within a structured and supervised training framework, by providing assistance in completing the basic calculations needed to define operating conditions for systems, size distribution systems and to specify required duties for plant and equipment. It is not the purpose of this guide to identify the most appropriate system for a particular application. Such decisions require knowledge, experience and analysis of the application.

This guidance is also not intended to be exhaustive or definitive. It will be necessary for users to exercise their own professional judgement, or obtain further advice from senior engineers within their organisation when deciding whether to abide by or depart from the guide. The calculation sheets are relevant to many design applications, but cannot be fully comprehensive or cover every possible design scenario. Every design project is different and has differing needs, and it is the professional duty of the responsible design engineer to consider fully all design requirements. Designers should exercise professional judgement to decide relevant factors and establish the most appropriate data sources and methodologies to use for a particular application.

Designers must be aware of their contractual obligations and ensure that these are met. Following this guidance - or any other guidance - does not preclude or imply compliance with those obligations. Similarly, it is the duty of the designer to ensure compliance with all relevant legislation and regulations.

It is hoped that design practices and individual designers will be encouraged to share knowledge and experience by extending and adding to the design watchpoints and design tips, and disseminating this work within their organisations. BSRIA would be pleased to receive any such contributions for incorporation into any future revisions of this publication to provide wider industry sharing of such knowledge.

GUIDE TO HVAC BUILDING SERVICES CALCULATIONS © BSRIA BG 30/2007 Heating loads Cooling loads Water flow Air flow Acoustics

CONTENTS Page

INTRODUCTION 2 Aim 2 Objectives 2 Intended users 2

THE BUILDING SERVICES DESIGN PROCESS 3 HVAC building services design tasks and design map 4

OVERVIEW OF CALCULATION SHEETS 5 Use of the guidance 6

OVERVIEW OF CALCULATION TOPICS 7

REFERENCES 8

CALCULATION TOPICS AND FLOW CHARTS 9 Heating loads and plant 9 Cooling loads and plant 39 Water flow distribution systems 67 Air flow distribution systems 93 Acoustics for building services 125

ALPHABETICAL LIST 134

GUIDE TO HVAC BUILDING SERVICES CALCULATIONS 1 © BSRIA BG 30/2007 Heating loads Cooling loads Water flow Air flow Acoustics

INTRODUCTION

BSRIA has been researching into the design process and design Aim methodology in the building services industry since the mid 1990’s. As a result of all these factors many of the leading organisations This has produced guidance on the use of engineering design involved in education and training in the building services industry, margins1, feedback to design2 and quality control systems for detailed 3 including BSRIA, CIBSE, ESTTL and HVCA and a number of technical design . The overall aim has been to develop systematic industrial contributors embarked on this project to develop simple guidance for the industry that would contribute to greater and clear guidance on building services calculation procedures that consistency in design and to an overall raising of design standards. would be applicable across the industry.

