PAS 2035:2019 Retrofitting Dwellings for Improved Energy Efficiency

PAS 2035:2019 was sponsored by the UK Government's Department for Business, Energy and Industrial Strategy (BEIS). This is the key document in a framework of new and existing standards on how to conduct effective energy retrofits of existing buildings, it covers how to access dwellings for retrofit, identify improvement options, design and specify Energy Efficiency Measures (EEM) and monitor retrofit projects.

The standard drives the 'whole house approach' including the 'fabric first' methodology. It defines the qualifications and responsibilities of individual retrofit roles and respective activities required prior and post EEM installation.  It also includes a risk assessment process that builds incrementally robust requirements depending on what requirement path (A, B, or C) the retrofit project is assessed to fall within.

It is not possible to be certified to PAS 2035:2019 in the way that it is with PAS:2030. In the case of PAS 2035:2019, TrustMark will the deliver of the compliance monitoring function rather than the certification bodies. TrustMark Registered Businesses carrying out work within its scope are required to be compliant with its requirements; subject to the transition arrangements outlined below.

PAS 2035 is inextricably linked to PAS 2030:2019, which is the new industry specification to replace PAS 2030:2017 and is the standard to which all energy efficiency installers must be certificated and compliant.

The standards framework has been revised in response to industry learning on good practice and the recommendations of the Each Home Counts review. As such the new specifications PAS 2035:2019 and PAS 2030:2019 came into effect from 30th June 2019.

The specifications are available from the BSI Shop.

PAS 2035 and TrustMark

TrustMark has incorporated the new specification into Annex B of our Framework Operating Requirements so that going forward, where a consumer engages with a TrustMark Registered Business in relation to the installation of energy efficiency measures, they can have confidence that the work is delivered to improved, recognised specifications and is underpinned by a compliance regime. 

PAS 2030 - TrustMark Data Warehouse Lodgement Flexibility Agreement (Update 26 May 2020)

The impact of the COVID-19 lockdown period has been reported as having a significant effect on the 60-day flexibility agreement originally published on 27th March 2020.

Due to the impact of the COVID-19 lockdown period and its restrictions a refreshed agreement becomes effective from 3rd June 2020 and succeeds the initial flexibility agreement which commenced 3rd April 2020.

In practice, this new agreement provides those business who have a backlog of work commenced under PAS 2030:2017 and were transitioned to PAS 2030:2019 on or before 3rd April 2020 a further 60 days to lodge those measures as PAS 2030:2017 compliant.

The Data Warehouse lodgement rules have been created based upon the TrustMark Framework Operating Requirements - Version Two; published after the Government response to the ‘ECO3: ‘Improving Consumer Protection Consultation’.  Therefore, projects lodged after a Registered Business has been certified to PAS 2030:2019 are required to be compliant with PAS 2035:2019 and lodged into the Data Warehouse by a qualified and TrustMark registered Retrofit Coordinator.

In recognition of the industry feedback it was agreed that TrustMark would introduce temporary flexibility into how measures can be lodged for businesses that had transitioned between these standards.

Therefore, from the date a Registered Business is certified to PAS 2030:2019, it will have a period of 60 calendar days during which it can lodge measures as PAS 2030:2017 compliant via the PAS 2030:2017 certificating body Scheme Provider, if the measure commenced under this valid certification.

The flexibility agreement will be reviewed if appropriate and any changes will be communicated in due course.
Where a Registered Business requires multiple administration accounts to support the lodgement of works completed under PAS 2030:2017, the business can contact TrustMark using the following email address:

It is the responsibility of the Registered Business to ensure that the work lodged is within the scope of the appropriate PAS certification. Once certified to PAS2030:2019 all work initiated must be delivered to that standard.

Businesses planning to change PAS 2030 certification bodies who are TrustMark Scheme Providers must check with their proposed new certification body to ensure that that their ability to make lodgement to the TrustMark Data Warehouse remains continuous.

