The drainage plane is critical to Green building

A critical aspect of building a home, not just a green one, is keeping the water outside of the home, not inside. Some of the older flashing details like drip edges and caps are making a comeback in architectural design for good reason, they keep water on the outside of the walls where it belongs. With tight envelope building the drainage plane becomes more critical than ever. Green builders seem to understand proper installation and placement of materials inside a wall or other system better than the uneducated masses. Think of this example for a second. If you are in the hot and humid southeast, and your building is cool inside, and it's hot and humid outside, where the two temperatures actually meet, there's going to be condensation similar to a glass of cold iced tea on a warm summers day. Where this meeting and condensation takes place in your structure can make or break you. This place is called the drainage plane, and you want it on the outside of the wall instead of the inside. This mistake has been made in many variations over the past, for instance an earlier energy program directed builders to apply a film of poly to the exterior walls before the sheetrock was applied. This moved the drainage plane for condensation inside the wall rather than on the exterior. We've got it better now with the introduction of housewraps, greenboard with tape, and thermoply sheathing. The moisture collects away from the sheathing, instead of on it. And as many builders have discovered, OSB without the addition of housewrap makes a rather crappy drainage plane. Ask your buider if he understands the concept of the drainage plane and if he's building green he will give you the correct answers.