Thermal regulations

Thermal regulations

Building Regulations Approved Document Part L - England

Building regulations in England set the standards for the energy performance of new and existing buildings and are currently set out in four parts -  L1A, L1B, L2A, L2B - for different building classifications. In essence Part L comprises of higher standards for windows, and the efficiency of heating, domestic hot water systems, mechanical ventilation, air conditioning and lighting as well as the building fabric.

The 2013 revised version of ‘Approved Document L: Conservation of fuel and power’ came into force on 6th April 2014 and for the first time covers England only.

For England the new 2013 ADL will require New Dwellings to deliver a further 6% reduction in CO2 emissions above 2010 standards and New build Non-Domestic an average 9% aggregate reduction above the 2010 standards.

The new carbon reduction measures are less than were initially expected, with Government looking to strike a balance between economic growth and zero carbon goals.

However despite the Government's commitment to update standards so that all new buildings will be close to ‘zero carbon’ by 2016, zero carbon remains under review after the policy was scrapped in 2015.

The next planned update to the Building Regulations, for both England and Wales, is expected in 2017/2018.

The latest set of amendments to Part L for England came into force on 6 April 2016 and can be found at:

Part L 2014 - Wales

Wales introduced their own version of Approved Document L on 31st July 2014, based on the same methodology but with different targets. These will affect those builders who build across both England and Wales.

More information can be found at:

The significant difference between the two sets of regulations for new homes is that the Welsh Government are not including a Fabric Energy Efficiency Standard as has been the case in England. To ensure that the fabric of the new home still performs adequately, the elemental backstops have been significantly tightened and are now mandatory so limiting the potential to relax the performance of those elements when altering the 'recipe'.

  2010 Value 2014 Mandatory Value
Roof (W/m2.K) 0.20 0.15
Wall (W/m2.K) 0.30 0.21
Floor (W/m2.K) 0.25 0.18
Party Wall (W/m2.K) 0.20 0.2
Windows/Doors (W/m2.K) 2.00 1.6
Air Tightness (m3/hr.m2) 10 10

Scottish Building Regulations

Scottish Building Regulations followed in 2015 for both domestic and non-domestic buildings with the intention of Section 6 to ensure that effective measures for the conservation of fuel and power are incorporated into buildings.  

The biggest change in this regulation came in 2007 with the transition to a single methodology for assessing carbon dioxide emissions for both carbon and energy performance in new buildings. 

Scotland published their Climate Change Act in 2009 which set an interim target of a 42% reduction in emissions by 2020 raising to 80% by 2050 when compared to 1990 emission levels. 

The introduction of the 2015 revision to Section 6 has seen the following reduction in emissions CO² being required:


  • 45% reduction in CO² emissions over 2007
  • 21% reduction in CO² emissions over 2010


  • 60% reduction in CO² emissions over 2007
  • 43% reduction in CO² emissions over 2010

The Technical Handbooks can be found here:



This Scottish Government presentation explains the changes made to Section 6 (Energy: Domestic 2015 changes) in October 2015: