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PAS 2035 (2023) Release: Key Information and Changes


The latest version of PAS 2035 (2023) has been published, featuring a number of important updates for retrofit professionals across the UK. This release follows the British Standards Institution’s public consultation on PAS 2035 earlier this year and aims to enhance the retrofit process.

Important note: the transition to PAS 2035:2023 has not been finalised. You should continue to use PAS 2035:2019 until advised otherwise.

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What is PAS?

PAS 2035 is the over-arching document in the retrofit standards framework, outlining the requirements for a home to achieve its energy efficiency potential through a ‘whole house’ or ‘whole building’ approach. More information can be found on the page: What Is PAS 2035?

PAS 2035 (2023) Update

The Elmhurst Energy team has reviewed the updated standard and has provided a summary of the important details below. Understanding the relevant details and changes in the PAS 2035 update is vital for the future implementation of the document – both for the assessment process and the internal auditing process.

The below summary is broken into sections, with references to the relevant pages and clauses located within the full document.


  • The Risk Path procedure has been removed. Changes have been applied to various factors, for example to the Retrofit Designer qualification requirements based on the number of measures being installed. (see later comments).
  • Traditional Construction definition has been updated and expanded. (Page 5).
  • A medium-term improvement plan is now required for all properties (5.3.1 & 8.1).
  • Scope has been added to cover distressed replacement of heating appliances (7.2).
  • The Retrofit Assessor report, where appropriate, will cover additional issues that may impact the project now and in the future (7.3.2.I).
  • The design criteria for airtightness/leakage strategy has been updated. Where EEMs improve the building fabric, an airtightness/leakage strategy is required. Should an airtightness target be set in this strategy, compliance must be proved by means of a test. Note, that an airtightness target is not mandatory if not set in the strategy. (8.2.35, & 8.2.36).
  • Where the Retrofit Designer finds issues with the Improvement option evaluation and medium-term improvement plan, these must be updated at the end of the design process. (8.2.38).
  • The Retrofit Coordinator shall collect evidence to satisfy them that the installation of EEMs has been undertaken correctly. This may include an in-person or virtual/remote site inspection or, where not possible, a third party can collect suitable evidence. However, if any measure listed in 9.2 connects to or penetrates another fabric EEM that is being installed or has been installed during the retrofit works, an in-person inspection is required by the Retrofit Coordinator (9.2).
  • In addition to the above point, a written record of any inspections must be maintained and provided with photographic evidence (9.3.1).
  • Guidance on retrofit at scale has been updated (5.4).


  • Retrofit Assessors: The criteria have been updated in line with the number of measures approach but remain the same.
  • Retrofit Coordinators: The criteria have been updated in line with the number of measures approach but remain the same.
  • Retrofit Designer: The criteria have been updated in line with the number of measures approach. Only a suitable qualified Retrofit Designer can undertake this task (A.3). This no longer includes the Retrofit Coordinator as previously allowed under Paths A & B.
  • Responsibility for design rests with the specialist designer, and not with the Retrofit Coordinator.
  • Qualification criteria for the number of measures, and where properties are of traditional construction have been amended and expanded to include additional options and requirements.


  • Ventilation has been updated in relation to the Building Regulations, introducing clauses as needed in Annex C, where they are of a higher standard than the standards in force for the relevant devolved nations.
  • Specifically, were the package of specified and existing EEMs falls into Category B or C under Approved Document F, or there is evidence of condensation or mould, the adequacy of the existing ventilation will be examined, and upgrades as defined are needed based on which category the ventilation issues fall within.

Significance Assessment:

  • PAS 2035 (2023) now includes a more detailed explanation with respect to significance assessments for buildings with aspects of significance, as well as a predefined survey checklist.

We strongly recommend that all professionals read the full PAS 2035 document, in addition to the points highlighted above, in order to gain a full understanding of the changes and relevant details.

To download the full document from the British Standards Institution (BSI) website, click the link below: https://www.bsigroup.com/en-GB/standards/pas-2035-2030/