Chip Henderson, AIA, CEM, LEED Faculty
July 22, 2012

As with most building products, housewraps are only effective when installed correctly. The goal is to create a water and air barrier behind the exterior cladding to protect the building enclosure. Homes and multi-family projects with housewrap just stapled to the exterior sheathing might seem covered, but there are enough seams, gaps, tears and holes at critical spots to render the housewrap ineffective.In addition, there is growing recognition among building scientists and building codes that walls also need to drain; and going forward, housewraps will increasingly be judged by how effectively they help to facilitate positive drainage and drying of the wall. According to a study by John Straube and Jonathan Smegal of Building Science Corporation, a 1mm drainage gap “will drain water at a rate considerably greater than rainwater is expected to penetrate behind cladding even in extreme conditions.”

Choices are expanding; there are many moisture management products currently on the market, including drainable housewraps, rainscreen systems, fluid applied, and fully self-adhering membranes. Choosing the right housewrap requires an understanding of the product’s key attributes, including water resistance, durability, vapor permeability and drainage. However, no housewrap on the market will do its intended job if it isn’t properly installed.