Building Regulations Approved Document L1 - Conservation of Fuel & Power in Dwellings

This Approved Document, which took effect on 1 April 2002, deals with the following Requirements which are contained in the Building Regulations 2000 (as amended by SI 2001/3335):


L1. Reasonable provision shall be made for the conservation of fuel and power in dwellings by -

  1. limiting the heat loss:
    1. through the fabric of the building;
    2. from hot water pipes and hot air ducts used for space heating;
    3. from hot water vessels
  2. providing space heating and hot water systems which are energy efficient;
  3. providing lighting systems with appropriate lamps and sufficient controls so that energy can be used efficiently;
  4. providing sufficient information with the heating and hot water services so that building occupiers can operate and maintain the services in such a manner as to use no more energy than is reasonable in the circumstances.



  • Performance
  • Introduction to provisions
    • Technical risk
    • Thermal conductivity and transmittance
    • U-value reference tables
    • Calculation of U-values
    • Roof window
    • Basis for calculating areas
    • Air permeability
    • Standard assessment procedure (SAP)
    • Historic buildings

Design and Construction

  • Alternative methods of showing compliance
  • Elemental method
    • U-values for construction elements
    • Heating efficiency
    • Areas for windows, doors and rooflights
    • Extensions to dwellings
    • Summary of provisions in the Elemental Method
    • Target U-value method for new dwellings
    • Optional allowance for solar gains
  • Carbon Index method
  • Constraints when using the calculation procedures
    • Poorest acceptable U-values
  • Limiting thermal bridging at junctions and around openings
  • Limiting air leakage
  • Space heating system controls
    • Zone controls
    • Timing controls
    • Boiler control interlocks
  • Hot water systems
  • Alternative approach for space heating and HWS systems
  • Commissioning of for heating and HWS systems
  • Operating and maintenance instructions for heating and HWS system controls
  • Insulation of pipes and ducts
  • Internal lighting
  • External lighting fixed to the building
  • Conservatories

Work on Existing Dwellings

  • Replacement of controlled services or fittings
  • Material alterations
  • Material changes of use
  • Historic buildings


  • Appendix A : Tables of U-values
  • Appendix B : Calculating U-values
  • Appendix C : U-values of ground floors
  • Appendix D : Determining U-values for glazing
  • Appendix E : Target U-value examples
  • Appendix F : SAP Ratings and Carbon Indexes

Source:   ODPM

             (Crown copyright material is reproduced with the permission of the Controller of HMSO and the Queen's Printer for Scotland.)

For more information on this source please visit Office of the Deputy Prime Minister.

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