Part L Explained by Crittall Windows Ltd

CI/SfB / / (31.4) / Xh2 / / June 2006 Catalogue No. 260X

S T E E L

Revised

PART L Explained

W I N D O W S

revised

PART L

The Revised Regulations

explained...

exempt from the Building Regulations. Conservatories

Introduction

L1A Work in New Dwellings

larger in area than 30 sq m have alternative requirements

The three routes to compliance set out in the 2002 version

• Achieve a maximum whole window U-value

of Part L are scrapped. In future The Target carbon dioxide

as follows:

of 2.0 W/m2K, or

With effect from April 2006 a revised Building Regulations

Emission Rate (TER) is required (see Definitions). Calculations

Approved Document Part L (Conservation of Fuel and

are required for both the designed and constructed

Power) was published. This supersedes the Part L document

home and the Target Emissions Rate must be the lower

published in April 2002.

of the two.

Heritage

The revised Part L differs from its predecessor in a number

The calculations (which require government SAP software)

Special allowance is made for buildings of historic,

of fundamental ways:

take account of solar transmittance of the glazing as

architectural or conservation value. (See page 5).

• Achieve a maximum glass centre pane value of 1.2 W/m2K.

well as heat loss, and so the energy aspects of the glazing • It is published in four, rather than two parts covering New

are taken into account.

L2A New Buildings Other Than Dwellings

For new dwellings the area-weighted maximum average

As with document L1A, the designer must calculate total

window U-value is 2.2 W/m2K. – the worst individual

carbon dioxide emissions for both the proposed and

element can have a U-value of 3.3 W/m2K.

completed building.

L1B Work in Existing Dwellings

Windows and rooflights can have an area-weighted

Dwellings, Existing Dwellings, New Buildings Other Than Dwellings and Existing Buildings Other Than Dwellings. • It scraps the three alternative routes to compliance in the 2002 document i.e. the Target U Value Method; the Elemental Method; and the Carbon Index Method. • In respect of windows the new Part L makes no

There are alternative methods of meeting the requirements

differentiation between different framing materials.

of the revised Part L for replacement windows as follows:

maximum average of 2.2 W/m2K. In cases where the building has a high internal heat gain there is allowance for this U-value to rise to 2.7 W/m2K.

Irrespective of the materials selected the designer must achieve either a specified whole window or maximum

• Achieve a whole window U-value of 2.0 W/m2K, or

average U-value or a maximum centre pane U-value.

• Achieve a glass centre pane U-value of 1.2 W/m2K, or

An alternative, where applicable, is a specified Window

should be no worse than 3.3 W/m2K.

• Achieve a window Energy Rating of Band E

Energy Rating.

Curtain Walling is now included within the scope of the

Extensions

revised regulations as follows:

flexibility in the manner in which they combine the

As a general rule the area of windows, roof windows

A limiting U-value of 2.2 W/m2K (area-weighted average)

attributes of the various building components and services

and doors in extensions should not exceed the sum of

or 3.3 W/m2K (for any individual element) should be

to meet the target carbon emissions rating for the structure.

25% of its floor area PLUS the area of any windows and

applied to the glazed area of the curtain wall. Display

doors that, as a result of the building work, no longer

windows are excluded from the regulations. There is no

exist or are exposed.

limit on the design flexibility for display windows but

The standard for new windows, roof windows or rooflights

in calculations.

The revised Part L offers the designer and specifier enhanced

Exclusions In this respect, no single building component can accurately be described as ‘complying with Part L’ but

The following are specifically excluded from

rather can contribute towards the level of compliance

the revised Part L:

their impact on CO2 emissions must be taken into account in extensions should be as follows:

that designers must in future be able to demonstrate. 1. Windows, doors and rooflights or roof The revised Part L tightens the requirements for energy

windows having less than 50% glazing

• Achieve a whole window U-value of 1.8 W/m2K, or

efficient building components established by its

on the internal face.

• Achieve a glass centre pane U-Value of 1.2 W/m2K, or

predecessor. It applies to windows in new build and replacement situations.

2. Display windows, shop entrance doors and similar glazing in buildings in use classes A1, A2, A3 and D2.

As this brochure demonstrates, designers can continue to specify steel windows with the confidence that they will form part of the building envelope demanded by the new regulations.

The U-value of any individual window, rooflight or door

• Achieve a Window Energy Rating of Band D

There are alternative methods of meeting the requirements of the revised Part L for replacement windows as follows:

The U-value of any individual window, rooflight or door should be no worse than 3.3 W/m2K.

