The Gap ASTM E2357 Was Built to Close
Material-level testing under ASTM E2178 answers a narrow question: does the sheet or board itself resist airflow? That is useful, but it says nothing about what happens where two pieces of membrane overlap, where a tape bonds to a rough opening, or where a fastener penetrates the barrier. Those details are where most real-world air leakage originates, and they only exist once the material has been assembled into something resembling a wall condition. ASTM E2357 exists to test that assembled condition directly, rather than assuming that a good material automatically produces a good assembly.
What Counts as an Assembly
An assembly, for the purposes of this test, is a mockup that reproduces how the air barrier is actually built in the field. That typically includes:
- The primary air barrier material
- Seams, laps, and joints between sheets or panels
- Fasteners and mechanical attachments
- Sealants and transition tapes
- Representative penetrations or rough openings, where the detail being evaluated calls for them
The mockup is built to resemble a real detail, not a laboratory abstraction, which is what makes the resulting rating relevant to actual specification decisions.
Inside the Test: Build, Stress, Remeasure
The procedure runs in three phases. First, the assembly mockup is built and installed in the test chamber, replicating the accessories and details used on site, and a baseline air leakage measurement is taken under standard conditions.
Second, the assembly is exposed to specified conditioning cycles. These are intended to simulate the kind of stress an installed assembly experiences over time, such as thermal movement or structural racking, though the exact parameters shift between editions and should be confirmed against the current version of the standard before they are cited in a spec.
Third, air leakage is remeasured after conditioning, and the before-and-after results are compared. A meaningful increase in leakage after conditioning points to a weakness in how the assembly was detailed, not necessarily in the base material.
Reading an E2357 Rating
The output is an air leakage rating for the assembly, expressed per unit area. It is worth being direct about what this number does and does not mean. The standard itself notes that results are intended for comparison purposes and may not represent the field-installed performance of the assembly once it is part of a complete system in a real building.
In practice, this data serves two audiences differently. A manufacturer uses it to validate that an accessory, such as a specific tape or sealant, performs as intended alongside a given membrane. A specifier uses it to compare assembly options against each other before a detail is finalized on a project. Neither use case substitutes for verifying the finished building once it is built.
Where This Fits on a BC Project
Air barrier performance is checked at three separate points in a project’s life, and it helps to see them side by side:
| Level | Test standard | What it answers |
|---|---|---|
| Material | ASTM E2178 | Does the sheet or board itself resist airflow? |
| Assembly | ASTM E2357 | Do the joints, fasteners, and penetrations hold up? |
| Whole building | ASTM E779 / E3158, CGSB-149.10 / 149.15 | How airtight is the finished building? |
On a BC Part 3 project, this middle tier sits between product-level compliance, which is tied to CAN/ULC-S741 and material testing, and the whole-building airtightness targets set under the BC Energy Step Code. Design teams typically reference assembly-level testing when choosing a system for a specific detail, particularly at complex transitions like window openings or roof-to-wall connections, rather than at the schematic stage. Code clause references should be verified before publication, since they vary by jurisdiction and edition.
What the Test Won’t Tell You
The standard is explicit that it does not establish all criteria necessary for selecting an air barrier assembly, and it does not cover every construction type. A lab mockup, however carefully built, cannot fully reproduce site conditions, workmanship variance, or years of weathering. Treat a favorable E2357 rating as a strong signal for the assembly design, not as proof of how the finished building will actually perform. That confirmation still has to come from the field, which is why large building airtightness testing remains a distinct and necessary step even after material and assembly testing have both been passed.
Conclusion
ASTM E2357 exists because good materials do not automatically add up to a good assembly. It tests the joints, seams, and transitions that material-level testing cannot see, and it gives specifiers a comparative basis for choosing between systems before construction starts. Monolith Housing Solutions carries that verification through to the finished building with large building airtightness testing, under the direction of founder Shahin Arvandi, a Level II Infrared Thermographer and Certified Air Tester with additional credentials as a Registered Energy Advisor and Certified Passive House Designer.
Frequently Asked Questions
The Basics
- What does ASTM E2357 test for? It tests the air leakage rate of a full air barrier assembly, including seams, fasteners, and transitions, measuring leakage before and after specific conditioning cycles.
- What counts as an “assembly” under ASTM E2357? A mockup that reproduces how the air barrier is actually built in the field, including the material, its seams and joints, fasteners, sealants, and any relevant penetrations or openings.
- What is the difference between ASTM E2357 and ASTM E2178? ASTM E2178 tests a single material in isolation. ASTM E2357 tests the same material once it has been assembled with its seams, fasteners, and transitions.
Reading the Results
- What are the conditioning cycles in ASTM E2357? A set of stress exposures applied between the baseline and final measurements, meant to simulate real-world conditions such as thermal movement. Exact parameters vary by edition.
- Can an ASTM E2357 rating predict field performance? Not directly. The standard states the results are for comparison purposes and may not represent how the assembly performs once installed in an actual building.
- How does ASTM E2357 relate to ASTM E1677? ASTM E1677 specifies air barrier systems for low-rise framed building walls, and assembly-level results from ASTM E2357 can inform decisions made under that specification.
On a Real Project
- Are window rough openings tested under ASTM E2357? They can be, when the detail being evaluated involves a rough opening as part of the assembly mockup.
- Do fasteners and tapes need separate testing? No. They are tested as part of the combined assembly, since the goal is to see how the components perform together, not in isolation.
- Does passing ASTM E2357 replace whole-building airtightness testing? No. It confirms the assembly design under lab conditions. Whole-building testing is still required to confirm airtightness once construction is complete.
