Commissioning Building Envelopes to Meet Energy Codes

by Marcy Marro | August 1, 2022 12:00 am

BECx Overview

The BEC process spans from pre-design to occupancy and is led by an enclosure expert (BECx provider/agent) with the intent of bringing the building enclosure into working order, as defined by the owner. A project’s commissioning team is made up of the owner, architect/engineer-of-record, the construction manager/general contractor, commissioning firm and related subcontractors.

BEC requires collaboration with the entire construction team starting early in the design phase. The owner’s requirements are typically established before the schematic design phase. “This process ensures the design meets the expectations of the owners, submitted products meet design intent, work is performed in a manner that supports the design through development of checklists and inspections, and final testing is performed to ensure building envelope components perform together as a whole,” shares Daniel Hodge, associate principal, Zero/Six Consulting LLC[1], Envelope Architecture, Galveston, Texas.

One of the reasons BEC is so important is that many of the critical systems and materials that keep the conditioned environment in and the harsh exterior environment—wind, water, heat, cold, etc.—out are often concealed by the building’s exterior finishes at the end of construction. “If at completion, the building envelope doesn’t do its job to separate indoor and outdoor environments in a manner that is durable for the building, efficient for the HVAC equipment to maintain, and comfortable for the building occupants, then there isn’t much recourse at this point to easily modify the design and/or construction in an effective manner. At least, not without a lot of money and destructive repairs,” explains Mike LaCrosse, BECxP, CxA+BE, BPI-BA, senior engineer, building envelope lead at energy engineering consulting firm Cx Associates[2], Burlington, Vt. “The commissioning process for the building envelope seeks to mitigate those risks through active involvement in envelope design and construction document review, on-site installation verification, field testing and post-occupancy followup. The result is a more durable envelope, fewer contractor callbacks, reduced longterm operating costs, and potentially reduced first costs in material and/or system installation. These outcomes almost always recover the initial costs associated with the commissioning process.”

Throughout the BEC process, the team is looking at all the individual pieces of the building envelope, as well as how they integrate to create a system. The building envelope is comprised of thermal, air, vapor and water control layers. “The exterior cladding, depending on its configuration, can be a fifth control layer known as a rainscreen,” says LaCrosse. “We’re reviewing and evaluating each of these control layers individually to ensure effectiveness of each across the field and at critical interfaces, like a wall-to-roof transition for example. We’re also reviewing the harmony of these control layers together as a whole assembly to ensure they are compatible in a manner that is durable for the building and its expected life span. Depending on the material choices made in design, some products used may serve more than one control layer role, and review of that material must give consideration to all roles it is intended to serve. We’re reviewing these layers for continuity, installation sequencing/constructability, durability with respect to its position in the whole assembly, value engineering opportunities, and general energy efficiency.”

Performance Testing

To ensure all parts of the building envelope are working as they are supposed to, the systems undergo testing. “Most building enclosure functional performance testing is geared toward water penetration, air leakage, and material durability, which require trained testing personnel, calibrated test equipment, site/building access, and access to a source of electric/water,” explains Ishmael “Ish” Keener, SE, PE, senior engineer–building science solutions at Intertek, Building and Construction[3], York, Pa. Since the building enclosure is difficult to modify for improved performance after installation, Keener adds that it’s important that the building enclosure field testing be performed after the installation of the primary control layers that provide air/water tightness, including all flashings and fenestration assemblies, but prior to the installation of the exterior cladding and interior finishes.

According to LaCrosse, the architect-of-record ultimately specifies in the project specifications which tests are to be employed for the building envelope systems on the project, though the commissioning provider will make suggestions for testing during the design phase to ensure the owner’s requirements are met and the general integrity of major systems is vetted during construction. “Testing can occur in the laboratory, on stand-alone mock-ups, and/ or in-situ,” he explains. “To what degree testing is incorporated often comes down to the owner’s risk tolerance and available budget for testing.”

Testing Options

For performance testing performed on-site, LaCrosse says it should occur close after the first installation of a given system, and then at additional percentages of total completion beyond that, if necessary. “Testing close to the first installation, or first instance, is critical as it gives the commissioning team an early look at how the tested material/system design and installation performs,” he says. “If a systemic issue is identified, then the lessons learned can be applied moving forward, as opposed to retroactively, which often adds costs and disrupts schedule.”

