Building Commissioning FAQ

This page answers the most common questions building owners, architects, and project managers ask about building commissioning. If you have a question that is not answered here, contact Prasino Engineering directly at info@prasinoeng.com.

General Questions

What is building commissioning?

Building commissioning (Cx) is a quality assurance process that verifies and documents that a building's systems — including mechanical (HVAC), electrical, plumbing, life safety, and building envelope — are designed, installed, tested, and capable of being operated and maintained to perform according to the owner's project requirements. It is led by an independent Commissioning Authority (CxA) who serves as the owner's advocate throughout the project.

What is the purpose of building commissioning?

The purpose of commissioning is to close the gap between design intent and actual building performance. Buildings are complex systems of systems, and without a systematic verification process, it is common for equipment to be installed incorrectly, controls to be programmed improperly, or systems to fail to work together as intended. Commissioning identifies and resolves these issues before they become costly operational problems.

What is the difference between commissioning, retro-commissioning, and re-commissioning?

Commissioning (NCx) is performed on new construction projects. It begins during pre-design and continues through the first year of occupancy.

Retro-commissioning (RCx) is the application of the commissioning process to an existing building that was never commissioned or was not commissioned to current standards. It is typically performed to address performance problems or to reduce energy costs.

Re-commissioning (ReCx) is the application of the commissioning process to a building that has been previously commissioned. Buildings drift from their original design intent over time, and re-commissioning restores them to their original performance baseline.

What is building envelope commissioning?

Building envelope commissioning (BECx) is a specialized form of commissioning focused on the performance of the building enclosure — the walls, roofs, windows, and doors that separate the interior from the exterior. Envelope commissioning verifies air barrier continuity, thermal performance, and moisture management to prevent air leakage, water infiltration, and energy loss.

Process and Scope Questions

When should commissioning begin on a project?

Commissioning should begin as early as possible — ideally during pre-design, before the first drawing is produced. Early engagement allows the Commissioning Authority to help develop the Owner's Project Requirements (OPR), review the design for performance and maintainability, and identify issues before they become costly changes in the field. The earlier commissioning begins, the greater the value it provides.

What systems are typically included in a commissioning scope?

A comprehensive commissioning scope typically includes: HVAC systems (air handling units, VAV systems, rooftop units, hydronic systems, building automation systems), electrical systems (emergency power, lighting controls, critical distribution), life safety systems (fire alarm, smoke control, integrated systems testing), and building envelope (air barriers, roofing, fenestration). The specific scope is defined in the commissioning plan and tailored to the project's requirements.

What is an Owner's Project Requirements (OPR) document?

The Owner's Project Requirements (OPR) is the foundational document of the commissioning process. It defines the owner's goals, expectations, and performance criteria for the building, including energy performance targets, indoor environmental quality requirements, system redundancy requirements, and operational expectations. Every commissioning decision is evaluated against the OPR.

What is a Functional Performance Test (FPT)?

A Functional Performance Test (FPT) is a documented test procedure that verifies a building system operates correctly under all modes of operation, including normal occupied and unoccupied modes, emergency and failure modes, and integrated systems testing. FPTs are developed by the Commissioning Authority and executed in the field with the contractor and controls technician present. All results are documented in the commissioning report.

Requirements and Compliance Questions

Is building commissioning required by code?

Yes, commissioning is required for most commercial buildings under the International Energy Conservation Code (IECC). The specific requirements vary by jurisdiction, but generally include commissioning of HVAC systems, lighting controls, and building envelope. Many states and municipalities have adopted the IECC with amendments that expand or clarify these requirements.

Is commissioning required for LEED certification?

Yes. The LEED (Leadership in Energy and Environmental Design) rating system requires Fundamental Commissioning as a prerequisite for all LEED projects. Enhanced Commissioning is an optional credit that provides additional points toward certification. Prasino Engineering has experience supporting LEED Gold and Silver projects and can provide all required commissioning documentation.

What ASHRAE standards govern the commissioning process?

The primary ASHRAE standards governing commissioning are ASHRAE Guideline 0-2019 (The Commissioning Process) and ASHRAE Standard 202-2018 (Commissioning Process for Buildings and Systems). These documents define the minimum requirements for a complete commissioning process and are referenced by LEED and many building codes.

Hiring and Cost Questions

Who hires the Commissioning Authority (CxA)?

The Commissioning Authority is hired directly by the building owner or developer. This direct relationship is essential for ensuring the CxA is an independent advocate for the owner's interests, free from conflicts of interest with the design team or the contractors. Some commissioning standards and LEED requirements mandate that the CxA be independent of the design and construction teams.

What should I look for when selecting a commissioning firm?

When evaluating commissioning firms, consider the following criteria:

Independence:The firm should be a true third-party provider, with no financial interest in the design or construction of the building.

Licensed Professional Engineers: Commissioning involves complex engineering judgments. Ensure the firm's team includes licensed Professional Engineers (P.E.) who are directly involved in your project.

Relevant Experience:The firm should have documented experience with projects of similar size, complexity, and building type.

In-House Technical Expertise: The firm should have deep, in-house expertise across all systems in your commissioning scope — mechanical, electrical, life safety, and envelope — rather than relying on subcontractors.

Diagnostic Equipment: A professional commissioning firm should own and bring its own calibrated diagnostic equipment, including airflow measurement tools, thermal imaging cameras, and building pressure testing equipment.

Communication and Documentation: Commissioning is a documentation-intensive process. Evaluate the firm's sample reports and communication practices to ensure they meet your standards.

How much does building commissioning cost?

The cost of commissioning varies depending on the size, complexity, and scope of the project. However, commissioning consistently delivers a strong return on investment. Studies conducted by Lawrence Berkeley National Laboratory found that commissioning of new construction buildings has a median payback period of approximately 4.2 years, with a median energy savings of 16%. For existing buildings, the median payback period is approximately 1.1 years.

The cost of commissioning is best understood not as an expense, but as an investment that reduces change orders, lowers energy costs, extends equipment life, and protects the owner's capital investment.