Architectural Commissioning (ARCx), a more comprehensive term for Building Enclosure Commissioning (BECx), is a systematic process of ensuring that the exterior elements of a newly-constructed or renovated building provide effective environmental separation between the exterior environment and interior occupied space according to the building Owner’s Performance Requirements (OPR) for the intended use.
The primary role of ARCx is that of risk management, as 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. This exposure can expand to encompass architects and specifiers as errors and omissions liability, and to contractors and subcontractors in the form of “callbacks” for re-work and warranty claims.
While most of the conversation surrounding ARCx is devoted to its role in evaluating the building façade, roofing is just as much a part of the building enclosure and plays an equal if not more critical role in energy efficiency and waterproofing. A roof system must provide not only a moisture barrier, but also an effective thermal barrier to maintain indoor comfort and minimize heating and cooling costs. It may also contain a vapor barrier to prevent the diffusion of moisture from the building into the roof. And, it must do so while maintaining structural integrity under forces such as wind uplift and hail impact, and while meeting an evolving array of building codes and standards. There are also mandated “green” rating targets from programs such as LEED®, GreenGlobes™ and ENERGY STAR® Cool Roof Rating.
Scope of the Roofing System Subject to ARCxThe mission of ARCx is to verify that the building envelope - including the roofing - meets the applicable requirements of all of these mandates. This means that all aspects of the roofing system are subject to review, evaluation and confirmation that they will perform as advertised, delivered as specified and installed as required to achieve the intended performance.
The International Building Code (IBC) defines “Roof Assembly” as “a system designed to provide weather protection and resistance to design loads. The system consists of a roof covering and roof deck or a single component serving as both the roof covering and the roof deck. [It] includes the roof deck, vapor retarder, substrate or thermal barrier, insulation and roof covering.” The National Institute of Building Sciences (NIBS) Guideline 3, Exterior Enclosure Technical Requirements for the Commissioning Process, also includes roof terminations (e.g., fascia and perimeter flashing), penetrations (including vent hoods, pipe chases, skylights, sloped glazing and smoke vents), flashing at corners, intersections, valleys, eaves, curbs and parapets, and drainage systems (scuppers, gutters and downspouts).
The ARCx ProcessTraditional concepts of building commissioning tended to focus on the construction stage; but, experience demonstrates the need for early involvement at project inception and continuing through completion and building occupancy. NIBS Guideline 3 outlines the basic framework for ARCx, which unfolds in five project stages.
1. Pre-Design Stage: Among the first orders of business is the selection of the ARCx Agent - the individual or firm responsible for the ARCx activities. The selected ARCx Agent immediately begins working with building owners to develop and document the OPR and review the architect’s design concepts for realizing the OPR. An overall ARCx Plan or Specification should be prepared to guide the building enclosure design process for congruence with the OPR, integrate the construction process and reduce the potential for conflict and confusion.
2. Design Stage: As part of this stage, the ARCx Agent reviews the project drawings and specifications for constructability, expected performance and compatibility among systems and materials. This is to confirm that there are no issues inherent in the design that may cause the system to not function as intended. Several roofing-related performance factors are considered, again depending on the requirements stated in the OPR:
• Structural considerations. Although not specific to the defined roofing system, factors such as snow load, service load paths, ponding loads (if drainage is blocked), and “green roof” dead loads due to soil and water are evaluated as part of the overall ARCx scope. • Uplift analysis due to interior pressure and wind. Perimeter flashing is often worthy of particular attention. The majority of roof covering failures occur when wind suction or pressure overcomes the resistance strength of the metal flashing fascia and/or wood nailer cant strip assembly. The roof covering is then vulnerable and may be easily peeled back, leaving the insulation and deck unprotected.
• Heat transfer (R-value) and air infiltration analysis. The ARCx Agent reviews simulation/test reports and may perform thermal analysis of various aspects of the system. “Cool Roof” credentials (reflectivity and emissivity) are verified from laboratory test reports.
