If you have ever driven past a building wrapped in a tent, then you have seen the sad result when rain gets into the exterior of a building. Eastside Harvest house aims to last for a century or more, so it has to be really good at keeping rain out.
Fortunately, a couple decades of studying rain intrusion failures have increased professional understanding of what does not work, and of what does. We consulted a building scientist for this house because they have developed details at windows and other wall penetrations that effectively keep rain outside where it belongs. And then we tested the first window installation to make sure we were right.
The test, ASTM E1105, is essentially an artificial rain storm. An array of sprinkler heads sprayed water on the outside of the window at the rate of 5 gallons per hour per square foot. Inside, a fan combined with a plastic sheet tried to suck the water in through any gaps, simulating wind-driven rain.
The pressure gauge read 0.397 inches of water column, equivalent to 100 pascals, which is twice the pressure that we will be using later to test the whole house for air leaks. The torture test lasted 15 minutes and if there was no sign of water inside, then the window passed.