The studies have involved considerable discussions with industrial Objectives partners on their current and future needs, and several visits to the The resulting guidance is intended to be suitable as an in-company design offices of a number of industrial contributors to the projects. learning resource, in order to improve quality and communication A majority of those organisations consulted said that a lack of formal within the design process. This should reduce the risk of design design guidance and inadequate recording of calculations was a calculation errors and omissions, simplify the task of calculation major barrier to quality improvement in design. Many also felt that checks and improve the overall efficiency of the design process. standardised formal procedures would help improve the quality of design outputs. A comprehensive review of current building services design practice and calculation procedures was carried out in consultation with the BSRIA’s research also revealed that there is a lack of standardisation industry. This was closely linked to current industry design guides in design procedures, both between companies and between and reference material in order to develop this good practice individuals. Many companies have developed their own design guidance for building services calculation procedures, including: guidance and approaches to calculation procedures, leading to considerable diversity within the industry. This can make it • An overview of the building services design process; difficult to cross-check work done by others, which could lead to • Flowcharts of key calculation sequences; differences in system design parameters and sizes, and even • Practical procedures and calculation sheets covering 30 key calculation and design errors. There are many specific examples of building services calculation design topics; design errors and issues that should have been considered during • Clear cross-referencing to the CIBSE Guide and other design calculations and have led, (or could have led) to operational appropriate reference sources. problems or subsequent litigation4, including: The calculation sheets provide an overview of each procedure, • Omission of HEPA filter resistance from fan-pressure with guidance on design information, inputs and outputs, design calculations, requiring subsequent fan motor replacement which tips and watchpoints and worked examples, to aid the design then required additional silencing process and reduce errors. They are supplemented with illustrations • Omission of duct sizes and flows from drawings, leading to and guidance on how to use appropriate tables, figures and design incorrect sizes being installed information correctly. • Incorrect pipe and pump sizing for a constant temperature heating circuit, necessitating replacement of system distribution Intended users network This guidance is intended for practising building services design engineers, and will be particularly relevant to junior engineers and • No allowance for pipework expansion on a heating mains. students on building services courses. Junior engineers would be Although there is considerable design guidance and data available to expected to use it under supervision, (for example within a formal inform the design process much of it is intended for use by company training scheme) as part of their practical design work. experienced engineers, who have fulfilled a programme of Students can use it within the taught framework or industrial education and training and have design experience. For example, training component of their course, guided by course tutors as while the design guides published by the Chartered Institution of appropriate. The guidance should also encourage clear recording Building Services Engineers (CIBSE)5 provide essential design data and referencing of calculation procedures which will aid quality for building services engineers, they are intended for use by assurance requirements and allow simpler and easier in-house experienced engineers, and therefore do not always show how to checking of design work. design in detail by giving every necessary calculation step. They also do not show how different calculation routines link together to The guidance complements the CIBSE Guides, in particular Guide build up the design process. A covering design data, Guide B covering heating, ventilation and air conditioning, and Guide C covering reference data. It Research has also shown that many employers are currently finding especially complements the CIBSE Concise Handbook8 a it difficult to recruit design engineers with appropriate building companion volume showing the use and practical application of services skills and experience, which necessitates recruiting and commonly used design data from other CIBSE Guides. retraining engineers from other disciplines.6 Output from building services courses is currently falling, 7 which implies there will be no The Practical Guide to Building Services calculations also closely complements the BSRIA Guide: BG 4/2007 Design Checks for short term improvement in this situation. 3 HVAC – a quality control framework (Second edition) . This provides These recruits, with no building services training or experience, good practice guidance for building services technical procedures will require close supervision and considerable training which can and design management, including design guidance sheets for 60 place a heavy burden on company resources. key design topics and check sheets that can be used in project quality assurance procedures. While there is no substitute for an appropriate quality control framework and adequate supervision by qualified senior staff, good New entrants to building services may find it helpful to read the training resources and technical support can provide an invaluable overview information given in the BSRIA illustrated guides 9 adjunct to company training provision. volumes 1 and 2.

2 GUIDE TO HVAC BUILDING SERVICES CALCULATIONS © BSRIA BG 30/2007 Heating loads Cooling loads Water flow Air flow Acoustics

THE BUILDING SERVICES DESIGN PROCESS

Calculation procedures are a necessary component of design but Figure 1: Simple example of a building services design process. it is important to see them in the context of the whole design process. Decisions made as part of initial design and during the calculation procedures will affect system design, installation, operation and control.

The BSRIA publication Design Checks for HVAC – a quality control framework (Second edition)3, provides a useful and relevant discussion of the building services design process. As part of this work, a detailed analysis of design procedures and tasks was carried out for building services design and a simple linear model of the building services design process derived was derived as shown. This gives a single design sequence, from statement of need, through problem analysis, synthesis and evaluation to final solution and enables design tasks to be clearly linked to both preceding and succeeding actions. Some primary feedback loops are shown, but in practice there are often feedback loops between all tasks and even within specific tasks.

This work also mapped the building services design process, both as a sequence of design tasks and as a series of topics that make up the design process. This detailed map of the process is shown opposite. The map is shown as a linear view of design, (with iteration and intermediate feedback omitted) in the form of an Ishikawa or fishbone diagram. The process originates from the client’s need on the left with various branches feeding into the main design line to eventually reach design completion and design feedback. The map may be of particular benefit to junior engineers as it will enable them to put their contribution to the whole design process in context. When engineers carry out load calculations or pipe sizing, it is easy to forget that this is part of a larger process with consequences for impact on future system installation, operation and control.

