Build Regs L2

8/2/2019 Build Regs L2

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The Building Regulations 2000

Conservation of fuel and power

APPROVED DOCUMENTL2

L2 Conservation of fuel and power in buildingsother than dwellings

Coming into effect 1 April 2002

The Stationery Office

2002 EDITION


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Correction

Approved Document L1

ISBN 0 11 753609 1

In paragraphs 0.17, 0.18 and 1.28 substitute new paragraphs for existing text.


ISBN 0 11 753610 5

In paragraph 0.26 substitute new paragraph (b) for existing text.


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BUILDING ACT 1984

NOTICE OF APPROVAL OF REVISIONS TO DOCUMENTS GIVING PRACTICAL

GUIDANCE WITH RESPECT TO THE REQUIREMENTS OF THE BUILDING

REGULATIONS 2000 (AS AMENDED)

The Secretary of State for Transport, Local Government and the Regions hereby gives

notice under section 6(3) of the Building Act 1984 that he has approved under section

6(4) the following amendments to two documents approved by him under section 6 for thepurposes of giving practical guidance with respect to the requirements of the Building

Regulations 2000 (as amended):

a) in Approved Document L1: Conservation of fuel and power in dwellinas. 2002Edition:

i) for paragraphs 0.17 and 0.18, substitute:

0.17 SAP means the Governments Standard Assessment Procedure for Energy Rating

of Dwellings. [18] The SAP is explained and defined, along with appropriate reference

data and a calculation worksheet, in The Governments Standard Assessment Procedurefor Energy Rating of Dwellings: 2001 Edition[19].

0.18 The SAP provides the methodology for the calculation of the Carbon Index whichcan be used to demonstrate that dwellings comply with Part L (see paragraph 1.27).;

ii) for paragraph 1.28, substitute:

1.28 The edition of the SAP used for the calculation of the Carbon Index should be the2001 Edition (see paragraphs 0.17 and 0.18).;

iii) in paragraph 2.3(a) (Windows, doors and rooflights), at the end, add a newsentence

(Where a contract for the provision of replacement windows, rooflights, roof windows

or glazed doors has been made before 1 April 2002, the work does not start until on orafter that date, and it is completed before 1 July 2002, reasonable provision would be

for the work to be done using fittings of the kind that would have been used if the work

had begun before 1 April 2002).;

iv) Appendix G (Carbon Index) is deleted;

b) in Approved Document L2 : Conservation of fuel and power in buildings other thandwellinas. 2002 Edition:

i) in paragraph 0.26, for subparagraph (b), substitute


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(b) A building constructed using external fabric sub-assemblies manufactured

before 1 April 2002, that have been obtained from a centrally held stock or from the

disassembly of buildings on other premises, would normally be considered to meet

the requirement if the fabric thermal resistance, or the prospective annual energy

use, will be no worse than the relevant performance standards given in the 1995

edition of Approved Document L.;

ii) in paragraph 4.3(a) (Windows, doors and rooflights), at the end, add a new sentence

(Where a contract for the provision of replacement windows, rooflights, roof

windows or doors has been made before 1 April 2002, the work does not start until

on or after that date, and it is completed before 1 July 2002, reasonable provisionwould be for the work to be done using fittings of the kind that would have been

used if the work had begun before 1 April 2002).

These amendments are approved with effect from the date of this notice.

Signed by the authority of the Secretary of State for Transport,Local Government and the Regions

Paul F Everall

An Assistant Secretary in the Department for Transport,Local Government and the Regions

12 February 2002


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MAIN CHANGES IN THE 2002 EDITION

1 This Approved Document L2 replaces the content of the 1995

edition of Approved Document L that relates to buildings other

than dwellings. The main changes made by the Building

(Amendment) Regulations 2001 and in the guidance in this

document are as follows.

Changes in the requirements

2 Part L of Schedule 1, which sets out the legal requirements forthe conservation of fuel and power in buildings, has been

subdivided into Part L1, covering dwellings, and Part L2,

covering other types of buildings. This Approved Document

only gives guidance on complying with Part L2.

3 The requirements now address the summer performance of

buildings through provisions for limiting exposure to solar

overheating and heat gains through the fabric.

4 The requirement applying to heating and hot water systems has

been changed to encompass overall system performance rather

than just controls. This means that boiler seasonal efficiency

and inspection and commissioning are now covered.

5 New requirements have been introduced to address the

performance of air conditioning and mechanical ventilation

systems that serve floor areas of more than 200 M2,and the

insulation of cold air distribution ducting and chilled water and

refrigerant services.

6 The requirement applying to lighting systems has been changed

to encompass luminaires in some types of buildings as well as

lamp performance, but the limit on application to floor areas in

excess of 100 M2remains unchanged.

7 A new requirement calls for information to be provided to enable

building occupiers to operate and maintain the building and its

services effectively.

8 In Regulation 2 the definition of controlled service has been

expanded to include services and fittings in relation to which

Part L2 imposes a requirement. This means that replacement

work in existing buildings on windows and other glazed

elements, and the heating, hot water, air conditioning,

mechanical ventilation and lighting services are now controlled.

9 Regulation 18 is amended to enable local authorities to test the

compliance of buildings and controlled services and fittings for

compliance with the technical requirements in Part L2.

Changes in the technical guidance

10 A summary guide to the use of this Approved Document L2

(ADL2) is given at page 5. In mixed-use development, where

dwellings are proposed as well as other buildings, it will be

necessary to consult Approved Document L1.

11 The provisions for allowing lesser performance when buildings

have low levels of heating and use are retained but they are

now included in a sub-section of special cases which also

addresses historic buildings and buildings constructed from

sub-assemblies to meet temporary accommodation needs.

12 The Elemental Method now includes building airtightness,

avoiding solar overheating, heating system efficiency, lighting

and air conditioning and mechanical ventilation (ACMV) as well

as fabric insulation and includes limited provisions for trading off

between the performance standards:

The standards of fabric insulation have improved bychanging the methods of calculating U-values to those in

the European Standards and by setting lower (i.e. better)

values. Metal windows are given some credit for their

thinner framing members and hence the increased useful

winter solar gain.

The guidance on reducing thermal bridging has been

improved and new guidance is given on reducing

unwanted air leakage. A way of achieving compliance with

these requirements is to adopt robust construction detail

designs.

New guidance is given for limiting exposure to solar gain

including calculations and performance criteria supported

by a new Appendix H. New guidance is also given on

conservatories, atria and similar sunspaces. For lighting systems there are new performance standards

for luminaires in offices and storage buildings (supported

by a new Appendix F) and for display lighting in all

buildings.

For ACMV systems a new Carbon Performance Rating

Method of showing compliance (supported by a new

appendix G) is given.

13 The Calculation Method and Energy Use Method have been

replaced by the Whole-building Method and the Carbon

Emissions Calculation Method that assess potential annual

carbon emissions (one more rigorously than the other).

14 New guidance is given on: testing thermal insulation continuity and airtightness of

buildings,

commissioning of heating, hot water, lighting and ACMV

systems, and

producing information and the provision of energy meters

that enable building occupiers to operate and maintain the

building effectively.

15 The guidance on material alterations and changes of use has

been placed in a new section along with guidance on work on

controlled services in existing buildings and the guidance

relevant to conservation and restoration work in historic

buildings.

16 Section 2 suggests the provision of certificates or declarations

of compliance from suitably qualified persons, in relation to

building fabric and building services systems.

