How to Write a Stage Advice Letter Under PAS2035

A Stage Advice Letter is a critical document in the PAS2035 retrofit coordination process. It sets out the technical specifications, retrofit measures, and performance expectations following the initial assessment phase. This guide outlines the essential components and practical steps for producing an effective Stage Advice Letter that meets PAS2035 requirements.

Understanding the Purpose

The Stage Advice Letter transitions from assessment to design. It communicates findings from your evaluation of the building's current condition and recommends specific retrofit measures tailored to the property. This letter forms the basis of the retrofit specification and must be clear enough for installers, clients, and warranty providers to understand and action.

The letter should demonstrate that you have considered the building's characteristics, occupant needs, and regulatory requirements before recommending measures.

Essential Content Requirements

Your Stage Advice Letter must include:

• Property identification — full address, property type, age, and construction details
• Assessment summary — key findings from your in-situ testing and desktop review
• Recommended measures — specific retrofit interventions with technical justification
• Performance predictions — expected energy savings and thermal improvements
• Quality assurance requirements — testing protocols and compliance standards
• Cost estimates — indicative pricing for budgeting purposes
• Timeline — phasing and sequencing of works if multi-stage
• Risk and limitations — any constraints or site-specific issues affecting delivery

Structuring Your Letter

Begin with an executive summary that captures the property type, headline measures, and estimated improvements. This helps clients quickly understand the proposal before detailed sections follow.

For each recommended measure, provide:

1. Technical description of the work
2. Materials and specifications to be used
3. Expected performance uplift (U-values, air tightness, etc.)
4. Installation quality standards required
5. Compatibility with other measures
6. Indicative costs

This structured approach ensures consistency and reduces ambiguity during installation.

Technical Specifications

Be precise when specifying retrofit measures. Rather than stating "improve insulation," specify:

• Product type and thermal conductivity (lambda value)
• Installation thickness and method
• Coverage area and location
• Relevant British Standards or certification requirements
• Interface details with existing building elements

For example: "Rigid polyurethane insulation, lambda 0.023 W/mK, 100mm thickness, installed internally to external walls using mechanical fixings to prevent cold bridging."

Addressing Building Pathology

Your letter must acknowledge any building defects or issues that could affect retrofit success. Common examples include:

• Rising damp or moisture ingress
• Structural movement or cracks
• Poor ventilation causing condensation
• Asbestos or hazardous materials
• Limited accessible cavity width

Explain how proposed measures account for these issues, or recommend remedial action before retrofit installation. If a measure cannot proceed due to existing defects, state this clearly with supporting rationale.

Performance Prediction and Compliance

Include predicted performance metrics using recognised calculation methodologies. These should cover:

• Improved U-values for insulated elements
• Predicted air permeability post-retrofit
• Seasonal energy efficiency ratio (SEER) for heating systems
• Expected carbon emissions reduction
• Estimated energy cost savings

Clearly state which calculation tools were used and any assumptions made. This transparency helps clients and installers understand how figures were derived.

Quality Assurance and Testing

Specify the testing and inspection regime required during installation:

• Air tightness testing (post-retrofit blower door test)
• Thermal imaging surveys to identify bridging
• Workmanship inspections at defined stages
• Insulation thickness checks
• System commissioning and handover protocols

These quality measures verify that installed measures perform as designed and meet PAS2035 standards.

Risk Communication

Address potential limitations or risks transparently. These might include:

• Limitations of internal insulation in moisture-prone properties
• Reduced internal floor area from thickened walls
• Integration challenges with existing services
• Phasing constraints affecting overall performance
• Market availability of specified materials

Honest communication about constraints protects your professional standing and prevents disputes.

Client Sign-Off

Your letter should invite client agreement to proceed. Include a clear acceptance section confirming the client understands the scope, costs, and expected outcomes. This documented agreement provides evidence of informed consent and is essential if issues arise later.

Final Checklist

Before issuing your Stage Advice Letter, verify:

• All recommendations are based on robust assessment data
• Technical specifications are buildable and compliant with Standards
• Performance claims are realistic and supported by calculations
• Quality requirements are clearly defined for installers
• Risk and limitations are transparently stated
• Costs are transparent and reasonable
• The letter is dated and signed by a competent assessor

A well-drafted Stage Advice Letter demonstrates professional competence, manages client expectations, and provides installers with clear direction. This foundation is essential for successful retrofit delivery under PAS2035.