CIBSE Guide F - Energy Efficiency in Buildings (3rd Edition)

284 Pages·2012·4.24 MB·English

by  Butcher, Ken J.

CIBSE Guide F

Energy efficiency
in buildings

The Chartered Institution of Building Services Engineers

222 Balham High Road, London, SW12 9BS

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.

© Third edition May 2012; The Chartered Institution of
Building Services Engineers London
Registered charity number 278104

ISBN 978-1-906846-22-0

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
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adopter by doing so agrees to accept full responsibility for
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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 CIBSE Publications

Printed in Great Britain by The Lavenham Press Ltd.,
Lavenham, Suffolk CO10 9RN

Note from the publisher

This 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.

Contents

Principles of energy efficiency
—

1
Introduction
1-1

1.0
Objectives and scope
1-1

1.1
Energy efficiency drivers
1-1

1.2
How to use this Guide
1-7

References
1-8

Part A: Designing the building
—

Energy design checklist
—

2
The design process
2-1

2.0
General
2-1

2.1
Stages in the design process
2-2

2.2
The design team
2-3

2.3
The energy efficient brief
2-4

2.4
The design contract
2-5

2.5
Equipment selection
2-5

References
2-6

3
Developing a design strategy
3-1

3.0
General
3-1

3.1
Integrating fabric and services
3-1

3.2
Integrating services
3-2

3.3
Minimising requirements for services
3-3

3.4
Integrating human factors
3-6

References
3-7

Bibliography
3-8

4
Developing an energy strategy
4-1

4.0
Energy and low carbon strategy
4-1

4.1
Definition of zero carbon
4-1

4.2
Building Regulations Approved Document L2
4-1

4.3
Planning policy
4-2

4.4
Energy strategy reports in support of planning applications
4-2

4.5
Hierarchy for developing an energy strategy
4-4

4.6
Low and zero carbon technology options
4-5

4.7
Low and zero carbon technologies
4-6

4.8
Energy metering
4-14

References
4-17

5
Concept design
5-1

5.0
General
5-1

5.1
Site considerations
5-1

5.2
Built form
5-2

5.3
Services
5-17

5.4
Summary
5-18

References
5-18

Bibliography
5-19

6
Control strategies
6-1

6.0
General
6-1

6.1
Developing a strategy
6-2

6.2
Strategic control functions
6-4

6.3
Building energy management systems
6-5

6.4
Occupant controls
6-6

References
6-7

Bibliography
6-7

7
Ventilation and air conditioning design
7-1

7.0
General
7-1

7.1
Natural ventilation
7-2

7.2
Mechanical ventilation and air conditioning
7-2

7.3
Efficient air conditioning systems
7-6

7.4
Ventilation and air conditioning controls
7-11

References
7-13

Bibliography
7-14

8
Refrigeration design
8-1

8.0
General
8-1

8.1
Reducing demand for cooling
8-1

8.2
Designing energy efficient systems
8-2

8.3
Refrigeration efficiency
8-5

8.4
Primary plant
8-5

8.5
Distribution systems
8-9

8.6
Controls
8-10

References
8-13

Bibliography
8-14

9
Lighting design
9-1

9.0
General
9-1

9.1
Design objectives
9-1

9.2
Selecting luminaires
9-3

9.3
Selecting light sources
9-3

9.4
Control gear (ballasts)
9-6

9.5
Lighting controls
9-6

References
9-10

Bibliography
9-12

10
Heating and hot water design
10-1

10.0
General
10-1

10.1
Primary plant
10-1

10.2
Distribution systems
10-9

10.3
Controls
10-11

10.4
Energy consumption
10-16

10.5
Domestic heating
10-17

References
10-17

Bibliography
10-19

11
Motors and building transportation systems
11-1

11.0
General
11-1

11.1
Minimising the motor load
11-2

11.2
Motor sizing and selection
11-3

11.3
Motor drives
11-4

11.4
Controlling the motor load
11-4

11.5
Building transportation systems
11-8

References
11-10

12
Electrical power systems and office equipment
12-1

12.0
General
12-1

12.1
Large power users
12-1

12.2
Office equipment
12-2

12.3
Energy consumption
12-3

12.4
Heat gains and air conditioning
12-4

References
12-5

13
Checking the design
13-1

13.0
General
13-1

13.1
Checking internal loads and heat gains
13-1

13.2
Checking against energy targets
13-2

13.3
Checking against environmental targets
13-4

References
13-5

14
Commissioning, handover and feedback
14-1

14.0
General
14-1

14.1
On-site checks
14-1

14.2
The commissioning process
14-1

14.3
Handover and feedback
14-2

14.4
Documenting the building
14-3

14.5
Post-occupancy evaluation and feedback
14-4

References
14-5

Bibliography
14-6

Part B: Operating and upgrading the building
—

Why buildings fail on energy
—

15
Managing the building
15-1

15.0
General
15-1

15.1
Understanding the building
15-3

15.2
Developing an energy management strategy
15-4

15.3
Management structures
15-6

15.4
Occupant involvement
15-9

References
15-10

Bibliography
15-11

16
Acquisition and refurbishment
16-1

16.0
Acquiring a new or existing building
16-1

16.1
Refurbishing existing buildings
16-1

16.2
Energy efficient refurbishment
16-2

16.3
Building Regulations and refurbishment
16-2

16.4
Levels of refurbishment
16-5

16.5
Refurbishment measures
16-6

References
16-6

17
Maintenance and energy efficiency