Conservation of fuel and power ApprovedDocument L2


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PAGE

CONTENTS 1

Use of guidance 3

Summary guide to the use of thisApproved Document 5

The Requirements 8

Section 0 : General 10

Performance 10

Introduction to the provisions 10

Technical risk 10

Thermal conductivity and transmittance 11

U-value reference tables 11

Calculation of U-values 11

Roof window 12

Basis for calculating areas 12

Air permeability 12

Conversion between carbon and carbondioxide indices 12

Special cases 12

Low levels of heating 12

Low levels of use 12

Historic buildings 13

Buildings constructed from

sub-assemblies 13Mixed use development 13

Section 1 : Design 14

General 14

Alternat ive methods of showingcompliance 14

Elemental Method 14

Standard U-values for constructionelements 14

Thermal bridging at junctionsand around openings 15

Maximum areas of windows, doors androoflights 16

Trade-off between construction elements 16

Building air leakage standards 17

Avoiding solar overheat ing 17

Heating systems 17

Carbon intensities of centralisedheating plant 17

General 17

Calculating the carbon intensity

of CHP systems 18Calculating the carbon intensityof commumity heating 19

Other methods of heating 19

PAGE

Trade-off between construction elementsand heating system efficiency 19

Space heating controls 19

Hot water systems and their control 19

Insulation of pipes, ducts and vessels 20

Lighting efficiency standards 20

General lighting efficacy in office,industrial and storage buildings 20

General lighting efficacy in all otherbuildings 21

Display lighting in all buildings 21

Emergency escape and specialistprocess lighting 22

Lighting controls 22

Controls in offices and storagebuildings 22

Controls in buildings other thanoffices and storage buildings 22

Controls for display lighting(all building types) 22

Air condit ioning and mechanicalventilation (ACMV) 22

CPR method for office buildingswith ACMV 23

Methods for other buildingswith ACMV 24

Whole Building Method 24

Office buildings 24

Schools 24

Hospitals 24

Carbon Emissions Calculation Method 25

Conservatories, atria and similarsun-spaces 25

Section 2 : Construction 26

Building fabric 26

Continuity of insulation 26

Air tightness 26

Certificates and Testing 26

Inspection and commissioning of thebuilding services systems 26

Section 3 : Providing information 28

Building Log Book 28

Installation of energy meters 28

Section 4 : Work on existing buildings 30

Replacement of a controlled serviceor fitting 30

Material alterations 30

Material changes of use 31

Historic buildings 31

Contents

Conservation of fuel and powerApproved Document L2

1

L2


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PAGE

APPENDICES

Appendix A: Tables of U-values 33

Appendix B: Calculating U-values 47

Appendix C: U-values of ground floors 53

Appendix D: Determining U-valuesfor glazing 56

Appendix E: Calculation examples 57

Appendix F: Meeting the lighting standards 60

Appendix G: Methods for office buildings 64

Appendix H: Methods for solar overheating 70

Standards referred to 73

Other publications referred to 74


2

L2

Conservation of fuel and power


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THE APPROVED DOCUMENTS

This document is one of a series that hasbeen approved and issued by the Secretary ofState for the purpose of providing practical

guidance with respect to the requirements ofSchedule 1 to and regulation 7 of the BuildingRegulations 2000 (SI 2000/2531) for Englandand Wales. SI 2000/2531 has been amendedby the Building (Amendment) Regulations2001 (SI 2001/3335)

At the back of this document is a list of allthe documents that have been approved andissued by the Secretary of State for thispurpose.

Approved Documents are intended to provideguidance for some of the more commonbuilding situations. However, there may wellbe alternative ways of achieving compliancewith the requirements. Thus there is noobligation to adopt any particular solutioncontained in an Approved Document if youprefer to meet the relevant requirement insome other way.

Other requirements

The guidance contained in an ApprovedDocument relates only to the particularrequirements of the Regulations which thedocument addresses. The building work will

also have to comply with the requirements ofany other relevant paragraphs in Schedule 1 tothe Regulations.

There are Approved Documents which giveguidance on each of the Parts of Schedule 1and on regulation 7.

LIMITATION ON REQUIREMENTS

In accordance with regulation 8, therequirements in Parts A to K and N (except forparagraphs H2 and J6) of Schedule 1 to theBuilding Regulations do not require anything to

be done except for the purpose of securingreasonable standards of health and safety forpersons in or about buildings (and any otherswho may be affected by buildings or mattersconnected with buildings).

Paragraphs H2 and J6 are excluded fromRegulation 8 because they deal directly withprevention of the contamination of water. PartsL and M are excluded because theyrespectively address the conservation of fueland power and access facilities for disabledpeople. These matters are amongst thepurposes, other than health and safety, that

may be addressed by Building Regulations.

MATERIALS AND WORKMANSHIP

Any build ing work which is subject to therequirements imposed by Schedule 1 to theBuilding Regulations should, in accordancewith regulation 7, be carried out with proper

materials and in a workmanlike manner.

You may show that you have complied withregulation 7 in a number of ways. Theseinclude the appropriate use of a productbearing CE marking in accordance with theConstruction Products Directive (89/106/EEC)1

as amended by the CE Marking Directive(93/68/EEC)2 , or a product complying with anappropriate technical specification (as definedin those Directives), a British Standard, or analternative national technical specification ofany state which is a contracting party to theEuropean Economic Area which, in use, is

equivalent, or a product covered by a nationalor European certificate issued by a EuropeanTechnical Approval issuing body, and theconditions of use are in accordance with theterms of the certificate. You will find furtherguidance in the Approved Documentsupporting regulation 7 on materials andworkmanship.

Independent certification schemes

There are many UK product certificationschemes. Such schemes certify compliancewith the requirements of a recognised

document which is appropriate to the purposefor which the material is to be used. Materialswhich are not so certified may still conform toa relevant standard.

Many certification bodies which approve suchschemes are accredited by UKAS.

Technical specifications

Under section 1(a) of the Building Act, BuildingRegulations may be made for various purposesincluding health, safety, welfare, convenience,conservation of fuel and power and prevention

of contamination of water. Standards andtechnical approvals are relevant guidance tothe extent that they relate to theseconsiderations. However, they may alsoaddress other aspects of performance such asserviceability, or aspects, which although theyrelate to the purposes listed above, are notcovered by the current Regulations.

Use of guidance


3

L2THE BUILDING REGULATIONS 2000

1As implemented by the Construction ProductsRegulations 1991 (SI 1991/1620).

2As implemented by the Construction Products

(Amendment) Regulations 1994 (SI 1994/3051).


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When an Approved Document makes referenceto a named standard, the relevant version ofthe standard is the one listed at the end of thepublication. However, if this version has beenrevised or updated by the issuing standardsbody, the new version may be used as a sourceof guidance provided it continues to addressthe relevant requirements of the Regulations.

The appropriate use of a product whichcomplies with a European Technical Approvalas defined in the Construction ProductsDirective will meet the relevant requirements.

The Department intends to issue periodicamendments to its Approved Documents toreflect emerging harmonised EuropeanStandards. Where a national standard is to bereplaced by a European harmonised standard,there will be a co-existence period duringwhich either standard may be referred to. Atthe end of the co-existence period the nationalstandard will be withdrawn.

THE WORKPLACE (HEALTH,SAFETY AND WELFARE)REGULATIONS 1992

The Workplace (Health, Safety and Welfare)Regulations 1992 contain some requirementswhich affect building design. The mainrequirements are now covered by the BuildingRegulations, but for further information see:Workplace health, safety and welfare.Workplace (Health, Safety and Welfare)Regulations 1992. Approved Code of PracticeL24. Published by HSE Books 1992(ISBN 0 7176 0413 6).

The Workplace (Health, Safety and Welfare)Regulations 1992 apply to the common parts offlats and similar buildings if people such ascleaners and caretakers are employed to workin these common parts. Where therequirements of the Building Regulations thatare covered by this Part do not apply todwellings, the provisions may still be requiredin the situations described above in order tosatisfy the Workplace Regulations.

MIXED USE DEVELOPMENT

In mixed use developments part of a buildingmay be used as a dwelling while another parthas a non-domestic use. In such cases, if therequirements of this Part of the Regulations fordwellings and non-domestic use differ, therequirements for non-domestic use shouldapply in any shared parts of the building.

Approved Document L2Conservation of fuel and power

4

L2 THE BUILDING REGULATIONS 2000


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5

L2SUMMARY GUIDE

Summary guide to the use of this ApprovedDocument

Routes to compliance for non-domestic buildings

STEP TEST ACTION

DESIGN

Choose method of compliance

Elemental Go to 1

Whole building method Go to 25

Carbon emissions calculation method Go to 30

Compliance by Elemental method

1 Are all U-values the corresponding No Revise U-values and repeat 1 or Go to 3values from Table 1? Yes Continue

2 Are the areas of openings the Yes Go to 4corresponding values in Table 2? No Reduce opening areas and repeat 2 or continue

3 Is the average U-value to that of a No FAIL - revise design and go to 1 or go tonotional building of the same size and START and test compliance by another route

shape as described in paragraphs 1.15-1.16

and taking into account the heating system

efficiency as described in para 1.32?

4 Do all occupied spaces satisfy the solar No Adjust window areas or shading provisions

overheating criteria in para 1.20 et seq ? Yes Continue

5 Does any centralised heating plant as described Yes Go to 7

in paragraph 1.25 meet the carbon intensity

criteria of Table 5?

No Select different heating plant and repeat 5 or

continue

6 Is the average U-value Uref No FAIL revise design and go to 1 or go tofrom paragraph 1.32? START and test compliance by another route

Yes Continue

7 Do the heating system controls comply No FAIL revise controls and repeat 7 or go to

with paragraphs 1.33 and 1.34? START and test compliance by another route

Yes Continue

8 Does the HWS system and the associated No FAIL revise HWS system and controls and

controls comply with paragraphs 1.35 to repeat 8 or go to START and test compliance

1.37? by another route

Yes Continue

9 Does the insulation to pipes, ducts and No FAIL revise insulation specification and

vessels comply with paragraphs 1.38 to repeat 9 or go to START and test compliance

1.40? by another route

Yes Continue

10 Is there general or display lighting serving No Go to 19

more than 100m2? Yes Continue

11 Is the building an office, industrial or No Go to 14

storage building? Yes Continue

12 Is the average luminaire-lumens/circuit No Revise lighting design and repeat 12 or go to

watt 40? START and test compliance by another routeYes Continue

13 Do the lighting controls comply with Yes Go to 16

paragraphs 1.56 and 1.57?

