Understanding Building Enclosure Commissioning (BECx)

02 Dec 2025

How BECx improves building performance, reliability, and long-term value

Across the construction industry, the building enclosure is a frequent source of performance issues. Roof leaks, condensation, and uncontrolled air movement cause nearly 70 percent of construction defect claims. Building Enclosure Commissioning, or BECx, applies a structured quality-assurance process that helps project teams address these risks early and verify performance from design through occupancy.

BECx confirms that the enclosure, including the roof, walls, windows, below-grade areas, and foundation, meets design intent and performance criteria. Through testing and documentation, it helps owners, designers, and contractors reduce risk, improve energy efficiency, and extend the life of the building across North America’s varied climate zones.

The Role of the Building Enclosure

The building enclosure protects against weather, moisture, and temperature extremes. Its performance directly affects energy use, comfort, and durability. Poor detailing or installation can lead to water intrusion, air leakage, and premature deterioration.

BECx adds verification and testing to confirm that enclosure systems work together as intended. This approach supports compliance with evolving energy codes and sustainability standards while improving resilience and long-term performance.

Codes and Certification Drivers

Recent updates to national energy codes and sustainability programs have expanded the role of enclosure commissioning. The 2021 and 2024 International Energy Conservation Code (IECC) and ASHRAE 90.1-2016 or later editions include provisions for BECx that have now been adopted in many jurisdictions across the United States.

Projects pursuing LEED v4/v4.1 certification or registering under the new LEED v5 must engage in some level of BECx. LEED v4 requires the inclusion of building enclosure requirements in the Owner’s Project Requirements (OPR) and Basis of Design (BOD) as a part of the Fundamental Commissioning prerequisite. These projects have the option to implement basic BECx review and verification activities for additional points. LEED v5 raises the bar with more extensive design and submittal review as part of the prerequisite, and the addition of building enclosure testing requirements in the optional Enhanced Commissioning credit. Both versions extend commissioning beyond mechanical and electrical systems to include the full building enclosure, improving durability, energy performance, and occupant comfort.

How BECx Differs from Traditional Commissioning

Traditional commissioning focuses on mechanical and electrical systems. BECx applies the same systematic approach to the building enclosure, confirming that all six sides meet defined thermal, air, and moisture-control criteria.

BECx begins early in design and construction, when materials and detailing most affect long-term performance. Traditional commissioning typically takes place later, before occupancy. Together, these processes provide continuous quality assurance throughout the building lifecycle.

The People and the Process

Effective BECx programs are led by certified professionals. Credentials include the University of Wisconsin–Madison Building Enclosure Commissioning Provider (BECxP) and Commissioning Authority plus Building Enclosure (CxA+BE), as well as the IIBEC Certified Building Enclosure Commissioning Provider (CBECxP). Each requires education, field experience, and continuing development.

The BECx process typically includes:

• Design phase: establishing targets and reviewing drawings.
• Construction phase: observing installation, witnessing field testing, verifying compliance, and systems training.
• Occupancy phase: completing a ten-month review and final documentation.

Cost, Value, and Timing

While some owners view BECx as an added cost, it often pays for itself within two to six years through reduced maintenance, avoided rework, and improved energy performance. In some cases, the return on investment can be almost immediate with the selection and detailing of optimal enclosure materials and systems. Engaging a BECx consultant early in pre-design maximizes this return by identifying potential issues before they reach the field.

Field Testing and Documentation

Field testing is performed by an independent third party to maintain objectivity. The BECx consultant witnesses the test, which are incorporated into the final BECx report. Contractors use checklists, many times daily, to confirm field conditions and installation.

Before project closeout, the facility team receives a Building Enclosure Systems Manual with as-built drawings, product data, and maintenance guidance. Training on the building enclosure systems helps staff identify and address issues early, extending the service life of the enclosure.

Building Enclosures That Perform as Designed

BECx brings structure and accountability to one of the most failure-prone aspects of construction. By integrating testing and documentation from design through occupancy, BECx helps ensure that buildings perform as intended under real-world conditions.