17-1

17.0
General
17-1

17.1
Air conditioning inspections
17-1

17.2
Planning maintenance
17-1

17.3
Maintenance contracts
17-3

17.4
Monitoring maintenance
17-3

17.5
Checklist for maintenance and energy efficiency
17-4

References
17-4

Bibliography
17-4

Appendix 17.A1: Checklist for energy related maintenance issues
17-6

18
Energy audits and surveys
18-1

18.0
General
18-1

18.1
Retrofitting energy saving measures
18-1

18.2
Developing an energy savings carbon management programme
18-2

18.3
What are energy audits and surveys?
18-2

18.4
Planning a site survey
18-4

18.5
How to carry out energy audits and surveys
18-7

18.6
Preliminary audits
18-7

18.7
Site surveys
18-9

18.8
Assessing energy saving measures
18-11

18.9
Analysis and reporting
18-13

18.10
Implementing savings
18-15

18.11
Specific energy saving measures
18-16

References
18-16

Bibliography
18-16

Appendix 18.A1: Site survey checklist
18-17

19
Benchmarking, monitoring and targeting (M&T)
19-1

19.0
General
19-1

19.1
The m&t process
19-1

19.2
Using energy data
19-2

19.3
Setting up an m&t system
19-5

19.4
Data quality
19-6

19.5
m&t analysis techniques
19-7

19.6
Benchmarking end-uses
19-10

19.7
Setting targets
19-11

19.8
Maintaining the savings
19-12

References
19-13

Bibliography
19-14

Part C: Benchmarks
—

20
Energy benchmarks
20-1

20.0
General
20-1

20.1
Overall building benchmarks
20-1

20.2
Detailed component benchmarks
20-6

20.3
Detailed end-use benchmarks
20-7

References
20-16

Appendices
A-1

Appendix A1: Conversion factors, fuel data and correction
A-1
of meter readings

Appendix A2: Using consultants and model brief
A-2

Index
I-1

Principles of energy efficiency

The following principles have been developed from the CIBSE policy statement on energy (available via the CIBSE
website), and provide a framework for engineers to put the policy into practice. Where possible, building services engineers
should make every effort to follow the principles shown below.

Principle
Measures for implementation of principle
Relevant section(s) of CIBSE Guide F

Part A:
Part B:
Part C:

Designing
Operating and
Benchmarks

the building
upgrading the

building

Integrated building design
Design the most energy efficient buildings and services possible.
2 to 13
—
20

Provide holistic designs which are responsive to the external climate

whilst still meeting the needs of the occupants.

The energy efficient brief
Ensure the client’s brief includes energy efficient criteria and targets
2
—
20

for all buildings, new or refurbished. Review the project in relation

to these targets and criteria as the design progresses.

Benchmarking
Compare designs and in-use performance of buildings with
2 to 13
19
20

appropriate benchmarks to ensure that best practice energy efficiency

is being achieved.

The integrated design team
Work with other members of the design team in order to optimise
2
—
—

building energy performance.

Reduce demand
Keep energy demand to a minimum through careful design of built
2 to 13
—
—

form and services using renewable energy sources, ambient energy

and passive solutions. Make every effort to avoid the need for

air conditioning.

Design for operation
Design for commissionability, maintainability and manageability
2 to 13
—
—

by keeping solutions simple and eliminating potential failure

pathways.

Optimise plant
Select the most efficient plant, using certified or otherwise
7 to 12
18
—

independently verified product performance data, and ensure

that plant and equipment are not oversized.

Use effective controls
Introduce energy efficient controls which operate systems
6 to 11
18
—

efficiently, safely and economically, whilst still allowing individual

occupants to alter their own comfort levels, but avoiding systems

defaulting to ‘on’.

Ensure complete handover
Ensure that building services are properly commissioned and handed
14
—
—

over to managers, operators and occupants.

Improve operation
Encourage energy efficient operation of buildings through
—
15 to 19
20

management, policy, maintenance, monitoring and control.

Understanding the building
Provide managers, engineers, operators and occupants with suitable
14
15
—

documentation to ensure they understand the design intention and

how the buildings are meant to function.

Monitoring and feedback
Develop a strong element of feedback to improve understanding
13, 14
19
20

from previous good and bad experience related to these principles.

Introduce appropriate metering to improve information and to

detect faults rapidly.

Build-in energy efficiency
Always consider introducing energy efficient technologies
3 to 12
15–19
—

throughout the design and upgrade processes but avoid unnecessary

complications. Seek opportunities for improving existing buildings

during operation, maintenance, alteration and refurbishment.

Environmental impact
Minimise adverse effects on the external environment. Minimise
3 to 12
15–19
—

emissions and select environmentally friendly materials and fuels,

utilising renewable sources as much as possible.

