Commissioning Guideline offers best practices, approaches
ACG’s reimagined document recognizes new priorities now that commissioning is business as usual
The ACG Commissioning Guideline, first published by AABC in 2002 and updated and published as the 2nd Edition by AABC Commissioning Group in 2005, has long been recognized as a resource that explains the commissioning process properly and concisely.
The two previous editions of the guideline addressed commissioning primarily within the context of heating, ventilation and air conditioning systems because they were written by industry professionals experienced predominantly in the testing of these systems. However, the publication’s crisp presentation of commissioning process elements, step-by-step approach and roles and responsibilities kept it relevant even as the scope of commissioning grew over the past 15 years to encompass many additional building systems.
With the publication of the industry’s first consensus-based ANSI commissioning standard — ASHRAE Standard 202 – 2018: Commissioning Process for Buildings and Systems (which ACG supported) — the commissioning industry now has a common, continually maintained benchmark for the minimum requirements for building commissioning as a professional service.
ACG Building Systems Commissioning Guideline under development is responding to these broad changes by shifting the focus of the guideline to presenting best practice narratives for executing the process. These practical guides will offer insight and strategies from experienced providers on a variety of topics, designed to help providers get commissioning done in the real world — effectively and efficiently — while overcoming common challenges.
Guideline sections will cover topics including system-specific commissioning guidance, approaches for accomplishing key commissioning goals, managing processes, directing resources and producing valuable commissioning deliverables. To take one example: the ASHRAE Standard 202 requires that commissioning meetings take place, while the ACG Building Systems Commissioning Guideline explains what meetings to organize and when, who should lead and participate in them and what tools will help in scheduling, facilitating and documenting meeting activities.
The following is the first in a series of “sneak previews” of the guideline, in this case, a description of building enclosure commissioning by Brian Marsh, PE, Smith Seckman Reid Inc., Nashville.
Commissioning building enclosure systems
The building enclosure commissioning process delivers quality assurance measures to ensure the owner’s project requirements are achieved for systems that provide environmental separation between the outdoor and indoor environments. Building enclosure commissioning is an integral part of the total or whole building commissioning process as the building enclosure not only serves to shelter occupants from the elements, but also protects the many other commissioned systems and services critical to a building’s operation. Enclosure systems carefully designed and constructed with attention to durability and serviceability support a building’s mechanical systems to promote healthy interior environments for the life of the facility.
A successful BECx process can effectively help facility owners receive buildings that have been verified to meet an expected level of performance and promote solutions that mitigate risks of air and water leakage, as well as poor thermal and vapor control that commonly result in issues such as condensation, corrosion, decay, biological growth, occupant discomfort and increased energy consumption.
Systems commissioned in the BECx process typically include all interconnected assemblies, components and materials forming the six-sided building enclosure, with careful consideration of detailing at complex and challenging interfaces and transitions between systems. The process can be tailored to specific owner and project needs to focus on select systems of concern or be expanded to include all systems that create environmental separation.
Building enclosure systems and components routinely commissioned include the following:
- Air barrier.
- Moisture barrier.
- Vapor barrier.
Other notable systems that are often considered for inclusion in the BECx process when applicable and vital to the project include the following:
- Dynamic/automated systems (e.g., sunshades, electrochromic glazing).
- Partitions surrounding spaces with tightly controlled or extreme interior conditions (e.g., cleanrooms, ice rinks, biosafety laboratories).
- Interior waterproofing of wet areas (e.g., showers, pools, wet treatment rooms).
The owner and the building enclosure commissioning provider should identify not only the systems to be commissioned, but also the performance characteristics of each system that have the most influence on the owner’s and project’s goals established in the OPR. Water, air, vapor and thermal control normally top the list of performance characteristics most critical to the performance of the building enclosure.
Performance characteristics defined in the OPR and basis of design can define requirements for control of or resistance to, the following:
- Water leakage.
- Air leakage.
- Vapor diffusion.
- Thermal flows.
- Ultraviolet radiation.
- Infrared radiation.
- Light transmittance.
- Environmental contaminants.
- Forced entry.
- Blast pressures.
- Relative building pressures.
While building enclosure commissioning is rooted in the same core fundamentals and objectives as the commissioning of other building systems, the focus and approach are tailored to the unique challenges inherent to building enclosure systems. Enclosure failures and performance deficiencies typically occur at interfaces and transitions between components and systems and at conditions involving multiple trades. BECx reviews place a greater importance on how the properties and performance of individual assemblies and materials will interact and interface when multiple trades assemble them in the field to perform as a single, coordinated system.
Additionally, opaque wall assembly primary water, air, vapor and thermal control layers and their associated transitions, are usually concealed from view once the building is completed. As such, the BECxP must devote careful attention to the design of these systems and thoughtfully coordinate the timing of site observations during the course of construction to help ensure a successful outcome.
From project inception to construction, the design team establishes myriad assumptions about the building envelope that have significant implications on the simulated and as-built whole building performance. Early in design, initial energy models are developed using assumptions of air leakage rates, levels of insulation, cladding attachment, thermal bridging and glazing system performance.
