9.1 EBCx Process Fundamentals, Goals & CFR

9.1 EBCx Process Fundamentals, Goals & CFR

Quick Summary: Existing Building Commissioning (EBCx) is a systematic engineering process focused on optimizing the operation, energy efficiency, and indoor environmental quality of existing facilities without requiring major capital equipment replacements. Governed by ASHRAE Guideline 0.2-2015 and ASHRAE Standard 100, EBCx resolves operational drift, sensor calibration errors, mechanical binding, and manual control overrides. Rather than relying on prospective design assumptions, EBCx establishes the Current Facility Requirements (CFR) as its benchmark, bridging the gap between original design intent and modern operational realities through four structured phases: Planning, Investigation, Implementation, and Handover.

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The Genesis of Existing Building Commissioning: The Inevitability of Operational Drift

Modern commercial, institutional, and industrial facilities are complex, dynamic ecosystems comprising thousands of interconnected electromechanical, hydronic, pneumatic, and digital control components. Even when a building is delivered in a fully optimized, commissioned state at Substantial Completion, its operational performance inevitably degrades over time. Comprehensive studies by the Lawrence Berkeley National Laboratory (LBNL), led by Evan Mills (2009, 2020), have documented that commercial buildings experience systemic operational drift (or energy drift) of 10% to 30% within three to five years of occupancy.

Operational drift is driven by several compounding factors:

• Sensor Decalibration and Drift: Piezoresistive differential pressure sensors, relative humidity capacitive sensors, and air/water temperature thermistors drift from their factory calibration curves over thousands of operating hours, sending false process variables to the Building Automation System (BAS).
• Manual Operator Overrides: Faced with acute occupant hot/cold complaints or nuisance alarms, operating engineers frequently apply temporary software overrides (e.g., locking supply air temperature at 55°F, fixing minimum outdoor air dampers at 40% open, or disabling chilled water temperature reset schedules). These temporary workarounds are routinely forgotten and become permanent operational handicaps.
• Mechanical Wear and Linkage Slop: Actuator geartrains wear down, damper blade edge seals dry out and crack, damper linkages slip out of alignment, and control valve seats corrode or collect debris, preventing tight 100% shutoff.
• Space Reconfiguration and Density Escalation: Buildings rarely retain their original programmatic layouts. Private executive offices are demolished to create high-density open-plan collaborative spaces, storage closets are converted into high-heat-dissipating IT/server rooms, and corporate mergers double floor occupant densities without corresponding engineering adjustments to the air distribution or hydronic balancing networks.
• Deferred Maintenance and Budget Cuts: Deferred filter replacements, uncleaned heat exchanger tubes, scaled cooling tower fill, and neglected steam trap inspections progressively undermine thermodynamic efficiency.

Existing Building Commissioning (EBCx) emerged as the standardized engineering discipline designed specifically to counteract operational drift, uncover latent electromechanical defects, and tune existing building systems to operate at their highest thermodynamic efficiency.

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Core Terminology & Distinctions: The EBCx Taxonomy

Within the professional commissioning nomenclature established by ASHRAE Guideline 0.2-2015 (Commissioning Process for Existing Systems and Assemblies), several interrelated terms must be clearly distinguished:

Existing Building Commissioning (EBCx) Taxonomy:
┌─────────────────────────────────────────────────────────────────────────────┐
│               Existing Building Commissioning (EBCx) Umbrella               │
└──────────────────────────────────────┬──────────────────────────────────────┘
                                       │
         ┌─────────────────────────────┴─────────────────────────────┐
         ▼                                                           ▼
┌───────────────────────────────────┐       ┌───────────────────────────────────┐
│      Retro-Commissioning (RCx)    │       │       Re-Commissioning (Re-Cx)    │
├───────────────────────────────────┤       ├───────────────────────────────────┤
│ • Applied to an EXISTING building │       │ • Applied to a facility that was  │
│   that was NEVER previously       │       │   PREVIOUSLY commissioned         │
│   commissioned.                   │       │   (under NCCx or RCx).            │
│ • Establishes the baseline CFR    │       │ • Validates performance against   │
│   for the very first time.        │       │   updated CFR; restores tuning.   │
│ • Uncovers severe historical      │       │ • Performed periodically (e.g.,   │
│   installation & design defects.  │       │   every 3–5 years).               │
└───────────────────────────────────┘       └───────────────────────────────────┘
                                       │
                                       ▼
┌─────────────────────────────────────────────────────────────────────────────┐
│                  Ongoing / Monitoring-Based Commissioning (MBCx)             │
│ • Continuous data analytics, automated fault detection (AFDD), and ongoing  │
│   tracking to permanently prevent operational drift post-EBCx.              │
└─────────────────────────────────────────────────────────────────────────────┘

