Although the term “housewraps” is not brand new, there is still a fair amount of misunderstanding surrounding the word.
“Up until recently, you had building paper or nothing behind the cladding until housewraps and synthetic materials were introduced, but a wrap or a weather barrier was not required until about 2006 at least in residential codes,” says Alan Hubbell, residential marketing manager, Wilmington, Del.-based DuPont Building Innovations.
“That may be what you’re seeing in terms of the use of the word housewrap. The codes are driving the use of some kind of water-management system, and the codes are much more prescriptive,” he says.
“The International Residential Code [IRC] requires you have a weather-resistant barrier behind all exterior cladding and in some cases they require two layers, such as behind stucco,” says building science consultant, Steve Easley, Steve Easley & Associates Inc., Danville, Calif. “The reason for this is all exterior cladding leaks. It’s not a matter of if they leak; it’s a matter of when they leak. Typically, you see leaks happen at roof and wall intersections, around doors and windows, as well as at penetrations, such as dryer vents.”
“We talk about managing bulk or liquid water because obviously you want to keep that out of your wall system and also manage air leakage,” Hubbell says. “Moisture as vapor, of course, can also be carried by air, so by managing air, you’re also managing and reducing vapor transmission through the wall.”
Confusion About Barriers
“I think there’s a lot of confusion out there with respect to vapor barriers. In some cases you have to choose one type of vapor barrier to meet building codes, but if you use a certain cladding or a certain percentage of cladding, then you can choose a different type of vapor barrier; it’s not easy to decipher,” Hubbell says, noting DuPont is developing an application called Code Sense to help contractors and builders understand building- and energy-code requirements for air, water and thermal management in wood-frame walls, as well as provide instructions about how to meet these requirements for the specific code, climate zone and cladding type selected.
“The point is,” Hubbell adds, “not all housewraps are equal with respect to permeability, and although they may meet the minimum requirements for a water-resistive barrier, they may not meet the requirements for an air barrier because of the way they achieve permeability.”
Is building science clearly understood? “The answer is probably ‘no,’” Hubbell says. “You have to put your thinking cap on; you have to be very clear about what you want to know and about what you want to accomplish and then talk to somebody reputable. There is a lot of misinformation out there.”
The misapplication or incorrect installation of housewrap products potentially can lead to more problems than they solve. “These products, especially the wraps, are a small part of the spending on construction,” Hubbell says. “They probably don’t get the mind share from contractors they deserve. If done improperly, housewraps can be responsible for a large percentage of problems and callbacks.”
Hubbell adds that although his company’s specialists devote a good deal of time and attention to the housewraps themselves, they also spend time on the flashing products, which tie the windows, doors and other penetrations to the wraps.
The point where housewraps interface penetrations is particularly vulnerable to leakage problems. Hubbell advises contractors to think of the wall as they would a roof. “A wall is just a roof in a vertical configuration,” he says. “For example, you wouldn’t reverse shingle a roof, yet when people get to the wall they might consider it. But if you treat the wall like the roof, then you should be in pretty good shape at least in respect to water management.”