No Revise the controls and repeat 13 or go to

START and test compliance by another route

14 Is the average lamp plus ballast efficacy No Revise lighting design and repeat 14 or go to50 lamp-lumens per circuit watt? START and test compliance by another route

Yes Continue

15 Do the lighting controls meet the guidance No Revise the controls and repeat 15 or go to

in paragraph 1.58 START and test compliance by another route

Yes Continue

refact


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6

L2 SUMMARY GUIDE

Routes to compliance for non-domestic buildings Cont.

STEP TEST ACTION

16 Is there any display lighting? No Go to 19

Yes Continue

17 Does any display lighting have an average No Revise display lighting and repeat 17 or go to

lamp plus ballast efficacy 15 lamp-lumens START and test compliance by another route

per circuit watt? Yes Continue

18 Do the display lighting controls meet the No Revise display lighting controls and repeat 18

standards of paragraph 1.59? or go to START and test compliance by another

route

Yes Continue

19 Does the building have any air No Go to 23

conditioning or mechanical ventilation

systems that serve more than 200 m2 floor

area? Yes Continue

20 Is it an office building? No Go to 22

Yes Continue

21 Is the Carbon Performance Rating No Revise the ACMV design and repeat 21 or go tothe values in Table 11 START and test compliance by another route

Yes Go to 23

22 Is the specific fan power the values No Revise design of mechanical ventilation systemgiven in paragraph 1.67? and repeat 22 or go to START and test

compliance by another route

Yes Continue

23 Are there any sun-spaces? No PASS Elemental Method and go to 34

Yes Continue

24 Do the sun-spaces meet the criteria of No Revise sun-space design and repeat 24 or go to

paragraphs 1.77 to 1.79? START and test compliance by another route

Yes PASS Elemental Method go to 34

Compliance by Whole Building method

25 Select building type Office: Go to 26

School: Go to 28

Hospital: Go to 29

Other: Method not suited - go to START and test

compliance by another route

26 Is the whole office CPR the relevant value No FAIL Revise design and repeat or go toin Table 12 START and test compliance by another route

Yes Continue

27 Are the proposed building fabric performances No Revise details and repeat 28 or go to

no worse than those given in table 3 and START and test compliance by another route

paragraphs 1.9-1.11 and 1.17-1.19 respectively Yes PASS Whole Building Method - Go to 34

28 Does the school meet the requirements of No FAIL - Revise design and repeat 28 or go to

DfEE Building bulletin 87? START and test compliance by another route

Yes PASS Whole Building Method - Go to 34

29 Does the hospital meet the requirements of No FAIL - Revise design and repeat 29 or go to

NHS Estates guidance? START and test compliance by another route

Yes PASS Whole Building Method Go to 34

Compliance by Carbon Emission Calculation Method

30 Does the notional building meet the No Revise notional design and repeat 30 or go to

standards in paragraph 1.75? START and test compliance by another route

Yes Continue

31 Does the envelope of the proposed No Revise proposed building envelope and repeat 31 or

building meet the standards of paragraph go to START and test compliance by another route

1.75(b) Yes Continue

32 Has the calculation method been agreed as No FAIL - go to START and test compliance by

appropriate to the application (paragraph 1.76)? another route

Yes Continue

33 Is the carbon emitted by the proposed No FAIL revise design and repeat 33 or go tobuilding that emitted by the notional START and test compliance by another routebuilding? Yes PASS Carbon Emissions Calculation Method

- go to 34


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7

L2SUMMARY GUIDE

Routes to compliance for non-domestic buildings Cont.

STEP TEST ACTION

CONSTRUCTION

34 Is the building control body reasonably No FAIL carry out remedial work and repeat 34

convinced that the fabric insulation in the

actual building is continuous ? (paragraph 2.1) Yes Continue

35 Is the building control body reasonably No Identify leaks, seal and re-test to meet standards

convinced that the building is satisfactorily of paragraph 2.4.

airtight ? (paragraph 2.2) Yes Continue

36 Has inspection and commissioning been No Complete commissioning and repeat 36

completed satisfactorily? (paragraphs 2.5

and 2.6) Yes PASS Construction is satisfactory

continue

PROVIDING INFORMATION

37 Has the log-book been prepared No Prepare log-book and repeat 37

(paragraphs 3.1 and 3.2)? Yes Continue

38 Has a metering strategy been prepared and No Produce strategy / install meters and sub-meters

sufficient meters and sub-meters installed? and repeat 38

(paragraphs 3.3 et seq) Yes BUILDING COMPLIES


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CONSERVATION OF FUELAND POWERTHE REQUIREMENT L2

This Approved Document, which takes effect

on 1 April 2002, deals with the followingRequirements which are contained in theBuilding Regulations 2000 (as amendedby SI 2001/3335).

OTHER CHANGES TO THEBUILDING REGULATIONS 2000

Attent ion is particularly drawn to the fol lowingchanges to the provisions of the BuildingRegulations 2000 made by the Building(Amendment) Regulations 2001.

Amendment to Regulation 2

Interpretation

The definition of controlled service or fitting inRegulation 2(1) is amended to:-

controlled service or fitting means a service orfitting in relation to which Part G, H, J or L ofSchedule 1 imposes a requirement;

The Requirements


8

L2 CONSERVATION OF FUEL AND POWER

Requirement Limits on application

Buildings or parts of buildings other than dwellings

L2. Reasonable provision shall be made for the

conservation of fuel and power in buildings or parts

of buildings other than dwellings by

(a) limiting the heat losses and gains

through the fabric of the building;

(b) limiting the heat loss:

(i) from hot water pipes and hot

air ducts used for space heating;

(ii) from hot water vessels and

hot water service pipes;

(c) providing space heating and hot

water systems which are energy-efficient;

(d) limiting exposure to solar overheating;

(e) making provision where air conditioning and mechanical Requirements L2(e) and (f) apply only within buildings and parts

ventilation systems are installed, so that no more energy of buildings where more than 200m2 of floor area is to be servedneeds to be used than is reasonable in the circumstances; by air conditioning or mechanical ventilation systems.

(f) limiting the heat gains by chilled water and refrigerant

vessels and pipes and air ducts that serve air

conditioning systems;

(g) providing lighting systems which are energy-efficient; Requirement L2(g) applies only within buildings and parts of

buildings where more than 100 m2 of floor area is to be served by

artificial lighting.

(h) providing sufficient information with the relevant services so

that the building can be operated and maintained in such a

manner as to use no more energy than is reasonable in

the circumstances.


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Amendments to Regulation 3

Meaning of building work

Regulation 3(1) is amended as follows:

3(1)

(b) subject to paragraph (1A), theprovision or extension of a controlled

service or fitting in or in connectionwith a building;

New Regulation 18

Testing of building work

A new Regulation 18 is subtituted which says:-

Testing of building work

The local authority may make such tests of anybuilding as may be necessary to establishwhether it complies with regulation 7 or any ofthe applicable requirements contained in

Schedule 1.


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L2CONSERVATION OF FUEL AND POWER


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Performance

0.1 In the Secretary of State's viewrequirement L2 (a) will be met by the provisionof energy efficiency measures which:

a) l imit the heat loss through the roof, wall,floor, windows and doors etc by suitable meansof insulation, and where appropriate permit thebenefits of solar heat gains and more efficientheating systems to be taken into account; and

b) l imit the heat gains in summer; and

c) l imit heat losses (and gains whererelevant) through unnecessary air infiltration byproviding building fabric which is reasonablyairtight.

0.2 In the Secretary of State's viewrequirement L2 (b) will be met by limiting the

heat loss from hot water pipes and hot airducts used for space heating and from hotwater vessels and hot water service pipes byapplying suitable thicknesses of insulationwhere such heat does not make an efficientcontribution to the space heating.

0.3 In the Secretary of State's viewrequirement L2 (c) will be met by the provisionof space heating and hot water systems withreasonably efficient equipment such as heatingappliances and hot water vessels whererelevant, and timing and temperature controls,and suitable energy consumption metering, that

have been appropriately commissioned suchthat the heating and hot water systems can beoperated effectively as regards theconservation of fuel and power.

0.4 In the Secretary of States viewrequirement L2 (d) will be met by theappropriate combination of passive measures,such as limiting the area of glazing which is notshaded and providing external building fabricthat limits and delays heat penetration, withactive measures, such as night ventilation, sothat the effects of solar heat gains are keptwithin limits that are reasonable in the

circumstances.0.5 In the Secretary of States view, whenbuildings are proposed to be mechanicallyventilated or air conditioned, requirement L2 (e)will be met by:-

a) l imiting the demands from within thebuilding for heating and cooling and circulationof air, water and refrigerants; and

b) providing reasonably efficient plant anddistribution systems, and timing, temperatureand flow controls, and suitable energyconsumption metering, that have been

appropriately commissioned.0.6 In the Secretary of State's viewrequirement L2 (f) will be met by limiting theheat gains to chilled water and refrigerant

vessels and pipes and air ducts by applyingsuitable thicknesses of insulation includingvapour barriers.

