Monitoring Energy Performance After Retrofit
Effective monitoring of energy performance after retrofit works is essential to validate that predicted improvements have been realised and to identify any operational issues. PAS2035 emphasises the importance of establishing baseline measurements and ongoing performance tracking to ensure retrofitted buildings deliver their intended energy savings.
Establishing Your Baseline
Before retrofit works commence, establish a clear energy baseline. This involves:
- Collecting at least 12 months of historical energy data (consumption records, bills, and meter readings)
- Accounting for weather variations using degree days to normalise consumption figures
- Recording occupancy patterns, operating hours, and any operational changes during the baseline period
- Identifying anomalies or unusual consumption patterns that may skew comparisons
- Documenting building characteristics including floor area, number of occupants, and equipment specifications
A robust baseline allows you to calculate expected post-retrofit performance and provides the benchmark against which to measure actual results.
Monitoring During and Immediately After Works
During the retrofit period, maintain detailed records of:
- Work completion dates and installation commissioning information
- Any deviations from planned specifications or timescales
- Weather conditions during and after installation
- Temporary disruptions to building services or occupancy
- Photographs and inspections confirming installation quality
Immediately after completion, allow a stabilisation period—typically 4-8 weeks—before drawing conclusions about performance. This allows building systems to settle and occupants to adjust to new conditions.
Key point: Use weather-normalised comparisons when evaluating post-retrofit energy consumption. This removes the impact of seasonal variations and provides clearer insight into actual savings achieved from the retrofit measures.
Post-Retrofit Monitoring Strategy
Implement a structured monitoring plan covering the first year post-completion and beyond:
Frequency and Data Collection
- Monthly monitoring: Review utility bills and meter readings to track overall consumption trends
- Sub-metered data: If available, monitor heating, cooling, lighting, and hot water separately to identify where savings are occurring
- Quarterly reviews: Analyse performance against weather-normalised baselines and investigate significant variances
- Annual assessment: Produce comprehensive energy performance report comparing actual to predicted savings
Data Management
Establish a system for collecting and storing energy data:
- Use consistent units (kWh, m³ or kWh equivalent) throughout monitoring period
- Record meter readings on fixed dates to avoid estimated readings distorting results
- Maintain spreadsheets or energy management software with clear data logging protocols
- Keep copies of all utility invoices and supporting documentation
- Document any building operational changes that may affect consumption
Comparing Actual Versus Predicted Performance
PAS2035 requires comparison of actual savings with those predicted during the retrofit design phase:
- Calculate normalised post-retrofit consumption using the same methodology as the baseline
- Apply weather corrections using appropriate degree days for your region
- Account for any changes in occupancy, operating hours, or building use
- Calculate percentage and absolute savings achieved
- Identify variance between predicted and actual performance
- Investigate reasons for significant deviations (typically >10% variance warrants investigation)
Where actual performance falls short of predictions, examine whether this is due to installation quality, occupant behaviour, or unrealistic baseline assumptions.
Investigating Performance Gaps
If monitoring reveals energy savings below predicted levels, investigate systematically:
- Building inspection: Verify all retrofit measures have been correctly installed and commissioned
- System operation: Check heating, ventilation, and cooling systems are functioning as designed
- Occupant behaviour: Assess whether building users understand how to operate new systems efficiently
- External factors: Consider changes to weather patterns, occupancy levels, or operational schedules
- Data accuracy: Confirm baseline data was representative and monitoring methodology is consistent
Commissioning and Fine-Tuning
Post-retrofit commissioning is critical for performance realisation:
- Ensure building management system (BMS) controls are properly configured for seasonal operation
- Verify thermostatic radiator valves (TRVs) and temperature sensors are functioning correctly
- Provide occupant training on new heating controls, ventilation systems, and efficiency practices
- Conduct post-occupancy evaluation to gather feedback on comfort and system usability
- Make fine-tuning adjustments to controls based on initial monitoring data and feedback
Documentation and Reporting
Maintain comprehensive records for audit and compliance purposes:
- Baseline energy assessment report and methodology
- Predicted energy savings calculation and assumptions
- Monthly utility data with weather information
- Commissioning records and sign-off documentation
- Annual energy performance reports comparing actual to predicted savings
- Records of any building operational changes or system adjustments
Long-Term Performance Tracking
Continue monitoring for several years post-retrofit to identify:
- Seasonal variations and annual consumption patterns
- Degradation of installed measures over time
- Maintenance requirements to sustain performance
- Opportunities for further improvement based on actual performance data
This ongoing monitoring ensures retrofitted buildings continue delivering energy and carbon benefits whilst informing future retrofit programmes across building portfolios.