• Achieve a whole window U-value of 2.2 W/m2K, or • Achieve a glass centre pane U-value of 1.2 W/m2K

3. Conservatories with a floor area less than 30 sq m.

L2B Work In Existing Buildings That Are Not Dwellings

Conservatories

• Achieve a Window Energy Rating of Band E

Conservatories with a floor area less that 30 sq m are

Display windows are excluded from these requirements.

Historic Buildings

and others of special character

• Achieve a maximum whole window U-value of 2.2 W/m2K, or • Achieve a maximum glass centre pane value of 1.2 W/m2K In cases where the building has a high internal heat gain

Heritage

there is allowance for the whole window U-value to rise to 2.7 W/m2K.

It is often the case that existing buildings with steel

energy efficiency where, and to the extent that it is,

windows are buildings of an historic nature. As with its

practically possible, provided that the work does not

predecessor the latest version of Part L also recognises that

prejudice the character of the host building or risk the

there is a need to conserve the special characteristics of

long-term deterioration of the building fabric or fittings.

historic buildings, taking fully into account the views

The guidance given by English Heritage in its guidance

previously expressed by English Heritage.

note Building Regulations and Historic Buildings first published in 2002 should be taken into account.

Special allowance is made for buildings of historic, architectural or conservation value. (See page 5).

Extensions

the building on which work is to be carried out has

These include conventional extensions as well as enclosing

particular historic or architectural merit. Such buildings

existing structures that are partially enclosed (e.g. –

Definitions

covering over a courtyard).

TER is the Target carbon dioxide Emission Rate which is

are defined as follows: defined as the minimum energy performance required

A. Listed buildings

A balance needs to be struck between historic building conservation and energy efficiency improvements. The local authority’s conservation officer should always be approached for advice in these circumstances.

The revised document differentiates between large and

for new dwellings, expressed in terms of the mass of CO2

small extensions. Where an extension is greater than 100

emitted as a result of the provision of heating, hot water,

B. Buildings of local architectural and historical interest

establish the character of an elevation; they should not

sq m in area and greater than 25% of the floor area of the

ventilation and internal fixed lighting. The method of

and which are referred to as a material consideration

generally be altered in their proportion or details, especially

existing building it is to be regarded as a new building

calculating the TER is specified in L1A Page 16 of the

in a local authority’s development plan

when they are a conspicuous element of the design.”

and designers must refer to L2A for guidance.

Approved Document.

For smaller extensions the alternatives are as follows for

U-values shall be calculated using the methods and

new windows in extensions:

conventions set out in Building Regulations 443.

• Achieve a whole window U-value of 1.8 W/m2K, or

Scotland

C. Those buildings situated in conservation areas, national parks, areas of outstanding natural beauty and world

came into effect in May 2005. The Scottish Building Standards Agency was initiating a consultation in March

Conservatories with a floor area less that 30 sq m are

2006 on proposed changes to the regulations governing

exempt from the Building Regulations. Conservatories

energy efficiency with a view to bringing those changes

larger in area than 30 sq m have alternative requirements

into effect from May 2007.

L1A

2.2

(New Dwellings)

(maximum average)

L1B

2.0

(Existing Dwellings)

(whole window)

Extensions

(whole window)

1.8

Conservatories

2.0

(more than 30 sq m)

(whole window)

L2A

2.2

(New Non Dwellings)

(maximum average)

L2B

2.2

(Existing Non Dwellings)

(whole window)

Extensions

(whole window)

1.8

Conservatories

2.2

(more than 30 sq m)

(whole window)

conservation officer would be beneficial include:

A. restoring the historic character of a building that had

Centre Pane Value W/m2K

Relaxations

N/A

1.2

N/A

1.2

N/A

1.2

N/A

(with high internal heat gain)

1.2

(with high internal heat gain)

1.2

N/A

1.2

N/A

2.7 2.7

These definitions cover a wide range of properties, either as individual structures or within the context of their neighbourhood.

replacement windows, doors and rooflights B. rebuilding former historic buildings e.g. after a fire or in-filling a gap site in a terrace

When undertaking work on or in connection with

C. making provisions enabling the fabric of historic

buildings of special historic or architectural value, the

buildings to “breathe”, so to control moisture and

revised documents say the aim should be to improve

potential long-term decay problems

U-Value

as follows: U-Value W/m2K

Particular instances where advice from the local authority

conservation officer has advised that special considerations should apply in the particular case

The current version of the Building (Scotland) Regulations

Conservatories

Document

heritage sites where the local planning authority’s

English Heritage is quite clear that “window openings

been subject to previous inappropriate alteration e.g.

