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Building Regulation Note 1/2003

DescriptionPart J of the Technical Standards as applied to windows, doors and rooflights to alterations, extensions and replacements in existing dwellings
Official Print Publication Date
Website Publication DateFebruary 21, 2003


    Building Regulation Note 1/2003

    Part J of the Technical Standards as applied to windows, doors and rooflights to alterations, extensions and replacements in existing dwellings

    This document is also available in pdf format (35k)

    Distribution List enclosed
    Our ref: QTD 1/5

    21 February 2003

    Dear Sir or Madam

    Enclosed for your information is a copy of Building Regulation Note 1/2003.

    On 1 March 2003, the full effect of the elemental U-value changes in the Sixth Amendment to the Technical Standards will apply. The main purpose of this Note is to provide additional guidance on this subject to the glass and glazing industry, building contractors, local authorities, surveyors and designers and specifiers in general.

    Any enquiries regarding this Note should, in the first instance, be directed to:

    Gavin Peart
    Scottish Executive
    Building Standards Division
    Area 2-H
    Victoria Quay
    EH6 6QQ
    Tel: 0131 244 7452
    Fax: 0131 244 0404
    Email: gavin.peart@scotland.gsi.gov.uk

    Yours faithfully

    DR J P CORNISH signature

    Head of Building Standards

    Note No 1/2003



    1. Class Relaxation Direction 140 expires at the end of this month. On 1 March 2003 the full effect of the elemental U-value changes in the Sixth Amendment to the Technical Standards for compliance with the Building Standards (Scotland) Regulations 1990 will apply. The main purpose of this Building Regulation Note is to provide additional guidance on this subject to the glass and glazing industry, building contractors, local authorities, surveyors and designers and specifiers in general. Paragraphs 11, 12 and 13 of this Note give guidance on some miscellaneous technical glazing issues.

    Public awareness of changes

    2. For the purpose of making the general public aware of these changes, there is a page at the back of this document entitled "Energy-efficiency of replacement windows". You are invited to photocopy that page and use it as an information handout for general distribution. (Note:- If you do photocopy the page, please note that this document is part of a Scottish Executive publication and should not be amended or re-presented in any way).

    Transitional provisions

    3. The expiry of the Class Relaxation Direction will have the same effect as if new Technical Standards were to be introduced for glazing work on existing dwellings. In view of this, we have been requested to give guidance on transitional arrangements for replacement windows, doors and rooflights and for this, the following is recommended:

    • Class Relaxation Direction 140 applies to installations where contracts between the customer and the installer were signed before 1 March 2003; and
    • the work on these contracts should then commence before 1 May 2003; and
    • the work on these contracts should be completed by 30 June 2003; however
    • installation contracts signed on or after 1 March 2003 will need to be designed and built to the more demanding (lower) U-values (see paragraph 4 below).

    4. It should be stressed that this is not a postponement of the Technical Standards requirements. It is purely a mechanism that will allow existing glazing contracts to be met, whilst attempting to achieve a seamless shift to glazing of improved performance.

    5. For installations that form the subject of a building warrant to alter or extend a dwelling, the date that the building warrant was lodged will determine whether or not the Class Relaxation applies. Such applications lodged with local authority building control on 1 March 2003 or a later date will be subject to the full effect of the Sixth Amendment to the Technical Standards.

    Glazing and energy-efficient boilers

    6. Most of the existing dwellings will have heating systems that are not particularly energy efficient, in which case the elemental U-values of the new doors windows and rooflights will need to be:

    • 1.8 for those with plastic or timber frames
    • 2.0 for those with metal frames

    7. Some dwellings may be fitted with energy-efficient boilers that have SEDBUK ratings which are equal to or exceed the value in the table below:

    Minimum boiler SEDBUK which allows less demanding (higher) U-values to be used

    Central heating system fuel and boiler type

    Minimum SEDBUK (%)

    Mains natural gas (all boiler types)


    LPG (all boiler types)


    Oil (combination boilers)


    Oil (all other types of boilers)


    SEDBUK is a measure of energy efficiency for domestic boilers and is fully defined in "The Government's Standard Assessment Procedure for Energy Rating of Dwellings" 2001 edition (SAP 2001).

    8. The ratings in the table above enable the following less demanding (higher) U-values to be adopted for windows, doors and rooflights in dwellings:

    • 2.0 for those with plastic or timber frames
    • 2.2 for those with metal frames

    9. This energy efficiency trade-off should be allowed to take place where appropriate. The responsibility to check the boiler and establish the SEDBUK, however, should not rest with the glazing installer. We suggest that if the customer wishes to make use of this trade-off, they should confirm in writing the following to the glazing installer:

    • The make of the boiler; and
    • The fuel and boiler type; and
    • The SEDBUK

    The glazing installer can then check the rating the customer supplies against the table in this Note.

