Building Enclosure Commissioning for Medical & Educational Facilities

An evolving array of building codes and standards has been issued to quantify and enforce heightened levels of building performance. These include the International Energy Conservation Code (IECC), ASHRAE/IESNA 90.1 and ASHRAE/IESNA 189.1, the International Green Construction Code (IGCC) and the Green Building Initiative's (GBI) Commercial Green Building Standard, among others. And, of course, there are the green rating systems and their specific requirements.

In April 2011, USGBC introduced its latest green building rating system, LEED for Healthcare (LEED HC), to guide the design and construction of both new and major renovations of existing inpatient, outpatient and other medical-related structures. There is also the LEED for Schools Rating System, which recognizes the unique requirements of K-12 schools by addressing such issues as classroom acoustics and mold prevention.

BECx test set up to measure whole building air infiltration/exfiltration..

But, achieving rating credits and code compliance does not guarantee actual performance. While emphasis may be placed on selecting green components, there is often insufficient focus on whether the selected components are assembled into a properly functioning system that realizes the design intent.

Commissioning as the Solution
An increasingly recognized solution to the performance gap is a robust building commissioning program—a process intended to ensure that building systems are installed and perform in accordance with the design intent.

Recognizing this, LEED 2009 for New Construction and Major Renovations, as well as LEED for Healthcare and LEED for Schools, includes a prerequisite for "Fundamental Commissioning" of building energy systems.

Traditional commissioning plans have targeted only the mechanical, electrical and plumbing (MEP) elements, and most commonly the HVAC system. However, if the exterior enclosure is allowing air and/or moisture to pass uncontrolled, the air handling system becomes increasingly difficult to control, let alone operate efficiently. As a result, there is increased focus on the ability of the building enclosure to perform effectively as a thermal barrier, moisture barrier, air barrier, acoustical boundary and structural element, while still serving as a source of beneficial daylighting and making an aesthetic architectural statement.

To truly provide whole building commissioning, the program must include both MEP commissioning and Building Envelope

The Case for Building Enclosure Commissioning (BECx)
The building enclosure is a sophisticated system composed of multiple interactive layers of highly-engineered materials that serve to let in and keep in desirable elements while screening out undesirable elements (or allowing them to escape). Moreover, today's high-performance "green" building enclosures are complex amalgams of innovative materials and technologies, assembled in new and often quasi-experimental ways that involve heightened interaction between the environment and HVAC systems. Recognizing the enclosure as an interlinked and interdependent system that delivers these functions— rather than a mere collection of discrete, independent components— is inherent in BECx philosophy.

Building enclosure failure can impose significant losses on building owners in the form of repairs, higher operating and maintenance costs, occupant dissatisfaction and legal liability proceedings based on water damage, indoor environmental degradation or health-and-safety issues.

Consequently, there is increasing interest in total building commissioning where the building envelope elements are commissioned as well as all the MEP systems. It is a systematic process of ensuring that the exterior elements of a building provide the needed environmental separation according to the building Owner's Performance Requirements (OPR) for the intended use.

Special Purpose
Issues Healthcare and educational facilities require a number of unique considerations in their design, construction and operation. Performance attributes of special significance include:

Sound
In classrooms, background noise generated by adjacent classrooms, music rooms, mechanical rooms, HVAC systems and/or outdoor noise sources affects the learning environment.

Moisture
Controlling moisture penetration is a critical function of the building enclosure.

Air Exchange
Controlled ventilation through the building envelope is important to the proper operation of the HVAC system.

Energy
The OPR should specify targeted energy performance, which can be based on references to the many existing codes and standards.

The BECx Process
Because the building enclosure cannot be easily manipulated after installation, given the inaccessibility of many components post-construction, effective BECx begins at project inception and continues through completion and building occupancy. The BECx process unfolds in five stages as outlined within the NIBS Guideline 3, Exterior Enclosure Technical Requirements for the Commissioning Process, and also per Canada's CSA Z320-11, Building Commissioning:

1. Pre-Design Stage, which includes the selection of the independent third-party BECx Agent who will serve as the owner's advocate and as coordinator and validator of the design/build process; the development of the Owner's Project Requirements (OPR) that outlines the owner's expectations for building features and performance; and writing the BECx specification and a BECx plan to tailor the scope of activities to the particular building.
2. Design Stage, during which the established performance objectives are referenced and project drawings and specifications reviewed to confirm that there are no issues inherent in the design that may cause the system to not function as intended.
3. Pre-construction Stage, which features a review of construction sequencing, scheduling and coordination of trades.
4. Construction Stage, during which the BECx Agent works with the individual contractors and trades to periodically inspect and evaluate work in progress and supervise field quality assurance testing.
5. Post-construction and occupancy stage, which involves compiling project close-out documentation and which may include training for building maintenance personnel.

Conclusion
The benefits of commissioning include reduced energy use, lower operating costs, fewer contractor callbacks, improved occupant productivity and verification that the systems perform per the owner's project requirements (OPR).

Rather than being a bottleneck, the commissioning process usually helps streamline construction by improving schedules, identifying potential problems in advance, improving productivity and preventing costly post-installation changes and call-backs to tweak the new building into proper operation.

BECx is especially beneficial in green building projects because they often incorporate novel or complex features such as innovative cladding technologies. Cutting edge design options and materials may individually earn green rating credits, but can collectively fall short of overall performance objectives when not fully integrated from a systemic viewpoint. Nevertheless, all require serious performance verification before building owners can feel comfortable that their investment is truly "green."

John Runkle, PE, Director—Building Sciences, Architectural Testing, Inc.

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