Performance testing on a stand-alone mock-up gives the project the opportunity to vet design and work quality well in advance of in-place installation, LaCrosse notes. There is usually a nice schedule buffer between the mock-up and actual construction, leaving opportunity to discuss results, correct any issues, and retest without impact to the project.”

“Upfront communication and clarity about all testing requirements are key to ensuring testing is smoothly incorporated into the project schedule,” LaCrosse says. “There are lots of variables with any given test that need to be made clear such as test size, quantity, locations, test pressures (if applicable), pass/fail thresholds, interpretation of qualitative results, and what happens in the event a result is not satisfactory. Additionally, contractor responsibilities must also be a part of this communication. It is not uncommon for the testing agent to require several provisions be made by the contractor to facilitate testing. For example, the use of a boom lift for test access. A good commissioning specification will outline these needs as well. If testing needs on a project are relatively complex, test readiness may also be verified by the commissioning provider via issuance of functional performance testing sheets to contractors.”

Energy Codes

Building envelope commissioning also ensures buildings meet any relevant energy code requirements. Recent energy codes based on ASHRAE 90.1-2019 and the 2021 International Energy Conservation Code (IECC) include mandatory enclosure commissioning requirements for insulation installation and air barrier construction. “These requirements include design reviews, functional performance testing and documentation of compliance,” says Krishnan Gowri, Ph.D., BEMP, LEED AP, ASHRAE Fellow, director of building performance–building science solutions at Intertek, Building and Construction, Tacoma, Wash. “Inspection of insulation installation in walls, roofs and floors is required to ensure thermal barrier continuity and to verify the thermal performance of the materials and assembly to meet the overall R-value or U-factor requirements. Both model codes require that the air barrier must be continuous for all assemblies that serve as the thermal envelope of the building and across all joints, transitions and envelope penetrations. Air barrier materials and assemblies are required to comply with the manufacturer requirements and/or be tested to meet code specified whole building air leakage requirements.”

As Gowri explains, energy code requirements for BEC are covered by the inspection checklists generated by COMcheck, which can be used by field inspectors to document the compliance of the insulation installation and air barrier requirements. “Whole building air barrier testing in IECC 2021 requires that the measured air leakage rate shall not exceed 0.40 cfm/ft2 (2.0 L/s. m2) at a pressure differential of 0.3 in. w.g (75 Pa). A review of construction documents and field inspection reports of air barrier installation is required to demonstrate compliance as an alternate to whole building air barrier testing. Any identified deficiencies should be addressed with corrective actions as part of the final commissioning report. Third-party field inspections to address energy code requirements for building enclosure requirements is highly recommended as code requirements become more complex and stringent.”

“Drawing reviews alone help to ensure that proper R-values are met and continuity of envelope systems are achieved as required by building codes,” adds Hodge. “QA/QC inspections by a commissioning agent that sees multiple projects on an annual basis provides assurance that the contract documents, and state and local codes will be followed.”

Since the 2015 IECC, LaCrosse says blower door testing has been a pathway option for air barrier compliance. However, any air barrier compliance pathway in the 2021 IECC now requires either commissioning and blower door testing, or just blower door testing. “There are exceptions written within, but this will apply to most projects,” he says. “In brief, the commissioning requirements set are largely specific to the air barrier and include verification of certain code requirements that are defined. It does not prescribe a comprehensive commissioning scope, but it is a start. Blower door testing defined in the 2021 IECC pertains to both the whole-building and compartmentalization testing of up to 20% of individual sleeping or dwelling units, if applicable. The former is required to meet an infiltration rate of 0.40 CFM75/SF, and the latter an infiltration rate of 0.30 CFM50/SF.”

As newer versions of the IECC develop and there are more stringent versions at the state and municipality level, LaCrosse says air leakage requirements will only continue to ratchet down. “It is becoming increasingly difficult for designers and builders without extensive air barrier experience to produce a building that will satisfy these requirements,” he says. “Building envelope commissioning can help bridge that gap to avoid costly recourse that might otherwise occur during a failed blower door test at the end of a project.”

Similarly, as R-value requirements for buildings continue to increase, LaCrosse says architects will be seeking clever ways to satisfy code while also maintaining building durability. “This might include trying new products on the market, utilizing multiple materials that aren’t typically used together, etc. Building envelope commissioning can bring a deep building science resource to ensure that material selections not only satisfy code requirements but will work for the long haul.”

Source URL: https://www.metalarchitecture.com/articles/commissioning-building-envelopes-to-meet-energy-codes/

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