Building Envelope Commissioning Increasingly Important

Elevated performance requirements for energy and infiltration are calling for more attention to envelope design and construction.


https://facilityexecutive.com/2015/03/building-envelope-commissioning/
Elevated performance requirements for energy and infiltration are calling for more attention to envelope design and construction.
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Building Envelope Commissioning

Building Envelope Commissioning Increasingly Important

By Darren Draper, PE, CxA, LEED AP BD+C

Envelope commissioning, just like mechanical, electrical, plumbing (MEP) commissioning, is a third-party process of verifying the design and construction of the building envelope per the owner’s needs and the design intent. Portions of this process have been commonplace (i.e., waterproofing consulting or blower door testing); however, the ideal envelope commissioning process begins early in the design phase and continues through the warranty phase. Additionally, the bar has been raised for building energy performance.FE-WebOnlylogo

Even though it has not enjoyed the same exponential growth that MEP systems commissioning has over the past decade, envelope commissioning is becoming more prominent due to increasingly stringent envelope performance requirements for energy and infiltration. As a result, envelope commissioning is a necessary service in the building construction industry with plenty of room to grow. This is especially true for buildings in the Southeast United States.

Unfortunately, those in the construction industry might only be familiar with blower door testing or waterproofing consulting for the design team, but recent enhancements in building codes and increasing facility complexity are quickly converting envelope commissioning from a nice-to-have option to a necessity.

ASHRAE 90.1-2010 and the 2012 Energy Conservation Code are putting a large emphasis on envelope design and construction. Modern facility construction has grown increasingly complex. Gone are the days of a simple, four-sided box with brick and storefronts. Today’s facilities have numerous materials from metal paneling to structural glazing, and interaction of all of these materials makes construction more challenging when considering both air and water infiltration.

Design
The value of the process is truly maximized when envelope commissioning begins in design, with at least one full review of the design documents. The review should be conducted by a qualified and experienced envelope expert and should focus on continuity for air and water tightness, potential points of failure, and constructability. Additionally, complicated interactions of assemblies are targeted with thorough reviews of envelope elevations and details.

Another important task is the development of testing requirements for the envelope to be included in the construction documents. Not every project or owner is the same, so testing should be customized based on building complexity, project location, and budget considerations. Testing requirements might be different for an office building in the Northeast (Cold Climate = Air Tightness Testing) than a higher education building in the Southeast (Warm/Wet Climate = Water Infiltration Testing). The key is to incorporate testing strategies into specifications to ensure the construction team provides or supports testing as needed.

Building envelope mock-up
Building envelope mock-up

Construction
Once a project is into construction, the process turns towards verification that the design intent is met for envelope components. One of the main activities necessary to accomplish this is to conduct pre-installation meetings for each envelope assembly (waterproofing, air barrier, roofing, curtainwall, etc.).

These meetings are coordinated by the general contractor and attended by the envelope commissioning provider and all affected envelope subcontractors. The purpose is to discuss the process of assembly construction and to define the roles and responsibilities of each subcontractor. A common problem in construction is finger pointing when components or assemblies fail, so the pre-installation meeting is the venue to define construction responsibilities and expectations clearly.

Mock-up
In addition to periodic visits to the site to observe envelope construction, another point of emphasis is the review of the construction of an envelope mock-up. Not every project can justify a standalone mock-up, but all projects can benefit from a standalone or in-situ mock-up. Through the specification and construction of a mock-up, the envelope commissioning provider and the architect can review all components and assemblies related to the building enclosure. Standalone mock-up can be constructed to represent each detail, and it is often not to full scale.

Whether in stages on the facility, or standalone with all components visible and represented, this process provides the opportunity for pertinent feedback to the construction team on acceptability of installation methods as well as to provide a model for proper construction of an assembly.

Performance Testing
As construction of a facility is nearing completion, one of the last major undertakings for envelope commissioning is envelope performance testing. The amount of envelope testing available to any new facility is an exhaustive and detailed list far too long to be laid out in this article, but there are a few that are worth considering for every project: AAMA 501.2; AAMA 503-03; ASTM C1060; and ASTM E779. The latter two testing procedures have been in use on many projects for several years and extensively on federal facilities in construction.

Testing in progress with AAMA 503
Testing in progress with AAMA 503

AAMA 501.2. One of the most common testing methods currently administered, commonly referred to as water nozzle testing. This test involves water applying 30 to 35 psi of water to a fixed storefront at a distance of 12″ from the assembly. Pattern and duration are also important, but the main takeaway is that this test is a very cost-effective means of determining if an assembly allows water infiltration. Ideally, this test would be administered for 10% of each storefront type on a project. That would be a good starting point for sampling and could increase from there.

AAMA 503-03. Considered a more stringent test than the AAMA 501.2, this test is a combined air and water test. Water is applied to exterior of a curtainwall assembly at a fixed pressure while a temporary chamber is assembled and applied on the interior of the assembly with a uniform negative pressure applied for 15 minutes. This test simulates a heavy rain event and therefore is a productive test to consider for facilities subject to heavy downpours.

ASTM C1060. Infrared thermography testing is a valuable tool to discover missing insulation, thermal bridging, and moisture intrusion in envelope assemblies. This test requires a temperature differential from indoors to outdoors of at least 12 to 18 degrees.

ASTM E779. Commonly referred to as blower door testing (ASTM E779). The blower door test, which is also becoming common in the residential setting, is a measure of air tightness of a facility. The requirements for test pressures and leakage may vary by locale, but the intent is to determine if air tightness meets design requirements. This test can be combined with infrared thermography given the proper ambient conditions to determine locations of air leaks to be resolved after initial testing. This can be particularly true in the Southeast and along the coast.

The envelope commissioning process will add cost to any project, but it is worth pointing out that MEP Commissioning does as well, in fact often more than Envelope Commissioning. And, it has been commonly adopted because the process has proven itself on projects around the world by finding issues and correcting them prior to owner occupancy of a building. And even MEP issues such as malfunctioning temperature control can be resolved without too much disruption to the building occupants after turnover. Compare that to water infiltration in an occupied office building, and the value of the process becomes quite clear.

Cost avoidance due to operation shutdown and occupant production can escalate very quickly when the building envelope experiences failures.  For this reason, among others, the envelope commissioning process should be considered for every new facility.

 

D_DraperDraperis the commissioning department manager and oversees and directs all Envelope and MEP Commissioning activities for the Epsten Group, which is based in Atlanta, GA. His experience extends to a wide range of facilities including university buildings, laboratories, healthcare facilities, and data centers. Darren performs commissioning and retro-commissioning for HVAC, DDC controls, electrical, and plumbing systems. He also serves as the manager and team member for retro-commissioning projects. In addition to his commissioning experience, Darren spent seven years before and during college as a HVAC technician for residential and light commercial facilities. 

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