Summary of Part L 2013


The new Approved Documents for Part L of the Building Regulations in England were published by the Government’s Department for Communities and Local Government (CLG) in 2013.  They came into effect on 6th April 2014.  The corresponding Approved Documents for Wales will be in force from 31st July 2014.

Headlines for Part L (England) 2013:

  • New homes need to emit 6% less carbon dixoxide (CO2) than previously
  • 9% reduction in CO2 emissions for new non-dwellings
  • Introduction of Fabric Energy Efficiency Standard for new dwellings
  • No changes to Window Energy Ratings (WERs) or Window U values in exisiting dwellings:
    • Minimum band C for WERs
    • Maximum Window U value of 1.6 W/m2K
  • Introduction of Doorset Energy Ratings (DSER) for existing dwellings (minimum band E)
  • Restrictions remain in place on the use of centre pane U-values in measuring compliance
  • Recognition of the benefits of supplementing existing single glazing with low-e secondary glazing
  • No major changes to window requirements in exisiting non-dwellings  

Headlines for Part L (Wales) 2014:

  • 8% aggregate reduction in CO2 emissions (domestic)
  • 20% aggregate reduction in CO2 emissions (non-domestic)
  • Mandatory limiting fabric standards (domestic)
  • Consequential improvements extended (triggered by extensions)
  • No change for domestic window and door replacements:
    • Minimum band C for WERs
    • Maximum Window U value of 1.6 W/m2K
  • Current exemption for conservatories remains (subject to conditions)

Further information

For more information on Part L 2013, or our range of products, please contact our Technical Advice Centre (email us at or phone on 01744 692000).