Air Leakage Testing: Recent Developments Add to Architects’ Body of Knowledge

by Marcy Marro | April 1, 2021 12:00 am

Testing Underway

To understand the impact of the code changes, a proactive testing project is proceeding, orchestrated by the Metal Building Manufacturers Association[1] (MBMA), in collaboration with the North American Insulation Manufacturers Association[2] (NAIMA) and the Metal Building Contractors and Erectors Association[3] (MBCEA). The air leakage testing is being completed according to the ASTM E 779 Standard Test Method for Determining Air Leakage Rate by Fan Pressurization with modifications from the U.S. Army Corps of Engineers’ (USACE’s) Air Leakage Test Protocol for Building Envelopes. The protocol requires that both pressurization and depressurization tests do not exceed a specified air leakage rate target. Diagnostic tools, including synthetic smoke and thermography, are used to locate leakage paths.

The testing objectives are to see how well metal buildings comply with the code air leakage requirements and to determine what specific elements of metal buildings may contribute to significant leakage. Having completed several tests, and with more on the way, the testing confirmed that, when the right materials are specified and correctly installed, metal buildings indeed pass the air leakage tests with flying colors. However, the project team cautions that architects, specifiers and installers need to pay attention to four areas:

• Overhead doors
• Fenestrations
• Transition areas
• Intersections in a building’s insulation system

To date, the MBMA/NAIMA/MBCEA collaboration has tested metal buildings with a variety of insulation systems in the states of Florida, Minnesota, North Carolina and Washington, but additional tests in other climate zones and states are ahead.

One test was completed on a warehouse in North Carolina that had a loading dock with four overhead doors on one side, plus two overhead doors on an adjacent side. First, pressurization and depressurization tests were performed with the overhead doors sealed, resulting in an average leakage rate of 0.13 cfm/sf. Then, a pressurization test with the doors unsealed was completed, with a result of 0.21 cfm/sf. Although the installed overhead doors contributed significantly to the air leakage, under the coming IECC and ASHRAE 90.1 requirements, where the allowable leakage is 0.40 cfm/sf, the building passes.

Comparing the tests with the doors sealed and unsealed confirmed that there is the potential for significant leakage associated with overhead doors. Specifying the appropriate door and perimeter seals that are correctly installed according to the manufacturer’s directions, reduces the air leakage potential, and increases the likelihood of the building passing the test.

Beyond Overhead Doors

As shown by thermography and synthetic smoke, all exterior openings, such as windows and regular doors, are also areas where architects should be careful to reduce opportunities for air leakage. Synthetic smoke also identified other transition areas that may contribute to air seepage, such as joints between dissimilar building envelope materials, such as where the exterior wall meets the floor slab, and floor slab joints extend into the exterior. Metal building contractors should pay attention to these locations to prevent them from becoming a significant source of air leaks.

Insulation, with its air barrier, is essential, but its details and installation can be make-or-break factors in air leakage test results. Intersections in a building’s insulation system—such as where the walls meet other walls or the roof—are particularly important. In addition to specifying the appropriate insulation system, installing it correctly is key. Be aware that the more complicated the building envelope, the more places there are that could lead to leakage issues.

Extra Value

Air leakage testing, in addition to enabling a building to meet energy code requirements, can contribute to earning LEED 4.1 credits. These may be awarded in both the Building Design and Construction and the Residential BD+C Multifamily Homes programs. These categories cover a range of low-rise structures such as warehouses, distribution centers, schools, retail buildings and multifamily communities. LEED credits can be earned under the EA Prerequisite: Minimum Energy Performance category by complying with ASHRAE 90.1-2016 when using either the prescriptive provisions contained in Chapter 5 “Envelope,” or the performance provisions in Appendix G “Performance Rating Method.” Additionally, credits can be earned from the EA Credit: Enhanced Commissioning category. Air leakage testing is part of the path that can earn up to four LEED credits.

Detailed information is available by contacting mbma@mbma.com and by downloading our recent publication, “Air Leakage Testing: New Research is on the Way” at blog.mbma.com/air-leakage-testing-new-research-is-on-the-way[4].

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Vincent E. Sagan, P.E., F.ASCE, is the senior staff engineer for Metal Building Manufacturers Association. To learn more, visit www.mbma.com[5].

Source URL: https://www.metalarchitecture.com/articles/air-leakage-testing-recent-developments-add-to-architects-body-of-knowledge/

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