Supply Chain Advice Pack: Main Changes of PAS 2035:2023 from 2035:2019
Introduction
PAS 2035 was created in response to the recommendations of the Each Home Counts report (2016)1 and is the Publicly Available Specification (PAS) which “offers comprehensive guidance for energy retrofitting in existing homes, ensuring efficiency, sustainability, and improved performance”2.
Published: July 2025
Contents
Welcome to the Supply Chain Advice Pack: Main Changes of PAS 2035:2023 from 2035:2019
First published in 2019, PAS 2035 outlines how retrofit projects should be managed and delivered. It aims to guide a holistic approach which considers a building as a system of elements, interfaces and occupants that interact and not as a set of elements that are independent of each other.
The first version of the standard was PAS 2035:2019 and this was subsequently updated several times before the publication in September 2023 of PAS 2035:20233, which is available to download free from the BSI website.
PAS 2035 is the overarching document in the Retrofit Standards Framework and all other standards referred to in PAS 2035 are part of the framework (see section 15 of PAS 2035). PAS 2035 and the Retrofit Standards Framework can be applied to all domestic retrofit activity.
All retrofit projects being delivered under Warm Homes funding, must use PAS 2035:2023.
For projects which have had assessments done using PAS2035:2019, they will be able to convert those assessments to PAS 2035:2023-compliant assessments, for a limited period (see TrustMark website).