Note that CIBSE Guides B1 to B5 have been combined to form Guide B – Heating, Ventilation, Air Conditioning and Refrigeration. This publication provides references to both individual B guides and the combined B Guide where appropriate.

GUIDE TO HVAC BUILDING SERVICES CALCULATIONS 3 © BSRIA BG 30/2007 Heating loads Cooling loads Water flow Air flow Acoustics

THE BUILDING SERVICES DESIGN PROCESS

4 GUIDE TO HVAC BUILDING SERVICES CALCULATIONS © BSRIA BG 30/2007 Heating loads Cooling loads Water flow Air flow Acoustics

OVERVIEW OF CALCULATION SHEETS

The calculation sheets are organised into five sections covering over 30 topics relevant to building services design: Heating loads and plant This section covers the key topics and calculations relevant to establishing heat loads for a space or building and sizing heating plant, covering infiltration, U values, heat loss, heating load, radiator sizing and boiler sizing. It explains how to use design data from different sources to establish heat losses and heating loads and explains the different components that make up plant loads. Cooling loads and plant This section covers the key topics and calculations relevant to establishing cooling loads for a space or building and sizing cooling plant, covering internal gains, external gains, cooling load, supply air temperature, cooler battery sizing and humidifier duty selection. It provides an overview of heat gains, explains maximum simultaneous loads and explains how to determine acceptable supply air temperatures and size plant components. Water flow distribution systems This section covers the key topics and calculations relevant to the sizing of water flow distribution systems, covering pipe sizing, system resistance, pump sizing and water system pressurisation. It explains how to read information from pipe sizing tables, how to work out pressure loss through pipe fittings, and how to determine the index run. Air flow distribution systems This section covers the key topics and calculations relevant to the sizing of air flow distribution systems, covering duct sizing, system resistance, fan sizing, grille and diffuser sizing, and space For each calculation topic the guidance provides the following pressurisation. It explains how to read information from the CIBSE information, as appropriate: duct sizing chart, how to convert from circular to rectangular duct sizes, discusses practical selection of duct sizes to enable economic Overview system installation, explains how to work out pressure loss through An overview of the calculation topic and procedure explaining duct fittings, and how to apply corrections for air density changes. what it is and where and when it is used to put it in context. Acoustics This section shows how acoustics must be considered in building Design information required services design as most items of mechanical plant or equipment This explains literally what you need to know to carry out a generate noise. This noise can be transmitted through the building particular calculation, such as the design information necessary to its occupants and outside the building to the external for a procedure, for related design decisions, system layouts or environment. selection of equipment. This could include design data such as an internal design temperature or a mass flow rate, fluid type Calculation flowcharts are provided at the beginning of each and temperature, and other design information such as duct section as shown opposite. These show the calculation material, insulation details and floor to ceiling heights. procedures in that section and help to explain how different calculation routines link in sequence to build up the design Key design inputs process. This enables any one calculation sequence to be Key technical data (with units) essential for that particular viewed in the context of the broader design process. Some calculation procedure such as mass flow rate, heating load, and other relevant design inputs and related processes are also shown limiting pressure drops. for completeness, although they are not included in this current guidance as detailed calculation procedures. Design outputs

The required design output from a particular calculation Although the calculation procedures provided in this guide are procedure which will be used to either inform future design, or grouped into four sections with calculation sequence flowcharts to form part of the specification or design production, such as given for each section, during a real design process all the schedules of loads, schematic diagrams, system layout drawings sections will inter-link. For example, emitter and boiler sizing with sizes and design data included, and schedules of equipment will require consideration of pipe sizing, boiler sizing needs, sizes and duties. details of heater batteries, duct sizing requires consideration of heating and cooling loads and ventilation requirements.