An energy efficient building provides the required internal environment and services
with minimum energy use in a cost effective and environmentally sensitive manner

Introduction
1-1

The document promotes a holistic approach to design and
operation by recognising that there is a strong interaction
between the building envelope, heating and cooling
systems, lighting etc. The overall design intent should
always be considered before implementing individual
measures.

1.1
Energy efficiency drivers

The UK government has committed the UK to legally
binding targets to reduce carbon emissions by 80% by
2050(1). Carbon emissions from the UK’s non-domestic
buildings (comprised of commercial offices, hotels, shops,
schools, hospitals, factories and other buildings), are
responsible for 18% of the UK’s total(2). In 2010, total UK
net emissions of carbon dioxide were provisionally
estimated to be 491.7 million tonnes (Mt)(3).

All building professionals have a responsibility to reduce
this through the application of good practice. The key
drivers for energy efficiency are:

—
legislation, in particular, Building Regulations
Approved Documents L2A(4) and L2B(5) and the
Carbon Reduction Commitment Energy Efficiency
Scheme (CRC)(6)

—
planning policies that relate to energy often include
energy efficiency as well as a target contribution
from low/zero carbon technologies

—
reduced operating costs through lower energy use

—
fiscal penalties or incentives, such as the climate
change levy, enhanced capital allowances and the
feed-in tariff

—
risks to professional reputation due to poor
performance; this includes Energy Performance
Certificates, Display Energy Certificates, the CRC
league table etc.

There are also benefits from occupying an energy efficient
building, which include:

—
an improved perception of the building when it is
being sold or let

1.0
Objectives and scope

This Guide shows how to improve energy performance,
reduce running costs and minimise the environmental
impact of buildings by:

—
designing energy efficient new buildings and
refurbishment of existing buildings

—
managing and operating buildings in an energy
efficient way

—
upgrading buildings to improve ongoing energy
efficiency

—
enabling engineers to overcome barriers to energy
efficiency in discussions with clients and other
members of the design and construction team

—
demonstrating the value of energy efficiency to
clients, developers and tenants.

An energy efficient building provides the required internal
environment and services with minimum energy use in a
cost effective and environmentally sensitive manner. There
is, therefore, no conflict between energy efficiency and
comfort. Hence, energy efficiency can be combined with
other aspects of sound engineering practice, as set out in
other CIBSE Guides.

This document is primarily targeted at building services
engineers and takes a holistic approach to designing and
operating buildings. The early sections will also be useful
to other members of the design team including architects
and surveyors. The latter sections should also be useful to
other building professionals such as energy managers,
facilities managers, developers, clients, property agents and
occupiers. Sections of particular relevance to each reader
are shown in section 1.2.

This document covers opportunities for achieving energy
efficiency. It complements existing guidance by CIBSE and
others and refers readers to more detailed information
where relevant.

It does not cover process energy nor detailed design
methods. Although it concentrates on non-domestic
buildings, much of the information is also relevant to the
domestic sector.

1
Introduction

1.0
Objectives and scope

1.1
Energy efficiency drivers

1.2
How to use this Guide

Operating and
upgrading the building

Managing the building

Acquiring/refurbishing

Maintenance

Upgrading energy
efficiency

Checking by M&T

Maintaining the savings

Introduction

Benchmarks

Designing the building

The design process

Design strategy

Concept design

Specific design

Checking the
design

Handover

Energy strategy

1-2
Energy effi ciency in buildings

—
the potential for improved occupant health and
wellbeing as low-energy buildings often have
improved levels of daylight, air quality and natural
ventilation.

1.1.1
Reducing national energy use
through improved staff
motivation

Studies (7) have shown that there is a large potential to
improve the energy effi ciency of existing buildings through
cost effective technologies and techniques.

The Intergovernmental Panel on Climate Change (IPCC)
report(8) suggests that commercial and public sector
buildings could achieve an 18% reduction (14.5 MtCO2) in
carbon emissions through no/low cost energy effi ciency
measures (i.e. costing less than £40/tCO2). There is the
potential for an additional 23% (18 MtCO2) through the
application of microgeneration technologies.

The breakdown of total carbon emissions by sector in the
UK is shown in Figure 1.1.

Typical energy breakdowns for various types of building are
shown in chapter 20. Figure 1.2 shows the breakdown of
CO2 emissions by end use in each sector.

Carbon emissions from non-domestic buildings have
remained relatively constant since 1990, often due to
increased amounts of offi ce equipment, and associated air
conditioning to remove internal heat gains emanating from
this offi ce equipment.

The current and proposed legislation and policy initiatives
(see section 1.1) for energy effi ciency in new and existing
buildings are intended to help to start reducing carbon
emissions from this sector.

1.1.2
Environmental issues

Burning fossil fuels contributes to atmospheric pollution,
resulting in a wide range of damage both to the environment
and public health, see CIBSE policy statement on Climate
Change (http://www.cibse.org/policystatements).

There is very high confi dence amongst the scientifi c
community that the increase in global average temperatures
since the mid-20th century is due to the increasing global
warming gases from human activities(8).

