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Applied Building Science: Taking the Mystery Out of Building Enclosure Commissioning​

Alan Scott Charlotte Metzler

In the previous two months, we explored the application of building science in material selection and specification, and in building enclosure improvements through analysis and careful detailing. These are important practices to avoid enclosure failures and building performance impacts due to design flaws that result in things like material incompatibility, moisture migration and thermal bridging. But what about imperfections in construction? Consider how many critical envelope components, from moisture barriers to flashing to sealant, are installed high above the ground in less than ideal weather conditions. Even the most skilled tradespersons are challenged. Likewise, the various components of a complete enclosure system are installed by different trades at different times—errors are bound to happen. Fortunately, building enclosure commissioning (BECx) provides an important level of quality assurance through design review, lab and on-site testing, and field observations.

While some principals of BECx are part of a typical building enclosure consulting scope, the comprehensive practice of enclosure commissioning is now coming into its own. New ASTM standards and guidelines like the National Institute of Building Science (NIBS) Guideline 3 have defined and standardized the practice, and the inclusion of BECx in LEED v4 has increased mainstream awareness. BECx may be performed independently or as part of a building system commissioning scope. In either case, the building enclosure commissioning agent (BECxA) represents the owner’s interests through an experienced eye, heading off potential problems before it’s too late or too costly to correct them. A typical BECx scope includes design review and specifications, submittal review, functional testing and construction inspection.

The building enclosure commissioning process begins with a series of design reviews conducted during the design development (DD) and construction document (CD) phases. The Enhanced Commissioning process in LEED v4 requires only two reviews, but additional reviews are recommended. The review covers both drawings and specifications from a building enclosure perspective, compared to industry best practices and the Owner’s Project Requirements (OPR) and Basis of Design (BOD) documents. The BECxA looks at critical enclosure details while considering their ability to prevent water infiltration, air leakage, vapor migration, condensation, and heat loss through thermal continuity. In addition, they review completeness and constructability of the proposed design, compatibility of adjacent materials, and future maintenance requirements.

The BECxA also develops a building enclosure commissioning specification for inclusion in the project manual. The BECx specifications outline the roles of all parties involved in the commissioning process and identify the specific building enclosure systems to be reviewed and the functional performance tests to be conducted. This important step sets the expectations for BECx during construction.

Early in the construction phase, the BECxA conducts a commissioning kick-off meeting with the owner/owner’s representative, design team, construction manager, general contractor, and all trades performing or interfacing with enclosure work. During the meeting, the scope, frequency, and intent of enclosure commissioning inspections is discussed, as well as quality control process for each building enclosure system.

During construction, the BECxA will review building enclosure product data submittals and shop drawings. These submittals are reviewed against the OPR, BOD, construction drawings and project specification requirements. Performance standards are verified and adjacent products are reviewed for compatibility. Shop drawings are also reviewed for coordination between the installing contractors. Just like the design reviews, shop drawings are analyzed for heat, air, and moisture management issues, as well as durability, maintainability, and constructability of the proposed details.

Mock-up testing. Image courtesy of WSP.

As construction progresses, the construction team performs performance tests prescribed by the BECxA to validate the performance of the systems and the success of the installation. These tests are often performed on laboratory or on-site mock-ups of the enclosure system. Testing that is performed early in the construction process allows for revisions to be made before work commences on the actual the building enclosure, avoiding costly revisions. For example, a proposed wall and window system included a window extrusion that was not sealing properly to the substrate. The mock-up test revealed that air was leaking past the extrusion. The solution was to shift the structural support anchors so that they provided a solid substrate for the window extrusion to seal to. This change added no cost to the assembly as no additional materials were needed for the solution, and since it was discovered before installation began, did not require costly retrofits.

Depending on project circumstances, the BECxA will recommend different testing regimens, but tests often include static air Infiltration, static pressure water penetration (water spray), dynamic pressure water penetration (water spray with fan), and structural performance. The BECxA witnesses both laboratory and on-site testing, and then prepares a report with representative photographs illustrating the results and recommendations for any necessary corrective measures. Sometimes in-situ tests are performed on the completed enclosure to validate final performance of the installed system.

Finally, the BECxA conducts construction inspections to validate that building enclosure systems are installed in accordance with the design documents, product data submittals, shop drawings, manufacturer’s installation instructions, and industry standards. Given the rapid pace of construction, it is vital that these inspections are completed at regular frequencies to ensure that any deficiencies are identified and repairs are observed prior to the installation of subsequent enclosure systems. Ideally, inspections should align with the start of each new system’s installation. That way proper practices can be identified, achieved, and maintained throughout the construction process.

Regardless of the best intentions, the complexity of today’s designs and building enclosure systems requires careful attention to detail during the design and construction process. From the early design process through the final deliverables of summary documentation at the end of construction, enclosure commissioning is completed through a collaborative, inclusive, and detailed approach. Early and frequent communication is a key element to success of many relationships and this is certainly true for building design and construction process. While BECx adds an upfront cost that is often not considered in project budgeting, the long-term pay-offs of improved building performance, reduced post-occupancy failures, and lower operation and maintenance costs can clearly outweigh the initial investment.


Alan Scott, FAIA, LEED Fellow, LEED AP BD+C, O+M, WELL AP, CEM, is an architect with 30 years of experience in sustainable building design. He is a senior associate with WSP in Portland, Ore. Charlotte Metzler is a building enclosures commissioning agent and enclosure design consultant with WSP in Arlington, Va. To learn more, visit www.wsp.com/usbuiltecology and follow Scott on Twitter @alanscott_faia.