GUIDE TO HVAC BUILDING SERVICES CALCULATIONS 5 © BSRIA BG 30/2007 Heating loads Cooling loads Water flow Air flow Acoustics

OVERVIEW OF CALCULATION TOPICS

Heating loads and plant Water flow distribution systems

H1 Stack effect W1 Pipe sizing – General H2 Infiltration W2 Pipe sizing – Straight lengths H3 U values W3 Pipe sizing – Pressure drop across fittings H4 Condensation risk W4 System resistance for pipework – Index run H5 Heat loss W5 Pump sizing H6 Plant heating load W6 Control valve selection/sizing H7 Heating plant configuration and load matching W7 Water system pressurisation H8 Radiator sizing H9 Boiler sizing H10 Flue sizing

Air flow distribution systems

Cooling loads and plant A1 Duct sizing – General A2 Duct sizing – Selecting a circular duct size A3 Duct sizing – Circular to rectangular ducts C1 Internal heat gains A4 Duct sizing – Pressure loss through fittings C2 External gains A5 Duct system – Index run C3 Cooling plant loads A6 Fan sizing C4 Ventilation – Outdoor air requirements A7 Grille and diffuser sizing C5 Supply air quantity and condition A8 Air density correction C6 Heating/cooling coil sizing A9 Pressurisation of spaces C7 Return air temperature effects on coil duty C8 Humidifier duty C9 Dehumidification

Acoustics

AC1 Acoustics for building services

GUIDE TO HVAC BUILDING SERVICES CALCULATIONS 7 © BSRIA BG 30/2007 Heating loads Cooling loads Water flow Air flow Acoustics

REFERENCES

1 Lawrence Race G, BSRIA, Parand F, BRE, Engineering Design Margins, CIBSE Research Report RR04 1997. Available free to CIBSE members at www.cibse.org.

2 Lawrence Race G, Pearson C & De Saulles T, Feedback for Better Building Services Design, AG 21/98, BSRIA 1998 ISBN 0 86022 520 8

3 Lawrence Race G, Design Checks for HVAC – A Quality Control Framework (Second edition), BSRIA BG 4/2007. ISBN 978-0- 86022-669-7

4 From information gathered for the publication Design Checks for HVAC – A Quality Control Framework (Second edition), BSRIA BG 4/2007

5 CIBSE Design Guides, including Volumes: A Environmental Design, 2006, ISBN 1 903287 66 9; B Heating, Ventilating, Air Conditioning and Refrigeration., ISBN 1 903287 58 8, C Reference Data 2007, ISBN 9 781903287 80 4

6 H Connor, S Dench, P Bates, An Assessment of Skill Needs in Engineering. DfEE Skills Dialogues SD2, February 2001.

7 Professor D Gann & Dr A Salter, Interdisciplinary Skills for the Built Environment Professional, Arup Foundation 1999.

8 CIBSE, Concise Handbook, 2003, ISBN 1 903287 44 8

9 De Saulles, T, Illustrated Guide to Building Services, 27/99, BSRIA 1999, ISBN 0 86022 543 3, and Illustrated Guide to Electrical Building Services AG 14/2001, BSRIA 2001, ISBN 0 86022 586 0

8 GUIDE TO HVAC BUILDING SERVICES CALCULATIONS © BSRIA BG 30/2007 Heating loads Cooling loads Water flow Air flow Acoustics

ALPHABETICAL LIST SHEET NO PAGE

Acoustics for building services AC1 127 Air density correction A8 121 Boiler sizing H9 33 Condensation risk H4 20 Control valve selection/sizing W6 81 Cooling plant loads C3 44 Dehumidification C9 64 Duct sizing – Circular to rectangular ducts A3 103 Duct sizing – General A1 96 Duct sizing – Pressure loss through fittings A4 107 Duct sizing – Selecting a circular duct size A2 100 Duct system – Index run A5 109 External gains C2 43 Fan sizing A6 113 Flue sizing H10 36 Grille and diffuser sizing A7 117 Heat loss H5 24 Heating/cooling coil sizing C6 51 Heating plant configuration and load matching H7 29 Humidifier duty C8 62 Infiltration H2 14 Internal heat gains C1 42 Pipe sizing – Pressure drop across fittings W3 74 Pipe sizing – General W1 70 Pipe sizing – Straight lengths W2 72 Plant heating load H6 26 Pressurisation of spaces A9 123 Pump sizing W5 77 Radiator sizing H8 30 Return air temperature effects on coil duty C7 56 Stack effect H1 12 Supply air quantity and condition C5 48 System resistance for pipework – Index run W4 75 U values H3 17 Ventilation – Outdoor air requirements C4 46