Improving energy effi ciency will help reduce the risk of
dangerous climate change. Burning fossil fuels also results
in emissions of SOx and NOx, both of which contribute to
acid rain.

The UK has developed a policy framework to reduce
emissions. The key elements of this framework are set out
below:

—
The Climate Change Act(1) has set legally binding
targets to reduce greenhouse gas emissions by 80%
by 2050, with an interim target of 34% by 2020,
based on 1990 levels.

—
The UK government has set a target for 15% of
electricity to be generated from renewables by
2020(9).

—
The Low Carbon Transition Plan(10)
sets out how
the above targets could be achieved and includes a
proposed policy framework to deliver the savings.

—
The UK Government’s Carbon Plan(11) sets out a
series of actions and commitments for delivering a
low carbon economy.

—
The UK government has announced its aspiration
that all buildings will to be ‘zero carbon’ by 2019,
with earlier targets for schools and homes (2016)
and public buildings (2018)(12), see section 4.1.

 Domestic
 Commercial and public buildings
 Industrial buildings
 Industrial process
 Transpo
Transpo
T
rt

 Agriculture

 Industrial
 Retail
 Hotels, inns and restaurants
 Commercial offices
 Schools
 Further and higher education
 Government estate

 Sports
 Public offices
 Heritage and entertainment
 Healthcare
 Transpo
Transpo
T
rt/communications

 Miscellaneous

18

15
9

7

4

4

1

4

3

3

1

14

23

33%

22%

1%

26%

14%

4%
Non-domestic buildings

18%

In 2005, the UK emitted 560 MtCO2*
MtCO2 (2005)

* Source: Digest of UK Energy Statistics: BRE

Figure 1.1 Breakdown of
non-domestic buildings emissions
by sector (reproduced from
Building the future today(2), by
permission of the Carbon Trust)

Introduction
1-3

—
The Energy Performance of Buildings Directive(13)
has introduced higher standards of energy
conservation for new and refurbished buildings
and requires energy performance certifi cation for
all buildings when sold or leased. In addition it will
introduce regular inspections for larger air
condition ing systems and advice on more effi cient
boiler operation for commercial property. These
requirements are addressed as follows:

—
The 2010 changes to Building Regulations
Approved Documents L2A(4) and L2B(5),
include a 25% (aggregate) reduction in CO2
emissions for non-domestic buildings.

—
All properties when bought, sold, built or
rented need to have an energy performance
certifi cate (ePc). Larger public buildings
also need a display energy certifi cate (DEC).

—
Air conditioning inspections have to have
been completed on all existing systems over
12 kW by January 2011. New systems over
12 kW installed after January 2008 must be
inspected within 5 years of being put into
service. The inspections must be carried
out by an accredited energy assessor and
must be a maximum of fi ve years apart, see
section 17.1.

—
The UK government’s Planning Policy Statement
1(14) sets out how spatial planning should contribute
to reducing emissions and stabilising climate
change (mitigation), and take into account the
unavoidable consequences (adaptation). It requires
local authorities to develop a strategy for low/zero
carbon energy generation and to develop site-
specifi c targets. See section 4.3 for more information
on planning policy.

—
The CRC Energy Effi ciency Scheme(6) is a man-
datory scheme aimed at improving energy effi ciency
and cutting emissions in large public and private
sector organisations, see section 1.1.5.

—
Taxation: the Climate Change Levy was intro duced
in 2001 and affects almost all non-domestic
buildings. The levy is an additional cost on top of
the previous price of energy.

—
Financial support: enhanced capital allowances
(ecas) provide a tax incentive to encourage the
purchase of energy effi cient technologies as defi ned
on the energy effi ciency technology list (http://
www.eca.gov.uk). This covers a wide range of
technologies including ‘good quality’ combined
heat and power (chP), boilers, lighting, variable
speed drives, refrigeration, pipework insulation
and a wide range of controls.

Building professionals should also consider the wider
sustainability impacts of their decisions including:

—
reducing water use

—
considering the lifecycle impacts of materials and
equipment

—
adapting buildings for climate change etc.

These issues are covered in more detail in CIBSE Guide L:
Sustainability (15).

1.1.3
Building Regulations Approved
Document L2

The Building Regulations(16) for England and Wales impose
requirements* aimed at improving the energy effi ciency of
domestic and non domestic buildings. Building Regulations
Approved Documents offer various means for meeting
these requirements.

The 2010 revision of Building Regulation Approved
Document L2A(4) aims to improve the energy effi ciency
standards of new buildings by 25% compared to the 2006

Source: BRE, Carbon Trust analysis

End use

0%
20%
40%
60%
80%
100%

 Heating
 Lighting
 Cooling and

ventilation

 Catering
 Hot water
 Office equipment
 Other

Commercial offices

Schools

Further and higher education

Government estate

Healthcare

Sports

Heritage and entertainment

Transpo
Transpo
T
rt/communications

Public offices

Miscellaneous

Hotels, inns and restaurants

Retail

Industrial
Figure 1.2 Breakdown of CO2
emissions by end use in each
sector (2006) (reproduced from
Building the future today(2), by
permission of the Carbon Trust)

* Similar guidance is available for Scotland(17) and Northern Ireland(18)

1-4
Energy efficiency in buildings

edition. This is a step towards zero carbon new non-
domestic buildings.

