PAS2035 is the UK standard that governs the whole-house retrofit process for domestic properties. Published by the British Standards Institution and updated in 2023, it is a mandatory requirement for all major UK retrofit funding schemes — including the Warm Homes Social Housing Fund, Warm Homes Local Grant and the Boiler Upgrade Scheme for heat pump installations.
For housing associations, understanding PAS2035 is no longer optional. Non-compliance creates financial, legal and reputational risks that are difficult to recover from — and the documentation requirements mean that non-compliance is difficult to conceal.
Why PAS2035 Was Created
Before PAS2035, there was no mandatory standard governing the overall retrofit process in the UK. Individual measures had their own installation standards, but nothing governed the whole-house approach — how a property should be assessed, how a package of measures should be designed, or how the coordination between multiple parties should be managed.
The consequence was inconsistent quality across the sector. Measures were installed without proper assessment of the building as a whole. Ventilation was frequently overlooked. Moisture problems were sometimes created rather than solved. The Each Home Counts review, commissioned by government in 2016, identified these systemic failures and recommended the development of a comprehensive standard — which became PAS2035.
The Four Stages of PAS2035
PAS2035 divides the retrofit process into four defined stages, each with required outputs and compliance documentation.
Stage 1 — Pre-Retrofit Assessment
A qualified Retrofit Assessor carries out a whole-house condition survey and energy assessment of the property. The assessment produces an RdSAP report alongside condition data covering ventilation, moisture, structural defects and other factors that affect the choice of measures. All of this data must be reviewed by the Retrofit Coordinator before design can commence.
Stage 2 — Improvement Option Evaluation and Medium Term Plan
The Retrofit Coordinator produces the Improvement Option Evaluation — a document that models a range of retrofit measure combinations for the property, comparing their impact on SAP score, energy bills and carbon emissions. A Medium Term Plan is then agreed with the project client, setting out the phased approach to upgrading the property over time. Advice letters to residents are also produced at this stage.
Stage 3 — Retrofit Design
A qualified Retrofit Designer produces a detailed specification for the measures to be installed. The design must address ventilation and overheating risks as well as the primary energy efficiency measures, and must be reviewed and signed off by the Retrofit Coordinator. Stage 3 advice letters to residents are issued at this point.
Stage 4 — Installation and Handover
PAS2030-certified installers carry out the works. The Retrofit Coordinator oversees the installation process, conducts quality assurance checks and manages any non-conformities. On completion, the RC produces the claim of compliance and a project handover pack for the resident. The project is then lodged with TrustMark as the formal record of compliance.
The Retrofit Coordinator's Role
The RC is the central figure in PAS2035. Every project must have an accredited RC appointed — without one, a project cannot be TrustMark lodged and cannot access funded scheme payments. The RC is responsible for the whole process: not just the documentation, but the quality and coordination of every party involved. This independence from the installation team is a deliberate design feature of the standard.
RC accreditation requires holding the ABBE Level 5 Diploma in Retrofit Coordination and Risk Assessment, and registration with TrustMark as a Retrofit Coordinator. Accreditation is also held with at least one approved assessment body — Elmhurst, ECMK, Quidos or Property Tectonics.
What Happens If PAS2035 Is Not Met
The consequences of non-compliance are significant. TrustMark will not lodge a project that cannot demonstrate compliance with PAS2035 at each stage — meaning funding scheme payments cannot be claimed. Where non-compliance is discovered after installation, remediation is required before lodgement can proceed.
Beyond the immediate financial consequences, a failed lodgement creates a documented record of non-compliance that affects the organisation's ability to access future funding rounds. For housing associations with large retrofit programmes, this is a serious operational risk.
PAS2035:2023 — What Changed
The 2023 update to PAS2035 clarified a number of requirements that had been interpreted inconsistently in the field. It strengthened the ventilation assessment requirements, updated the documentation requirements for the handover pack and aligned the standard more closely with the current funding scheme conditions. All projects commenced after the 2023 publication date are required to comply with the updated standard.