Why commission the building enclosure?

by Sarah Said | September 19, 2018 9:19 am

by Mickey D. Parker, PE

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For many years, designers, contractors, and owners have understood the value of a systematic approach to ensure the mechanical and electrical systems in buildings meet the owner’s needs. This approach is known as the commissioning (Cx) process. As a result of implementing the Cx process into the design and construction of buildings, defect claims and litigation related to these commissioned systems are relatively low. The building enclosure (sometimes referred to as the building envelope), however, has often been excluded in the Cx process. Unlike mechanical and electrical systems, poorly performing building enclosures are the most common causes for construction claims and/or construction defect litigation.¹

Applying the Cx process to the building enclosure has been discussed as a concept within the construction industry for at least 10 to 15 years, but in the author’s experience, it has not yet been widely adopted. This article explores the commissioning process and how it can be used to improve the performance of a building enclosure. For the purposes of this article, the building enclosure commissioning process will be referred to as BECx.

What does it mean to commission a building? The commissioning process is a structured, quality assurance (QA) process intended to ensure a completed building meets or exceeds the owner’s requirements. There are three keys points to this definition.

First, commissioning is a structured process. The American Society of Heating, Refrigeration and Air-Conditioning Engineers (ASHRAE) publication Guideline 0 provides the framework for the commissioning process. Other publications available from ASHRAE and ASTM International provide guidance on how the commissioning process can be applied to ensure the satisfactory performance of the building enclosure.² Consistently following these published guidelines can ensure the commissioned building has been carefully planned and constructed in a way that meets the needs and expectations of the owner.

Second, it is critical to understand BECx is a QA process, focused on achieving the owner’s required level of quality. Quality control (QC), on the other hand, is monitoring work as it occurs, ensuring the work satisfies the project requirements, and enforcing corrective actions as needed. The commissioning process is a supplement to the contractor’s QC program, rather than a replacement for it.

Third, the end goal of a BECx program is to ensure the completed building meets the stated performance and quality goals of the owner. Commissioning professionals focus on the word “ensure” (to make certain, verify) as opposed to guarantee (a formal promise that certain conditions will be fulfilled). The BECx process strives to make certain a building performs as intended, but BECx offers no guarantees. Guarantees are the purview of the various product manufacturers and the contractors who install those products. Just as commissioning the mechanical and electrical systems has improved the performance and reduced the litigation related to those systems, the intent of the BECx program is to improve the performance of the building enclosure and to reduce the litigation (risks) associated with the failures of the enclosure systems.

For the BECx process to be effective, it needs a written plan. This plan is developed and modified throughout the project by the BECx professional, and it becomes the roadmap for the BECx throughout the remainder of the project. In the ideal situation, the BECx team is involved with the owner and the design team from the outset of the project. This allows for collaboration on the project from the development of the owner’s project requirements (OPR) through the schematic design, design development, and final construction documents.

The BECx plan should establish:

• each BECx action;
• who will be responsible for coordinating and performing each action; and
• when each action should be completed.

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Without an adequate plan, it is very probable BECx actions will be overlooked during design and construction. For many BECx actions, if they are not completed at the appropriate time, there will not be another opportunity to do so without complications, significant costs, and project delays. For example, consider a situation where the OPR indicates a maximum air leakage (infiltration and/or exfiltration) rate for the building, but the leakage rate is only tested after the building is substantially complete, and the measured leakage is found to exceed the maximum allowed by the owner. With the finish materials all installed, it would be extremely difficult to find and correct the deficiencies in the building’s air barrier assembly. Another example is testing the windows
on a building after the finish materials have been installed and finding out the windows leak. If tested at the appropriate times, necessary corrective actions can be generally limited to the failed item. When the defects are found later in the project, some trades may be forced to remove their completed work and then reinstall it when the identified deficiencies have been corrected.

The role of a BECx provider

Just as it is important to select a designer and contractors with experience in designing and constructing buildings similar in use, size, and geography to the project being considered, it is also important to select properly qualified professionals for building enclosure commissioning (BECx). The University of Wisconsin currently offers courses and exams for the certification of BECx providers (BECx-P) and BECx authorities (BECx-A). BECx-P are individuals who have demonstrated knowledge of how to perform various BECx activities. BECx-A are professionals who lead a commissioning team and are knowledgeable in the design, construction, and operation of systems. Although there are limited programs for certifying BECx professionals at this time, it is anticipated more opportunities for education and certification will become available as more designers specify, and owners request, certified commissioning professionals. Until then, building owners and project specifiers should take care to thoroughly vet prospective commissioning providers. A common question is “Who retains the BECx professionals?” Ideally, the BECx team is retained by the owner/developer of the proposed project. In this situation, the owner is in a position to require the designers and contractors to cooperate with, and accommodate, the activities of the BECx professionals. Although retained by the owner/developer, the BECx professionals do not normally serve as the owner’s agent. An owner’s agent typically has the authority to direct the designers and the contractor. Rather than this authoritative role, the BECx team strives to advise the designers and contractors on ways to ensure improved performance and to verify the installed components will meet the owner’s project requirements. The BECx team provides recommendations, not requirements. In this author’s experience, the BECx team is most often retained by the contractor as a result of requirements written into the project specifications.  A common way to manage the commissioning teams is to have them retained by the contractor but reporting to the owner/developer. Given the above described role of the BECx team, it is not surprising there can be some “push back” from designers and contractors. It has been this writer’s experience that by carefully handling the situation, BECx professionals can demonstrate they are acting to ensure the project is successful.