Approved Document L2B(5) applies to work relating to:

—
the construction of extensions

—
a material change of use or a change in a building’s
energy status

—
the provision or extension of a controlled fitting

—
the replacement or renovation of a thermal element.

More details on the scope of Approved Document L2B is
set out in section 16.3.

The key aspects of the criteria in L2A are:

(1)
An ‘aggregated’ approach, which requires some
buildings to achieve a greater improvement, others
less, with the overall improvement across the new
non-domestic building stock being 25%. This
recognises that some building types can save carbon
more cost effectively than others. The standards
have been set such that all building types achieve
their targeted improvement at similar levels of cost
effectiveness.

(2)
Criterion 1: Achieving the target emissions rate:

—
The target emissions rate is based on a
building of the same size and shape as the
actual building, constructed to a current
specification. There are three sets of spec-
ifications depending on the glazing in the
building or spaces in the building: one for
side-lit buildings (e.g. offices), one for roof-
lit buildings (e.g. some warehouses) and the
third for unlit buildings (e.g. plant rooms).
It is possible to comply with Building
Regulations Part L 2010(16) by exactly
meeting one of these current specifications.
There is still the freedom to vary the
specification, provided that the same overall
level of CO2 emissions is achieved or
bettered.

—
A design stage CO2 emission rate calculation
is required as part of the plans submitted
before construction. The builder has to
carry out a preliminary calculation before
construction starts and this is provided to
building control, along with the specifica-
tions that deliver the claimed performance.

(3)
Criterion 2: Limits on design flexibility:

—
There are limits on design flexibility for
building services to ensure that they have a
minimum level of energy efficiency as set
out in the Non-domestic Building Services
Compliance Guide(19) (referenced throughout
this Guide).

—
Appropriate controls should be provided to
enable reasonable standards of energy
efficiency in use (see chapter 6 for more
guidance).

—
Reasonable provision for energy meters
should be provided to meter the various end
use categories (heating, lighting etc.),
renewable energy systems, and to provide

automatic meter reading and data collection
facilities (see section 4.8.3).

—
The provision of centralised switching of
appliances should be considered, to allow
appliances to be switched off when they are
not needed.

(4)
Criterion 3: Limiting the effects of solar gains in
summer:

—
A limit on the solar gain per unit area of
façade is set. This limit applies to both
naturally ventilated and air conditioned
spaces. This will not prevent the use of
highly glazed facades, but where they are
proposed, it will require that good solar
protection is provided.

(5)
Criterion 4: Quality of construction and commis-
sioning:

—
The insulation should be reasonably
continuous
over
the
whole
building
envelope and the air permeability needs to
be within reasonable limits.

—
Fixed building services have to be commis-
sioned to ensure that they use no more fuel
and power than is reasonable. This includes
preparing a commissioning plan and
carrying out air leakage testing of ductwork
(see chapter 14 for more detail on com-
missioning).

(6)
Criterion 5: Provisions for energy efficient
operation of the building:

—
The owner of the building should be
provided with sufficient information about
the building to allow energy efficient
operation. This includes the provision of a
building log book (see section 14.4.1)

1.1.4
Energy Performance Certificates
and Display Energy Certificates

In England and Wales, there are two types of energy
certificates:

—
Energy Performance Certificates (EPCs): required
for all buildings when constructed, sold or rented

—
Display Energy Certificates (DECs): required for
buildings ‘with a total useful floor area over 1000 m2
occupied by public authorities and by institutions
providing public services to a large number of
persons and therefore frequently visited by those
persons’.

There are similar requirements in Northern Ireland.
Scotland has adopted a different approach, with Energy
Performance Certificates (EPCs) being used for display
purposes instead of DECs.

EPCs present the theoretical, design energy efficiency of
buildings. DECs show actual energy consumption over the
course of a year, benchmarked against other similar
buildings. Where buildings have both an EPC and a DEC,
this provides another means of comparing design and
actual energy use. Figure 1.3 shows an example of an EPC
and a DEC.

Introduction
1-5

The intrinsic building quality (illustrated by the EPC) has
an impact on the operational performance (shown in the
DEC), but does not cover all emissions. Other factors such
as unregulated loads (e.g. IT equipment, plug-in appliances
etc.) or building user behaviour also affect energy use and
emissions, which are reflected in the DEC.

1.1.4.1
Energy Performance Certificates

The EPC is a certificate that incorporates an ‘asset rating’
based on the ‘theoretical’ performance of a building as
calculated using an approved method such as SBEM(20) or
SAP(21). Its function is to enable like-for-like comparisons
between buildings used for similar purposes and influence
potential buyers’ and tenants’ decisions.

The rating is calculated as the ratio of the CO2 emissions
from the actual building (BER) to those from a reference
building using the ‘reference emissions rate’ (NER).

