Tags: #buildingscience #hygroscopic #materialsscience #roguetesting #waterresistance
Ponding tests: how this age-old technique offers new insights into the behavior of fluid coatings, coated glass facers, and integrated WRB panels.
Our industry uses ponding tests to evaluate a wide range of phenomena, from water resistance of sheet membranes to sealant adhesion under water immersion. Last year, I wondered – what would happen if we combined one of the simplest, least stringent WRB testing methods with a 5-hour test duration typically reserved for 21.6-inch hydrostatic head testing? In other words, how low can we go to demonstrate what happens by sandwiching hydrophilic, hygroscopic materials together? Some things that made an impression…
- Glass-facers absorb water. Lots of water.
- Some fluid-applied AWBs also absorb water. Lots of water.
- Sandwiching hydrophilic, hygroscopic materials together allows capillary suction and vapor diffusion to do the things they do. The gypsum core is wetted.
- If allowed, the gypsum core will readily release its water. If not allowed, it will not.
- Repeated cycling of this process has its consequences.
- Gypsum-based integrated WRB panels are no better than conventional gypsum panels.
- And I was wrong about gypsum-based integrated WRB panels. It doesn’t take 7 inches, nor 21.6 inches, of water to wet their gypsum cores. It requires less than 3/16” and less than 5 hours.