0.7 In the Secretary of State's viewrequirement L2 (g) will be met by the provision

of lighting systems that where appropriate:a) uti lise energy-eff icient lamps andluminaires, and

b) have suitable manual switching orautomatic switching, or both manual andautomatic switching controls, and

c) have suitable energy consumptionmetering, and

d) have been appropriately commissioned.

0.8 In the Secretary of States viewrequirement L2 (h) will be met by providing

information, in a suitably concise andunderstandable form, and including the resultsof performance tests carried out during theworks, that shows how the building and itsrelevant building services can be operated andmaintained so that they use no more energythan is reasonable in the circumstances.

Introduction to the Provisions

Technical Risk

0.9 Guidance on avoiding technical risks (suchas rain penetration, condensation etc) which

might arise from the application of energyconservation measures is given in BRE ReportNo 262: Thermal Insulation: avoiding risks,2002 Edition. As well as giving guidance onventilation for health, Approved Document Fcontains guidance on the provision ofventilation to reduce the risk of condensation inroof spaces. Approved Document J givesguidance on the safe accommodation ofcombustion systems including the ventilationrequirements for combustion and the properworking of flues. Approved Document E givesguidance on achieving satisfactory resistanceto the passage of sound. Guidance on somesatisfactory design details is given in therobust details publication 1.

Section 0: General guidance


10

L2 GENERAL

1Limiting thermal bridging and air leakage: Robustconstruction details for dwellings and similar buildings;TSO, 2001


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Thermal conductivity and transmittance

0.10 Thermal conductivity (i.e. the lambda-value) of a material is a measure of the rate atwhich that material will pass heat and isexpressed in units of Watts per metre perdegree of temperature difference (W/mK).

0.11 Thermal transmittance (i.e. the U-value) is

a measure of how much heat will pass throughone square metre of a structure when the airtemperatures on either side differ by onedegree. U-values are expressed in units ofWatts per square metre per degree oftemperature difference (W/m2K).

0.12 Exposed element means an elementexposed to the outside air (including asuspended floor over a ventilated orunventilated void, and elements so exposedindirectly via an unheated space), or anelement in the floor or basement in contactwith the ground. In the case of an element

exposed to the outside air via an unheatedspace (previously known as a semi-exposedelement) the U-value should be derived fromthe transmission heat loss coefficient2. Partywalls, separating two premises that canreasonably be assumed to be heated to thesame temperature, are assumed not to needthermal insulation.

0.13 In the absence of test information, thermalconductivities and thermal transmittances (U-values) may be taken from the tables in thisApproved Document or alternatively in the caseof U-values they may be calculated. However, if

test results for particular materials and makesof products obtained in accordance with aharmonised European Standard are availablethey should be used in preference.Measurements of thermal conductivity should

be made according to BS EN 12664 3, BS EN126674, or BS EN 129395. Measurements ofthermal transmittance should be madeaccording to BS EN ISO 89906 or, in the caseof windows and doors, BS EN ISO 12567-17.The size and configuration of windows fortesting or calculation should be representativeof those to be installed in the building, or

conform to published guidelines on theconventions for calculating U-values8.

U-value reference tables

0.14Appendix A contains tables of U-valuesand examples of their use, which provide asimple way to establish the amount ofinsulation needed to achieve a given U-valuefor some typical forms of construction. Theyyield cautious results that, in practice, areequal or better than the stated U values.However specific calculations whereproprietary insulation products are proposed

may indicate that somewhat less insulationcould be reasonable. The values in the tableshave been derived taking account of typicalthermal bridging where appropriate. AppendixA also contains tables of indicative U-valuesfor windows, doors and rooflights.

Calculation of U-values

0.15 U-values should calculated using themethods given in:

- for walls and roofs: BS EN ISO 69469

- for ground floors: BS EN ISO 1337010

- for windows and doors:BS EN ISO 10077-111 orprEN ISO 10077-212

- for basements: BS EN ISO 13370 or theBCA/NHBC Approved Document.13


11

L2GENERAL

2BS EN ISO 13789:1999 Thermal performance ofbuildings - Transmission heat loss coefficient -Calculation method

3BS EN 12664:2001 Thermal performance of buildingmaterials and products Determination of thermal

resistance by means of guarded hot plate and heatflow meter methods Dry and moist products of lowand medium thermal resistance

4BS EN 12667:2000 Thermal performance of buildingmaterials and products Determination of thermalresistance by means of guarded hot plate and heatflow meter methods Products of high and mediumthermal resistance

5BS EN 12939:2001 Thermal performance of buildingmaterials and products Determination of thermalresistance by means of guarded hot plate and heatflow meter methods Thick products of high andmedium thermal resistance

6BS EN ISO 8990:1996 Thermal insulation Determination of steady-state thermal transmissionproperties Calibrated hot box

7BS EN ISO 12567-1:2000 Thermal performance ofwindows and doors Determination of thermaltransmittance by hot box method Part 1: Completewindows and doors

8Conventions for the calculation of U-values, BRE:

expected publication date early 20029

BS EN ISO 6946:1997 Building components andbuilding elements Thermal resistance and thermaltransmittance Calculation method

10BS EN ISO 13370:1998 Thermal performance ofbuildings Heat transfer via the ground Calculationmethods

11BS EN ISO 10077-1:2000 Thermal performance ofwindows, doors and shutters Calculation of thermaltransmittance Part 1: Simplified methods

12prEN ISO 10077-2: Thermal performance of windows,doors and shutters Calculation of thermaltransmittance Part 2: Numerical method for frames

13 Approved Document Basements for dwellings,ISBN 0-7210-1508-5, 1997


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For building elements not covered by thesedocuments the following may be appropriatealternatives: BRE IP 5/9814 for curtain wallingthe CAB Guide15 or the methodology inCWCT guidance16,17, BRE guidance for lightsteel frame walls18, or finite element analysis inaccordance with BS EN ISO 10211-117 orBS EN ISO 10211-220 . BRE guidance on

conventions for establishing U-values8

can befollowed. Some examples of U-valuecalculations are given in Appendix B andAppendix C gives data for ground floorsand basements.

0.16 Thermal conductivity values for commonbuilding materials can be obtained fromBS EN 1252421 or the CIBSE Guide SectionA322, but for ease of reference a table ofcommon materials is given in Appendix A. Forspecific insulation products, data should beobtained from the manufacturers.

0.17 When calculating U-values, the thermal

bridging effects of, for instance, timber joists,structural and other framing, normal mortarbedding and window frames should generallybe taken into account using the proceduregiven in BS EN ISO 6946 (some examples aregiven in Appendix B). Thermal bridging can bedisregarded however where the difference inthermal resistance between the bridgingmaterial and the bridged material is less than0.1 m2K/W. For example normal mortar jointsneed not be taken into account in calculationsfor brickwork. Where, for example, wallscontain in-built meter cupboards, and ceilings

contain loft hatches , recessed light fittings,etc, area-weighted average U-values shouldbe calculated.

Roof window

0.18A roof window is a window in the plane ofa pitched roof and may be considered as arooflight for the purposes of this ApprovedDocument.

Basis for calculating areas

0.19 The dimensions for the areas of walls,roofs and floors should be measured between

finished internal faces of the external elementsof the building including any projecting bays. Inthe case of roofs they should be measured inthe plane of the insulation. Floor areas shouldinclude non-useable space such as buildersducts and stairwells.

Air permeabil ity

0.20Air permeabi lity is the physical propertyused to quantify airtightness of building fabric.It measures the resistance of the buildingenvelope to inward or outward air permeation.It is defined as the average volume of air (in

cubic metres per hour) that passes through unitarea of the structure of the building envelope(in square metres) when subject to an internalto external pressure difference of 50 Pa. It is

expressed in units of cubic metres per hour,per square metre of envelope area, at apressure difference of 50 Pa. The envelopearea of the building is defined as the total areaof the floor, walls and roof separating theinterior volume (i.e. the conditioned space)from the outside environment.

Conversion between carbon and carbondioxide indices

0.21 To maintain consistency with theGovernments Climate Change Programme, theperformance targets in this ApprovedDocument are quoted in terms of kg of carbonrather than kg of carbon dioxide, or in energyterms such as GigaJoules or MegaWatt-hours.To convert from the carbon to carbon dioxidebasis multiply by the ratio of atomic weights(Carbon Dioxide 44 : Carbon 12). For example9 tonnes per square metre per year of carbonis equivalent to {9 x (44/12)} = 33 tonnes of

carbon dioxide per square metre per year.


