Built Environment · Evidence Layer
Willows Health · Leicester, UK · FY2026
Pilot · pending VVB
IPMVP Measurement Engine
Option C whole-facility, weather-adjusted savings
ISO 14064-3 compatible, aligned with GHG Protocol and NHS Greener NHS methodology.
Method
Option C
Whole-facility, utility meter
Sites modelled
3
Existing sites only
Best R²
0.92
green
Worst CV(RMSE)
17.2%
amber
ASHRAE G14 < 15% = calibrated
Why Option C
Whole facility · utility-meter based · routine + non-routine adjustments
IPMVP Option CWhole facilityRoutine + non-routine adjustments
Savings = (Baseline energy − Reporting-period energy) ± Adjustments
Adjustments are routine (weather via heating degree-days) and non-routine (occupancy, retrofit fabric changes).
Model diagnostics
RAG on CV(RMSE) using ASHRAE Guideline 14 (< 15% monthly = calibrated)
| Site | R² | CV(RMSE) % | Baseline kWh | Actual kWh | Savings kWh (weather-adj.) | Savings tCO₂e | Uncertainty ±% |
|---|---|---|---|---|---|---|---|
| Willows Medical Centre | 0.92 | 11.4green | 141,800 | 128,600 | 13,200 | 2.70 | ±12.0% |
| Heatherbrook Surgery | 0.88 | 13.8green | 43,500 | 40,700 | 2,800 | 0.55 | ±18.0% |
| Clarendon Park Medical Centre | 0.79 | 17.2amber | 84,200 | 79,500 | 4,700 | 0.95 | ±24.0% |
Baseline vs actual — Willows Medical Centre
Weather-adjusted savings (kWh)
Uncertainty band (± at 68% CL)
Model fit — energy vs heating degree-days
Assumptions & provenance
- IPMVP Option C rationale: whole-facility, utility-meter reconciled — appropriate for portfolio-scale reporting.
- Weather source: heating degree-days (HDD) at nearest ECMWF station.
- ASHRAE Guideline 14 monthly calibration criteria: CV(RMSE) < 15% and NMBE < 5%.
- Savings uncertainty must be < 50% of annual reported savings at a 68% confidence level (per ASHRAE Guideline 14).
- ISO 14064-3 compatible, aligned with GHG Protocol and NHS Greener NHS methodology.
- Figures are pilot inputs pending independent verification; not yet VVB-assured.