A Breakdown of Air Leakage Testing in LEED v5 BD+C

Understanding the difference in the referenced ASTM standards.

Before examining how LEED v5 incorporates air leakage testing, it helps to differentiate the various referenced ASTM standards.

Standards incorporated into LEED v5 BD+C prerequisite EAp3 Fundamental Commissioning by reference via ANSI/ASHRAE/IES Standard 90.1-2019 (excerpt):

5.4.3.1.1 Whole-Building Air Leakage 

Whole-building pressurization testing shall be conducted in accordance with ASTM E779 or ASTM E1827 by an independent third party. The measured air leakage rate of the building envelope shall not exceed 0.40 cfm/ft2 under a pressure differential of 0.3 in. of water, with this air leakage rate normalized by the sum of the above-grade and below-grade building envelope areas of the conditioned space and semiheated space.

ASTM E779-19: Standard Test Method For Determining Air Leakage Rate by Fan Pressurization is the foundational whole-building pressurization test. It outlines how to conduct a "blower door test" to measure the airtightness and unintended air leakage of a building's envelope. A blower door system must depressurize or pressurize the entire building envelope across a range of induced pressure differentials, and the resulting data is curve-fitted to calculate an air leakage rate expressed in cubic feet per minute per square foot of envelope area (cfm/ft²) at a reference pressure of 75 pascals (Pa) (0.3 in. w.g.). E779 is a quantitative test – basically, it tells you how much air is leaking, but not where.

ASTM E1827-11(2017): Standard Test Methods for Determining Airtightness of Buildings Using an Orifice Blower Door is E779's close sibling. Both are whole-building pressurization tests using blower door equipment, and both produce a quantitative air leakage rate against the same metric. The difference is methodology. E1827 uses an orifice blower door (i.e., a calibrated metal plate with defined holes used in the testing fan to restrict and measure the volume of air passing through). It is capable of a single-point method (which determines building airflow at exactly one induced reference pressure – typically 50 Pa) and a two-point method (which measures the airflow required to maintain two different reference pressures). By gathering data at two distinct points via the two-point method, the blower door's software can calculate a building-specific exponent rather than assuming one, which provides much more accurate parameters for natural ventilation and energy modeling software. Simply put, E1827 functions as an adaptation of E779 to orifice blower doors. It is somewhat faster and more adaptable to a broader range of building configurations. For practical purposes on most commercial projects, either test would be acceptable for LEED v5 BD+C as Standard 90.1 references both. 

The BECx process standard referenced in LEED v5 BD+C credit EAc5 Enhanced Commissioning (excerpt):

PATH 2. ENHANCED COMMISSIONING FOR BUILDING ENCLOSURE (1 POINT)

Comply with all tasks and deliverables referenced with ASTM E2947-21a, "Standard Guide for Building Enclosure Commissioning," except Sections 7.2.4 and 7.4.3.

ASTM E2947-21a: Standard Guide for Building Enclosure Commissioning is a standard guide that establishes a systematic process for commissioning building enclosure systems – including roofs, walls, windows, doors, and below-grade assemblies – to verify that they are designed, constructed, and operated in accordance with the owner’s project requirements (OPR). E2947 defines roles, responsibilities, and documentation protocols for the commissioning process across all project phases, from pre-design through post-occupancy.

Standards referenced in LEED v5 BD+C credit EAc5 Enhanced Commissioning as options for building air leakage testing (excerpt):

Comply with the following field-testing requirements: 

Building air leakage testing per ASTM E783, ASTM E779, ASTM E1186, or ASTM E3158.

ASTM E783-02(2018): Standard Test Method for Field Measurement of Air Leakage Through Installed Exterior Windows and Doors is a field test for installed fenestration. Whereas E779 and E1827 (see above) measure the whole building, E783 measures individual windows, curtainwall panels, and/or doors as they are actually installed – including their respective rough opening interface, which a factory test does not capture. This distinction matters because a product can pass laboratory certification and still perform poorly in the field due to installation deficiencies. E783 fills that gap (excuse the pun).

ASTM E1186-22: Standard Practices for Air Leakage Site Detection in Building Envelopes and Air Barrier Systems outlines standardized methods for locating unintentional air leakage in building envelopes and air barrier systems. E1186 is qualitative rather than quantitative. It describes several specific testing practices for locating air leakage (e.g. smoke pencils, theatrical fog, tracer gases, and pressurized infrared thermography), which can be used individually or in combination depending on the structure. It does not produce a compliance number. Instead, it is the diagnostic complement to E779 or E1827: first you find the leaks (E1186), then you quantify the total (E779 or E1827).