12

L2 GENERAL

14IP 5/98 Metal cladding: assessing thermalperformance, BRE, 1998

15Guide to assessment of the thermal performance ofaluminium curtain wall framing, CAB, 1996

16Guide to good practice for asessing glazing frame

U-values, CWCT (1998, new edition in preperation).17

Guide to good practice for assessing heat transfer andcondensation risk for a curtain wall, CWCT (1998, newedition in preperation).

18U-value calculation procedure for light steel framewalls, BRE, to be published

19BS EN ISO 10211-1:1996 Thermal bridges in buildingconstruction Calculation of heat flows and surfacetemperatures Part 1: General methods

20BS EN ISO 10211-2:2001 Thermal bridges in buildingconstruction Calculation of heat flows and surfacetemperatures Part 2: Linear thermal bridges

21BS EN 12524:2000 Building materials and products Hygrothermal properties Tabulated design values

22CIBSE Guide A: Environmental design, Section A3:Thermal properties of building structures, CIBSE, 1999


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Special cases

Low levels of heating

0.22 Buildings or parts of buildings with lowlevels of heating or no heating do not requiremeasures to limit heat transfer through thefabric. The insulation properties of the fabriccontaining such spaces are chosen for

operational reasons and can be regarded asreasonable provision. Low levels of heatingmight be no more than 25W/m2, an examplebeing perhaps a warehouse where heating isintended to protect goods from condensationor frost, with higher temperatures providedonly around local work stations. A cold-storeis an example of a building where insulationproperties would be dictated byoperational needs.

Low levels of use

0.23 For buildings with low hours of use, lower

standards for heating and lighting systemsmay be appropriate, but fabric insulationstandards should be no worse than theguidance in this Approved Document.Buildings used solely for worship at set timescould be one example where this paragraphwould be relevant.

Historic Buildings

0.24Advice on the factors determining thecharacter of historic buildings is set out inPPG1523. Specific guidance on meeting therequirements of Part L when undertaking work

in historic buildings is given in Section 4 of thisApproved Document.

Buildings constructed from sub-assemblies

0.25 Buildings constructed from sub-assemblies that are delivered newly made orselected from a stock are no different to anyother new building and must comply with allthe requirements in Schedule 1.

0.26 In some applications however, such asbuildings constructed to accommodateclassrooms, medical facilities, offices andstorage space to meet temporary

accommodation needs, reasonable externalfabric provisions for the conservation of fueland power can vary depending on thecircumstances in the particular case.For example:-

a) A building created by dismantling,transporting and re-erecting on the samepremises the external fabric sub-assemblies ofan existing building would normally beconsidered to meet the requirement;

b) A building constructed from external fabricsub-assemblies obtained from other premises

or from a stock manufactured before 31December 2001, would normally be consideredto meet the requirement if the fabric thermalresistance or the prospective annual energy

use will be no worse than the relevantperformance standards given in the 1995edition of Approved Document L.

0.27 Enclosed and heated or cooled linksbetween such temporary accommodation,which may also be formed from sub-assemblies, should be insulated and madeairtight to the same standards as the buildings

themselves.

0.28 Where heating and lighting are to beprovided in such temporary accommodation,the requirements may be satisfied in thefollowing ways although the extent of theprovisions will depend on the circumstances inthe particular case:-

a) heating and hot water systems:providing on/off, time and temperature controlsas indicated in Section 1 of this ApprovedDocument.

b) general and display lighting: providinggeneral lighting systems with lamp efficaciesthat are not less than those indicated inparagraph 1.48 and providing display lightingwith installed efficacies not less that thoseindicated in paragraphs 1.50-1.52.

Mixed use development

0.29 When constructing buildings that haveparts used as dwellings as well as parts forother uses, account should be taken of theguidance in Approved Document L1.


13

L2GENERAL

23Planning and the historic environment, Planning PolicyGuidance PPG 15, DoE/DNH, September 1994. (In

Wales refer to Planning Guidance Wales PlanningPolicy First Revision 1999 and Welsh Office Circular61/96 Planning and Historic Environment: HistoricBuildings and Conservation Areas.)


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General

1.1 In order to achieve energy efficiency inpractice, the building and its services systemsshould be appropriately designed (Section 1)and constructed (Section 2). Information should

also be provided such that the performance ofthe building in use can be assessed (Section3). This Approved Document provides guidanceon meeting the requirements at each of theseimportant stages of procuring a building,whether it be a new building, an extension or arefurbishment project. More detailed guidanceon energy efficiency measures can be found inthe CIBSE Guide on Energy Efficiency inBuildings24.

1.2 When designing building servicesinstallations, provision should be made tofacilitate appropriate inspection and

commissioning (see paragraphs 2.5 2.6).

1.3 Specific guidance for work carried out onexisting buildings is given in Section 4.

1.4 In large complex buildings, it may besensible to consider the provisions for theconservation of fuel and power separately forthe different parts of the building in order toestablish the measures appropriate to eachpart.

1.5 Where alternative building servicessystems are provided (e.g. dual fuel boilers,and combined heat and power or heat pump

systems paralleled by standby boiler capacity),then the building should meet the requirementsin each possible operating mode.

Alternative methods of showing

compliance

1.6 Three methods are given fordemonstrating that reasonable provision hasbeen made for the conservation of fuel andpower. These different methods offer increasingdesign flexibility in return for greater demandsin terms of the extent of calculation required.

However the overall aim is to achieve the samestandard in terms of carbon emissions. Themethods are:

a) an Elemental Method (paragraphs 1.7 1.68). This method considers the performanceof each aspect of the building individually. Tocomply with the provisions of Part L, aminimum level of performance should beachieved in each of the elements. Someflexibility is provided for trading off betweendifferent elements of the construction, andbetween insulation standards and heatingsystem performance.

b) a Whole-Building Method (paragraphs1.69 - 1.73). This method considers theperformance of the whole building. For officebuildings, the heating, ventilation, air

conditioning and lighting systems should becapable of being operated such that they willemit no more carbon per square metre perannum than a benchmark based on the ECON19 data25. Alternative methods are alsoprovided for schools and hospitals.

c) a Carbon Emissions Calculation Method(paragraphs 1.74 1.76). This method alsoconsiders the performance of the wholebuilding, but can be applied to any buildingtype. To comply with the provisions of Part L,the annual carbon emissions from the buildingshould be no greater than that from a notionalbuilding that meets the compliance criteria ofthe Elemental Method. The carbon emissionsfrom the proposed building and the notionalbuilding need to be estimated using anappropriate calculation tool.

Elemental Method1.7 To show compliance following theElemental Method, the building envelope has toprovide certain minimum levels of insulation,and the various building services systems eachhave to meet defined minimum standards ofenergy efficiency as follows -

Standard U-values for construction elements

1.8 The requirement will be met if the thermalperformances of the construction elements areno worse than those listed in Table 1 (asillustrated in Diagram 1). One way of achievingthe U-values in Table 1 is by providinginsulation of a thickness estimated from theTables in Appendix A as illustrated in theexamples. An alternative for floors is to use thedata given in Appendix C.

Section 1: Design


14

L2 DESIGN

24 CIBSE Guide, Energy efficiency in buildings, CIBSE,1998

25Energy use in offices - Energy Consumption Guide 19,DETR, 1998


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Where an element is exposed to the outside viaan unheated space (e.g. an unheated atrium oran underground car park), either:

a) the unheated space may be disregardedso that the element is considered as directlyexposed to the outside, or

b) the U-value of the element may becalculated as the transmission heat losscoefficient through the unheated space dividedby the area of the element. The transmission

heat loss coefficient should be calculated asgiven in BS EN ISO 1378926.

Thermal bridging at junctions and aroundopenings

1.9 The building fabric should be constructedso that there are no significant thermal bridgesor gaps in the insulation layer(s) within thevarious elements of the fabric, at the jointsbetween elements, and at the edges ofelements such as those around window anddoor openings.

1.10 One way of demonstrating compliance

would be to utilise details and practice that havebeen independently demonstrated as beingsatisfactory. For domestic style construction, aselection of such satisfactory details is given inthe robust construction details publication27.

1.11An alternative way of meeting therequirements would be to demonstrate bycalculation or by adopting robust designpractices that the performance of the buildingis at least as good as it would be byfollowing paragraph 1.10. BRE InformationPaper IP 17/0128 and the MRCMA TechnicalReport No 1429 illustrate how this can be done.


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L2DESIGN

Table 1 Standard U-values of

construction elements

Exposed Element U-value(W/m2K)

Pitched roof 1, 2 with insulation between 0.20rafters

Pitched roof 1 with insulation between 0.16joists

Flat roof 3 or roof with integral insulation 0.25

Walls, including basement walls 0.35

Floors, including ground floors and 0.25basement floors

Windows, roof windows and personnel 2.2doors (area weighted average for thewhole building), glazing in metal frames4

Windows, roof windows and personnel 2.0doors (area weighted average for thewhole building), glazing in wood or PVCframes4

Rooflights 5, 6 2.2

Vehicle access and similar large doors 0.7

Notes to Table 1:1Any part of a roof having a pitch greater or equal to 70 can be

considered as a wall.2 For the sloping parts of a room-in-the-roof constructed as a

material alteration, a U-value of 0.3 W/m2K would be reasonable.3 Roof of pitch not exceeding 104 Display windows, shop entrance doors and similar glazing are not

required to meet the standard given in this table.5 This standard applies only to the performance of the unit excluding

any upstand. Reasonable provision would be to insulate anyupstand, or otherwise isolate it from the internal environment.

