The True Test of Enclosure Performance: Results Vary (Part 2)

by Marcy Marro | June 1, 2023 12:00 am

As we discussed, testing is a critical step in getting from the intended performance of the enclosure in design to the actual performance of the final installation. The most effective and informative means to test each system in the field depends on how that system or product was tested in the lab, and how the installed system will be tied into the enclosure control layers of adjacent systems and assemblies.

Sometimes what seems logical will not apply, so tailoring testing to your project takes additional effort. This could include discussing project specifics with the manufacturer and asking for recommendations, reviewing publications and research from academic and industry organizations, and bringing in an experienced consultant, such as a building enclosure commissioning provider (BECxP), to guide the development and execution of a testing plan.

One example of a system needing customized testing is continuous systems such as insulated metal panels (IMP) installed as an all-in-one building enclosure system. When these systems are tested in a lab, the test is performed on a limited assembly. This test specimen is typically limited to a few panels fitted into a “buck” in the lab so that the panels with typical parallel joints between them can be isolated and tested for the performance of the air control layer. However, in the field, the full system is more complex than the lab test specimen so a field test cannot reasonably re-create only the lab conditions. In this IMP example, the field installed system, unlike the lab specimen, includes both vertical and horizontal joints and the intersections of these joints, as well as transitions of the primary control layers to other adjacent assemblies, such as windows or other enclosure systems. The lab test isolates the panels and the primary sealant joint between them (see Horizontal Panel Joint detail), but the field installed system performance also depends on the sealing of the mending plate and the marriage bead sealant (see Vertical Panel Joint detail), as well as transitions to other systems.

To illustrate the point, let’s review the details of the testing. The lab test used for our example panel to quantify the air leakage rate is ASTM E283 and the corresponding field test is ASTM E783. This involves constructing a sealed test chamber, typically on the inside face of the specimen and applying a “tare bag” on the outside face (typically a polyethylene sheet taped in place) covering the entire specimen. Then calibrated equipment is used to negatively pressurize the test chamber to induce a uniform specified pressure across the specimen for a set period, recording the cubic feet per minute of infiltration. This test is performed once with the tare bag on and second time with the tare bag removed. The resulting difference in infiltration between the two is the collective leakage rate of the specimen. This number is valuable if we can use it to understand how this one piece contributes to meeting the whole building airtightness goal—aiding energy savings and reducing leakage that can result in interior condensation moisture issues.

Replicating this test in the field is difficult as the primary seals at the edges of any given section of panels to be tested are inaccessible so the tare bag cannot be secured to the seals. Without the field test specimen fully isolated, the infiltration rate cannot be accurately determined for that specific product. Similar challenges apply to other types of continuous enclosures systems, so what can a project team do to test performance in the field?

The most effective and informative means to test each system in the field depends on how that system or product was tested in the lab, and how the installed system will be tied into the enclosure control layers of adjacent systems and assemblies.

First, eliminate any testing that does not provide value, and work together to create a test plan that does. For IMPs, one alternative means to quantitative testing is to use qualitative testing such as theatrical smoke in combination with a negative pressure test chamber according to ASTM E1186 method 4.2.6. This test provides a visual understanding of if, and where, an installed panel system is leaking air. This can also be combined with water testing (AAMA 501.1 and/or ASTM E 1105) as an effective way to gauge how the system will perform regarding water intrusion. Ideally, the test plan should focus on conducting the first field tests on a mock-up and then early in construction to minimize the amount of work that would need to be remediated in the event of a failure.

The team must take a whole building view of the testing, based on the project requirements and performance goals, and ask the question: what testing will give us the most valuable information to understand a system’s performance? With the right tests performed as systems are installed, issues can be discovered and more easily corrected in a collaborative manner, reducing the potential for performance failures and disputes later, and giving building owners the high-performing buildings they expect.

---

Alan Scott, FAIA, LEED Fellow, LEED AP BD+C, O+M, WELL AP, CEM, is an architect and consultant with over 35 years of experience in sustainable building design. He is director of sustainability with Intertek Building Science Solutions (BSS) in Portland, Ore. Alex Connor, R.A., LEED AP, BECxP, CxA+BE is a senior consultant with Intertek BSS in Washington, D.C. To learn more, follow Scott on LinkedIn at www.linkedin.com/in/alanscottfaia/[1].

Source URL: https://www.metalarchitecture.com/articles/the-true-test-of-enclosure-performance-results-vary-part-2/

---