    10. If the customer cannot establish the information listed above for him or herself, the heating engineer who either installed the boiler or who services the boiler may be able to assist. In the absence of such information being provided by the customer, the glazing installer should design and install to the more demanding (lower) U-values.

    Roof window and rooflight

    11. A roof window can be considered to be a rooflight when using Part J. For the purposes of establishing thermal transmittance however, roof windows can be assessed in the vertical plane similar to a traditional window in an external wall. This will enable both BS EN ISO 10077-1:2000 and prEN ISO 10077-2:2000 to be used.

    Window and door system U-values - provision of certified data

    12. Tables A1, A2 and A3 of Appendix A to Part J of the Technical Standards give some indicative U-values for windows. These tables have a cautious approach as far as the design of windows, doors and rooflights is concerned. The Glass and Glazing Federation (GGF) Data Sheet 2.2 describes alternative methods of assessing the thermal performance of such elements. It is acceptable to use this Data Sheet as an alternative approach. This is consistent with the guidance given in the Building Research Establishment publication "Conventions for U-value calculations" (BR 443).

    Trade-off between windows, doors and rooflights of different U-values

    13. Appendix E in Part J demonstrates the method for trading off the U-values for individual windows, doors and rooflights. This ensures that the average for the entire installation does not exceed 1.8 W/m 2K for those with wood or plastic frames or 2.0 W/m 2K if they have metal frames. Where a mixture of framing materials is proposed, such a trade-off can only occur between windows, doors and rooflights of the same frame category. i.e., timber and plastic frames being one category and metal being the second category.

    Further Information

    14. Current Building Regulation Notes, Technical Standards and Class Relaxation Directions may be found on the Scottish Executive Building Standards Division website at - www.scotland.gov.uk/development/bc

    15. GGF Data Sheet 2.2 can be obtained from -

    The Glass and Glazing Federation Publications Department
    44-48 Borough High Street
    SE1 1XB
    Telephone: 020 7403 7177
    Fax: 020 7357 7458

    16. SAP 2001 can be found at - www.projects.bre.co.uk/sap2001

    17. SEDBUK ratings for boilers are available at - www.sedbuk.com

    18. Further information is available from:

    Scottish Executive
    Building Standards Division
    Victoria Quay
    EH6 6QQ
    First enquiries to: Gavin Peart
    Telephone: 0131 244 7452
    Fax: 0131 244 0404

    Energy-efficiency of Replacement Windows

    This "Question and Answer" handout on replacement windows for dwellings has been produced by the Building Standards Division of the Scottish Executive. It will complement the leaflet entitled "Low Emissivity Glass - Conserve Scotland's Fuel and Power", which has been produced for the benefit of the general public and industry by the Glass and Glazing Federation. The Executive welcomes the initiative taken to produce this leaflet.

    What is the purpose of this handout?

    This handout is to make you aware that, from the beginning of March 2003, better standards of energy-efficiency are required from replacement windows. This is a result of the Sixth Amendment to the Building Standards (Scotland) Regulations. In most existing dwellings, replacement windows will then need to have a U-value of not more than:

    • 1.8 for windows with plastic or wooden frames
    • 2.0 for windows with metal frames

    What is a U-value?

    A U-value is a measure of heat-loss from a building;, the lower the value the better the performance.

    Can I put in windows of poorer performance?

    Generally, no. However there are sometimes exceptions:

    • When a particularly energy-efficient gas or oil-fired central heating boiler has recently been installed in your house, your replacement windows may be able to have a slightly lower standard. If you think your boiler may qualify, speak to your glazing installer who will be able to advise on the written confirmation that he needs from you; or
    • If you put in windows that are close to being identical to the ones that you are taking out. This will usually occur when your house is "Listed" as being of historic interest.

    How will anyone be able to tell if I don't install the correct windows?

    If you don't have the correct windows installed, you could be storing up trouble for the future. When you eventually come to sell your house, a surveyor may use a glass analysis gauge to establish whether or not the correct glass has been used. If the glazing is wrong, you may have problems with the house sale.

    Do I need building control approval?

    No, but your windows do need to comply with all other appropriate aspects of the Technical Standards to the Scottish building regulations - e.g. emergency escape, safe-cleaning, safety-glass and ventilation.

    What about windows in an alteration or extension to a dwelling?

    Generally the contents of this leaflet are still appropriate, but you will need building control approval from your local council. Their number is in the phone book and they will be able to advise on the drawings and specifications they need to process your application.