6 For the purposes of Approved Document L, a roof window may beconsidered as a rooflight.

Diagram 1 Standard u-values fornon-domestic buildings

loft

unheated space

0.35

0.2

0.16

0.25

0.35

0.250.25c

0.35c

0.25

AverageU-value = 2.0a/2.2b

26BS EN ISO 13789:1999 Thermal performance ofbuildings - Transmission heat loss coefficient -Calculation method

27Limiting thermal bridging and air leakage: Robustconstruction details for dwellings and similar buildings;TSO, 2001

28BRE IP 17/01, Assessing the effects of thermalbridging at junctions and around openings in the

external elements of buildings29

Guidance for the design of metal cladding and roofingto comply with Approved Document L 2002 Edition:MCRMA Technical Note 14

a if windows have wood or PVC framesb if windows have metal framesc includes the effect of the unheated space


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Maximum areas of windows, doors androoflights

1.12 Provision should be made to limit the rateof heat loss through glazed elements of thebuilding. One way of complying would be tolimit the total area of windows, doors androoflights so that they do not exceed thevalues given in Table 2 - unless compensated

for in some other way.

1.13 Care should be taken in the selection andinstallation of glazed systems to avoid the riskof condensation. Guidance can be obtainedfrom BRE Report No 26230.

Trade-off between construction elements

1.14 In order to provide greater designflexibility, the U-values of construction

elements and the areas of windows, doors androoflights may vary from the values given inTable 1 and Table 2 provided that suitablecompensating measures are taken. If glazingareas are reduced from those given in Table 2,special care needs to be given to confirm thatlevels of daylight are adequate. Guidance ondesigning for daylight is contained inCIBSE LG1031.

1.15 Compliance with the provisions of Part Lwould be achieved if:

a) the rate of heat loss from the proposed

building does not exceed that from a notionalbuilding of the same size and shape that meetsthe criteria set out in Table 1 and Table 2; and

b) the U-value of any part of an element is noworse than the values given in the followingTable 3.

1.16As further constraints in these methodshowever:

a) if the U-value of the floor in the proposedbuilding is better than the performance given inTable 1 with no added insulation, the betterperformance standard is to be adopted for thenotional building; and

b) if the area of openings in the proposedbuilding is less than the values shown in Table2, the average U-value of the roof, wall or floorcannot exceed the appropriate value given inTable 1 by more than 0.02 W/m2K.

c) no more than half of the al lowablerooflight area can be converted into anincreased area of window and doors.


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L2 DESIGN

Table 3 Poorest U-values acceptablewhen trading off betweenconstruction elements

Element Poorest acceptableU-value(W/m2K)

Parts of roof 1 0.35

Parts of exposed wall or floor 1 0.70

Notes:1 Whilst parts of these elements may (within the limits given in thistable) have poorer U-values than those given in Table 1, it will notnormally be practical to make sufficient allowances elsewhere in thedesign for the whole element to be built to these standards.

Table 2 Maximum area of openings unless compensating measures are taken

Building type Windows 1 and doors as % of Rooflights as %the area of exposed wall2 of area of roof

Residential buildings (where peopletemporarily or permanently reside) 30 20

Places of assembly, offices and shops 40 20

Industrial and storage buildings 15 20

Vehicle access doors and display As required

windows and similar glazingNotes:1 For the purposes of this calculation, dormer windows in a roof may be included in the rooflight area.2 See paragraph 0.19, basis for calculating areas.

30 Thermal insulation: avoiding risks, BR 262, 2002Edition BRE, 2001

31CIBSE, Daylight and window design, LG10, CIBSE,1999


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Building air leakage standards

1.17 Buildings should be reasonably airtight toavoid unnecessary space heating and coolingdemand and to enable the effectiveperformance of ventilation systems.

1.18 Without prejudice to the need forcompliance with all the requirements in

Schedule 1 however, the need to provide foradequate ventilation for health (Part F) andadequate air for combustion appliances (Part J)should particularly be taken into account.

1.19A way of meeting the requirement wouldbe to incorporate sealing measures to achievethe performance standard given in paragraph2.4. Some ways of achieving satisfactoryairtightness include:

a) providing a reasonably continuous airbarrier in contact with the insulation layer overthe whole thermal envelope (includingseparating walls). Special care should be takenat junctions between elements and around doorand window openings. For domestic typeconstructions, some satisfactory design detailsand installation practice are described in therobust details publication25. Guidance for thedesign of metal cladding and roofing systemsto minimise air infiltration is given in theMCRMA Technical Report No 1427.

b) sealing gaps around service penetrations.

c) draught-proofing external doors andwindows.

Avoiding solar overheating1.20 Buildings should be constructed suchthat:

a) those occupied spaces32 that rely onnatural ventilation should not overheat whensubject to a moderate level of internal heatgain and

b) those spaces that incorporate mechanicalventilation or cooling do not require excessivecooling plant capacity to maintain the desiredspace conditions.

1.21 Ways of meeting the requirement would be

through:

a) the appropriate specification of glazing,and

b) the incorporation of passive measuressuch as shading (detailed guidance being givenin BRE Report No 36433), and

c) the use of exposed thermal capacitycombined with night ventilation (detailedguidance being given in GIR 3134).

1.22A way of achieving compliance for spaceswith glazing facing only one orientation would

be to limit the area of glazed opening as apercentage of the internal area of the elementunder consideration to the values given inTable 4.

1.23Alternative approaches to achievingcompliance include:

a) showing that the solar heat load per unitfloor area averaged between the hours of 07:30and 17:30 would not be greater than 25W/m2 ifthe building were to be subject to the solarirradiances for the particular location for themonth of July that were not exceeded on morethan 2.5% of occasions during the period 1976 1995. The procedure given in Appendix Hcan be used to do this.

b) showing by detailed calculationprocedures such as those described in chapter5 of CIBSE Guide A35, that in the absence ofmechanical cooling or mechanical ventilation,the space will not overheat when subjected toan internal gain of 10 W/m2.

Heating systems

1.24 Without prejudice to the need for

compliance with all the requirements inSchedule 1, the need to provide for adequateventilation for health (Part F) and adequate airfor combustion appliances (Part J) shouldparticularly be taken into account when makingprovisions for combustion systems such asboiler plant and direct-fired gas heaters.

Carbon intensities of heating plant

General

1.25 Heating plant should be reasonablyefficient. For heating plant serving hot waterand steam heating systems, electric heating

and heat pumps (irrespective of the form ofheat distribution), a way of complying with therequirement would be to show that:


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L2DESIGN

Table 4 Maximum allowable area ofglazing

Orientation of opening Maximum allowable areaof opening (%)

N 50

NE/NW/S 40

E/SE/W/SW 32

Horizontal 12

32This guidance is not applicable to non-occupiedspaces such as stacks and atria intended to drivenatural ventilation via buoyancy.

33Solar shading of buildings, BR 364, CRC Ltd, 1999.

34

Energy Efficiency Best Practice programme, Avoidingor minimising the use of air-conditioning, GIR 31,TSO, 1995.

35Environmental design, Guide A, CIBSE, 1999.


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a) the carbon intensity of the heat generatingequipment at the maximum heat output of theheating system36 is not greater than the valueshown in Table 5 column (a) and

b) the carbon intensity of the heat generatingequipment when the system is producing 30%of the maximum heat output of the heatingsystem is not greater than the value shown in

Table 5 column (b).

1.26 In some applications electric resistanceheating might be appropriate. In such casesthe designer will need to improve envelopeinsulation standards to trade-off against thehigher carbon intensity of such forms ofheating (see paragraph 1.32).

1.27 The carbon intensity of the heating plantis based on the carbon emitted per useful kWhof heat output. Where there are multiple piecesof heat generating equipment, the carbon

intensity of the heating plant is the ratingweighted average of the individual elements.This definition of carbon intensity is applicableto boilers, heat pump systems and electricalheating, and is given by:

(1)

where:

c = the carbon intensity of the heating system(kgC/kWh of useful heat).

R = the rated output of an individual elementof heat raising plant (kW).

t = the gross thermal efficiency of thatelement of heat raising plant (kWh of heatper kWh of delivered fuel). For mostpractical cases, the efficiency may betaken as the full load efficiency for thatelement but, where appropriate, a partload efficiency based on manufacturerscertified data may be used as analternative.

Cf = the carbon emission factor of the fuelsupplying that element of heat raisingplant (kg of carbon emitted per kWh ofdelivered fuel consumed) (Table 6).