The reference building:

—
is the same size and shape as the actual building

—
has the same activity schedules

—
has a defined servicing strategy including gas
heating and seasonal mixed mode cooling systems

—
uses natural gas as the primary fuel for heating and
hot water, and electricity for lighting, cooling, fans
and pumps

—
has CO2 emissions equivalent to the target emissions
rate (TER) of a building that complies with Part L
(2010) with the provisions as above.

The asset rating is then represented on an arithmetic scale
consisting of seven bands, labelled A to G. The EPC also
displays the asset rating in context with the current
Building Regulations Part L standard based upon the
actual building and in comparison with a typical existing
example building.

1.1.4.2
Display Energy Certificates

The Display Energy Certificate (DEC) is a certificate that
incorporates a numerical indicator of performance, known
as the Operational Rating (OR), which is the ratio of actual
measured energy use of the building over a year to a
benchmark figure for buildings of that type.

DECs must be displayed in a prominent position and be
renewed every 12 months. The certificate must be accom-
panied by an advisory report which is valid for up to seven
years. The certificate must be at least A3-size.

The OR is calculated using approved software and is based
on a complete year of measured energy data. The rating
takes account of mixed uses, local heating degree-days,
extended hours of use, and some special ‘separable’ energy
uses.

Main heating fuel:
Gas
Building environment:
Air Conditioned
Total useful floor area (m2): 2927
Building complexity
(NOS level):
4

Certificate Reference Number:
1234-1234-1234-1234

Energy Performance Certificate
Non-Domestic Building

Less energy efficient

A 0-25
B 26-50
C 51-75
D 76-100
E 101-125
F 126-150
G Over 150

More energy efficient
A+

Net zero CO2 emissions

This is how energy efficient
the building is.
92

Benchmarks
Technical information

If typical of the
existing stock

If newly built

Buildings similar to this one
could have ratings as follows:

Jubilee House
High Street
Anytown
A1 2CD

58

94

This certificate shows the energy rating of this building. It indicates the energy efficiency
of the building fabric and the heating, ventilation, cooling and lighting systems. The rating
is compared to two benchmarks for this type of building: one appropriate for new buildings
and one appropriate for existing buildings. There is more advice on how to interpret this
information on the Government’s website www.communities.gov.uk/epbd.

Energy Performance Asset Rating

(a)

(a)
(a)

(b)

Figure 1.3 Examples of (a) an Energy Performance Certificate and (b) a Display Energy Certificate

1-6
Energy efficiency in buildings

The OR is a linear scale running from 0 (true zero-carbon)
to 100 (CO2 emissions at typical stock median performance
levels) and beyond. This scale is grouped into increments
of 25 to provide the A to G banding, so median performance
lies at the D to E boundary. All buildings with emissions
over 150% of the benchmark value are classed in the G
band. The DEC also shows separate performance indicators
and benchmarks for annual use of electricity and of fuel or
heat.

The DEC benchmarks, published as CIBSE TM46(22), are
based on a rationalisation and considerable simplification
of values taken from many sources and consultation with
industry. Although the system identifies a total of 237
different building types, each is assigned to one of 29
benchmark categories, based on the building use.
Benchmarks are set at the median level for each category
(as far as these were known) for annual use of electricity
and of fuel or heat. Mixed-use benchmarks, e.g. for a school
with a swimming pool, can be built up, using the specific
component benchmarks and their respective areas.

‘Separable’ energy end-uses (specific ‘process’ uses that are
not included in the benchmark because they are either
unusual for the benchmark category or highly variable) can
be excluded from the operational rating calculation,
although they remain in the carbon footprint shown on the
DEC. The energy use can only be separated if it meets the
criteria as set out in CIBSE TM46(22).

1.1.4.3
Energy Performance of Buildings
Directive (recast)

The Energy Performance of Buildings Directive (recast)(13)
has reduced the threshold size for buildings that have to
display energy performance certificates as follows:

—
From 9 July 2012 legislation, regulations and
administration provisions for 500 m2 threshold
must be ‘adopted and published’.

—
From 9 January 2013 provisions for 500 m2
threshold must be applied, i.e. must have come into
force.

—
From 9 July 2015 the threshold is lowered to 250 m2.

1.1.5
CRC Energy Efficiency Scheme

The CRC Energy Efficiency Scheme(6) (formerly known as
the Carbon Reduction Commitment) is a mandatory
scheme aimed at improving energy efficiency and cutting
emissions in large public and private sector organisations.
The scheme will promote energy efficiency by:

—
requiring participants to buy allowances from
Government each year to cover their emissions in
the previous year; this means that organisations
that decrease their emissions can lower their costs
under the CRC scheme

—
publishing an annual performance league table that
ranks participants on energy efficiency performance

—
increasing awareness of energy use from a require-
ment to report energy use and the requirement for
senior management being responsible for the
reporting.

The ranking on the league table includes ‘early action
metrics’ for the first two years of the scheme. These metrics
reward participants on the percentage of their electricity
and gas supplies that is covered by voluntary automatic
meter readings (amrs) (see section 4.8.3) and the proportion
of the organisation’s CRC emissions certified under the
Carbon Trust Standard(23) or an equivalent scheme.