1. Existing Building Commissioning (EBCx): The overarching, broad term encompassing all commissioning activities applied to existing buildings, mechanical equipment, electrical switchgear, envelope assemblies, and building management systems.
2. Retro-Commissioning (RCx): The commissioning process applied to an existing building that has never previously undergone formal commissioning (neither during initial construction nor during subsequent renovations). RCx projects frequently uncover fundamental installation blunders, missing equipment components, incorrect piping connections, and un-tuned PID loops that have persisted unnoticed since the day the building opened.
3. Re-Commissioning (Re-Cx): An EBCx process applied to a facility that was previously commissioned—either at initial construction turnover (New Construction Commissioning, NCCx) or through an earlier RCx project. Re-Cx is typically triggered by scheduled cyclical intervals (e.g., every 3 to 5 years per corporate policy or local municipal energy mandates) or by substantial changes in building ownership, tenant occupancy profiles, or central plant renovations.
4. Ongoing Commissioning (OCx) / Monitoring-Based Commissioning (MBCx): A continuous, data-driven operational process that integrates automated fault detection and diagnostics (AFDD), continuous system trending, and routine engineering reviews to maintain facility performance indefinitely, preventing the recurrence of operational drift after an EBCx project concludes (detailed in Chapter 11).

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Owner Drivers and Value Proposition of EBCx

Building owners rarely commission existing facilities purely out of academic curiosity; EBCx is driven by acute business drivers, regulatory pressures, and risk-management imperatives:

1. Energy and Greenhouse Gas (GHG) Reduction

According to the LBNL national commissioning studies, EBCx delivers median whole-building energy savings of 16%, with median simple payback periods ranging from 1.1 to 2.0 years. Unlike capital retrofits that require multi-million-dollar capital outlays, EBCx delivers rapid, measurable reductions in electrical demand (kW), electrical consumption (kWh), and fossil fuel use (therms/natural gas or Mlbs/steam) by optimizing existing control code, realigning operating schedules with true occupancy, and eliminating simultaneous heating and cooling.

2. Indoor Environmental Quality (IEQ) & Thermal Comfort

Tenant dissatisfaction and chronic comfort complaints directly damage commercial asset value and tenant retention. EBCx systematically resolves:

• Persistent hot/cold complaints caused by uncalibrated zone thermostats, jammed VAV dampers, or hunting reheat valves.
• Inadequate outdoor air ventilation rates violating ASHRAE Standard 62.1, causing lethargy, sick building syndrome (SBS), and elevated indoor carbon dioxide ($CO_2$) levels.
• Space humidity excursions resulting in mold growth, microbial colonization, and envelope condensation during humid summer months, or static electricity and respiratory irritation during dry winter months.

3. Operational Reliability & Equipment Life Extension

Un-tuned control loops subject expensive central plant machinery to severe mechanical stress. Centrifugal chillers short-cycling under light loads, condensing boilers experiencing thermal shock from cold return water, and VFD fan motors hunting erratically between 20 Hz and 60 Hz suffer premature bearing, motor, and compressor burnout. EBCx stabilizes operating regimes, eliminates unnecessary run-hours, and protects equipment capital assets.

