The latest Part L changes were released on 15th December 2021, so you’d be forgiven for perhaps not yet being quite aware of all the ins and outs of this latest uplift in Building Regulations standards – just before Christmas is certainly not the easiest time to assimilate such essential new knowledge!

As yet, there is no SAP 10.2 software available to accurately analyse the impact that these Part L changes will have on Building Regulations applications from 15th June 2022, we must currently rely upon the 10.1 Beta version, and of course there will be a number of changes that will need to be factored in.

So what are the key changes to Part L of the Building Regulations that have been announced? Here’s our summary:

  • Commencement of works will now related to individual plots, rather than entire sites. This measure has been brought in to prevent large phased developments being built under previous versions of Part L, thus avoiding the changes implemented to improve energy efficiency.
  • A proper analysis of high efficiency alternative heating systems must be undertaken for each new dwelling or building (Regulation 25A). Although this has been a requirement since Part L 2013, in practice it has rarely been asked for by Building Control. The scope and detail of Regulation 25A has also been expanded. 
  • The process for confirming continuity of insulation and thermal bridging details has been made more rigorous in the latest changes to Part L. On-site audits, including photographs, will now be required for each dwelling. SAP assessors will need to have copies of all sign-off sheets and photographs before they are able to provide as-built reports and EPCs.
  • Specific thermal bridging calculations may be required for each build, rather than relying on current accredited construction details. We are awaiting the release of updated software, but plan to have the ability to complete these calculations as part of our services by June 2022.
  • Air tightness testing will now need to be undertaken for every plot, rather than a proportion of each dwelling type on a development.
  • Developers will need to supply a Home User Guide for every plot upon completion. This must contain information on the installed services, and include an overheating assessment under Part O.
  • Under the latest Part L changes, heating systems will need to be designed to operate at lower flow temperatures, to facilitate the use of heat pumps. In practice, this means that radiators will need to be bigger than for a conventional boiler-fired heating system.
  • Lighting efficiency is now to be included within SAP calculations, with the number of lamps recorded.
  • Unsurprisingly, the Part L changes have been written to move away from gas and towards heat pump installation. Gas heating will be difficult to design in accordance with this latest version of the Building Regulations, due to the Primary Energy Rate calculation. We have been running tests using our Beta software, and we can only achieve compliance for a gas system when PV is also added to the specification. Developers will likely have to cmake a choice between heat pumps or gas boilers with a long list of upgrades in addition.
  • As well as the Part L changes, a new Approved Document O on Overheating Mitigation was released on 15th December. This legislation needs to be considered in conjunction with the uplifted standards of Part L, as it sets maximum glazing percentages for schemes as well as the need for an overheating assessment, which may impact SAPs in terms of shading, glazing performance, MVHR etc.
  • Additionally, there is a new Approved Document S on Infrastructure for the charging of electric vehicles. While not directly related to SAPs, it is something that you would have to take into account under the new legislation.


To find out more about how we can help you to achieve Building Regulations compliance in the light of the latest Part L changes, call us on 01206 266755 or email