PAS 2035:2019 - Reduction of Inherent Technical Risk Scores of Energy Efficiency Measures Through the Use of TrustMark Recognised Industry Quality Assurance Schemes

PAS 2035:2019 Annex B Clause B.2 introduces a mechanism that permits the reduction of inherent technical risk scores for a measure(s) where a closely defined criteria is met.  Where the intended Retrofit Installer operates under an ‘industry quality assurance scheme’ that has the features as listed in the relevant section of the PAS, a reduction of the inherent technical risk scores by one for the measure(s) covered by that scheme is permitted.  Please see the applicable sections of PAS 2035:2019 for further information.

TrustMark, working closely with our Retrofit Coordinator Scheme Providers and the wider interested parties, has agreed that a consistent approach must be in place so that a TrustMark Registered Retrofit Coordinator considering this provision of the PAS works to a common consistent standard.

Therefore, the following is a list of TrustMark recognised organisations delivering such industry quality assurance schemes as permitted by PAS 2035:2019.  Retrofit Coordinators can recognise these schemes when deciding whether a valid reduction by one can be made to inherent technical risk score for the respective measure(s) within a project.

The list may be added to as further schemes become recognised by TrustMark:

Current Recognised Schemes:

CIGA Guarantee under the quality assurance framework of The IAA

Use online application or website contact details

SWIGA Guarantee

Use online application or website contact details

Should your organisation operate an industry quality assurance scheme as described in PAS 2035:2019 and you require to be considered for TrustMark recognition, you can obtain the published criteria and understand more about the application process for TrustMark recognition by contacting TrustMark directly.

Where the organisation wishes to progress its interest, we will require a formal request to do so, supported by comprehensive and auditable evidence to meet the recognition criteria.

TrustMark, the Energy Company Obligation (ECO) and PAS 2035

The Electricity and Gas (Energy Company Obligation) (Amendment) Order 2019 came into force on 1st January 2020 and includes a requirement for ECO measures to be installed by, or under the responsibility of, a person who is registered with TrustMark for the measure and for the work to be lodged into the TrustMark Data Warehouse.

The requirement for TrustMark registration and the incorporation of PAS 2035 into our Framework is the vehicle to drive the new standards in ECO.

Further information can be found here

Transitional Arrangements:

It is recognised that some transitional arrangements are required to support the industry uptake of the new specifications. The transitional arrangements apply to TrustMark Scheme Providers and TrustMark Registered Businesses involved in the delivery of energy efficiency measures under ECO and those delivered outside of the scope of ECO but where compliance is claimed with these specifications.

The transitional arrangements are as agreed with:

  • The British Standards Institution (BSI)
  • The Department for Business, Energy and Industrial Strategy (BEIS)
  • The Office of Gas and Electricity Markets (Ofgem)
  • The United Kingdom Accreditation Service (UKAS)
Transitional Arrangements V2.0



It is important to understand that when a PAS 2030:2017 certified business becomes certified to PAS 2030:2019 the requirements of PAS 2035:2019 commence. This includes the requirement for a project to be overseen and lodged into the TrustMark Data Warehouse by a qualified and TrustMark registered Retrofit Coordinator.




The Approach to Compliance

This table summaries the PAS requirements for TrustMark Registered Businesses both during and post PAS 2035:2019/2030:2019 transition period in respect of measures that fall within the scope of PAS 2035:2019, PAS 2030:2019 and PAS 2030:2017.

PAS 2035:2019 Retrofit Roles

PAS 2035 specifies the retrofit roles as follows:

  • Retrofit Advisor
  • Retrofit Assessor
  • Retrofit Coordinator
  • Retrofit Designer
  • Retrofit Evaluator

Further information on the retrofit roles and qualifications can be found here

Interested in becoming a TrustMark registered Retrofit Assessor and/or Retrofit Coordinator?

To find out more about the TrustMark Schemes you can become registered with, please visit our 'How To Join' page. Use the 'Select Trade' function to find a Scheme Provider that can support your application.

Further Resources

If you would like to learn more about why PAS 2035 was created or more about how it works, you may find the following external links useful:

PAS 2035: An interview with Dr. Peter Rickaby (the technical author of PAS 2035)

The Retrofit Academy

Retrofit Works - Model

BSI Shop 


This page is under regular review and will be updated frequently. Last updated 29 May 2020.