Table Of ContentBG 31-12 (illustrated mechanical guide) cover 3_D3-2010 Legislation cover.qxd 04/04/2012 16:05 Page 1
A BSRIA Guide
www.bsria.co.uk
The Illustrated Guide to
Mechanical Building Services
Second Edition
By David Bleicher
BG 31/2012
ACKNOWLEDGEMENTS
This publication is an update to BSRIA AG 15/2002 The Illustrated
Guide to Mechanical Building Services, which was written by Tom de
Saulles and included considerable contribution from Gay Lawrence
Race.
The original publication was part-funded by the former Department
of the Environment, Transport and the Regions (DETR), under the
Partners in Innovation collaborative research programme, and part-
funded by the Chartered Institution of Building Services Engineers
(CIBSE). The members of the original steering group were:
Andrew Ford Fulcrum Consulting (Representing DETR)
Dr Hywel Davies CIBSE (Representing CIBSE & CCC)
John Killey Citibank (Representing CIBSE)
John Deal CIBSE (Representing CIBSE)
Nicholas Rowe Gardiner & Theobald (Representing BCO)
Hans Haenlein Hans Haenlein Architects
John Armstrong Ove Arup & Partners
BSRIA would also like to thank the following organisations that kindly
provided the photographs or diagrams which have made this illustrated
guide possible:
Airedale International Air Conditioning Ltd.
AmbiRad Ltd.
ArmstrongIntegrated Ltd.
Clivet UK Ltd.
Colt International Ltd.
Daikin UK Ltd.
DE-VI Electroheat Ltd.
Displacement Design Ltd.
Dravo Environmental Services Ltd.
Frenger Ltd.
Geoff Sumner
Hudevad Ltd.
Kensa Heat Pumps
Kohlbach Holdings GmbH
Mitsubishi Electric
Peter Brotherhood Ltd.
Powrmatic Ltd.
S&P Coil Products
Toshiba Air Conditioning
Trox UK Ltd.
Vortice Ltd.
This publication was designed and produced by Ruth Radburn, final
editorial control of this document rested with BSRIA.
This publication has been printed on Nine Lives Silk recycled paper, which is
manufactured from 100% recycled fibre.
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 2012 April 2012 ISBN 978 0 86022 709 0 Printed by ImageData Ltd.
ILLUSTRATED GUIDE TO MECHANICAL BUILDING SERVICES 1
© BSRIA BG 31/2012
PREFACE
This illustrated guide provides basic reference information on mechanical
building services systems for construction clients and professionals in
other areas of the construction industry. The topics covered are:
Heating
Ventilation
Air-conditioning
Controls.
For construction clients, this guide provides a simple insight into the
main system options discussed during the briefing process and can
consequently assist dialogue with the design team. It can also help clients
to identify and raise technical questions which they feel are relevant to
their organisation’s specific needs. For construction professionals, the
guide provides a quick reference to building services systems and can
assist their working knowledge of the subject.
To ensure the guide is simple and quick to use, a brief introduction to
each system is provided, followed by a list of key points. Photographs
and simple drawings are used to help explain the appearance and
operation of each system.
It is acknowledged that the design team’s role includes assessing and
recommending appropriate design solutions for a given project. This
guide does not aim to provide a route for system selection other than
pointing out typical applications for many of the systems covered.
Since the previous edition of this guide, further information has been
added on pumps, pressurisation, low carbon heat sources, MVHR
systems, commissioning, handover and project evaluation along with
updates of the original information.
BSRIA has also published a companion guide BG 5/2005, The Illustrated
Guide to Electrical Building Services – Second edition. This provides
information on electrical systems including, power supply and
distribution, fire detection and alarm systems, security systems, lighting
systems, uninterruptible power supplies and structured cabling. More
detailed information on systems covered in this guide can be found in the
following publications:
BG 2/2009 The Illustrated Guide to Ventilation
BG 1/2010 The Illustrated Guide to Mechanical Cooling
BG 1/2008 The Illustrated Guide to Renewable Technologies
BG 7/2009 Heat Pumps
BG 2/2007 CHP for Existing Buildings.
