How to Conduct a PAS2035-Compliant Retrofit Assessment

PAS2035:2019 establishes the specification for the assessment and reporting of physical properties to improve their energy efficiency. Conducting a compliant retrofit assessment requires systematic planning, detailed data collection, and rigorous documentation. This guide outlines the practical steps to ensure your assessment meets the standard's requirements.

Pre-Assessment Planning

Before visiting a property, establish a clear assessment scope and gather existing information. This foundation determines the quality of subsequent work.

• Define assessment objectives: Clarify whether the assessment is for full retrofit design, targeted improvements, or compliance verification
• Collect baseline data: Request EPC certificates, building plans, service records, and any previous survey reports from the property owner
• Prepare documentation: Create an assessment checklist aligned with PAS2035 requirements specific to the building type and age
• Establish client expectations: Confirm the scope, timescale, and deliverables with the client before commencing on-site work

Physical Survey Methodology

The on-site survey must capture sufficient detail to inform retrofit design decisions. A systematic approach ensures consistency and completeness.

Building Envelope Assessment

• Conduct a visual inspection of external walls, roof, and foundation condition, recording material types and visible defects
• Test thermal bridging at key junctions: eaves, corners, party walls, and window frames using thermographic imaging where appropriate
• Measure cavity widths in cavity wall construction; verify fill material presence through core samples if necessary
• Document window and door specifications, including frame material, glazing type, and condition of seals
• Identify infiltration sources such as gaps around services, damaged weather seals, and ventilation arrangements

Heating and Hot Water Systems

• Record boiler type, model, age, and efficiency rating; photograph the nameplate for reference
• Assess distribution pipework insulation and routing, noting exposed runs and potential heat losses
• Evaluate hot water cylinder type and insulation thickness; measure dimensions for accurate storage capacity
• Document controls systems: thermostat type, location, and responsiveness to occupant needs
• Inspect heat emitters (radiators or underfloor heating) for sizing appropriateness and operational condition

Ventilation and Indoor Air Quality

• Identify ventilation provision: natural, extract-only, or mechanical ventilation with heat recovery (MVHR)
• Check for evidence of condensation, mould, or dampness indicating ventilation deficiencies
• Measure extract fan performance where present; assess blockages or filter condition
• Document CO₂ levels if measuring indoor air quality compliance

Occupancy and Use Patterns

Understanding how occupants use the building is critical for retrofit design effectiveness.

• Record occupancy profiles: number of residents, working arrangements, typical daily patterns
• Document heating preferences and comfort expectations
• Identify behaviour patterns affecting energy use: window opening habits, thermostat adjustment frequency
• Note any special requirements such as drying space or cooling needs during specific seasons

Data Collection and Recording

Meticulous documentation supports both design and future compliance verification.

1. Photography: Capture building elevations, roof condition, boiler, controls, and any defects. Ensure images are dated and referenced to location plans
2. Measurements: Record room dimensions, window sizes, and external wall thickness. Use measured dimensions rather than calculations from plans
3. Material identification: Document construction types with sufficient precision for modelling: brick dimension and bond, cavity width, insulation type and thickness
4. Digital recording: Use structured forms or digital tools to ensure consistent data capture and reduce transcription errors
5. Site-specific notes: Record observations about building orientation, overshadowing, local microclimate factors, and access constraints affecting retrofit feasibility

Energy Modelling Foundation

Assessment data must be sufficient to populate energy performance modelling software accurately.

• Ensure all building element areas are calculated or measured
• Record U-values for existing construction; specify test evidence if performance certificates are available
• Document renewable energy potential: solar orientation, shading analysis, and wind exposure
• Capture renewable technology constraints: structural capacity, space availability, and planning considerations

Compliance and Reporting Requirements

• Assessor competence: Verify that the assessor holds appropriate certification under a PAS2035-registered scheme
• Quality assurance: Ensure assessments undergo peer review or quality check before finalisation
• Client report: Provide clear, evidence-based recommendations with estimated energy savings and cost-benefit analysis for retrofit options
• Technical specification: Generate detailed specifications suitable for retrofit design and procurement
• Record retention: Maintain comprehensive assessment records for the minimum period required by your professional indemnity insurance

Common Assessment Pitfalls to Avoid

• Relying solely on building plans without site verification of actual construction
• Underestimating thermal bridging effects in retrofit design
• Failing to identify hidden defects such as cavity wall moisture or structural movement
• Neglecting occupant engagement; low retrofit uptake often results from poor understanding of expected benefits
• Insufficient detail in baseline documentation, compromising post-retrofit verification

A thorough PAS2035-compliant assessment balances comprehensive data collection with practical feasibility. By following this structured approach, you establish a reliable foundation for retrofit design that delivers real energy and carbon savings whilst meeting occupant needs.