Overview

U-STUCCO™ has been independently tested in accordance with ASTM E96/E96M-10, Standard Test Methods for Water Vapor Transmission of Materials. This standard evaluates how materials manage moisture vapor, ensuring proper breathability while providing resistance to water intrusion.

Test Methodology

Test Standard:

ASTM E96/E96M-10, Procedure A (Desiccant Method)

Testing Period:

September 24 – October 2, 2014

Specimens:

Three lightweight stucco insulation panels (average thickness ~1.28 in / 3.25 cm)

Procedure:

- Specimens were sealed to trays with desiccant.

- Weight measurements were taken periodically after equilibrium was reached.

- Water vapor transmission and permeance values were calculated per ASTM E96.

Results

Average Water Vapor Transmission:

5.33 grains/ft²/hr

Equivalent to 89.4 g/m²/24hr

Average Permeance:

12.8 perms

Equivalent to 734 ng/Pa·s·m²

Conclusion

Based on ASTM E96 results, U-STUCCO™ lightweight stucco insulation:

Meets requirements for a Grade D Water-Resistive Barrier (minimum 35 g/m²/24hr, ICC-ES AC38).

Provides an excellent balance of breathability and water resistance, preventing trapped moisture while ensuring durability.

What This Means

U-STUCCO™ is proven to be a high-performance water-resistive barrier that allows structures to “breathe” while protecting against water penetration. This makes it ideal for:

- Coastal and humid environments

- Wood-frame and gypsum assemblies prone to moisture issues

- Energy-efficient wall systems where vapor management is critical

- Sustainable construction projects requiring code-approved moisture performance

Benefits of ASTM E96 Performance

- Reduces risk of mold and mildew

- Improves indoor air quality

- Extends building envelope service life

- Enhances compliance with ICC, IBC, and Title 24 codes