InSite | Wales new building regulations for energy efficiency, ventilation and overheating

Wales new building regulations for energy efficiency, ventilation and overheating

Published date: 23 November 2022

Amendments to building regulations are being made in Wales. There are changes to Parts F (ventilation) and L (conservation of fuel and power), alongside new Approved Documents L and F that give guidance on application. In addition, a new Part O for overheating has been introduced with a new Approved Document. These are in association with amendment regulations to the Building Regulations, and all of these applied from 23rd November 2022 for dwellings and other residential buildings in certain situations.


Further changes to Parts L and F came into force from 29th March 2023 for buildings other than dwellings.


Why are changes being made?


As part of the Welsh Governments intention to make new homes more energy efficient and to take action on climate change, they consulted on updates to both Parts L and F of the building regulations and have introduced these changes as an interim step to further improved standards in 2025.


They also recognise that improving the energy efficiency of new homes can have unintended consequences and increase the risk of overheating; therefore, they widely consulted on changes which have resulted in the new Part O for Overheating.


When do the changes start, and are there transitional provisions?


The amended Approved Documents and regulations came into force on 23rd November 2022.


However it is normal for building regulation changes to be introduced through a transitional period, during which time and assuming qualifying criteria are met, the existing regulations remain in force. 


Therefore, the November 2022 changes will not apply where an initial notice was given to a local authority before 23rd November 2022 and the building work to which it relates starts before 23rd November 2023. 


Yet for these changes, the qualifying criteria of 'work commenced' will differ slightly and apply on an individual plot/block/building basis. This means that work to individual buildings on a notice made before 23rd November needed to commence before 23rd November 2023 to benefit from the transitional arrangements.


If you are undertaking work in Wales, it is essential that you watch our short introductory video on the changes and the transitional provisions that apply.


View our short introductory video on the changes, commencement and transitional provisions:




How do you define “work commenced”? (Building control only)


We have contacted the Welsh Government and they have indicated that commencement of work would usually be marked by the following:

  • Excavation for strip or trench foundations or for pad footings;
  • Digging out and preparation of ground for raft foundations;
  • Vibrofloatation (stone columns) piling, boring for piles or pile driving;
  • Drainage work specific to the building(s) concerned.


Premier Guarantee's building control service expands on this definition with a series of examples.


Foundations for a substantive start:


  • An independent pile that forms part of the building
  • A strip or trench foundation concreted to a full elevation per plot
  • Raft foundation excavated with compacted subbase installed
  • Shared basement car park substructure below multiple blocks commencement of all plots.


Drainage work specific to the building(s) concerned:


  • Drainage installed within the curtilage of each plot and connected to the main sewer
  • Alternatively, all drainage installed and backfilled within the curtilage of the plot ready for connection


How do you define "work commenced" for warranty cover?


Where a Premier Guarantee warranty product is provided, these additional details should be satisfied.


What would 'not likely' be commencement?


The following are not likely to constitute commencement:

  • Removal of vegetation;
  • Demolition of any previous buildings on the site;
  • Removal of top soil;
  • Removal or treatment of contaminated soil;
  • Excavation of trial holes;
  • Dynamic compaction;
  • General site servicing works (e.g. roadways).


What should I do next?


For more information, follow the following links to the Welsh Government website for detail on the changes:


For dwellings and residential buildings (From 23/11/2022):



For buildings other than dwellings (From 29/03/2023):



We are currently reviewing the changes in greater detail and will be providing webinar updates in due course.  Sign-up to receive our blog round-up and be notified when updates are available.


If you need any further information or clarification please use this enquiry form or you can discuss your plans with your Premier Guarantee Building Control Surveyor or your Account Manager.


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Every care was taken to ensure the information in this article was correct at the time of publication (November 2022). Guidance provided does not replace the reader’s professional judgement and any construction project should comply with the relevant Building Regulations or applicable technical standards. For the most up to date Premier Guarantee technical guidance please refer to your Risk Management Surveyor and the latest version of the Premier Guarantee Technical Manual.

Ref: MK-3398

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