Calculating the carbon intensity of CHPsystems

1.28 Where a combined heat and power system(CHP) is proposed, the carbon intensity of theCHP (chp) can take account of the benefit ofthe on-site generation in reducing emissionsfrom power stations feeding the national grid.The adjustment can be made using equation(2). This adjusted carbon intensity can then beused in equation (1) to determine the carbon

intensity of the overall heating system at 100%and 30% of heating system output.

(2)

where:

t is the gross thermal efficiency of the CHPengine (kWh of useful heat per kWh of fuelburned);

HPR is the heat to power ratio (kWh of useful

heat produced per kWh of electricityoutput). This is equivalent to the ratio ofthe thermal and power efficiencies of theCHP unit;

Cdisplaced is the carbon emission factor for grid-supplied electricity displaced by theCHP (kg/kWh). This should be takenas the factor for new generatingcapacity that might otherwise be built ifthe CHP had not been provided, i.e.the intensity of a new generation gas-fired station: 0.123 kgC/kWh.

HPR =chp

t

CdisplacedC f

R

= 1c

t

R.C f


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L2 DESIGN

Table 5 Maximum allowable carbonintensities of heating systems

Maximum carbon intensities (kgC/kWh)at stated % of the maximum heatoutput of the heating system.

Fuel (a) (b)at maximum At 30% of maximumheat output heat output

Natural gas 0.068 0.065

Other fuels 0.091 0.088

Table 6 Carbon emission factors

Delivered fuel Carbon emission factor(kgC/kWh)

Natural gas 0.053

LPG 0.068

Biogas 0

Oil 1 0.074

Coal 0.086

Biomass 0

Electricity2 0.113

Waste heat 3 0

Notes:1 This value can be used for all grades of fuel oil.2 This is the estimated average figure for grid-supplied electricity forthe period 2000 2005. If there is on-site generation of electricityfrom photovoltaic panels or wind power, this could be accounted forusing the carbon emissions calculation method (see paragraph 1.74et seq). Short term energy supply arrangements such as greentariffs are not appropriate ways of complying with the requirements.

3 This includes waste heat from industrial processes and from power

stations rated at more than 10MW electrical output and with apower efficiency > 35%

36The maximum heat output of the heating systemoccurs when all the items of heat generatingequipment capable of operating simultaneously areproducing heat at their rated output.


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1.29 Where the CHP has no facility for heatdumping, the gross thermal efficiency is simplythe CHP heat output divided by the energycontent of the fuel burned. Where the CHPincludes facilities for heat dumping, the grossthermal efficiency should be based on anestimate of the useful heat supplied to thebuilding, i.e. the heat output from the CHP

minus the heat dumped. Certification underthe CHPQA37 scheme would be a way ofshowing that the gross thermal efficiency hasbeen estimated in a satisfactory way.

Calculating the carbon intensity ofcommunity heating

1.30 When calculating the carbon intensity ofthe heat supplied to the building by acommunity heating system, account should betaken of the performance of the whole system,(i.e. the distribution circuits, and all the heatgenerating plant including any CHP or waste

heat recovery) and the carbon emission factorsof the different fuels. Certification under theCHPQA37 scheme would be a way of showingthat the thermal and power efficiencies havebeen estimated in a satisfactory way.

Other methods of heating

1.31 In buildings such as factories, warehousesand workshops it can be more efficient toprovide local warm air or radiant heatingsystems. GPG 30338 provides guidance on theapplication of such systems.

Trade - off between construction elements

and heating system efficiency

1.32 In order to allow greater design flexibility,there can be a trade-off (in either direction)between the average U-value of the envelopeand the carbon intensity of the heating systemprovided that the rate of carbon emissions isunchanged. A way of complying would be toadjust the average U-value of the buildingfabric such that it is no worse than the valuedetermined from the following equation.

(3)

where:

Ureq = the required average U-value.

Uref = the average U-value of the buildingconstructed to the elemental standardsof Table 1.

ref = the carbon intensity of the referenceheating system at an output of 30% ofthe installed design capacity. Thisshould be taken from Table 5 column (b)for the fuel type used in the actual

heating system.

act = the carbon intensity of the actualheating system at an output of 30% ofinstalled design capacity.

Space heating controls

1.33 The building should be provided withzone, timing and temperature controls suchthat each functional area is maintained at the

required temperature only during the periodwhen it is occupied. Additional controls maybe provided to allow heating during extendedunusual occupation hours and to provide forsufficient heating to prevent condensation orfrost damage when the heating system wouldotherwise be switched off.

1.34 Ways of meeting the requirement include:

a) in bui ldings with a heating systemmaximum output not exceeding 100 kW, tofollow the guidance in GPG 132 39.

b) in larger or more complex buildings,

to follow the guidance contained inCIBSE Guide H40. Certification by a competentperson that the provisions meet therequirements may be accepted by buildingcontrol bodies.

Hot water systems and their control

1.35 Hot water should be provided safely,making efficient use of energy and therebyminimising carbon emissions. Ways ofachieving the requirement include -

a) avoiding over-sizing of hot water storage

systems.b) avoiding low-load operation of heat raisingplant.

c) avoiding the use of grid-supplied electricwater heating except where hot water demandis low.

d) providing solar water heating.

e) minimising the length of circulation loops.

f ) minimising the length and diameter ofdead legs.

1.36A way of satisfying the requirements for

conventional hot water storage systems wouldbe to provide controls that shut off heatingwhen the required water temperature isachieved. The supply of heat should also beshut off during those periods when hot water isnot required.

U =req Urefrefact

.


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L2DESIGN

37Quality Assurance for Combined Heat and Power,CHPQA Standard, Issue 1, DETR, November 2000.

38GPG 303, 2000: The designers guide to energy-efficient buildings for industry, Energy Efficiency Bestpractice programme, BRECSU.

39

GPG 132, 2001: Energy Efficiency Best PracticeProgramme, Heating controls in small commercial andmulti-residential buildings, BESCSU.

40CIBSE Guide H, 2000: Building Control Systems.


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1.46 This guidance need not be applied inrespect of a maximum of 500 W of installedlighting in the building, thereby allowingflexibility for the use of feature lighting etc.

1.47Appendix F gives examples that show howthe luminaire efficacy requirement can be meteither by selection of appropriate lamps andluminaires or by calculation.

General lighting efficacy in all other buildingtypes

1.48 For electric lighting systems serving otherbuilding types, it may be appropriate to provideluminaires for which photometric data is notavailable and/or are lower powered and useless efficient lamps. For such spaces, therequirements would be met if the installedlighting capacity has an initial (100 hour) lampplus ballast efficacy of not less than 50 lamp-lumens per circuit-watt. A way of achieving thiswould be to provide at least 95% of the

installed lighting capacity using lamps withcircuit efficacies no worse than those in Table8.

1.49 For the purposes of Approved DocumentL, high efficiency control gear means low lossor high frequency control gear that has a power

consumption (including the starter component)not exceeding that shown in Table 942.

Display lighting in all buildings

1.50 For the purposes of Approved DocumentL, display lighting means lighting intended tohighlight displays of exhibits or merchandise,or lighting used in spaces for publicentertainment such as dance halls, auditoria,conference halls and cinemas.

1.51 Because of the special requirements ofdisplay lighting, it may be necessary to acceptlower energy performance standards for displaylighting. Reasonable provision shouldnevertheless be made and a way of complyingwould be to demonstrate that the installedcapacity of display lighting averaged over thebuilding has an initial (100 hour) efficacy of notless than 15 lamp-lumens per circuit-watt. Incalculating this efficacy, the power consumedby any transformers or ballasts should be takeninto account.

1.52As an alternative, it would be acceptable if

at least 95% of the installed display lightingcapacity in circuit-Watts comprises lightingfittings incorporating lamps that have circuitefficacies no worse than those in Table 10.


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Table 8 Light sources meeting thecriteria for general lighting

Light source Types and ratings

High pressure Sodium All types and ratings

Metal halide All types and ratings

Induction lighting All types and ratings

Tubular fluorescent 26mm diameter (T8) lamps, and

16mm diameter (T5) lamps ratedabove 11W, provided with highefficiency control gear. 38mmdiameter (T12) linear fluorescentlamps 2400mm in length

Compact fluorescent All ratings above 11W

Other Any type and rating with anefficacy greater than 50 lumensper circuit Watt.

Table 9 Maximum power consumptionof high efficiency control gear

Nominal lamp rating Control gear power(Watts) consumption (Watts)

Less than or equal to 15 6

Greater than 15,Not more than 50 8

Greater than 50,

Not more than 70 9Greater than 70,Not more than 100 12

Greater than 100 15

Table 10 Light sources meeting thecriteria for display lighting

Light source Types and ratings

High pressure Sodium All types and ratings

Metal halide All types and ratings

Tungsten halogen All types and ratings

Compact and tubularfluorescent All types and ratings

Other Any type and rating withan efficacy greater than 15lumens per circuit Watt.