ASTM E3158-18: Standard Test Method for Measuring the Air Leakage Rate of a Large or Multizone Building is a standard quantitative field-test procedure used to measure how much air leaks into or out of a large or multizone building envelope. It utilizes fan-induced pressure differentials (like large-scale blower doors) to assess the airtightness of the building. It was developed specifically to address a practical problem: achieving and maintaining 50 or 75 Pa of pressure differential across a large or complex commercial building envelope, which is often logistically difficult or impossible. E3158 uses a single induced pressure point at 25 Pa, making it more tractable for large institutional buildings (e.g., university facilities, hospitals, large office towers) where E779's multi-point ramp would be impractical. The trade-off is reduced precision compared to E779's curve-fitting approach.

The prerequisite: EAp3: Fundamental Commissioning sets code compliance as the floor.

The LEED v5 BD+C EAp3 Fundamental Commissioning prerequisite implements air-leakage testing by reference rather than by prescription. It requires projects to comply with Standard 90.1's commissioning requirements – specifically Standard 90.1-2019 for projects registered before January 1, 2028, and Standard 90.1-2022 for projects registered on or after that date – with the notable provision that the exceptions noted in Section 4.2.5.2 of Standard 90.1 do not apply.

What this means for air leakage testing is that the whole-building pressurization requirement in Section 5.4.3.1.1 (see above) of Standard 90.1 becomes a LEED prerequisite. That section requires testing by an independent third party in accordance with ASTM E779 or ASTM E1827, with a maximum measured air leakage rate of 0.40 cfm/ft² under a pressure differential of 0.3 in. of water. The air leakage rate is normalized by the sum of above-grade and below-grade building envelope areas.

The Fundamental Commissioning prerequisite also pulls in Standard 90.1's continuous air barrier alternative: projects that cannot achieve or document whole-building testing results can instead implement a continuous air barrier design and installation verification program conducted by an independent third party, as described in Section 5.4.3.1.1 (see exception 3). This pathway substitutes documented design review and periodic field inspection for the quantitative pressurization test.

The intent of EAp3 is establishing a minimum floor of performance. ASTM E783, E1186, and E3158 are not referenced at this level. The scope is deliberately bounded: prove that the building envelope, as a whole, does not exceed a defined leakage rate.

The optional credit: EAc5: Enhanced Commissioning is scoped to verify how the enclosure actually performs.

The LEED v5 BD+C EAc5 Enhanced Commissioning credit goes beyond code-level compliance verification to implement a commissioning process that will begin during the design phase and carry through measurement and verification after construction. 

EAc5 requires projects to follow ASTM E2947-21a: Standard Guide for Building Enclosure Commissioning, for the full BECx process. Within that expanded scope, the credit explicitly requires field testing for air leakage using ASTM E783, E779, E1186, or E3158 – a notably broader menu than EAp3's E779/E1827 pairing. Water penetration testing and infrared imaging are also required in addition to the air-leakage scope outlined here.

The inclusion of E783 reflects a recognition that whole-building test results do not reveal whether individual fenestration systems – particularly curtainwall and storefront assemblies that are so common in institutional and higher education buildings — are performing as designed. A building can pass a whole-building E779 test while still having significant localized leakage at curtain wall interfaces that a component-level E783 test would expose.

Noting E1186 acknowledges that finding leaks is as important as counting them. Infrared thermography and smoke testing during pressurization give the commissioning team – and ultimately the owner – a qualitative map of the envelope that a single compliance number cannot provide.

Including E3158 is practically significant for large buildings. On a 200,000 square foot academic building, the logistics of achieving 50 to 75 Pa across the entire envelope with E779 can be prohibitive. E3158's lower-pressure single-point approach is more achievable and still provides meaningful data.

One area of ambiguity in EAc5 that project teams should address early: the credit does not specify the minimum number of tests required. It establishes the acceptable standards without defining scope in terms of sample size, number of fenestration units tested under E783, or the extent of E1186 diagnostics. This means the commissioning provider (CxP) needs to be engaged during design – not construction – to define testing protocols, ensure they are incorporated into project specifications, and set owner expectations around cost and schedule.

Framing the air-leakage scope in LEED v5 BD+C: it is all about quality assurance.

The two-tiered (i.e., prerequisite vs. credit) structure of implementing air-leakage testing in LEED v5 BD+C reflects a deliberate approach. The EAp3 prerequisite establishes what every LEED project must demonstrate as a baseline – a level of air leakage performance that aligns with the energy code. The EAc5 credit rewards projects that go beyond compliance to understand and document envelope performance in ways that inform operations, maintenance, and future capital decisions.

For project owners, the practical consequence is that EAp3 will cost something – whole-building blower door testing on a large commercial building is not trivial – but it is clearly scoped and predictable. EAc5 represents a meaningfully larger commitment with regard to budget, coordination, and schedule, but it delivers something EAp3 cannot: a documented understanding of how the envelope actually performs at the system and component level, before the walls are closed and after the building is handed over.

For nonresidential projects, where leaky enclosures will exacerbate energy costs and compounded issues from envelope failures may become costly capital issues, the question of whether EAc5 is worth pursuing is less about LEED points and more about hedging long-term financial risk with quality assurance.