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First steps
Following the established Cx guidelines, the first step in the commissioning of a building is to develop a thorough understanding of how the building will
be used and how the owner expects the building to perform. These understandings and expectations are compiled into the OPR document. With regard to building enclosures, the OPR would include (but would not be limited to): the location of the building; the anticipated interior operating conditions; and the sensitivity to water intrusion, temperature control, and air infiltration. The OPR establishes how quality and success will be measured for the project. To put it another way, the OPR establishes the goals for the building before the design process begins. It is easy to see how the expectations of the owner of an indoor swimming pool in Montana will be very different from the expectations of the owner of a data center in Florida. Therefore, it is important everyone has a clear understanding of the OPR at the outset of a project.

Once the OPR is established, the design team can develop the materials and systems that will become the basis of the design (BOD) for the project. At a minimum, the building enclosure BOD will include material and system descriptions for:

• the foundation drainage;
• below-grade waterproofing;
• water vapor control (above and
  below grade);
• air infiltration;
• insulation;
• fenestrations (doors, windows,
  louvers, etc.);
• exterior finish materials; and
• roofing systems.

Then, the construction documents (the project drawings and specifications) are developed based on the OPR and the BOD. The design must integrate the OPR with the requirements of the applicable building codes, the effects of the environment where the building will be located (temperature, humidity, rainfall, etc.), the effects of the owner’s use of the building, the requirements of the manufacturers of the BOD products, and the applicable industry standards of care. This can be a significant challenge. For most routine building uses in familiar geographic locations (hygrothermal regions such as hot-humid, hot-dry, or severe cold), well-established design and construction practices are relied upon during the design of the building. For sensitive projects, buildings in difficult locations, and situations with complex uses, dynamic hygrothermal modeling of the various assemblies may be required to ensure the building is going to perform as desired and designed.³ It is the responsibility of the project design team to decide whether established materials and methods are appropriate or whether hygrothermal modeling is necessary.

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Review design documents
The next step in the BECx process is a review of the design documents. As indicated above, it is preferable for the BECx team to be a part of the development of the design from the very outset of the project. This early involvement can potentially avoid having to substantially change a design at a time when such changes would lead to project delays and/or unanticipated expenses. During the design review or collaboration, the BECx team is not replacing the designer of record (DOR). Rather, the reviewers are comparing each phase of the design with the OPR, the BOD, manufacturer’s requirements, common constructability concerns, and the industry standards of care. Further, experienced reviewers will be drawing on lessons learned from past projects. A good review includes not only comments on potential problems, but also areas where the DOR could consider an alternate approach for the benefit of the building. The design review is an attempt to identify as many potential construction problems as possible before the work begins. This step in the BECx process is critical because identifying a design error later, during construction, will typically lead to project delays and unanticipated costs (change orders), and it is in everyone’s best interest to address those potential issues as early as possible.

The BECx plan should include a review of the product submittals and shop drawings before construction begins. Skipping this step typically results in materials being installed on the building that are not consistent with the design intent, materials added that were not a part of the design, material incompatibility, or materials being omitted, preventing the satisfactory performance of the building enclosure.

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A crucial part of the BECx plan, to be implemented once construction has begun, is building envelope-related QA observations. The QA observations should not be confused with the day-to-day QC efforts of the general contractor. Rather, the QA observations serve as an objective, extra set of eyes on the project. Unfettered by concerns over liability, cost, or schedule, the BECx site observations are
able to focus on ensuring the building enclosure is being constructed in a way that meets the OPR, the requirements of the construction documents,
the industry standards of care, and the individual product manufacturer’s requirements. The BECx professional does not have authority during the design or construction of a building.  Rather, the BECx team provides recommendations for the designers and contractors to consider. The purpose of those recommendations is to reduce risk and to improve the performance of the building enclosure.

As in the design review, an experienced QA observer brings additional benefits to the project. The experienced QA observer will not only look at what has been accomplished prior to the day of the site visit, but they will look forward at the next steps in the construction process in an effort to eliminate potential problems or issues before they occur. The QA observations also provide an opportunity to identify areas of concern that were not addressed by the design documents, and the observer can help the contractor to communicate those concerns with the DOR.