Organisations are eligible for CRC if they (and their
subsidiaries) have at least one half-hourly electricity meter
(hhm) settled on the half-hourly market. Organisations
that consumed more than 6000 megawatt-hours (MW·h)
per year of half-hourly metered electricity during 2008
qualify for full participation and registration with the
Environment Agency, which is the administrator for the
scheme.

For more information refer to the Department of Energy
and Climate Change website (http://www.decc.gov.uk).

1.1.6
The role of building
professionals

Building services engineers work within an industry that
has significant environmental impacts. Building services
engineers are directly responsible for ensuring that
buildings:

—
provide acceptable thermal comfort for occupants

—
use minimum amounts of fuel and energy

—
are adequately and attractively lit

—
provide good indoor air quality

—
are adaptable to climate change

—
are properly operated and maintained.

All of these responsibilities have a direct impact on the
energy performance of buildings. CIBSE has taken a
leading role over the pursuit of energy efficiency in order to
reduce the risk of dangerous climate change.

For these reasons, all building professionals should always
encourage clients, owners and operators to include energy
efficiency in the brief at all stages in a building’s life
whether designing, operating or upgrading. Clients and
financiers should be made aware of the investment case for
energy efficiency. Building professionals should help
clients to develop a brief which sets out both user and client
requirements and constraints, balancing these against
capital costs, running costs, whole life costs and
environmental objectives.

Building professionals will benefit by:

—
helping clients to meet current and forthcoming
legislative/policy targets

—
providing an added-value service to their clients by
improving their buildings

—
reducing plant capital cost, particularly where
mechanical cooling has been avoided or minimised

—
enhancing the standing of all building pro fessionals
by improving occupants’ use and perception of
buildings

Introduction
1-7

—
increasing building marketability by promoting
buildings as assets in which to invest

—
obtaining repeat work through satisfied customers.

The overall goal is ‘better buildings’ and this can often be
achieved by focussing on energy efficiency. Research(24,25)
has indicated that buildings that are designed and managed
in an energy efficient way can be more comfortable and
their staff more productive, making investment in good
energy efficient design and management even more cost
effective to a client organisation.

1.2
How to use this Guide

1.2.1
Structure

This Guide starts by setting out an overall framework for
energy efficiency within which the building professional
has the freedom to design, operate or upgrade a building.
The ‘principles of energy efficiency’ stated at the front of
this Guide are broadly based on the CIBSE policy statement
on energy (http://www.cibse.org/policystatements), and
aim to help professionals put the policy into practice.

The main body of this Guide is divided into three parts as
shown in Figure 1.4.

—
Part A: Designing the building: consists of chapters 2
to 14 and deals with new buildings and major
refurbishment.

—
Part B: Operating and upgrading the building: consists
of chapters 15 to 19 and covers the manage ment

and maintenance of buildings, high lighting
measures that can be retrofitted in existing
buildings. The reader is referred back to Part A
where there is a large element of design.

—
Part C: Benchmarks: consists of chapter 20 and
provides ‘typical’ and ‘good practice’ energy
benchmarks for a wide range of buildings,
components and end-uses.

A thumbnail icon at the top of the first page of each chapter
indicates the relationship of that chapter to the rest of the
Guide.

The first chapter in each part provides a strategic overview
of the process being covered. The last two chapters in each
part help check that the main options have been considered
and that the final outcome meets expectations. The chapters
of this Guide particularly relevant to readers from various
professions are shown in Table 1.1. Appendix A1 gives
some standard conversion factors and properties of fuels.
Appendix A2 considers the role of energy consultants and
provides model briefs for commissioning energy audits and
surveys.

Managing the building

Aquisition and refurbishment

Maintenance and energy efficiency

Energy audits and surveys

Benchmarking, monitoring and
targeting

Designing the building

Principles of energy
efficiency

15

16

17

18

19

Introduction

2

3

4

5

6

7

8

9

10

11

12

13

14

Operating and upgrading
the building
Part A
Part B

The design process

Developing a design strategy

Developing an energy strategy

Concept design

Control strategies

Ventilation and air conditioning design

Refrigeration design

Lighting design

Heating and hot water design
Motors and building transportation
systems

Electrical power systems and office
equipment

Checking the design

Commissioning, handover
and feedback

1

20 Energy benchmarks

Benchmarks
Part C

Figure 1.4 Structure of the Guide

Table 1.1 Sections relevant to readers from various professions

Reader
Part
Section

Building services designers
Designing the building
1–14

Building owners/operators
Operating and upgrading
15–20

the building

Energy managers/consultants
Operating and upgrading
15, 18–20

the building

Architects/surveyors
Designing the building
1–14

Developers/financiers
Designing the building
1–6, 15

1-8
Energy efficiency in buildings

1.2.2
Investing in energy efficiency

Many organisations are now investing in energy efficiency
to improve their overall environmental perfor mance. This
usually results in an overall corporate social responsibility
(csr) policy, either laid down by senior management or as a
result of government initiatives in the public sector. It is
recognised by these organisations that measuring and
reporting environmental performance against targets can
significantly enhance the corporate image, which may
influence future investors.