42The values in the table are in line with EuropeanDirective 2000/55/EC 18 September 2000 : On energyefficiency requirements for ballasts for fluorescentlighting


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Emergency escape lighting and specialistprocess lighting

1.53 For the purposes of Approved DocumentL, the following definitions apply:

a) Emergency escape lighting means thatpart of emergency lighting that providesillumination for the safety of people leaving an

area or attempting to terminate a dangerousprocess before leaving an area.

b) Specialist process lighting means lightingintended to illuminate specialist tasks within aspace, rather than the space itself. It couldinclude theatre spotlights, projectionequipment, lighting in TV and photographicstudios, medical lighting in operating theatresand doctors' and dentists' surgeries,illuminated signs, coloured or stroboscopiclighting, and art objects with integral lightingsuch as sculptures, decorative fountains andchandeliers.

1.54 Emergency escape lighting and specialistprocess lighting are not subject to therequirements of Part L.

Lighting controls

1.55 Where it is practical, the aim of lightingcontrols should be to encourage the maximumuse of daylight and to avoid unnecessarylighting during the times when spaces areunoccupied. However, the operation ofautomatically switched lighting systems shouldnot endanger the passage of buildingoccupants. Guidance on the appropriate use of

lighting controls is given in BRE IP 2/9943.

Controls in offices and storage buildings

1.56A way of meeting the requirement wouldbe the provision of local switches in easilyaccessible positions within each working areaor at boundaries between working areas andgeneral circulation routes. For the purposes ofApproved Document L2, reference to switchincludes dimmer switches and switchingincludes dimming. As a general rule, dimmingshould be effected by reducing rather thandiverting the energy supply.

1.57 The distance on plan from any localswitch to the luminaire it controls shouldgenerally be not more than eight metres, orthree times the height of the light fitting abovethe floor if this is greater. Local switching canbe supplemented by other controls such astime switching and photo-electric switcheswhere appropriate. Local switches couldinclude:

a) switches that are operated by thedeliberate action of the occupants eithermanually or by remote control. Manualswitches include rocker switches, push buttonsand pull cords. Remote control switchesinclude infra red transmitter, sonic, ultrasonicand telephone handset controls.

b) automatic switching systems which switchthe lighting off when they sense the absence ofoccupants.

Controls in buildings other than offices andstorage buildings

1.58A way of meeting the requirement wouldbe to provide one or more of the following

types of control system arranged to maximisethe beneficial use of daylight as appropriate:

a) local switching as described in paragraph1.57;

b) time switching, for example in majoroperational areas which have clear timetablesof occupation;

c) photo-electric switching.

Controls for display lighting (all buildingtypes)

1.59A way of meeting the requirement wouldbe to connect display lighting in dedicatedcircuits that can be switched off at times whenpeople will not be inspecting exhibits ormerchandise or being entertained. In a retailstore, for example, this could include timersthat switch the display lighting off outside storeopening hours, except for displays designed tobe viewed from outside the building throughdisplay windows.

Air-conditioning and mechanical ventilation(ACMV)

1.60 For the purposes of Approved Document

L, the following definitions apply:

a) mechanical ventilation is used to describesystems that use fans to supply outdoor airand/or extract indoor air to meet ventilationrequirements. Systems may be extensive andcan include air filtration, air handling units andheat reclamation, but they do not provide anyactive cooling from refrigeration equipment.The definition would not apply to a naturallyventilated building, which makes use ofindividual wall or window mounted extract fansto improve the ventilation of a small number ofrooms.

b) air conditioning is used to describe anysystem where refrigeration is included toprovide cooling for the comfort of buildingoccupants. Air conditioning can be providedfrom stand-alone refrigeration equipment in thecooled space, from centralised or partlycentralised equipment, and from systems thatcombine the cooling function with mechanicalventilation.


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43Photoelectric control of lighting: design, set-up andinstallation issues, BRE Information Paper IP 2/99


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c) treated areas; these are the floor areas ofspaces that are served by the mechanicalventilation or air conditioning system in thecontext and should be established bymeasuring between the internal faces of thesurrounding walls. Spaces that are not servedby these systems such as plant rooms, serviceducts, lift-wells etc. should be excluded.

d) process requirements; in office buildingsprocess requirements can be taken to includeany significant area in which an activity takesplace which is not typical of the office sector,and where the resulting need for heating,ventilation or air conditioning is significantlydifferent to that of ordinary commercial offices.When assessing the performance of airconditioning or mechanical ventilation systems,areas which are treated because of processrequirements should be excluded from thetreated area, together with the plant capacity,or proportion of the plant capacity, that is

provided to service those areas. Activities andareas in office buildings considered torepresent process requirements would thusinclude:

q Staff restaurants and kitchens;

q Large, dedicated, conference rooms;

q Sports facilities;

q Dedicated computer or communicationsrooms.

e) In the following text, air conditioningand/or mechanical ventilation systems as

defined above are collectively described asACMV.

1.61 Buildings with ACMV should be designedand constructed such that:

a) the form and fabric of the building do notresult in a requirement for excessive installedcapacity of ACMV equipment. In particular, thesuitable specification of glazing ratios and solarshading are an important way to limit coolingrequirements (see paragraphs 1.20 1.23).

b) components such as fans, pumps andrefrigeration equipment are reasonably efficient

and appropriately sized to have no morecapacity for demand and standby than isnecessary for the task.

c) suitable facilities are provided to manage,control and monitor the operation of theequipment and the systems.

CPR method for office buildings with ACMV

1.62 In the case of an office development, oneway of achieving compliance (if there are noinnovative building or building servicesprovisions) is to show that the CarbonPerformance Rating (CPR) is satisfactory.

Where there are innovative features in thedesign the carbon emissions calculationmethod, or another acceptable alternativewould be more appropriate.

1.63 The CPR is a rating based onstandardised occupancy patterns that relatesthe performance of the proposed building to abenchmark based on the measuredconsumption data contained in ECON1923. Therating of the proposed building is calculatedfrom the rated input power of the installedequipment as this combines the effect of load

reduction by good envelope design and energyefficient system design into a single parameter.The detail of the CPR calculation is containedin Appendix G. If there are any areas in thebuilding with significant process loads (e.g. amajor computer suite), such areas and theirassociated plant capacity should be excludedfrom the calculation of the CPR. However, inorder to facilitate comparison with operationalperformance, such discounted loads should beseparately metered (see paragraph 3.6d)). Foran illustration of this calculation method, seeAppendix G.

1.64 For new ACMV systems, compliancewould be achieved if the CPR is no greaterthan the values shown in Table 11.

If both new air conditioning and mechanicalventilation systems are to be installed in abuilding, the system types and their treatedareas should be dealt with separately and theappropriate CPR achieved for each.

1.65 For a building that already contains anACMV system and substantial alteration isbeing made to that existing ACMV system,compliance would be achieved if the CPR isimproved (i.e. reduced) by 10% as a result of

the work, or does not exceed the values inTable 11 column b), whichever is the leastdemanding.


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Table 11 Maximum allowable Carbon

Performance Ratings

Maximum CPR (kgC/m2/year)for a new system installed in:

System type a) a new b) an existingbuilding building

Air conditioning 10.3 11.35

Mechanicalventilation 6.5 7.35


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1.66 When the work solely comprisesreplacement of existing equipment, the productof the installed capacity per unit treated area(P) and the control management factor (F)should:-

a) be reduced by at least 10%, OR

b) meet a level of performance equivalent to

the component benchmarks given in CIBSETM2244 (i.e. the product of service provision,efficiency and control factor), whichever is theleast demanding.

Methods for other buildings with ACMV

1.67 For other buildings, it is only possible atpresent to define an overall performancerequirement for the mechanical ventilationsystems (whether or not the air being suppliedand/or extracted is heated or cooled). In suchcases, the requirement can be met if thespecific fan power (SFP) is less than the values

given in the following sub-paragraphs. Thespecific fan power is the sum of the designtotal circuit-watts, including all losses throughswitchgear and controls such as inverters, ofall fans that supply air and exhaust it back tooutdoors (i.e., the sum of supply and extractfans), divided by the design ventilation ratethrough the building.

a) for ACMV systems in new buildings,the SFP should be no greater than2.0 W/litre/second.

b) for new ACMV systems in refurbishedbuildings, or where an existing ACMV system in

an existing building is being substantiallyaltered, the SFP should be no greater than3.0 W/litre/second.

These SFP values are appropriate to typicalspaces ventilated for human occupancy.Where specialist processes or higher thannormal external pollution levels requireincreased levels of filtration or air cleaning,higher SFPs may be appropriate.

1.68 Mechanical ventilation systems should bereasonably efficient at part load. One way toachieve this would be to provide efficient

variable flow control systems incorporating forinstance variable speed drives or variable pitchaxial fans. More detailed guidance on thesemeasures is given in GIR 4145.

Whole-building Method

1.69 To show compliance following the Whole-building Method, the carbon emissions orprima

Build Regs L2

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