Skip to content

Search the knowledge portal

  • PublisherCIBSE
  • Product CodeGVB2/16
  • Number of pages
  • 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

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. 

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.

These are, with links as appropriate:
Chapter B0: Applications and activities focuses on how different types of building and different activities within buildings influence the choice of system. This chapter is not available in printed form, but can be downloaded 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.

Another Section of Guide B, designated as Guide B0:  Applications and Activities:HVAC Strategies for Building is available in pdf format only but as a free download from here.
In addition, a Combined Index to Parts B1 to B4 can be found and freely downloaded here.

The 4 hard copy volumes of Guide B are available to purchase as a set at a discounted price 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 Mixedmode 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