• Achieve a glass centre pane U-value of 1.2 W/m2K

Under the revised Part L special considerations apply if

For residential projects

Crittall Products

Crittall offers:

Crittall offers the designer and specifier a range of steel windows, any of which can be used with confidence in contributing to a design that meets the requirements of the revised Part L of the Building Regulations which came

FAQs

into force in April 2006. All products are hot-dipped galvanised and Duralife polyester powder coated to the specifier’s colour choice.

Q. When did the revised Part L come into effect?

Steel-framed windows also offer a slim profile and

A. On April 6, 2006.

unmatched strength for added security.

ALL CRITTALL STEEL WINDOW PRODUCTS MEET THE CENTRE PANE U-VALUE OF 1.2 W/m2K.

Q. Will it apply to building work started before this date? A. It will not apply if work started before April 6 2006 with full building plans approval. If plans have been fully

The range of Crittall products include:

approved but work has not started before this date, it must start by April 1 2007, otherwise the new regulations

Corporate 2000 Range

Corporate W20 Range

Homelight Range

A high performance steel window and door range particularly

Extensively used in refurbishment projects and versatile

These offer the same size and styles as the original imperial

suited to new build projects.

in design.

range of steel windows.

Indicative U-value range of 1.9 W/m2K – 2.5 W/m2K

Indicative U-value range of 1.7 W/m 2K – 2.4 W/m 2K

Indicative U-value for Homelight L 1.7 W/m2K – 2.1 W/m2K

depending on configuration, glass type and size.

Centre Pane U-value 1.2 W/m2K using 4mm float, 4mm low

Centre Pane U-value 1.2 W/m2K using either 4mm float,

Centre Pane U-value 1.2 W/m2K using 4mm float, 4mm low

A. No. They will apply in England and Wales. See separate

4mm low E soft coat and 6mm air gap (xenon gas) or 4mm

E soft coat and 6mm air gap (xenon gas) – DG Range; or

paragraph on Scotland. In Northern Ireland, amendments

float, 4mm low E soft coat and 8mm air gap (krypton gas).

4mm float, 4mm low E soft coat and 16mm air gap (argon

to Part F of the Building Regulations (Northern Ireland)

gas) – L Range.

came into force in June 2006.

will apply.

Q. Are Part L regulations mandatory? A. Yes, they are.

E soft coat and 20mm air gap (argon gas).

Full details on each product range with steel performance technical information are available from Crittall on:

www.crittall-windows.com

Q. Do they apply throughout the UK?

Q. Which part of the regulations apply if a new building is constructed with areas used for accommodation and for commercial purposes? A. Approved Document L1A should be used for guidance in relation to individual dwellings within the building

Or contact:

and Approved Document L2A for the non-dwelling parts of a building e.g. in the case of a mixed use

Technical Department,

development, for commercial or retail elements. NB:

Crittall, Springwood Drive, Braintree, Essex CM7 2YN.

the term ‘dwelling’ refers to self-contained dwelling

Tel: 01376 324106 Fax: 01376 349622.

units. Buildings that contain ‘rooms for residential

Email: hq@crittall-windows.co.uk

purposes’ e.g. in nursing homes, are not considered to be dwellings per se and so Approved Document L2A would apply.

Crittall is a member of FENSA.

Crittall Windows Limited, Springwood Drive, Braintree, Essex, CM7 2YN Tel: +44 (0) 1376 324106 Fax: +44 (0) 1376 349662 Email: hq@crittall-windows.co.uk www.crittall-windows.com Crittall Windows Limited, Scottish Regional Office 39 Durham Street, Glasgow G41 1BS Tel: +44 (0) 141 427 4931 Fax: +44 (0) 141 427 1463

Further Information Building Regulations Approved Document Part L (Conservation of Fuel and Power) Building Regulations 443 (2002) (U-values) NB: currently under review Available from Department for Communities and Local Government (formerly the Office of the Deputy Prime Minister). Copies and supporting information can be downloaded from the ODPM website at: www.odpm.gov.uk/index.asp?id=1130474 Building Regulations and Historic Buildings: An interim guidance note on the application of Part L Published by English Heritage (2002 – reprinted 2004) can be downloaded from the English Heritage website at: www.english-heritage.org.uk/server/show/nav.1046 This publication gives a general description of the product and materials. It is the responsibility of the user of this document to ensure that their use is appropriate for any particular application and that such application complies with all relevant local and national legislation, standards, codes of practice and other requirements. Crittall Windows Ltd hereby disclaim all liability howsoever arising from any error in or omission from this publication and all consequences of relying on it. Crittall Windows Limited also reserve the right to modify the details in this publication as products and specifications are updated and improved.

Crittall™, Homelight™, Corporate™, and Duralife™ are registered trademarks.