Water system pressurisation W7 91

134 GUIDE TO HVAC BUILDING SERVICES CALCULATIONS © BSRIA BG 30/2007 A BSRIA Guide www.bsria.co.uk

Choosing building services

A practical guide to system selection

By John Langmaid

BG 9/2004

PREFACE

This publication and accompanying CD Rom provide information to help clients obtain an understanding of building services in order to satisfy functional needs in buildings. The guide will enable a client to specify the type of environment it wants rather than a particular building services solution. They do not provide in-depth technical information as this is readily available elsewhere and is unlikely to be needed by the client in making essential business-related decisions.

The two publications help the client and the professional design team to ask the right questions, and arrive at reasoned answers, in order to identify the most appropriate and cost-effective solutions to clients’ business needs. They are therefore of greatest value to clients during the design process.

Both the CD Rom and the publication will also be of use to experienced professionals in architecture, design and construction in that they provide information on building services in straightforward, non-technical language. They will also enable an audit trail to be established which directly links the original needs of the business to the actual operation of the building services.

Of the multitude of services generically aggregated under the term building services, this publication concentrates on mechanical and electrical services.

The publication contains many questions. The most important two that the client can ask when presented with a technical proposal are why and how:

• Why that solution and not another one? • why those functions? • why are those functions missing? • why does this compromise my use of the space? • why do I need such high maintenance equipment? • why do I need this level of complexity? • how will this affect my business? • how will users operate this? • how do I maintain this? • how can I increase the value? • how can I achieve the same function with less complexity?

The main aim of this publication is to avoid unmanageable complexity and an excessive dependency on technology and management. It helps give control tasks to the occupants and to cut waste, especially energy.

CHOOSING BUILDING SERVICES

CONTENTS

1 BACKGROUND 1

2 USING THE DOCUMENT 3

3 BEING A CLIENT 7

4 FUNCTIONAL SPACE 9 4.1 The concept 9 4.2 Descriptions 9 5 BUILDING SERVICES 11

6 PROCUREMENT, DESIGN AND HANDOVER 13 6.1 Health and safety 13 6.2 Comfortable environment 13 6.3 Power requirements 16 6.4 Domestic hot water 18 6.5 Fundamentals of energy and resource efficient design 19 6.6 Access and risers 21 6.7 Plant rooms 22 6.8 Spatial co-ordination 22 6.9 Commissioning 23 6.10 Lease agreements 24 7 OPERATING THE BUILDING 26 7.1 Environment 26 7.2 Flexibility and adaptability 28 7.3 Operation 31 8 MAINTAINING THE BUILDING 34 8.1 Equipment life 34 8.2 Maintenance 37 9 REFURBISHMENT AND DECOMMISSIONING 43 9.1 Refurbishment 43 9.2 Decommissioning 44 9.3 Legislation 44 REFERENCES 47

CHOOSING BUILDING SERVICES

TABLES

Table 1: Functional spaces 10 Table 2: Office power requirements 16 Table 3: Conference room power requirements 17 Table 4: Power outlet requirements 17 Table 5: Expected economic life of various types of mechanical and electrical services 36

FIGURES

Figure 1: The introductory page of the decision tool 4 Figure 2: Example of a functional space table in the decision tool 4 Figure 3: A filled in example from part of the decision table 5 Figure 4: The professional response form 6 Figure 5: Relation to well-known process maps 8 Figure 6: Comparison of calculated internal gains to composite guidance values 20 Figure 7: Building life-cycle flow 26 Figure 8: Achievable level of operational savings 32 Figure 9: Achievable levels of carbon emissions 32 Figure 10: A maintenance logic tree 39

