The question of whether to use some type of moisture barrier on a house’s exterior wall has been settled for many years. Products such as felt, building paper, and housewraps are known to be an important part of keeping wall assemblies dry. They “permit water vapor transmission but prevent bulk water from penetrating,” the Upper Marlboro, Md.–based NAHB Research Center says on its website. “And this is a good thing because if the wall cavity gets wet, [weather-resistant barriers] need to permit drying of the wall to the exterior.”
But while weather barriers serve an important function, there is a vast amount of confusion on what type of product to use. No wonder there are so many choices. Known by product names such as Tyvek, Typar, and RainDrop, plastic-based weather-resistive barriers made from polyethylene or polypropylene seem to have become the norm. The products are lightweight and easy to install, but they’re not the only game in town.
Horsham, Pa.–based Benjamin Obdyke, which manufactures products for rainscreen applications, has entered into an agreement with Hickory, Tenn.–based Fiberweb, manufacturer of the Typar housewrap brand. As a result, Fiberweb now markets and sells two products that feature Benjamin Obdyke’s Home Slicker matrix technology bonded to Typar housewrap.
Essentially, builders get a weather barrier and a product that creates an airspace so walls dry out faster.
Housewraps now come in liquid form, as well. Atlanta-based Sto Corp. offers StoEnergy Guard, a product that provides three benefits in one. It “integrates a fluid-applied waterproof air barrier, sheathing joint and rough opening protection, proven drainage technology, and approved continuous insulation into a flexible system that can be designed to meet individual climate zone and building code requirements,” the company says. It can be used under a variety of different cladding.
Wilmington, Del.–based DuPont Building Innovations manufactures a host of Tyvek-branded housewrap products, including ThermaWrap, a weather barrier that also includes a low-emissivity metallized surface to minimize summer heat gain and winter heat loss. Earlier this year the company also announced a new fluid-applied product.
No matter what type of weather barrier you use, proper installation is key. According to the International Association of Certified Home Inspectors in Boulder, Colo., housewrap should be installed before windows and doors; upper layers should be lapped over lower layers; horizontal joints should be lapped at least 6 inches and vertical joints should be lapped 6 inches to 12 inches; staples or roofing nails measuring at least an inch long should be used and spaced 12 inches to 18 inches apart; and joints should be covered with tape. Do these things, and your housewrap is likely to perform well for years to come.
