Understanding Stage Advice Letters in PAS2035

The PAS2035 standard establishes a rigorous framework for domestic retrofit, with Stage Advice Letters forming a crucial checkpoint in the project lifecycle. These documents bridge the gap between the initial energy assessment and the formal retrofit design, providing tailored guidance that reflects both the property's specific characteristics and the proposed retrofit strategy. Understanding what must be included in a Stage Advice Letter is essential for retrofit coordinators, housing associations, and installers to ensure compliance and project success.

Core Technical Requirements

Property-Specific Assessment Data

A comprehensive Stage Advice Letter must begin with detailed information about the building itself. This includes:

This foundational data ensures that all subsequent advice is grounded in the actual condition of the property, rather than assumptions or generic guidance.

Identified Retrofit Measures

The letter must specify which retrofit measures are being proposed or considered. This is not a final specification, but rather a preliminary assessment of suitable options, such as:

Each measure should be linked to the property's identified performance gaps and heat loss pathways.

Advisory and Guidance Content

Risk Assessment and Mitigation

A critical element of the Stage Advice Letter is the identification of retrofit risks specific to the property. These may include:

For each identified risk, the letter must outline proportionate mitigation strategies. This demonstrates reasoned decision-making and protects all parties involved in the retrofit process.

Technical Rationale and Performance Expectations

The advice letter should explain why specific measures are being recommended. This includes reference to the property's thermal performance modelling, U-values, and how proposed measures will address identified deficiencies. Quantified energy savings or performance improvements, where available, add credibility and help set realistic expectations.

Information for Site Assessment and Planning

Site-Specific Considerations

The letter must address practical delivery factors that will influence how measures are implemented:

These details ensure that the retrofit coordinator and installer can make informed decisions during the detailed design and delivery stages.

Sequencing and Interdependencies

Where retrofit measures have logical or practical dependencies, the Stage Advice Letter should indicate the preferred sequence. For example, improved insulation measures may need to precede heating system design, or ventilation improvements may be prerequisite to certain fabric upgrades.

Client Communication and Sign-Off

Accessibility and Clarity

Whilst Stage Advice Letters must contain technical information, they should also be written in a manner accessible to non-specialist audiences. Key findings, recommendations, and any limitations should be clearly highlighted. Diagrams, sketches, or photographs can enhance understanding and engagement.

Approval and Confirmation

The letter typically concludes with a statement of the assessor's qualifications and confirmation that the advice is based on PAS2035 compliance. It should be clear which recommendations are mandatory for energy performance and Building Regulation compliance, and which are advisory or optimisation measures.

Documentation and Record-Keeping

Stage Advice Letters must be properly dated, signed (or digitally authenticated), and retained as part of the project file. They serve as a critical audit trail demonstrating that retrofit decisions were evidence-based and compliant with the standard. This documentation is essential for warranty purposes, regulatory compliance, and future reference.

A well-constructed Stage Advice Letter sets the foundation for a successful retrofit project, ensuring that all stakeholders proceed with aligned expectations and a clear understanding of both opportunities and constraints.