Although the policy framework is becoming stronger, in
practice cost savings often drive energy efficiency. This
Guide therefore concentrates on cost effective measures.
Savings in operating costs will flow directly into the
building user’s profits. Well-managed organisations tend to
re-invest some of the savings in further energy efficiency
measures. Additional investment may also be justified for
environmental reasons, e.g. emissions trading.

Energy efficiency measures should generally be considered
in their order of economic payback, complexity and ease of
application. Measures fall into three broad types:

—
no-cost/low-cost: requiring no investment appraisal

—
medium cost: requiring only a simple payback
calculation

—
high capital cost: measures requiring detailed design
and a full investment appraisal.

Investment in energy efficiency should be treated on the
same basis as any other financial decision, and should have
no more onerous conditions placed upon it than any other
investment. A variety of financial appraisal methods can be
used to assess the viability of energy saving measures (see
section 18.8). Assessments should always take into account
the wider benefits such as improvements in comfort and
the environment. This can be achieved using a life-cycle
approach.

Energy efficient buildings need cost no more to build than
conventional buildings. The integration of the fabric and
services design can present opportunities to reduce capital
cost. For example, the cost of external shading can be offset
by minimising or avoiding air conditioning plant.

References

1
Climate Change Act 2008 Elizabeth II Chapter 27 (London: The
Stationery Office) (2008) (available at http://www.legislation.gov.
uk/ukpga/2008/27) (accessed June 2011)

2
Building the future today — Transforming the economic and carbon
performance of the buildings we work in CTC765 (London: The
Carbon Trust) (2009) (available at http://www.carbontrust.co.uk/
Publications) (accessed June 2011)

3
Department of Energy and Climate Change (DECC) Digest of
United Kingdom Energy Statistics 2010 (London: The Stationery
Office) (2010) (available at http://www.decc.gov.uk/en/content/
cms/statistics/publications/dukes/dukes.aspx) (accessed June
2011)

4
Conservation of fuel and power in new buildings other than dwellings
The Building Regulations 2000 Approved Document L2A
(London: NBS/RIBA Publications) (2010) (available at http://
www.planningportal.gov.uk/buildingregulations/approveddocu-
ments/partl) (accessed June 2011)

5
Conservation of fuel and power in existing buildings other than
dwellings The Building Regulations 2000 Approved Document
L2B (London: NBS/RIBA Publications) (2010) (available at
http://www.planningportal.gov.uk/buildingregulations/approved
documents/partl) (accessed June 2011)

6
CRC Energy Efficiency Scheme (website) (London: Department
of Energy and Climate Change) (2011) (http://www.decc.gov.
uk/en/content/cms/emissions/crc_efficiency/crc_efficiency.
aspx) (accessed June 2011)

7
Building a low-carbon economy — the UK’s contribution to tackling
climate change (London: The Stationery Office) (2008) (available at
http://www.theccc.org.uk/reports/building-a-low-carbon-economy)
(accessed June 2011)

8
Pachauri RK and Reisinger A (Eds.) Contribution of Working
Groups I, II and III to the Fourth Assessment Report of the
Intergovernmental Panel on Climate Change (Geneva, Switzerland)
(2007) (available at http://www.ipcc.ch/publications_and_data/
publications_ipcc_fourth_assessment_report_synthesis_report.
htm) (accessed June 2011)

9
The UK renewable energy strategy Cm. 7686 (London: (The
Stationery Office) (2009)

10
The UK low carbon transition plan: national strategy for climate and
energy (London: The Stationery Office) (2009) (available at
http://www.decc.gov.uk/publications) (accessed June 2011)

11
Carbon Plan (website) (London: Department of Energy and
Climate Change) (2011) (http://www.decc.gov.uk/en/content/cms/
tackling/carbon_plan/carbon_plan.aspx) (accessed June 2011)

12
Zero carbon for new non-domestic buildings: Consultation on policy
options (London: Department for Communities and Local
Government) (2009) (available at http://www.communities.gov.
uk/publications/planningandbuilding/newnondomesticcon-
sult) (accessed June 2011)

13
Directive 2010/31/EU of the European Parliament and of the
Council of 19 May 2010 on the energy performance of buildings
(recast) Official J. of the European Union L153 13–35 (18.6.2010)
(available at http://eur-lex.europa.eu/JOHtml.do?uri=OJ:L:201
0:153:SOM:EN:HTML) (accessed June 2011)

14
Planning Policy Statement 1: Delivering Sustainable Development
(London: The Stationery Office) (2005) (available at http://
www.communities.gov.uk/publications/planningandbuilding/
planningpolicystatement1) (accessed June 2011)

15
Sustainability CIBSE Guide L (London: Chartered Institution of
Building Services Engineers) (2007)

16
The Building Regulations 2010 Statutory Instruments 2010 No
2214 (London: The Stationery Office) (2010) (available at http://
www.legislation.gov.uk/uksi/2010/2214)
(accessed
December
2011)