The basic installation premise is to think like a raindrop. Imagine a drop of water hitting the side of your house at the top of the wall. Gravity pulls the drop down along the face of the wall, and as long as all the courses, joints, tears, and penetrations are sealed and lapped in shingle fashion, the drop eventually will reach the ground. The moment that raindrop finds a puncture, a reverse lap, or an unflashed component it will seep behind the housewrap and into the framing.
Start every housewrap installation from the bottom
and work your way up, making sure to overlap all horizontal joints at least 6 in. and all vertical joints 12 in. If you apply housewrap to the sheathing before raising the wall, be sure to leave enough material to cover the band joist. Horizontal laps are as important as vertical laps because windblown rain can travel sideways, or even up and over a properly installed lap.
Air Infiltration Diagram Caption: Homes and buildings account for 42 percent of U.S. carbon emissions, and 39 percent of our primary energy, according to the Building Envelope Research Group at Oak Ridge National Laboratory. That’s more than either industry or transportation. According to the U.S. Department of Energy (DOE), random air infiltration through gaps and cracks is a leading cause of energy loss in homes, accounting for 25 to 40 percent of the energy loss in most residential structures.
You should always install housewrap with the same care and attention that you would devote to siding. Although no one will see your good work underneath the siding, correctly installed housewrap still pays off in the long run.
