Siding may be a building’s primary barrier to air leaks and water infiltration, but house wrap can play an important role. Builders place house wrap, typically made of lightweight synthetic material, directly over a home’s sheathing and behind the siding. The wrap serves as a secondary defense against air and water penetration and enhances the home’s energy efficiency and thermal performance. To ensure the maximum benefit of house wrap, homeowners should consider its durability, water resistance, vapor permeability, and UV resistance.
House wrap made of a weak material can crack, split, or tear. Great tensile strength and resistance to temperature extremes are essential for the durability of house wrap.
While the primary function of house wrap is to prevent water infiltration, it must allow moisture to exit the building and not keep it trapped inside the walls. The permeability unit of measure in the United States is US perm; one US perm equals one grain of water vapor per hour, per square foot, per inch of mercury. Professionals recommend choosing house wrap materials with a permeability of 10 to 20 US perms to optimize the inward and outward vapor flow in the walls.
Finally, prospective house wrap buyers should consider the material’s UV resistance, especially for a new building. Construction may take several weeks, leaving house wrap exposed to direct sunlight. A house wrap material without UV protection may start crumbling during construction.