2 ILLUSTRATED GUIDE TO MECHANICAL BUILDING SERVICES
© BSRIA BG 31/2012
CONTENTS Page
OVERVIEW
Building design and building services 5
Location of building services 7
Thermal comfort 8
HEATING
Introduction 9
Boilers 10
Low carbon heat 11
Radiators 12
Convectors 13
Underfloor heating 14
Radiant heating 15
Warm air unit heaters 17
VENTILATION
Introduction 18
Natural ventilation 19
Powered window actuators 21
Single-sided ventilation 22
Cross ventilation 22
Stack ventilation 23
Stack and wind ventilators 24
Mechanical ventilation – Extract only 25
Mechanical ventilation – Supply only 26
Supply and extract systems 27
Mechanical ventilation with heat recovery 28
AIR-CONDITIONING SYSTEMS
Introduction 29
Constant volume (CV) 32
Variable air volume (VAV) 33
Displacement ventilation 34
Fan coil units 35
Chilled ceilings 37
Chilled beams 38
Room-based heat pumps (Versatemp system) 39
Split systems 40
Variable refrigerant flow systems (VRF) 41
Chillers, dry coolers and cooling towers 42
Air diffusers 43
CONTROL SYSTEMS AND COMPONENTS
Introduction 44
Analogue and direct digital control (DCC) systems 47
Building management systems (BMS) 48
Integrated control systems 49
COMMISSIONING, HANDOVER AND EVALUATION 50
INDEX 51
ILLUSTRATED GUIDE TO MECHANICAL BUILDING SERVICES 3
© BSRIA BG 31/2012
The Illustrated Guide
to Mechanical Building Services
Complementing the current series of BSRIA’s Illustrated Guides, this
second edition of The Illustrated Guide to Mechanical Building Services
outlines the most common mechanical building services systems,
covering heating, ventilation, air-conditioning and controls.
Illustrated with simple line diagrams and photos, the Guide
demystifies the subject of mechanical building services
for lay people and experienced engineers alike.
Other guides in the series include The Illustrated Guide to Electrical Building Services,
The Illustrated Guide to Mechanical Cooling, The Illustrated Guide to Ventilation
and The Illustrated Guide to Renewable Technologies.
All of these guides are available from the BSRIA Bookshop
www.bsria.co.uk/bookshop or Tel: +44 (0)1344 465529
4 ILLUSTRATED GUIDE TO MECHANICAL BUILDING SERVICES
© BSRIA BG 31/2012
OVERVIEW – BUILDING DESIGN AND
BUILDING SERVICES
The design of a building will affect many of the costs which an operator
will encounter during the life of a building. The building services can
account for around 30% of the capital cost and 50% of the operating cost
for a typical office building. It is therefore important that the services
form an integral part of the overall building concept to help ensure they
will operate efficiently. Involving the specialist building services engineer
at an early stage in the design process can help achieve this objective.
If the services are not considered until a later stage, problems which
could have been overcome by simple measures may require a more
complex technical solution. A well-designed building may cost a little
more initially, but the overall cost of ownership should be reduced. Life-
cycle costs of building services systems should be considered, as the cost-
in-use element can form a large proportion of the total cost, outweighing
the initial capital cost.
Decisions about which services to incorporate into a building design
require consideration of many factors including the following:
Cost
Both initial costs and life cycle costs.
Level of thermal comfort required
See overview: thermal comfort, page 8.
Level of control required
See control systems and components, page 44.
Complexity
What type of system is appropriate and will it be difficult to
operate and maintain? For example a full air-conditioning system
provides close control of air temperature and humidity, but this
comes at a price.
Noise levels
Will heating, ventilation and air-conditioning plant adversely
affect noise levels in occupied areas? What about noise from
outside the building? The noise rating (NR) is a European
measure of sound levels which relates to the sensitivity of the
human ear. It is often used to specify an acceptable interior or
exterior sound level, for example NR 35 - 40 for offices, NR 20
for a concert hall.
Adaptability and flexibility
To meet possible future requirements.
Energy use
Mechanical building services plant can account for a major part
of a building’s energy use.
Plant space
Air-conditioning systems can require a large amount of space to
accommodate the refrigeration and air handling plant. Access for
operation, maintenance and replacement must be considered (see
overview: location of building services, page 7).
It is not always possible to design a building that can utilise all possible
energy-saving measures. Urban noise and pollution may dictate the need
for sealed buildings incorporating mechanical ventilation or air-
conditioning system. The activities in some buildings can also necessitate
air-conditioning to offset a high internal heat gain.
ILLUSTRATED GUIDE TO MECHANICAL BUILDING SERVICES 5
© BSRIA BG 31/2012
If internal heat gains are sufficiently low and the external High internal heat gains and/or the need to have sealed windows to
environment is suitable, natural ventilation can provide a low keep out external noise and pollution means that some buildings
energy solution to cooling and ventilating a building. cannot avoid the use of mechanical ventilation or air-conditioning.
Some basic energy efficiency strategies relevant to most building types
are:
During cold weather useful heat gains should be maximised and
heat losses minimised while ensuring adequate ventilation.
Heat gains during warm weather should be minimised to avoid
overheating. Correct orientation, external shading and
fenestration can all reduce heat gains.
Natural ventilation should be used wherever practicable. Deep-
plan depths and substantial partitioning can preclude this. Where
natural ventilation alone is not adequate for cooling, a mixed-
mode system (combined natural and mechanical ventilation) may
be sufficient as opposed to an air-conditioning system.
Where mechanical ventilation is used, outside air should be
employed directly for cooling in preference to operating
refrigeration plant. This technique is known as free cooling.
