It’s inevitable: moisture will eventually find its way behind the wall cladding. And left unchecked, moisture in a wall cavity can lead to a range of costly consequences – from rotting wood to mildew and mold. Fortunately, modern building science has developed products and test methods to ensure that any moisture that gets in also gets out before causing trouble.
Drainable Weather-Resistive Barriers
A drainage weather-resistive barrier typically has raised “bumps” or a textured surface that performs in 2 ways. First, these patterns create drainage channels to carry water down and out of the wall assembly. They carry an efficiency rating which indicates how much bulk water is drained out of the wall. ASTM E2273 is the test protocol used to determine this efficiency. Currently, Oregon requires these drainable wraps to pass with at least 75% efficiency (R703.1.1 Exterior Wall Envelope here). The ICC Acceptance Criteria for Weather-Resistive Barriers (AC38) requires a weather-resistive barrier to pass ASTM E2273 with at least 90% efficiency to be a drainable wrap. Second, the bumps and texture create air space that allows the wall to dry more quickly.
A rainscreen is an exterior wall detail in which the weather-facing (cladding) surface is fixed at least 6mm (just shy of ¼”) away from the weather-resistive barrier surface on the wall. That gap creates a capillary break, or drainage plane, that allows moisture to drain and evaporate before it can cause problems. The gap is key. It can be created by use of furring strips that keep the cladding separated from the wall sheathing. There are also convenient drainage mat products that are comprised of a tangle of polypropylene strands that prevent cladding from compressing against the wall. In many areas like coastal regions of the southeast, local codes are requiring use of some type of rainscreen with a 6mm or greater gap.
A number of fiber cement cladding manufacturers like James Hardie require use of drainable WRB’s that have at least 90% drainage efficiency in moist climates, and some advocate the use of a rainscreen in the wettest areas.
Henry® WeatherSmart® Solutions
Henry offers two WRB solutions that provide greater than 95% drainage efficiency.
- Blueskin® VP100: A patented self-adhesive air and water barrier that improves energy efficiency by reducing air leakage. The textured face of VP100 provides above-code drainage efficiency.
- WeatherSmart Drainable: Patented drainage technology at >95% efficiency ensures wall protection in wet climates. WeatherSmart Drainable is one of the products recommended by James Hardie to meet their requirements in most of the United States.
Ideal for stucco and compatible with all cladding types, WeatherSmart Rainscreen features a 3D matrix that creates a 6mm ventilation and drainage gap between the weather-resistive barrier and exterior cladding. The matrix consists of polypropylene strands that channel water down and out of the wall assembly, and it’s backed with a built-in fabric to protect the wall gap from debris and promote unobstructed airflow.
Henry WeatherSmart solutions will help protect buildings from the risks of mold, rot, and mildew (and help protect from costly call-backs). They also help designers and installers meet a range of code requirements. When these products are used as part of the complete Fortifiber Moisture Control System™, they are covered by a 15-year material PLUS labor warranty for product defects.
Contact a Henry weatherization expert for advice and support on your next job.