The In-Use Optimisation and Evaluation (IOE) report represents a critical milestone in the PAS2035 retrofit journey. For retrofit coordinators and building control professionals, understanding what this report must contain isn't just about compliance—it's about demonstrating that retrofit measures are performing as designed and that occupants are genuinely benefiting from improvements.

What Is the IOE Report?

The IOE report forms part of the PAS2035 Post-Construction Phase. It evaluates how well retrofit measures are functioning in real-world conditions after installation, capturing data on both technical performance and occupant behaviour. Crucially, it's not optional—it's a mandatory requirement for scheme sign-off.

The report bridges the gap between predicted performance modelling and actual operational reality, ensuring that energy savings projections align with genuine outcomes.

Core Documentation Requirements

Building Performance Data

Your IOE report must include:

• Energy consumption readings from utility bills covering a minimum 12-month period post-retrofit
• Comparison data showing consumption before and after works
• Breakdown of consumption by fuel type (electricity, gas, oil, etc.)
• Identification of any anomalies or unexpected variations in usage patterns
• Evidence of meter readings and how data was collected

This quantitative evidence forms the backbone of any audit. Auditors will scrutinise the methodologies used to collect data and cross-reference figures against predicted performance models prepared during the design phase.

Technical Performance Assessment

The report must document performance of installed retrofit measures:

• Physical inspections confirming measures are correctly installed and operating
• Commissioning records and functional testing results
• Thermal imaging or other diagnostic assessments where relevant
• Details of any remedial works undertaken post-installation
• System maintenance records and any faults identified and rectified

Auditors expect evidence that you've verified retrofit measures are actually delivering what was promised. Photographic records and site inspection notes demonstrate due diligence.

Occupant Feedback and Behaviour

PAS2035 recognises that human behaviour significantly impacts retrofit outcomes. Your report should include:

• Documented feedback from occupants regarding comfort levels, heating/cooling effectiveness, and moisture control
• Evidence of engagement or training provided to occupants on operating new systems
• Records of any occupant concerns raised and how these were addressed
• Details of any behavioural adjustments or changes in usage patterns observed

This qualitative information demonstrates that you've taken a holistic approach beyond simply installing technical measures.

Analysis and Variance Explanation

A strong IOE report doesn't just present raw data—it analyses it. Key elements include:

• Performance variance analysis: Clear explanation of any significant differences between predicted and actual energy savings, with documented reasons
• Climate adjustment factors: Acknowledgment that weather variations affect consumption year-on-year
• Normalisation of data: Adjustment for occupancy changes, weather, or other factors affecting comparability
• Lessons learned: Honest reflection on what worked well and what could be improved

Auditors appreciate transparency here. If performance falls short of predictions, demonstrating you've investigated why and understand the root causes strengthens your audit position considerably.

Documentation and Evidence Trail

Audit success hinges on what you can evidence. Ensure your report includes:

• Site inspection photographs with dates and descriptions
• Maintenance and fault logs
• Commissioning certificates from installers
• Correspondence with occupants and records of feedback received
• Building Control sign-off documentation
• Links back to original design calculations and predictions

Create a clear narrative thread connecting predicted performance, installed measures, operational data, and actual outcomes. Auditors will follow this trail to verify each stage.

Timing and Submission

The IOE report must cover a minimum of 12 months of post-retrofit operation, allowing for genuine assessment of year-round performance. Plan for report preparation 13-14 months after completion, allowing time for data collection and analysis before submission.

Final Considerations

The IOE report is your opportunity to demonstrate that retrofit work has been executed properly and is delivering real benefits. Treat it as a professional summary of your project's performance, backed by comprehensive evidence.

Auditors are looking for competence, transparency, and genuine engagement with the retrofit process. A well-structured, thoroughly evidenced IOE report reflects all three—and significantly improves your prospects of audit success.