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  • PublisherCIBSE
  • Product CodeGVB2/16
  • Number of pages157
  • Publication DateMay 2016
  • ISBN9781906846756

GVB2/16 CIBSE Guide B2: Ventilation and Ductwork 2016


PDF Format







PDF Format






GVB2/16 CIBSE Guide B2: Ventilation and Ductwork 2016

Notice about delivery of hard copy publications during the current coronavirus situation

As a result of the coronavirus lockdown, we are only able to post hard copy publications every few weeks. Apologies for any inconvenience this may cause. To check on the status of your order, please email

Guide B provides guidance on the practical design of heating, ventilation and air conditioning systems. It represents a consensus on what constitutes relevant good practice guidance. This has developed over more than 70 years, with the Steering Groups for each edition of the Guide expanding and pruning the content to reflect the evolution of technology and priorities.

Since the last edition of Guide B in 2005, the European Energy Performance of Buildings Directive has been introduced. This requires national building energy regulations to be based on calculations that integrate the impact of the building envelope and the building services systems, formalising what was already recognised as good design practice. In addition, the use of voluntary energy efficiency and sustainability indicators has increased. 

These changes have influenced the content of Guide B, but the emphasis remains on system design. 

NoteAn important standard relating to filters is referenced in this title, BS EN 779: 2012 'Particulate air filters for general ventilation. Determination of the filtration performance'. This replaced the previous 2002 edition, but is now itself withdrawn. It was superseded in July 2018 by BS EN ISO 16890 (in 4 parts).

The new classifications are based on expanded tests for particulates and there is no 1-to-1 relationship with the EN 779-based classes. There are implications for both new and existing HVAC systems and potentially for guidance on natural ventilation. In due course, CIBSE guidance will be updated to reflect this change but in the mean time, you should note it.


This Eurovent document provides a useful summary of the changes:

Corridenda (May 2018)

A Corrigenda has been issued making corrections to the following pages: 2-16, 2-19, 2-21, 2-22, 2-32, 2-33, 2-35, 2-38, 2-43, 2-44 and 2-59 (and dated 15 May 2018). The Corrigenda itself can be downloaded here.

Purchasers of the hard copy will receive this with the book and it will be incorporated in a reprint at the earliest opportunity. The pdf of the Guide downloadable using the button above will be corrected with these changes and clearly identified as such.

Structure of the Guide

Guide B deals with systems to provide heating, ventilation and air conditioning services, and is divided into several chapters which are published separately. It will usually be necessary to refer to several – perhaps all – chapters since decisions based on one service will commonly affect the provision of others.

This edition of CIBSE Guide B was published in 2016 in five separate chapters plus a combined index across all five. These are:

  • Chapter B0: Applications and activities. This Chapter on how different types of building and different activities within buildings influence the choice of system. This chapter is now available in printed form, but can be freely downloaded as a pdf from the CIBSE website. For many activities and types of building, more detailed design information is available in specialist guidance.

Chapters B1 to B4 address issues relating to specific services. There are usually several possible design solutions to any situation, and the Guide does not attempt to be prescriptive but rather to highlight the strengths and weaknesses of different options. These are available as hard copy or pdf:

All chapters of CIBSE Guide B can be downloaded or purchased from our website.

Since August 2018 a full set of all 6 Chapters is available to purchase at a discounted price from here.

Guide B2 Ventilation and ductwork

Ventilation is the process by which fresh air is provided to occupants and concentrations of potentially harmful pollutants are diluted and removed from a space. It is also used to cool a space and as a mechanism to distribute thermally conditioned air for heating and cooling. It is a fundamental component of building services design since it plays a major role in the comfort, health and productivity of occupants. In addition, ventilation can contribute significantly to a building’s energy load and, in some cases, can account for 50 per cent or more of total heating or cooling loss. To stem energy loss from uncontrolled air change there is growing demand for airtightness combined with demandcontrolled ventilation and heat recovery.

In large buildings, the ventilation system can be extremely complex and is invariably integrated with the heating and cooling system. Hence there is a strong connection between ventilation, heating and cooling systems, building envelope, fire protection and structural design issues. This impinges on the wholelife costs and performance of buildings. Since building services are required to operate throughout the life of the building, their operating costs are a very significant element of the wholelife costs of the system.

For all these reasons, there is a need for uptodate guidance on the design of ventilation systems. The overall process of design development, from the initial outline design through to system selection and detailed equipment specification, is summarised schematically in Figure 2.1. Cooling systems are separately covered by CIBSE Guide B3 (2016) and heating systems are covered in CIBSE Guide B1 (2016).

This document, which forms chapter 2 of CIBSE Guide B, is intended to be used by practising designers who hold a basic knowledge of the fundamentals of building physics and building services engineering.

Contents of Guide B2

2.1 Introduction

2.1.1 Introduction

2.1.2 Scope

2.1.3 Definitions

2.1.4 Energy and carbon considerations

2.1.5 System costing

2.2 Design criteria

2.2.1 Introduction

2.2.2 Contaminant control

2.2.3 Fresh air supply rates

2.2.4 Ventilation for thermal comfort

2.2.5 Humidity

2.2.6 Ventilation to avoid interstitial condensation

2.2.7 Air movement: limiting air velocities

2.2.8 Air distribution

2.2.9 Noise

2.3 Systems

2.3.1 Introduction

2.3.2 Ventilation systems

2.3.3 Filtration systems

2.3.4 Ventilation heat recovery systems

2.3.5 Duct systems

2.3.6 Ventilation control systems

2.4 System design

2.4.1 Introduction

2.4.2 Designing for natural ventilation

2.4.3 Mechanical ventilation design

2.4.4 Mixed-mode ventilation design

2.4.5 Ductwork principles of design

2.4.6 Ventilation design calculation techniques

2.4.7 Ventilation design measurement techniques

2.5 Other design considerations

2.5.1 Introduction

2.5.2 Noise

2.5.3 Fire and smoke protection

2.5.4 Air leakage

2.6 Equipment

2.6.1 Fans

2.6.2 Air control units

2.6.3 Mixing boxes

2.6.4 Air terminal devices: diffusers and terminals

2.6.5 Ventilation air intake and discharge points

2.6.6 Process exhaust hoods

2.6.7 Duct equipment

2.6.8 Ductwork connections

2.6.9 Natural ventilation equipment

2.7 Commissioning, operation and maintenance

2.7.1 Testing and commissioning

2.7.2 Maintenance and cleaning



Appendix 2.A1: Recommended sizes for ductwork

Appendix 2.A2: Space allowances

Appendix 2.A3: Maximum permissible air leakage rates

Appendix 2.A4: Methods of fire protection

Appendix 2.A5: Example calculations

Appendix 2.A6: Techniques for assessment of ventilation


Guide B2 Steering Committee:

Peter Warren (Chair), Wayne Aston, Nick Barnard, Colin Biggs, Craig Booth, Eric Curd, Justin Davies, Alan Green, Danny Hall, Jon Hill, Roy Jones, Ray Kirby, Martin Liddament, Peter Rogers, Wander Ter Kiule, Paul White


John Armstrong, Steve Irving, Marialena Kolokotroni