    Accounts Commission
    Anglian Windows Ltd
    Architects and Surveyors Institute
    Architectural Heritage Society of Scotland
    Association for the Conservation of Energy
    Association of British Solid Fuel Appliances Manufacturers
    Association of Building Component Manufacturers Limited
    Association of Building Engineers
    Barbour Index Ltd plc
    Barratt Homes Limited
    Beazer Homes Plc
    Bell College of Technology
    Bett Homes
    Boiler and Radiator Manufacturers Association
    Bovis Construction (Scotland) Limited
    British Board of Agrément
    British Institute of Architectural Technologists
    British Plastics Federation Windows Group
    British Rigid Urethane Foam Manufacturers Association
    British Standards Institution
    British Woodworking Federation
    Building Regulations Advisory Committee (England & Wales)
    Building Research Establishment
    Building Research Establishment (Scotland)
    Building Services Research and Information Association
    Building Societies Association
    Building Standards Advisory Committee
    Bullen Consultants
    Cala Homes (Scotland) Ltd
    Caradon Doors and Windows Limited
    Care and Repair Forum
    Carillion Specialist Services Ltd
    Century 21 Replacement Window Co Ltd
    Chartered Institute of Building
    Chartered Institute of Building in Scotland
    Chartered Institute of Building Services Engineers (Scotland)
    Chartered Institute of Housing in Scotland
    Complete Picture UK
    Confederation of British Industry (Scottish Office)
    Construction Industry Research & Information Association
    Construction Products Association
    Construction Service - Northern Ireland
    Convention of Scottish Local Authorities (CoSLA)
    Cruden Homes (Scotland) Ltd
    Department of the Environment - Republic of Ireland
    Door and Shutter Manufacturers Association
    Edinburgh Architectural Association
    Energy Action Scotland
    Eurisol UK Limited
    Everest Ltd
    Fire Service College
    Flat Glass Association
    Glasgow Caledonian University
    Glasgow College of Building and Printing
    Glass and Glazing Federation
    Heating and Ventilation Contractors Association
    Heating and Ventilation Manufacturers Association
    Health and Safety Executive
    Heriot-Watt University - Department of Building Engineering & Surveying
    Historic Scotland
    Independent Glass Ltd
    Institute of Energy
    Institution of Mechanical Engineers
    Institution of Plant Engineers
    Institution of Structural Engineers
    J Smart & Co
    Kingspan Insulation
    Local Authority Chief Executives
    Masonry Industry Alliance
    McLean Homes (Scotland)
    Ministry of Defence Estate Organisation
    Muir Construction Limited
    Napier University
    National Association of Hospital Fire Officers
    National Cavity Insulation Association
    National House Building Council (NHBC) Scotland
    NHS in Scotland - Healthcare, Engineering & Environment Unit
    Office of the Deputy Prime Minister (ODPM) - Building
    Regulations Division
    Paisley University
    Penicuik Windows and Conservatories
    Phenolic Foam Manufacturers Association
    Pilkington Brothers Limited
    Polyethylene Foam Insulation Association
    Ratcliffe Grove Partnership
    Ravensby Glass Co Ltd
    Royal Environmental Health Institute of Scotland
    Royal Incorporation of Architects in Scotland
    Royal Institution of Chartered Surveyors in Scotland
    Royal Society of Health
    Solaglass Ltd
    Scotia Double Glazing Ltd
    Scottish Association of Chief Building Control Officers
    Scottish Building
    Scottish Civic Forum
    Scottish Construction Environment Group
    Scottish Court Service
    Scottish Federation of Housing Associations
    Scottish Firemasters
    Scottish Gas
    Scottish & Northern Ireland Plumbing Employers Federation
    Scottish Parliament Information Centre
    Scottish Prison Service
    Scottish Timber Trade Association
    CR Smith
    Society of British Gas Industries
    Solid Fuel Advisory Service Scotland
    Strathclyde Glass Ltd
    Strathclyde University
    Technical Indexes Ltd
    The Federation of Environmental Trade Association
    Thermal Economics Limited
    Thermal Insulation Contractors Association
    Timber Frame Industry Association (TFIA)
    Timber Research & Development Association: Scottish Registered Office
    Total Window Systems
    Trade Windows (Scotland) Ltd
    University of Dundee, Dept of Civil Engineering
    University of Edinburgh, Dept of Architecture
    Walker Homes (Scotland) Limited
    Wimpey Homes Holdings Limited
    Window Advice Centre
    Wood Wool Slab Manufacturers Association
    Yule, AC