Micro drainage planes: Do they work, and if so, how do they work? And what factors should we consider in their application?
Here is one that I designed. Simple and intuitive. Its geometry, and composition, are optimized to ‘slice’ water droplets and encourage their path downward – and more importantly – to disperse and facilitate evaporation. That is the true advantage of the micro drainage plane. It’s not drainage per se, it’s dispersion and the ease of transitioning to the vapor state.
It’s important to appreciate that displacement is not drainage. If one drop must be pushed by another to disperse or to release, then the process is governed by displacement – something keenly assessed by ASTM E2273 and misinterpreted as ‘drainage’.
I’ve demonstrated some very high drainage efficiencies; with some very thin drainage planes; using some very low flow application rates. Micro drainage planes can work, but not by geometry alone. Other factors are also in play. And when they do work, we must keep in mind, that micro drainage planes must be integrated with the remaining WRB system – assuming they are applied to it. Each rise in the WRB’s surface topography creates a challenge for our tapes and flashings. So, it’s key to optimize surfaces and plane geometry with their paired WRB accessories.