Water resistance is a critical performance factor for a building envelope, especially in climates where wet, wind-driven rain is a common condition. Keeping water out of wall assemblies is crucial for the long-term health of buildings and their occupants. As with other aspects of building envelope performance, there is a test for that. It is called ASTM E331.

ASTM E331 – Testing Water Resistance In The Laboratory

The full title of ASTM E331 explains its purpose: Standard test method for water penetration of exterior windows, skylights, doors, and curtain walls by uniform static air pressure difference. The test is applicable for testing water resistance of an entire curtain wall or a window, skylight or door alone.

Intended to simulate a realistic scenario, the test requires the construction of a specimen wall with all components to be tested at full size using the same details as in an actual wall assembly. This could include an air barrier or water-resistive barrier as part of the assembly.

The specimen is installed on one side of a sealed test chamber, which is equipped with a water spray grid with nozzles that spray water on the specimen uniformly at a minimum rate of 3.4 L/m²-min. The chamber also has a blower or compressed air system that provides a constant air flow at a fixed pressure. The idea is to create a pressure differential of 137 pascals (Pa), unless otherwise specified. For a skylight, the specimen should be angled as it would be in an actual building installation.

The specimen is then subjected to the water spray and air pressure for a period of 15 minutes. Test technicians observe the test specimen and record any and all points of water penetration on the inside face of the specimen.

ASTM E1105 – Testing Water Resistance In The Field

What about testing water resistance of a wall in the field? Obviously, the method defined in ASTM E331 would be difficult to replicate on site. That’s where ASTM E1105 comes in. It defines a standard test method for determining water penetration of installed curtain walls, windows, doors, and skylights in the field. The wall or fenestration is fitted with an apparatus that creates either uniform pressure or cyclic pressure on the inside surface. A calibrated spray rack with nozzles on the exterior surface sprays water at the installed wall assembly or fenestration at a rate of 3.4 L/m²-min. In this way, ASTM E1105 attempts to simulate the real-world conditions of wind-driven water, similar to the lab water penetration test method described in ASTM E331—with the added advantage of optionally using cyclic pressure, which may replicate conditions more realistically.

Contact A Local Air Barrier Specialist Today

Both ASTM E331 and ASTM E1105 can provide invaluable information on the water resistive performance of curtain walls and fenestrations – either beforehand in the lab or on the project site as construction is underway. Call your local air barrier specialists today at Atlas Supply. Our specialists will help you to select the optimal air barrier for your application and answer any installation questions you might have. Call now!

Citations

• GCP Applied Technologies – ASTM E 331 and ASTM E 1105: Testing Water Resistance of Exterior Walls (original publication)
• GCP Applied Technologies – Air barriers: An essential part of the building envelope
• GCP Applied Technologies – Air Barriers & Flashing for Advanced Weatherproofing
• ASTM E331-00(2016) – Standard Test Method for Water Penetration of Exterior Windows, Skylights, Doors, and Curtain Walls by Uniform Static Air Pressure Difference
• ASTM E1105-15 – Standard Test Method for Field Determination of Water Penetration of Installed Exterior Windows, Skylights, Doors, and Curtain Walls, by Uniform or Cyclic Static Air Pressure Difference
• Atlas Supply – GCP Applied Technologies (WR Grace Waterproofing).