The mechanical engineer uses enclosure airtightness assumptions to determine volumes of outside air needed to maintain building pressurization and calculate external loads to size mechanical equipment. The BECxP should be capable of identifying and evaluating these assumptions as designs are being developed to ensure they are reasonable and attuned to the vision established in the OPR. The BECx process should support the project team in advancing these assumptions from concepts to operational reality.
The commissioning process is most effective when the commissioning provider is an independent third-party contracted to the owner. While the BECxP does not design building enclosure systems or components as part of the commissioning process, reviewers must be able to objectively evaluate the architect’s accuracy and effectiveness in translating the owner’s enclosure requirements into the technical requirements conveyed to the contractor in the construction documents.
The BECxP’s team should include individuals that specialize in the design and commissioning of building enclosures and oftentimes include multiple individuals that subspecialize in specific building enclosure systems such as waterproofing, roofing and curtain walls. These individuals should bring considerable technical expertise and experience in building enclosure systems that can enhance and expand the project team’s abilities.
The design team often calls on the BECxP to provide technical support to facilitate resolution to challenges such as control layer discontinuity at system transitions with complex geometry, material compatibility concerns and component layer sequencing and constructability challenges. However, sole responsibility for designing a fully functional building enclosure must remain with the architect/engineer of record.
Buildings are uniquely designed and constructed using a variety of materials and systems in numerous configurations. Given the realities of design schedules and budgets, fully detailed design documents are seldom achieved before the start of construction. If projects only used proprietary closed specifications, the design team could develop project-specific details for contractors to imitate for every unique transition and condition to be encountered on the building given generous time and resources.
For the vast majority of projects using open specifications, the final coordination of detailed design is carried forward with construction coordination documents — product submittals and shop drawings — that demonstrate the contractor’s understanding of the design intent using the specific products and systems being supplied to the project.
Where many building systems commissioning providers review submittals and shop drawings for commissionability only, BECx reviews also consider product selections and detailing with regard to control layer continuity, durability, serviceability, constructability and coordination between trades at transitions and interfaces between systems. To facilitate this collaboration and coordination between trades, the BECxP will often participate in pre-construction or pre-installation meetings.
In addition to the challenges created by design complexities encountered when joining materials and systems in multiple configurations, the interfaces and transitions between systems are constructed by teams of trade contractors and tradespeople unique to each project. The opportunity for a test-run of building enclosure construction in the form of a mock-up can provide numerous benefits to the project team by further facilitating and fostering trade collaboration and coordination.
A carefully thought-out mock-up program should incorporate enclosure systems and details that the project team deems crucial to project success. A standalone, off-building, laboratory or site-built mock-up constructed before the start of building construction allows the project team to make observation, perform tests and provide acceptance to demonstrate that the designed systems can and will, be installed to collectively function to meet the OPR.
Many critical enclosure systems — especially opaque wall systems — are fully site-fabricated and installed using multiple materials and layers that provide unique functions. Oftentimes, building enclosure primary control layers (e.g., air barriers, thermal insulation, water-resistive barriers) and their transitions to other systems are concealed with subsequent layers and cladding when complete. The layered nature of wall assemblies necessitates periodic BECx site visits that are thoughtfully and diligently coordinated to occur during the early or first installation of a critical component in order to observe and document enclosure construction.
When the BECxP is not on-site, building enclosure installation checklists can be a useful tool to emphasize to contractors the important systems or material requirements and to document that contractors are providing some level of quality control. However, the level of workmanship conveyed is highly dependent on the training and judgment of the individual completing the checklist. Building enclosure checklist completion can also be challenging to manage because the systems reviewed do not include discrete pieces of equipment with defined startup periods and the critical components are concealed when systems are put into service.
Issues noted in site observation or on testing reports are logged into an issues and resolutions log as the party largely responsible for trade coordination, the general contractor is usually best suited to respond to enclosure system issues on the BECx issues and resolutions log. Photographic documentation of repairs can often serve to resolve outstanding issues without delaying construction progress while the project team waits for BECxP on-site verification before concealment.
Verification testing, such as fenestration air and water leakage testing, is preferably performed throughout the course of enclosure construction when critical control layers are easily accessible. Problems discovered during final verification testing and acceptance just before occupancy can be daunting and costly to diagnose and resolve; therefore, greater emphasis is typically placed on tests performed during the course of construction.
Given that the building enclosure is largely comprised of static systems that do not require extensive operational knowledge to function, operations and maintenance phase activities are primarily focused on resolving new or ongoing issues during occupancy and training facility operations staff to understand the maintenance schedules and techniques required to ensure ongoing system performance. The post-occupancy site visit provides a valuable opportunity to interview facility personnel about ongoing issues and review maintenance requirements.
Building enclosure commissioning summary reports that provide illustrations of multilayered assemblies with descriptions of the function of each component can educate facility personnel on the consequences for lack of maintenance or alterations to the in-service building.