Developed by the British Standards Institution (BSI), it underpins the UK’s net zero strategy by ensuring that retrofit projects are designed and delivered in a consistent, high-quality, and accountable manner.

The specification requires a whole-house approach, where a dwelling’s construction, existing condition, ventilation strategy, and occupancy profile are fully assessed before retrofit measures are designed. This prevents the risks associated with piecemeal improvements and ensures measures work together as an integrated system.

‍PAS 2035 defines specialist roles to maintain technical rigor and accountability throughout the process:
Retrofit Advice – provides impartial guidance to households, helping them understand their retrofit options, available funding, and the benefits and risks of different measures.
‍Retrofit Assessor – responsible for carrying out condition surveys, occupancy assessments, and energy performance evaluations.
‍Retrofit Coordinator – provides end-to-end project management, ensures compliance with PAS 2035, oversees quality assurance, and manages risks.
‍Retrofit Installer – carries out the physical installation of energy efficiency measures, working to PAS 2030 standards to ensure quality and compliance.
‍Retrofit Designer – produces the technical design specifications, integrating multiple measures into a coherent whole-building solution.
‍Retrofit Evaluator – conducts post-installation monitoring and evaluation to confirm that the retrofit meets intended outcomes.

The framework places strong emphasis on indoor environmental quality, durability of measures, and the long-term performance of the building. This ensures that retrofits do not create unintended consequences such as condensation, poor air quality, or structural damage.

PAS 2035 is a mandatory requirement for government-funded programmes such as the Energy Company Obligation (ECO), making it a cornerstone of the UK’s retrofit standards framework and a critical tool in achieving carbon reduction and fuel poverty targets.
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The framework places strong emphasis on indoor environmental quality, durability of measures, and the long-term performance of the building. This ensures that retrofits do not create unintended consequences such as condensation, poor air quality, or structural damage.

PAS 2035 is a mandatory requirement for government-funded programmes such as the Energy Company Obligation (ECO), making it a cornerstone of the UK’s retrofit standards framework and a critical tool in achieving carbon reduction and fuel poverty targets.