CHOOSING BUILDING SERVICES

BACKGROUND BACKGROUND 11

1 BACKGROUND Building services engineers provide the internal environmental conditions that enable business processes to function at an optimum level while providing comfort conditions for occupants to achieve their maximum performance potential. 1

This quote from a CIBSE publication contains several truths. Unfortunately, these truths tend to become forgotten in the rush for project start and completion, the smoke-screen of technology, and the unswerving aim to keep to budget. However, added value comes from increasing the functionality required by the client and not necessarily from reducing costs.2

Providing an internal environment which enhances the business process requires that all aspects of the system provided are linked to that process. Unless the system designer acquires an in-depth understanding of what the client needs to support and augment the business process, any proposed solution may prove to be invalid.

Providing what the client needs (and only what the client needs) is the key to providing value and satisfaction. Unfortunately, from a supplier’s viewpoint, defining client value can be a stumbling block and something more often avoided rather than overcome.

From the client’s viewpoint, trying to ensure that the technical proposal meets business needs can be a daunting task. Clients are forced to rely on advisors to avoid spending a great deal of time and effort in penetrating what can, at times, seem to be an arcane art. With the best will in the world, these advisors do not fully recognise that what they have successfully provided to others may not be the best answer for other clients.

Clients must also accept that, for an advisor to gain the necessary in- depth understanding of what the client’s business is about and how the proposed project will enhance that business, time and money must be expended at the outset of the project. This is often time and money which the client is unwilling to commit.

The quality of the air (and other environmental factors) provided for the workforce has been shown by many researchers to be fundamental to good productivity, especially in commercial or service environments. For example, ASHRAE3 has reported relationships between air quality and the following factors:

• Absence from work • sick leave, accidents and injuries • interruptions to work • controlled independent judgements of work quality • self assessments of productivity • speed and accuracy of work • output from pre-existing work groups • cost of the product or service • exchanging output in response to graded reward • volunteer overtime • cycle time from initiation to completion of process

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1 BACKGROUND

• multiple measures at all organisational levels • visual measures of performance, health and well-being at work • development of measures and patterns of change over time.

The ASHRAE Journal4 also quotes that operational productivity may be influenced by up to 17% by addressing factors such as noise, temperature fluctuation, lighting and glare, comfort, relocation frequency, layout and the users’ perception and level of control.

A study by Dorgan and Dorgan5 concluded that the American economy could be improved by US$55 bn per annum for a one-time investment of US$120 bn to improve poor air quality in all buildings.

This benefit is achieved because people work better (and therefore more productively) as a direct result of good air quality.

This does not mean that all buildings require full air-conditioning. They do not. What it does emphasise very strongly is that, given the 1:5:200 ratio6 (where 1 represents the cost of construction of a facility, 5 the cost of operating and maintaining that facility, and 200 the cost of the business process being undertaken in the facility) there is a convincing argument that the money needed to fully and properly define and plan the M&E services in a facility is easily recoverable within a short period of occupation.

CRISP Report 00/047 states that 87% of survey responders (representing companies who commission building projects) said that they received what they expected – but this was not necessarily what they wanted. It should not be surprising, then, to find that no facilities managers were involved in the development of the client statement of requirements (often called the client brief).

In an attempt to ensure client satisfaction without understanding what that client’s adjudication will be based upon, it would seem, that architects, designers, and development surveyors specify the highest level of implementation achievable within the budget that can be forced from the client, irrespective of whether the functionality thus provided is required or not. If this is the case, the level of unwanted function and therefore unnecessary cost, must be considered excessively high.

The primary objective of the rules of thumb contained in this publication is not to provide prescriptive or quantative answers. Rather, they are designed to assist the client and the clients advisors towards asking – and getting answers to – the questions that are fundamental to understanding the business needs and thus the available generic solutions.

The identification and definition of business needs, which are the drivers in most construction projects, are two important factors in achieving a high client perception of value for money.

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USING THE DOCUMENTUSING THE DOCUMENT 22

2 USING THE DOCUMENT The document is split into two parts.

Part 1 discusses many of the issues surrounding the whole-life of the proposed installation and guides clients towards the questions which must be addressed during the early stages of the project. Part 1 also lists further reading and useful web addresses.

