What Is Retro-Commissioning (RCx)?

Retro-commissioning (RCx) is the systematic process of evaluating and optimizing the performance of an existing building’s systems—HVAC, controls, air distribution, hydronic systems, and supporting equipment. Unlike major capital upgrades, RCx focuses on improving what you already have. Over years of operation, buildings drift: schedules change, sensors lose calibration, economizers get overridden, and equipment begins operating out of sequence.

EEI’s commissioning engineers see this across all facility types, from healthcare and higher education to transit infrastructure and commercial portfolios. Even well-operated buildings contain hidden inefficiencies that impact comfort, increase energy use, and create operational challenges. RCx uncovers these issues, corrects them, and verifies improved performance.

Today, more owners are adopting RCx due to regulatory, energy, and operational pressures—including the Washington Clean Buildings Standard, Seattle Building Performance Standards, Denver Energize, and NYC Local Law 97—all of which emphasize improved performance in existing buildings.

Why a Retro-Commissioning Checklist Matters

A clear and repeatable RCx checklist ensures that no system, component, or sequence is overlooked. For portfolio owners, a consistent process also brings transparency—documenting findings, corrective measures, savings, and operator training.
Key advantages include:

• Ensures a standardized, whole-building evaluation
• Captures energy and comfort opportunities that may be missed during routine operations
• Verifies the impact of RCx measures and cost savings
• Supports compliance with key building performance regulations
• Provides a roadmap for ongoing optimization or future MBCx

Step-by-Step Retro-Commissioning Checklist

1. Preliminary Planning and Goal Setting

• Define scope and goals: Energy savings, comfort, compliance, carbon reduction, MBCx readiness
• Review utility history
• Select priority systems
• Develop the commissioning plan

EEI Note: For hospitals, labs, and critical facilities, EEI integrates occupancy, safety, and specialized system constraints.

2. Initial Facility Assessment

• Walk-throughs
• Operator interviews
• Documentation review
• BAS alarm and history review

3. System Testing and Building Performance Measurements

• Airflow and hydronic testing
• Functional testing of central and terminal units
• Controls sequence verification
• Identify performance gaps

Example: EEI recently corrected a failed discharge air temperature reset at a university building, eliminating constant reheat and reducing energy use.

4. Diagnostics and Root-Cause Analysis

• Trend reviews
• Economizer evaluation
• Valve/damper testing
• Override root-cause identification

EEI Approach: Complex buildings often require trend-based diagnostics and short-term monitoring to validate true operating behavior.

5. Prioritize Energy-Efficiency Opportunities

• Low/no-cost measures
• Operational improvements
• Capital recommendations only when needed
• Energy and emissions savings estimates

6. Implement Corrective Actions
Examples:

• BAS scheduling updates
• DCV tuning
• Reset strategies (SAT/CHW/HW/static pressure)
• Sensor calibration
• Rebalancing
• Sequence updates
• Reducing simultaneous heating and cooling

7. Verification and Re-Testing

• Functional retesting
• Controls verification
• Baseline comparison
• Savings validation

8. Documentation, Reporting, and Operator Training

• Final RCx report
• Updated O&M documentation
• Operator training
• Monitoring plan for ongoing commissioning or MBCx transition

How RCx Supports Compliance

• Washington Clean Buildings Standard
• Seattle Building Performance Standards
• Denver Energize
• NYC Local Law 97

Leading into Monitoring-Based Commissioning (MBCx)

RCx establishes the foundation for MBCx by correcting drift, aligning controls, and stabilizing building operation before analytics take over.
Benefits of Retro-Commissioning

• 10–25% energy savings typical
• Improved comfort and ventilation
• Reduced system wear
• Fewer reactive maintenance calls
• Documented compliance
• Strong foundation for MBCx

Start Improving Your Building’s Performance

EEI delivers RCx for healthcare campuses, universities, transit agencies, and commercial portfolios. Our approach blends technical depth, diagnostics, and long-term operational value.