ASTM E2178 Air Leakage Rate and Calculation of Air Permeance

Standard: ASTM E2178 Standard Test Method for Determining Air Leakage Rate and Calculation of Air Permeance of Building Materials

Scope: The ASTM E2178 test method is to determine the air leakage rate of building materials at various pressure differentials with the intent of calculating an assigned air permeance rate of the material at the reference pressure difference (ΔP) of 75 Pa.

Products: ASTM E2178 was written with the intent to assess flexible sheet or rigid panel-type materials but can be used to assess all materials used as an air barrier. Some examples include: fluid-applied membranes, self-adhered sheets, spray foam insulation, mechanically-fastened commercial building wraps, and board stock air barriers.

Procedure: The sealed test specimen is installed on the test chamber, and the compression frame is installed over the specimen, compressing the gaskets as required. The extraneous air leakage rate (Qei) of the test apparatus/specimen is measured at various static pressure differentials (ΔP) as follows: 25 Pa, 50 Pa, 75 Pa, 100 Pa, 150 Pa, and 300 Pa.

The top section of the polyethylene film is then cut, and the total air leakage rate (Qti) is measured at various static pressure differentials (ΔP), correcting the air flow rate values to standard temperature and pressure (STP). The air leakage rate of each specimen is determined per ASTM E283 at a minimum of six static pressure measurements (25 Pa, 50 Pa, 75 Pa, 100 Pa, 150 Pa, and 300 Pa).

After measuring the air leakage rate at the maximum static pressure differential (ΔP) of 300 Pa, the air leakage rate is remeasured at 100 Pa, 75 Pa, and 50 Pa to determine if the measurement process affected the air leakage rate of the material. If the difference between the two measured air leakage rates is greater than 10 %, the cause of the air leakage rate change must be identified.

Result: At each pressure, the flow rate through the specimen (Q) is determined by subtracting the extraneous air flow rate (Qei) from the total air leakage rate (Qti). The air permeance (P) of a specimen at a given pressure differential (ΔP) is calculated and reported.