Wherever possible, maximum use of daylight should be made to
reduce the energy used by artificial lighting.
6 ILLUSTRATED GUIDE TO MECHANICAL BUILDING SERVICES
© BSRIA BG 31/2012
LOCATION OF BUILDING
SERVICES
The amount of space taken up by the services is among the
many criteria upon which a well-designed building can be
judged. Project specific factors, such as the amount of
servicing required, means that it is not possible to lay down
specific guidelines on the spatial requirements for building
services. However, as a rough guide, the space taken up by
the services in a simple office building will be in the order of
6 – 10% while for a highly serviced building it will be
around 15 – 30%.
An example of a building with minimal mechanical services
is illustrated opposite. A radiator heating system is supplied
with hot water from a basement plant room. A vertical riser
links the radiator circuit on each floor with the boiler plant.
The building is naturally ventilated and consequently there is
no ductwork or related air handling plant.
The illustration below is an example of a more highly
serviced building, typical of many air-conditioned offices.
Each floor has a ceiling void containing a range of services
which might include hot/chilled water pipes, ventilation
ductwork, fan coil units and luminaires. The riser contains
pipework linking boiler plant in a basement plant room
with the ceiling voids on each floor and the rooftop plant
room. The riser also contains ductwork to link air handling
Example of a simple heating system distribution layout.
and refrigeration plant in the rooftop plant room with the
ceiling void on each floor.
Centralised air systems generally require the most
space for distribution, as air is a relatively poor
carrier of heat compared to water.
Large and/or highly serviced buildings often
require several plant rooms, one or more of
which may be on an intermediate floor or
located separately from the building.
Boiler plant is often located in a basement or
ground floor plant room, while air handling
and refrigeration plant is located at high level to
ensure a clean fresh air supply and good heat
rejection for the refrigeration plant (see chillers,
dry coolers and cooling towers, page 42). In
addition to heating and cooling plant, central
plant areas can also contain a variety of other
equipment such as electrical transformers and
standby generators.
Both illustrations show systems with centralised
plant. Some types of systems make use of
decentralised plant, located at strategic points
throughout the building.
Example of an air-conditioned building showing the additional
plant and distribution space that is required.
ILLUSTRATED GUIDE TO MECHANICAL BUILDING SERVICES 7
© BSRIA BG 31/2012
THERMAL COMFORT
Creating an internal environment in which all the occupants
feel comfortable can be difficult to achieve, as the factors
which determine comfort affect each of us in varying ways.
There are seven parameters that determine thermal comfort.
These can be grouped in the following way:
Personal factors
Metabolism
Clothing
Skin temperature.
Environmental factors
Heat exchange between people and their surroundings.
Air temperature
Surface temperature of walls and partitions
Air velocity
Relative humidity.
While personal factors are dependent on the individual, the
environmental factors relate to the weather, building type and
use and the operation of any mechanical services that may be
installed. Design conditions for a space usually specify the
environmental factors, with air temperature, surface
temperature and air velocity often combined into a single
index called resultant temperature.
For critical applications, such as for the production of
pharmaceuticals, it may be essential to maintain relatively Typical temperature variation in a space heated by radiators.
constant temperature and humidity levels. This requires a
high degree of servicing and is consequently expensive.
For the majority of building types it is acceptable for The adaptive thermal comfortmodel recognizes that
internal conditions to vary within limits, without having a people adapt their clothing to the prevailing external
significant effect on the comfort of the occupants. conditions. Hence, satisfactory thermal comfort can be
Therefore, for buildings such as offices, the internal achieved within a broader range of internal
conditions may be specified as requiring a resultant temperatures, for example as low as 18°C in the winter
temperature of 22 2C. and as high as 28°C in the summer. Significant energy
savings can be achieved this way, however occupants of
If humidity control is required, such as in a fully air- such buildings must be given control over their
conditioned building, it is typically specified as needing to environment, for example by allowing them to open and
maintain a level of relative humidity (RH) between an close windows.
upper and lower limit, for example 40% – 60%RH. For
buildings without a full air-conditioning system, control of Conditions, particularly air temperature and velocity, will
the humidity level is either limited or non-existent and it fluctuate within a space due to buoyancy effects, thermal
is able to float in response to internal and external response of the building and its services, localised heat
conditions. However, humidity levels in buildings with gains and the type of heating/cooling system used. For
only a comfort cooling system (in other words, without example, the temperature within a space heated by
humidity control – see air-conditioning – introduction, radiators can vary considerably between floor and ceiling
page 29) will generally stay within the limits of comfort level as shown above. The accumulation of hot air at high
which are approximately between 30% – 70%RH. level is known as stratification.
8 ILLUSTRATED GUIDE TO MECHANICAL BUILDING SERVICES
© BSRIA BG 31/2012
