Last week we joined a webinar led by Denali Jones, Technical Director of the Rainscreen Association in North America (RAiNA). His talk focused on a question that turns out to be surprisingly tricky:
How can we keep the envelope of a building dry?
Turns out the answer isn’t just about installing the right cladding or adding a tougher barrier. It’s about creating space for walls to breathe. Here are 7 key takeaways.
Point 1: Rainscreens Are Not Products. They’re Assemblies.
A rainscreen isn’t something you buy in a box. It’s a system of components:
- an outer cladding layer
- an inner weather-resistant barrier (WRB), and
- a cavity in between.
That cavity, even if it’s as thin as 3/16" (per ASTM E2925), makes the difference between a wall that drains and dries, and one that traps moisture until mold sets in.
Working together, these components form an assembly that creates an aesthetic, protects the building, manages moisture, and improves thermal performance.
Point 2: Moisture Intrusion Runs Rampant.
Here are the stark stats: An EPA study of 100 buildings showed 85% had evidence of moisture damage. In addition, up to 90% of wall failures trace back to water. The culprits are many:
- Capillary action that wicks water uphill,
- Kinetic energy that drives rain into siding,
- Vapor that pushes itself through wall assemblies,
- Condensation at dew points inside walls, and
- Pressure differences created by wind.
In other words: water has plenty of ways to get inside the envelope. Our job as designers and builders is to make sure it also has a way out.
Point 3: Wet Makes Bad Things Happen.
Jones shared stories that many architects and contractors know all too well, including:
- A Cape Cod home with wood shingles, no drainage plane, and $100,000 in repair costs.
- A stucco-clad house in the Pacific Northwest where poor flashing details led to sheathing that could be scooped away by hand.
In both cases, a modest rainscreen gap could have saved the owners six figures and years of frustration.
Point 4: Mold Doesn’t Wait.
Perhaps the most sobering reminder was the timeline for mold growth.
Mold can colonize in 3–12 days, become visible within three weeks, and start causing health and structural issues long before homeowners notice.
That leaves just a 48- to 72-hour window for materials to dry before mold takes hold…a window rainscreens are designed to keep open.
Point 5: We Can Use Design to Reduce Risk.
Jones described a spectrum of choices for envelope design:
- Direct-applied walls (cladding right on WRB) are still common, but risky.
- Drained assemblies allow incidental drainage but lack airflow to dry the wall.
- Drained and vented assemblies add a bottom outlet for water escape.
- Drained and ventilated assemblies, with both top and bottom openings, represent the gold standard. They allow air movement to accelerate drying and vent solar-driven moisture from absorptive claddings like brick, stucco and fiber cement to the exterior.
Point 6: Your Water-Resistant Barrier is Key.
The performance of a rainscreen depends heavily on the WRB.
Whether it’s felt paper, housewrap, integrated sheathing, or drainable wraps, installation quality is critical.
Jones emphasized that every WRB will be punctured by thousands of fasteners in a typical structure.
Rainscreens provide the “belt and suspenders” that make those inevitable imperfections survivable.
Point 7: In Case You Forgot, Keeping Buildings Dry Matters.
Rainscreens aren’t about over-engineering. They’re about managing risk.
Climate, cladding type, and wall design all affect the moisture load of a given building. Rainscreens provide a reliable way to protect owners, reduce liability, and extend the life of the building envelope.
As Jones put it, “We’re not building submarines. Buildings will get wet. The question is whether they can dry before the damage starts.”