4. Transition from Reactive to Proactive Maintenance

In many uncommissioned facilities, facility engineers operate in a permanent state of crisis management—running from one catastrophic failure or hot/cold call to another. EBCx identifies failing components (e.g., leaking valves, slipping belts, seized damper linkages) before they manifest as catastrophic failures, enabling maintenance leadership to transition to structured, predictive Computerized Maintenance Management System (CMMS) scheduling.

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NCCx vs. EBCx Paradigms: The Critical Transition from OPR to CFR

The most fundamental conceptual difference between New Construction Commissioning (NCCx) and Existing Building Commissioning (EBCx) lies in the core foundational document that governs performance acceptance criteria:

Core Governance Paradigm Comparison:
NCCx Paradigm:  Owner's Project Requirements (OPR)  ──►  Basis of Design (BOD)  ──►  Field Acceptance
EBCx Paradigm:  Current Facility Requirements (CFR)  ──►  Field Diagnostics    ──►  Optimization

The Owner's Project Requirements (OPR) in NCCx

In new construction, the commissioning process is anchored by the Owner's Project Requirements (OPR), authored during pre-design per ASHRAE Standard 202 and Guideline 0. The OPR defines what the owner wants to build: prospective spatial requirements, future occupancy estimates, theoretical environmental setpoints, sustainability targets (e.g., LEED Platinum), and future equipment redundancy criteria. The design team then creates the Basis of Design (BOD) to explain how their proposed engineering design will satisfy those prospective owner goals.

The Current Facility Requirements (CFR) in EBCx

In an existing building, the original OPR is almost universally obsolete—if it was ever documented at all. The building owner, tenants, space layouts, and mechanical systems have evolved. An existing building cannot be judged against what someone intended twenty years ago; it must be assessed against how the facility is actually used today.

Under ASHRAE Guideline 0.2-2015, the foundational governance document for EBCx is the Current Facility Requirements (CFR). The CFR is a formal written document that defines the current operational needs, environmental tolerances, occupancy patterns, and operating constraints of the facility as it currently exists. It establishes the authoritative baseline against which all diagnostic test results, operational sequences, and proposed energy conservation measures (ECMs) are evaluated.

Reconciling Original Design Intent with Current Operational Realities

Developing the CFR requires the Commissioning Provider (CxP) to lead a rigorous reconciliation process between legacy documentation and physical operational facts:

1. Occupancy Profile and Density Evolution: The original design may have anticipated an occupant density of 1 person per 150 usable square feet with fixed 8:00 AM to 5:00 PM operating schedules. Field audits may reveal open-plan call centers operating with 1 person per 65 square feet, rotating shifts, and hybrid telecommuting schedules that leave entire wings empty on Mondays and Fridays.
2. Partition and Space Utilization Modifications: Private perimeter offices converted into conference rooms, interior storage rooms converted into computer training labs, or enclosed breakrooms added without ductwork modifications alter the thermal zone balance, rendering original airflow balancing schedules invalid.
3. Operating Schedule Realignment: Original HVAC sequences designed for a 50-hour operating week may now run 168 hours per week (continuous 24/7 operation) because a single small department requires evening access. The CFR identifies these disconnects, enabling the CxP to propose dedicated after-hours terminal solutions rather than conditioning the entire facility.
4. Thermal and Plug Load Changes: Legacy lighting power densities (LPD) of 1.8 W/ft² (fluorescent T12/T8) may have dropped to 0.4 W/ft² following LED retrofits, dramatically reducing internal sensible heat gains during winter and causing perimeter zones to suffer heating deficits. Simultaneously, dense workstation multi-monitor setups and localized server racks introduce concentrated plug loads never envisioned in original load calculations.
5. Environmental Setpoint Boundaries: The CFR explicitly documents the owner's permissible space temperature deadbands (e.g., 70°F heating setpoint, 75°F cooling setpoint with a mandatory 5°F deadband per ASHRAE Standard 90.1), relative humidity limits (e.g., 30% to 55% RH per ASHRAE Standard 55), space pressurization cascades (e.g., positive pressure for clean corridors, negative pressure for restrooms and chemical storage), and acoustic noise criteria (NC curves).

