What Is PAS 2035?
PAS 2035:2019 is the overarching specification for the retrofit of domestic buildings in the UK. Published by the British Standards Institution, it establishes a framework of roles, responsibilities, and processes that must be followed whenever energy efficiency improvements are made to existing homes — particularly where government funding is involved.
The standard was introduced to address a persistent problem in the UK retrofit sector: well-intentioned energy improvements that were poorly designed or badly installed, leading to unintended consequences such as damp, mould, and structural damage.
Why Does It Matter?
PAS 2035 compliance is mandatory for all domestic retrofit projects funded through government schemes including ECO4, the Great British Insulation Scheme (GBIS), and the Social Housing Decarbonisation Fund (SHDF). Non-compliance can result in rejected funding claims, costly remediation, and reputational damage.
Beyond compliance, the framework delivers genuine quality benefits. Projects managed under PAS 2035 are significantly less likely to experience defects, occupant complaints, or performance shortfalls.
Key Roles Under PAS 2035
The standard defines several professional roles, each with specific qualifications and responsibilities:
Retrofit Assessor — Carries out property surveys and produces assessment reports identifying suitable improvement measures. Must hold a Level 3 Retrofit Assessor qualification.
Retrofit Coordinator — Manages the overall retrofit process from design through installation to handover. Responsible for the Medium-Term Improvement Plan and quality oversight. Must hold a Level 5 Retrofit Coordinator qualification.
Retrofit Designer — Produces detailed design specifications for improvement measures, ensuring they are technically appropriate for the specific property.
Retrofit Installer — Carries out the physical installation of improvement measures in accordance with the design specification. Must be registered with TrustMark.
Retrofit Evaluator — Monitors the quality of retrofit projects through independent sampling and review.
Compliance Essentials
To achieve PAS 2035 compliance, a retrofit project must demonstrate:
- Proper risk assessment — Each property must be assessed for risk level (Path A, B, or C), which determines the extent of professional involvement required.
- Qualified professionals — All roles must be filled by appropriately qualified individuals registered through the TrustMark framework.
- Documented process — Every stage from assessment to handover must be documented and lodged on the TrustMark Data Warehouse.
- Whole-house approach — Measures should be considered in the context of the whole dwelling, not in isolation, to avoid unintended consequences.
- Ventilation strategy — Any changes to the building fabric must be accompanied by an appropriate ventilation assessment.
Common Pitfalls
Treating PAS 2035 as paperwork — The standard requires genuine professional oversight, not just documentation. Coordinators who do not visit sites or review installer work are not meeting the requirements.
Ignoring ventilation — Adding insulation or improving airtightness without addressing ventilation is one of the most common causes of post-retrofit damp and mould issues.
Measure-by-measure thinking — PAS 2035 requires a whole-house approach. Installing a single measure in isolation, without considering its interaction with other building elements, undermines the quality benefits of the framework.
Underestimating the Coordinator role — The Retrofit Coordinator carries significant responsibility for project quality. Organisations that treat this as an administrative role rather than a technical leadership function often experience quality problems.
How Synavo Can Help
Synavo provides qualified Retrofit Assessors and Coordinators who understand PAS 2035 from a technical, practical, and regulatory perspective. We work with housing associations, local authorities, and private landlords to deliver compliant, high-quality retrofit programmes.
If you are planning a retrofit project and need guidance on PAS 2035 compliance, get in touch with our team for an initial consultation.