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 27 March 2020)

It has become clear that TrustMark Registered Businesses starting retrofit projects under PAS 2030:2017 certification and completing them following certification to PAS 2030:2019 are experiencing challenges when lodging measures into the TrustMark Data Warehouse.  Primarily this is caused by the businesses not having the mandatory processes/resources in place for compliance with PAS 2035:2019 after being certified to PAS 2030:2019.

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 complaint 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 has been agreed that TrustMark can introduce temporary flexibility into how measures can be lodged for businesses that have transitioned between these standards to help them.

Therefore, from the date a Registered Business is certified to PAS 2030:2019, it will have a 60 calendar day period during which it can lodge measures as either PAS 2030:2017 or PAS 2030:2019 compliant, depending under which valid certification the measure was started.  This arrangement becomes effective from 3rd April 2020 and will be reviewed for a closure date as appropriate, that will be communicated.

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.


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 31 March 2020.