• Water resistance evaluation. Susceptible locations, such as roof terminations, interface conditions at rooftop dormers, interfaces between roof and exterior wall assemblies and at roof penetrations, receive careful attention for leak-resistant design.
• Vapor barrier evaluation verifies the need and type of vapor barrier. Building use, insulation thickness and reflectance are considered to evaluate the condensation risk.
• Impact resistance – Test results and certifications are reviewed. For example, Architectural Testing Inc. (ATI) certifies to FM4473 or UL2218 for hail impact.
• Fire rating – Manufacturers’ test results for conformance with standards such as ASTM E108 are confirmed.
3. Pre-Construction Stage: The pre-construction stage includes a review of construction sequencing, coordination and scheduling to ensure the building enclosure is erected according to the specifications, maintains the critical path and realizes the design intent. Meetings are conducted to ensure all parties involved in the construction of the building enclosure understand their responsibilities. Construction quality control checklists are finalized.
Functional Performance Testing (FPT) may be conducted at this stage to verify performance of certain materials, manufactured products or subsystems. This activity, which should be spelled out in an FPT Specification, can range from laboratory tests and/or computer performance simulations of material or product samples, to construction and testing of large-scale wall section mockups.
Most of the individual component materials and products that comprise a roofing system will have been individually tested according to prescribed ASTM, SPRI, UL, FM or other standards (as dictated by relevant codes and the OPR). Here, the ARCx task is essentially one of reviewing the various test reports or certifications to verify compliance. It should be noted that compliance with a specific standard does not necessarily make an individual product an ideal choice for a given functional mission. It is in helping ensure that this is indeed the case where ARCx proves its real value.
4. Construction Stage: To help avoid problems inherent in coordinating the work of multiple trades and errors in the interfacing of various separately-installed components, the ARCx Agent works with the individual contractors to periodically inspect and evaluate work in progress, providing technical guidance and performing or supervising field quality assurance testing.
Roofing-specific field tests that may be conducted on installed roofing often include “bubble gun” tests to verify waterproofing and seam probing to verify seam integrity.
5. Post-Construction and Occupancy Stage: The post-construction stage involves compiling project close-out documentation, and may include training for building maintenance personnel. A post-occupancy performance evaluation program to collect and analyze actual performance data is often implemented.
The ARCx SpecificationThe ARCx Specification should spell out the expected roles of the project team members at each stage of the commissioning process.
For example, the architect’s responsibilities typically include:
• Providing copies of project drawings and specifications.
• Providing written responses to design review comments from the ARCx Agent or other parties.
• Attending design, pre-construction and construction stage coordination meetings.
• Participating in testing/inspection procedures meetings.
• Participating in resolving field conflicts.
Contractor's ResponsibilitiesThe roofing contractor’s responsibilities typically break down (as applicable to the specific project) as follows:
• Attending pre-construction and construction-stage building enclosure coordination meetings to discuss construction sequencing, the coordination of trades and the general contractor’s project-specific quality control program.
• Participating in testing/inspection procedural meetings concerning any field quality control tests and inspections required by the contract documents.
• Performing or assisting with the scheduled testing and inspections.
• Providing applicable cut sheets, shop drawings, coordination drawings, material certificates, letters of compatibility and other relevant information to the ARCx Agent as required.
• Constructing any on-site mock-ups to review constructability, including roof-to-wall interfaces, and providing a representative to observe air and water leakage performance testing on the mock-up.
• Providing a written protocol and timeline for the repair of any deficiencies noted during the performance testing.
• Reimbursing the owner for tests and inspections of non-compliant components.
• Addressing current punch list items.
• Participating in final review and acceptance meeting.
• Providing input for final commissioning documentation as applicable.
Conducting a full ARCx program can forestall many functional and coordination problems experienced with multifaceted high-performance buildings. Particularly as green construction mandates and increasingly tighter, more complex building codes govern construction projects, ARCx is an effective risk-management tool for owners, architects, contractors and component manufacturers to optimize building performance and reduce energy use, while minimizing liability concerns and remediation costs.