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Distinguishing EBCx from ASHRAE Energy Audits (Levels 1, 2, and 3)

A frequent source of confusion among building owners and facility managers is the distinction between an ASHRAE Energy Audit (conducted per ASHRAE Procedures for Commercial Building Energy Audits, PCBEA) and an Existing Building Commissioning (EBCx) project (conducted per ASHRAE Guideline 0.2-2015). While both disciplines aim to reduce energy consumption, their core philosophies, diagnostic methods, field testing rigor, and capital investment requirements differ substantially.

The Three Tiers of ASHRAE Energy Audits

• ASHRAE Level 1 (Walk-Through Analysis): A preliminary visual survey and high-level utility billing analysis. It identifies glaring energy waste, establishes baseline energy use intensity (EUI), and screens potential capital energy conservation measures (ECMs) for further study. It involves zero functional field testing or continuous data logging.
• ASHRAE Level 2 (Energy Survey and Analysis): An in-depth engineering analysis that breaks down annual energy consumption by end-use (cooling, heating, fans, lighting, plug loads, domestic hot water). The auditor evaluates detailed utility tariffs, performs engineering calculations or building energy modeling, and presents a detailed capital expenditure (CapEx) investment plan with financial return metrics (Internal Rate of Return, Net Present Value, Life-Cycle Cost Analysis).
• ASHRAE Level 3 (Investment-Grade Audit): A highly sophisticated engineering and financial audit designed to support major project financing or Energy Savings Performance Contracts (ESPC). It requires rigorous sub-metered data logging, calibrated hourly dynamic computer simulation (e.g., DOE-2, EnergyPlus), and detailed bid-ready engineering cost estimates to de-risk massive capital replacements.

The Fundamental Contrast: Capital Replacement vs. Operational Optimization

The fundamental distinction can be stated simply:

• Energy Audits answer: "What new capital equipment should the owner purchase and install to replace old equipment?" (e.g., replacing a 20-year-old constant-speed centrifugal chiller with a variable-speed magnetic-bearing chiller; replacing DX split-systems with a heat recovery VRF network; replacing fluorescent luminaires with networked LED fixtures).
• EBCx answers: "How can we make the owner's existing equipment, controls, and distribution networks work correctly, stably, and efficiently as originally intended, or better?" (e.g., tuning uncalibrated chilled water sensors, reprogramming unstable PID loops, eliminating simultaneous heating and cooling, implementing automated dynamic static pressure resets, repairing broken economizer linkages, and restoring hydronic balance).

Furthermore, while an energy audit relies heavily on theoretical calculations and spreadsheet models, EBCx requires hands-on physical functional testing, continuous BAS trend diagnostics, and temporary data logging. An energy auditor looks at a VAV box and calculates the energy savings of replacing it; a commissioning provider opens the ceiling tile, connects a digital manometer to the flow cross, strokes the damper actuator through its 0% to 100% travel, verifies reheat valve seat tightness, checks the calibrated $K$-factor in the digital controller, and eliminates airflow hunting.

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EBCx vs. Energy Audit Comparison Matrix

The following matrix summarizes the critical engineering and administrative distinctions between the two processes:

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The Four Phases of the EBCx Process Lifecycle

Under ASHRAE Guideline 0.2-2015, the execution of an existing building commissioning project is organized into four sequential, rigorous phases:

The Four Structured Phases of Existing Building Commissioning:
┌──────────────────────┐       ┌──────────────────────┐
│   1. PLANNING PHASE  │ ────► │ 2. INVESTIGATION     │
│                      │       │    PHASE             │
│ • Facility Scoping   │       │ • Historical Data    │
│ • Team Assembly      │       │ • Site Walkthrough   │
│ • Develop Draft CFR  │       │ • Diagnostic Testing │
│ • Author EBCx Plan   │       │ • Findings Log       │
└──────────────────────┘       └──────────┬───────────┘
                                          │
                                          ▼
┌──────────────────────┐       ┌──────────────────────┐
│  4. HANDOVER &       │ ◄──── │ 3. IMPLEMENTATION    │
│     PERSISTENCE      │       │    PHASE             │
│ • Operator Training  │       │ • Owner Selection    │
│ • Systems Manual Upd │       │ • Execute Low-Cost   │
│ • Final EBCx Report  │       │ • Verify & Retest    │
│ • Ongoing Cx Plan    │       │ • M&V Energy Impact  │
└──────────────────────┘       └──────────────────────┘

