Architects are taught to design spaces that inspire the occupants that work or live in them. One example of this is the entrance that artist and architect Richard Meier created for the D’Amato U.S. Courthouse in Central Islip, New York. All visitors enter through a nine-story rotunda in the form of a cone, top-lit from a large skylight. As awe-inspiring as this was intended to be, unfortunately, in 2011, visitors’ experiences were hampered due to a large net blocking the skylight while the leaks around the skylight were being fixed, only 11 years after the building was opened. With the proper building enclosure commissioning (BECx) services, it is quite possible the leaks could have been prevented.

Commissioning services emerged in World War II, when detailed processes for testing were used to verify that all systems were working properly on naval ships. The practice continued to expand to include detailed protocols for testing computer centers in the 1960s. Over time, these services were applied to increasing numbers of facilities and were specifically focused on mechanical, electrical and plumbing (MEP) components such as heating, ventilating and air conditioning (HVAC) systems. The testing was intended to keep building infrastructure from failing in critical facilities like data centers, computer rooms and hospitals. Over the years, HVAC systems and other MEP elements have evolved and become a regular part of the design and construction practice. This has led to the development of standardized protocols for commissioning services as defined by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE).

As MEP systems have progressed, so have the building materials used to construct the physical facilities. In the early 2000s, the notion of verifying systems grew from HVAC to considering testing protocols for the portion of the building that separates the interior from the exterior, known as the building enclosure. Building enclosure systems have become increasingly more complex as the science behind the materials has advanced. The need to verify that these systems were detailed and built to meet the owner’s requirements has increased.

This is what led the National Institute of Building Sciences (NIBS) to create its Guideline 3 in 2006 and 2012 to help guide professionals in performing commissioning for the enclosure. Later, ASTM International created E2813 and E2947, and the International Organization for Standardization (ISO) recently released ISO/21105-1 to further help building owners and commissioning professionals define the building enclosure commissioning process. LEED v4 has also included BECx in the building certification points structure.

While both types of services — MEP commissioning and BECx— focus on verifying that systems meet the owner’s project requirements and follow the ASHRAE guideline processes, they are quite different; each requires a unique set of skills.

Differences in Testing

MEP commissioning helps validate that systems are working the way they were designed and intended to be installed. This process involves challenging the system by running a functional testing script uniquely written for that system. The functional test takes the system through a list of commands developed to challenge the HVAC and electrical systems to react based on the sequence of operation for the system being tested. The functional test is, for the most part, mechanical in nature. A command may open a chilled water valve or create a transition for one electrical system to another.

In contrast to testing HVAC and electrical systems by stressing the system, BECx focuses on the building’s passive reactions. BECx concentrates on air and moisture movement through the enclosure system to prevent mold and air quality issues. While the tests performed are dynamic, the reactions the building has to them are passive. The building enclosure professional will review the failure criteria set forth by the owner or architect and determine a location in the building to test the enclosure. If the enclosure fails, air and water will find their way into the building. When the enclosure functions properly, air and water will be directed to the outside. Rather than the commissioning provider creating the tests, as the professional would for MEP commissioning, the BECx tests have been written by ASTM International or the American Architectural Manufacturers Association (AAMA).

Building Enclosure Failure Versus HVAC Failure

If an electrical system, generator or HVAC breaks down or malfunctions, it is typically known quickly and can be addressed relatively easily. There are replacement parts that can, for the most part, be replaced without destroying the building or taking a portion of the building out of service for more than a few hours.

When an enclosure system fails, it may take a few years before it is noticed. Many times, in the case of failure due to water penetration, a system may have built-up capacity to hold water in portions of the envelope. Over time the water may migrate slowly without evaporating, leading to mold and other damage. In a slow migration pattern, as water follows the path of least resistance, a leak may be detected hundreds of feet from its source. Once failure is detected, a building enclosure is typically not easily fixed because enclosure systems are built on layered materials. These layers of differing materials and their connection points can be very costly and time consuming to replace.


