Building Insights: New BECx Requirements in LEED v5: What Developers and Building Owners Need to Know

The biggest cause of building failure is often not water itself, but deficiencies in the building envelope that allow water to penetrate, accumulate, and cause damage over time. Issues include deficient flashing, unsealed penetrations, thermal bridging, window and curtain wall installation errors, roofing defects, air barrier discontinuity, and waterproofing lapping failures.  All of which could have been addressed early-on through a robust quality assurance and verification program – Building Enclosure Commissioning (BECx).

The release of LEED v5 for Building Design and Construction (BD+C) marks a significant shift in commissioning requirements. One of the most notable changes is that BECx is now a required component of Fundamental Commissioning, rather than an optional strategy under Enhanced Commissioning.

This change reflects the industry's growing recognition that the building enclosure, as the primary barrier between interior and exterior environments, directly affects energy efficiency, occupant comfort, durability, indoor environmental quality, and operating costs.

Building Enclosure Commissioning: The Baseline

LEED v5 now makes BECx a prerequisite for commissioning credits.

This stems from LEED v5's adoption of commissioning provisions within ANSI/ASHRAE/IES Standard 90.1-2019 and ASHRAE 90.1-2022, both of which include requirements for design and quality review of building thermal envelope systems and components. As a result, projects pursuing LEED v5 certification must address enclosure performance as part of the commissioning process.

For owners and developers, this means planning for enclosure commissioning early to establish performance objectives and coordinate commissioning activities throughout project delivery.

By incorporating BECx into the Fundamental Commissioning prerequisite, LEED v5 elevates the enclosure to the same level as MEP systems. This helps ensure that enclosure performance objectives related to energy efficiency, durability, moisture management, and occupant comfort are addressed throughout design and construction.

Key BECx Activities Now Required Under LEED v5 Fundamental Commissioning

Why It Matters

Building enclosure deficiencies are a leading source of post-occupancy performance issues. Air leakage, water intrusion, thermal bridging, condensation, and premature façade deterioration increase energy consumption, generate costly repairs and warranty claims, and negatively affect occupant satisfaction.

LEED v5 addresses these risks through design reviews, testing, verification, and documentation that confirm the enclosure is designed and constructed to meet the owner's performance expectations and sustainability goals.

The Importance of the Owner's Project Requirements

LEED v5 requires that the Owner's Project Requirements (OPR) define building enclosure performance objectives. Under LEED v5, Building Enclosure Commissioning (BECx) and MEP commissioning are equal, parallel commissioning processes. BECx is a separate discipline requiring specialized expertise in thermal continuity, air/water control, and building envelope performance. In simple terms, MEP commissioning addresses the core functional systems while BECx addresses the complexities of the shell that protects them.

Establishing performance expectations early helps align project stakeholders, guide design decisions, and create criteria for construction-phase verification. The OPR becomes the foundation for evaluating whether the completed enclosure meets the owner's objectives for energy efficiency, durability, maintainability, and occupant comfort.

Where G&T Adds Value

G&T works with developers and owners to establish practical, measurable enclosure performance goals aligned with project objectives, budgets, risk profiles, and sustainability targets.

We translate objectives into requirements incorporated within the OPR and Basis of Design (BOD), supporting both LEED compliance and building performance. G&T's Certified Building Enclosure Commissioning Providers (BECxP) bring expertise in building science, façade systems, waterproofing, air barrier continuity, thermal performance, field testing, and enclosure quality assurance.

G&T performs technical enclosure-focused design reviews, specification evaluations, mock-up and field-testing observations, enclosure-related installation observations, and generates commissioning documentation. By integrating enclosure expertise with project and cost management services, we help identify issues early and reduce post-occupancy remediation risk.

LEED v5, NYC Codes, and Building Enclosure Performance

For projects in NYC, enclosure commissioning offers benefits beyond LEED. Recent updates to the NYC Building Code and Energy Conservation Code place greater emphasis on enclosure performance, air-leakage control, thermal continuity, commissioning, and energy efficiency.

Many activities required for LEED v5 BECx support local code compliance. The 2025 New York City Energy Conservation Code (NYCECC), based on the 2024 IECC and ASHRAE 90.1-2022, introduces expanded documentation requirements, updated testing provisions, enhanced thermal-bridge requirements, and air-leakage verification. Mandatory whole-building air-leakage testing for many projects underscores the importance of enclosure performance.

The relationship between BECx, evolving energy codes, and Local Law 97 (carbon emissions compliance) is increasingly important. An underperforming enclosure can undermine energy-model assumptions, increase heating and cooling loads, and contribute to greenhouse gas emissions. Validating enclosure performance helps owners manage energy use, reduce compliance risk, and support carbon-reduction goals.

Conclusion

LEED v5 BECx changes mean that industry authorities recognize that high-performance buildings begin with high-performing enclosures.

For owners and developers, BECx isn’t just meant for checking LEED credit boxes. BECx is an opportunity to reduce risk, enhance building performance, improve durability, and advance sustainability objectives. By engaging G&T's certified BECx providers early, project teams can establish measurable performance criteria, support LEED or NYC code compliance, and verify that enclosure systems perform as intended while protecting long-term asset value.

NOTE:  Although LEED v5, the NYC Energy Conservation Code, and the NYC Building Code serve different purposes, they are increasingly aligned around the same ASHRAE 90.1-based enclosure performance principles. The Energy Code establishes the required level of envelope performance, the Building Code governs execution and compliance, and LEED v5 Building Enclosure Commissioning provides the verification process that helps ensure those requirements are achieved in practice. As building owners face increasing pressure from Local Law 97, BECx serves as a valuable bridge between design intent, code compliance, and long-term operational performance.

For more information, contact Christina Mueller — Director, Enclosures & Facades

c.mueller@gardinerusa.com