1. The Planning Phase

The Planning Phase establishes the project framework, administrative boundaries, and engineering expectations:

• Facility Scoping & Initial Assessment: Reviewing facility size, age, HVAC system types, past renovation history, and owner motivations.
• Commissioning Team Assembly: Establishing the multi-disciplinary team, comprising the Commissioning Provider (CxP), Owner's Project Manager, Facility O&M staff, Controls Contractor, and Test, Adjust, and Balancing (TAB) professionals.
• Developing the Current Facility Requirements (CFR): Conducting workshops with executive ownership, building operators, and tenant representatives to document thermal criteria, occupancy schedules, indoor air quality mandates, and energy reduction targets.
• Authoring the EBCx Plan: Creating the master roadmap detailing project milestones, diagnostic testing protocols, safety requirements, logging procedures, and data deliverables.

2. The Investigation Phase

The Investigation Phase is the intensive diagnostic core of EBCx, where latent operational failures are uncovered:

• Historical Data & Utility Analysis: Collecting 24 to 36 months of continuous utility data, weather-normalizing consumption via degree days, benchmarking against ENERGY STAR Portfolio Manager, and auditing electric rate tariffs (detailed in Section 9.2).
• Facility Staff & Occupant Interviews: Extracting institutional knowledge, identifying chronic complaint zones, and discovering undocumented manual control overrides.
• Detailed Physical Field Walkthrough: Inspecting AHUs, central plants, valves, damper seals, sensors, and variable frequency drives (detailed in Section 9.3).
• Diagnostic Functional Testing & Data Logging: Executing controlled step-response tests and deploying portable data loggers to capture dynamic process behavior.
• Developing the Master EBCx Findings Log: Logging all identified operational deficiencies, root causes, estimated energy savings, implementation costs, and simple payback periods.

3. The Implementation Phase

In the Implementation Phase, approved optimization measures are physically executed and verified:

• Owner Measure Prioritization: The owner reviews the Findings Log and selects which low-cost/no-cost operational improvements to execute immediately and which capital projects to defer to future capital budgets.
• Implementation Oversight & Execution: The CxP coordinates with in-house facility staff, mechanical contractors, and controls vendors to reprogram DDC logic, replace failed sensors, realign damper linkages, and eliminate software overrides.
• Verification Testing & Retesting: The CxP repeats functional diagnostic tests and examines post-implementation trend logs to empirically verify that every implemented measure operates correctly and achieves its intended thermodynamic performance without creating unintended side effects.
• Measurement and Verification (M&V): Quantifying actual utility bill reductions in accordance with the International Performance Measurement and Verification Protocol (IPMVP Option B or Option C).

4. The Handover and Persistence Phase

The final phase ensures that the energy and operational gains achieved during EBCx persist over the long term:

• Facility Operator Training: Conducting hands-on classroom and field training with O&M staff to explain newly implemented control sequences, reset schedules, and diagnostic troubleshooting routines.
• Updating the Facility Systems Manual: Revising the Systems Manual (per ASHRAE Guideline 1.4) with updated sequences of operation, calibrated setpoints, single-line diagrams, and preventive maintenance schedules.
• Publishing the Final EBCx Report: Documenting the entire project history, baseline energy consumption, identified findings, implemented measures, verified utility savings, and final financial return metrics.
• Ongoing Commissioning (OCx) Plan: Establishing continuous monitoring procedures, automated fault detection algorithms, and periodic re-benchmarking protocols to prevent the facility from drifting back into operational inefficiency.