Compared to MEP commissioning, which typically has definitive scope based on the number and complexity of the systems, the guidelines for BECx allow for different levels of scope. ISO 21105-1 has a table that guides a building owner to pick the level of enclosure commissioning recommended for a project by examining the risk factors that could contribute to a building enclosure issue and recommending the level of commissioning needed to help reduce the risk of enclosure failure.

Design and Submittal Reviews

Although both MEP commissioning and BECx review the design against the owner’s project requirements, the design review processes can differ. During design reviews for MEP commissioning, the commissioning team performs a quality assurance function, checking to see that systems can be operated, maintained and tested. For BECx, reviews include evaluating liquid and air migration through the enclosure system, along with how moisture and air is moving through the system, and where it stops. The assembly’s ability to dry, if moisture accumulates in the system from exterior or interior sources of water, is also evaluated. Maintenance is reviewed to determine if methods to safely clean or inspect the enclosure system have been designed into the building.

During the submittal process, typically for MEP commissioning, the mechanical and electrical reviews mainly focus on the controls and the sequence of operation. BECx focuses on the enclosure materials’ tolerances, installation sequence and time of year the installation will happen. The reviewer also checks material compatibility and adhesion to other building enclosure materials. A lot of building adhesives are water soluble. If you install them at the wrong temperature, humidity level or at the dew point temperature you will not get the right connection to the substrate material.


For MEP commissioning, it is common that after designs are reviewed there is a break in time based on the construction path, sometimes up to a year, until the team returns to continue its commissioning services. This typically takes place at the time the rough-in happens for the mechanical and or electrical systems. With BECx, there is no gap in the timeline for services. Enclosure submittals and mock-up tests occur shortly after the design team issues the construction set of drawings.

The HVAC systems are typically tested after the building is finished. However, testing of the enclosure is recommended to begin when only 10% of the window systems are installed, because testing windows, walls and roof systems early allows for a quicker discovery of manufacturer, construction or design issues and can help prevent costly rework down the line.

Construction Checklists

Pre-functional checklists for MEP commissioning services help the team document how systems are installed and started up prior to functional testing toward the end of a project. Most contain a sequence of installation of components in a system along with tasks to perform before functional testing. One checklist can contain items from different pieces of equipment that make up the system.

In contrast, BECx checklists focus on installation procedures, temperature and humidity requirements, substrate requirements, and sequencing for each material that makes up the system. The focus is on documenting that the installation of the materials was done according to the manufacturer’s requirements.


After the project has been turned over to the owner, a continual commissioning plan or recommissioning plan is created for MEP components so that systems can be reexamined and retested after a certain number of years.

BECx differs from this by focusing on a service life plan that will allow operation and maintenance staff to understand how to maintain the enclosure systems. These service life plans offer suggestions on what to include in a preventive maintenance program for the building’s enclosure system as well as applicable systems’ warranty review requirements. Often this includes diagrams to indicate maintenance access to facades and other aspects of the envelope.

MEP commissioning, when performed properly, can have a payback to the owner of a building by reducing energy and operational costs. BECx reduces the risk of enclosure material failures. Failures can be costly to fix and potentially could take part of the building out of use. Replacing the facade could cost more than the cost of the building to construct. However, the greatest value in BECx is being able to experience the aesthetic of the building as it was envisioned by the architect.

There is great value in both types of commissioning services, and it is important to keep in mind the differences to help improve the life span and operational efficiencies of a building or facility.


It can be common to underestimate the importance of performing the commissioning process for large projects, such as a newly constructed plant or facility. Learn more about the value of commissioning services across many different industries.

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David Meyers is director of commissioning for Burns & McDonnell. He manages 140 commissioning professionals in 23 cities, providing services to healthcare, higher education, government, manufacturing, aviation, commercial, retail and corporate clients.