Although the QA and QC programs are fundamental parts of verifying the construction, there is simply no substitute for field performance testing. What good is it to have a material, or system, that functions well in a laboratory environment, but fails to perform when installed by construction workers at the project site? Field workers may be dealing with a difficult environment, potentially facing extreme heat or cold, rain, dust, and damage from other trades. In addition, some installers may have both limited training and a limited understanding of how their work is supposed to integrate with the materials and systems of others. With this in mind, the only means of ensuring the installed materials and systems perform as intended is to test them.

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There are numerous building enclosure test protocols available from ASTM International, the American Architectural Metal Association (AAMA), Factory Mutual (FM) Global, and others. The following are some of the commonly specified and utilized field performance tests:

• ASTM C1153, Standard Practice for Location of Wet Insulation in Roofing Systems Using Infrared Imaging (understanding the use of infrared equipment and the implementation of infrared scanning techniques is required, and core samples of the scanned roof are also necessary.)
• ASTM E2128, Standard Guide
  for Evaluating Water Leakage of Building Walls
• ASTM E783, Standard Test Method for Field Measurement of Air Leakage Through Installed Exterior Windows and Doors
• ASTM E1105, Standard Test Method for Field Determination of Water Penetration of Installed Exterior Windows, Skylights, Doors, and Curtain Walls, by Uniform or Cyclic Static Air Pressure Difference
• ASTM D4263, Standard Test Method for Indicating Moisture in Concrete by the Plastic Sheet Method (This a low-tech, “old school” method.)
• ASTM F1689, Standard Test Method for Measuring Moisture Vapor Emission Rate of Concrete Subfloor Using Anhydrous Calcium Chloride
• ASTM F2170, Standard Test Method for Determining Relative Humidity in Concrete Floor Slabs Using in situ Probes (This test can be a bit destructive, but gives clear results at the site.)
• AAMA 501.1, Standard Test Method for Water Penetration of Windows, Curtain Walls and Doors Using Dynamic Pressure (This a really cool test if you happen to have an airplane engine mounted to a trailer for field testing, otherwise this is typically used for off-site mock-ups.)
• AAMA 501.2, Quality Assurance and Diagnostic Water Leakage Field Check of Installed Storefronts, Curtain Walls and Sloped Glazing Systems (This test is not intended for operable items.)
• AAMA 502, Voluntary Specification
  for Field Testing of Newly Installed Fenestration Products
• AAMA 511, Voluntary Guideline for Forensic Water Penetration Testing of Fenestration Products.

When construction is complete
The BECx process does not end when the building is complete. As we design and build increasingly complex buildings, it is imperative the people responsible for operating the building are properly trained. The end user needs more than just operation and maintenance manuals. They need to understand what was expected from the building (OPR), what was used during construction (BOD), how to troubleshoot the systems if they are not performing as expected or desired, what to do (or not to do) if an issue arises, and who to call for help.

A few months before the contractor’s warranty expires (typically about nine months after substantial completion), the Cx teams should return to the building to see how the structure has performed, what problems were discovered,  and what needs to be adjusted or repaired.

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According to an ASHRAE article published in 2008, there are roughly $10 billion in construction defect claims each year, and 69 percent of those claims are related to water infiltrating a building from the exterior environment (i.e. failures of the building enclosure), 53 percent are related to faulty installation, and about 19 percent are attributable to faulty designs (note the percentages cited for design and installation included building enclosure-related components as well as other building components).⁴ This author had multiple conversations in 2016 with providers of insurance for architects, engineers, and contractors related to the more common source of construction defect insurance claims. The conversations indicated these percentages have remained relatively consistent since the ASHRAE report was published. It is clear the designers and constructors continue to struggle with the building enclosure. From the development of the OPR through the training of the end user, a thorough BECx program is a good way to reduce these frustrating and costly mistakes.

 

Notes
¹ See “Preventing Defect Claims in Hot, Humid Climates,” K. Grosskopf, P. Oppenheim, and T. Brennan,  ASHRAE Journal, July 2008.
² These publications include ASTM E2947, Standard Guide for Building Enclosure Commissioning, which is a replacement for National Institute of Building Sciences (NIBS) Guideline 3, Building Enclosure Commissioning Process BECx; American National Standards Institute (ANSI)/ASHRAE/Illuminating Engineering Society (IES) Standard 202, Commissioning Process for Buildings and Systems; and ASTM E2813, Standard Practice for Building Enclosure Commissioning.
³ One example of hygrothermal modeling software was developed by the Department of Hygrothermics at Fraunhofer IBP.
⁴ See Note 1.

Mickey D. Parker, PE, is practice area leader, building sciences, with Rimkus Building Consultants. Parker has broad experience in all aspects of contract negotiation, planning, design, and construction. His work focused on performing forensic evaluations of buildings, preparing structural engineering designs, providing roofing consultant services, and providing building envelope consulting services. He has been involved in projects including agricultural, single-family, multifamily, commercial, retail, medical, hospitality, assembly, industrial, emergency services, and military facilities. He possesses a BS in civil engineering. He can be reached at mparker@rimkusbc.com[8].

Source URL: https://www.constructionspecifier.com/why-commission-the-building-enclosure/

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