Drop by Drop: Water Infiltration Testing

In a previous post I discussed air infiltration testing both in the lab and in the real world, so I wanted to touch on a related topic — wind-blown rain and water intrusion.

With respect to lab testing, we run similar tests on the same equipment for both of these. And while it is very common to conduct air infiltration testing (i.e., blower door tests) on actual houses, wind-blown rain and water intrusion testing on actual homes is very rare. Air infiltration problems can be difficult to remedy after a home is closed in and completed but any related problems usually only result in higher energy costs. On the other hand, a water intrusion problem can result in mold, mildew, rot, structural damage, and potential health problems.

Roof leaks are the most common water intrusion issue but they are often diagnosed early, before major problems set in. Water intrusion into walls usually persists for a longer time before the problem becomes evident — the extended time period is what contributes to resulting mold and rot problems. Water intrusion into walls typically results from poor flashing around windows, doors, and penetrations. The combination of heavy rain and high winds results in wind-driven rain where water can be forced through every crack and crevice in the wall system. It is amazing how much water can get through a system that looks impenetrable. I recall one test that I was sure would pass, but to my amazement, a few minutes into the test small water droplets began to emerge on the inside of the wall. It required a magnifying glass to find the source of the leaks.

There are many different weather resistant barrier and flashing products on the market. The Home Innovation has run the ASTM E331 Standard Test Method for Water Penetration of Exterior Windows, Skylights, Doors, and Curtain Walls by Uniform Static Air Pressure Difference on a number of different products and systems. This test uses a full size specimen and subjects it to a water spray equivalent to 8 inches of rain per hour. At the same time, a pressure of 137 pascals (2.86 lb/ft2), equivalent to approximately a 34 mile per hour wind, is applied to the specimen in order to force the rain through any leakage path. The system must withstand these conditions for 15 minutes without any evidence of leakage. The Home Innovation’s wind-blown rain chamber can also run ASTM E283 to measure air infiltration and it is common to run both air infiltration and water intrusion on the same system. The Home Innovation lab continues to help product manufacturers find ways to verify and improve product performance. If you would like to see how your products perform under our real-world simulation tests, contact us.

If you are a builder, you should always be sure the weather resistant barrier and flashing products you use have been appropriately tested and properly installed — a full list of Home Innovation certified products is available on our website, but we don't list all products we've tested; if you have questions about a specific product, let us know. 

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