Part 2 (on CD-ROM) deals with the definitions of building services and functional spaces. It provides look-up tables for matching functional space (see example in Figure 2) to building services (useful for new construction) it also matches building service to functional space (useful when dealing with refurbishment and existing facilities).

Included on the CD is a fill-in decision table primarily designed for client use. The data collected via this table (see example extract in Figure 3) is to be used by the professional team in the development of alternate options for meeting the client’s business needs.

A professional response form, is available for use by a professional team (see Figure 4). As a first pass the form should be used to identify contentions within the client’s functional requirements and to propose solutions to those contentions. Once the contentions have been successfully resolved, the form should be used to formalise the professional teams recommended solution for the named functional space.

The objective is to guide the client towards an understanding of the issues and topics which need to be addressed to ensure that the client’s requirements are met.

The guide provides background information to enable a client and a professional team to engage in useful and value-adding dialogue.

The publication cannot provide definitive or quantative data. This would not be possible given the scope of building services and the innumerable variables within the construction and business environments.

Clients should not feel that the decision table must be completed in isolation. The reverse applies – a professional team should be consulted regarding the meaning that the client is placing on each statement of requirement and the reasons behind the client’s responses.

By completing the decision table, a client can provide a professional team with a concise, non-technical statement of the functions required to be performed by the building service. This will provide the team with the scope to recommend alternative and innovative solutions while still ensuring that no functionality is lost and no unwanted functions (and thus unnecessary cost) remain.

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2 USING THE DOCUMENT

Figure 1: The introductory page of the decision tool.

Figure 2: Example of a functional space table in the decision tool.

4 CHOOSING BUILDING SERVICES

USING THE DOCUMENT 2

Figure 3: A filled in example from part of the decision table. Decision Table Project title Headquarteres Bldg - Bracknell Date 19/08/04 Client BSRIA Ltd Project number FN0070820 Functional space Go to functional space 1st floor open plan office Size (square metres) 400 Number of occupants:

Comments on Initial: 50

Contains some high heat output areas Growth ( 25 in 5 years) Component 1 2 3 Comments Activity level 3 Occupancy pattern Normal 8h30-17h00 Space requires high protection 3 Environment High degree of remote indication 3 Simple control 3 Provide individual control of temperature, ventilation 3 Perimeter lighting control separate air, and lighting Provide adjustable floor diffusers with under-floor 3 displacement air supply systems From main body Provide maximum access to natural daylight and 3 views to the outdoors Minimise external noise Maximise conditioning through natural means/methods 3 Clean appearance/ Aesthetically neutral 3 Heat/cool large spaces 3 See comments above No false ceilings 3 No false floors 3 Clean ceiling appearance 3 Close temperature control ±( 2°C) 3 Good temperature control 3 Flexible working hours 3 High occupant comfort 3 Maximise energy efficiency Specify materials and furnishings that are low 3 emitters of indoor air contaminants such as volatile organic compounds (VOC). Minimise recirculation while assuring energy 3 efficiency through energy recovery. Provide recessed grates, 'walk off' mats, and other 3 techniques to reduce the amount of dirt entering the Reqd in receptions building No haze, loss of light transmission, or colour change, 3 during entire expected service life of glazing Space requires special solid waste disposal 3 Space requires special liquid waste disposal 3 Stated environment maintained 100% of time 3 Stated environment maintained less than 100% of tim 3 Separate ventilation from cooling and heating 3 Minimise water usage 3 Capital, operation and maintenance Low maintenance complexity Low operating complexity Low maintenance cost Low operating cost

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2 USING THE DOCUMENT

Figure 4: The professional response form.

Professional Team Response Project titles Date

Client Project number Functional space1 Size in square metres Number of occupants Comments on space2 Initial Growth (……..in…….years)

Contentions in functional requirements identified and why contention exists

Options available to resolve contention (state business advantages and disadvantages, plus functionality provided beyond that required by client)

Chosen solution

State:

1 Functionality provided beyond that required above and why this cannot be removed 2 Functionality required by client which cannot be provided by chosen solution and why this cannot be provided

6 CHOOSING BUILDING SERVICES