The building envelope plays a crucial role in a home’s energy efficiency, and the weather-resistant barrier or housewrap is one component no longer being overlooked.
“It’s changing now, but in the past, there was zero education on housewraps,” says Brian Kirn, marketing manager for CertainTeed, which manufactures CertaWrap. “Now people are actually understanding that there’s a science to it, and to have the optimal building envelope, you want to have the optimum performing housewrap.”
Many building scientists use the phrase “build it tight, ventilate right.” Weather-resistant barriers must now address water management, including water resistance and vapor permeability as well as air resistance to provide an energy-efficient solution for a home.
“The construction industry is moving toward more and more energy-efficient homes,” says Tom Cullivan, marketing manager for Tremco Barrier Solutions. “The most important thing is not the fact that we’re building tighter homes, it’s that we’re building tighter, more energy-efficient homes that need to be ventilated correctly.”
The most recent trends in weather-resistant barriers support this emphasis on energy efficiency. Manufacturers are eliminating uncapped fasteners, increasing drainage options, trying new materials, discussing permeability, and highlighting surfactant resistance.
Eliminating uncapped fasteners
“The materials have been changing for some time, moving over to the plastic-type housewraps,” says George Caruso, director of product development for Benjamin Obdyke.
Alpha Protech www.alphaprotech.com
Benjamin Obdyke www.benjaminobdyke.com
Dow Chemical www.dow.com
James Hardie Building Products www.jameshardie.com
Owens Corning www.owenscorning.com
Quality Craft/Durabuild www.qualitycraft.com
Benjamin Obdyke manufactures HydroGap, a plastic-based housewrap that has three layers. Two layers are non-woven, and they sandwich the breathable film layer that provides water resistance and vapor permeability, according to Caruso.
Even with these newer, plastic-based materials, the housewrap must still be attached to the home. One growing solution is capped fasteners.
“It’s been recommended but now we are requiring that the product be installed with a capped nail or a capped staple,” says Bijan Mansouri, technical manager of Typar for Fiberweb. “By using these, you are reducing the chances of moisture intrusion as well as air leakage through the staple or nail.”
Caruso says capped fasteners can reduce the potential for tearing, not just during the application process but also when the housewrap is exposed.
Using capped fasteners, however, is not the only way to eliminate the perforations and leak points of uncapped fasteners.
Some manufacturers are now turning to a fully adhered product in which the housewrap membrane itself does not require fasteners.
“Fully adhered products are a relatively new thing,” says Peter Barrett, product manager for Cosella-Dörken, manufacturer of Delta-Vent, which has a full-surface coating with a vapor-permeable pressure-sensitive adhesive. “As adhesive technology changes, the biggest advantage to a fully adhered product is the lack of penetration for the fasteners.”
Some manufacturers are eliminating fasteners by producing a fluid-applied weather-resistant barrier instead of a housewrap.
“People look at weather-resistive barriers, fluid-applied, as new, but they are not,” says Cullivan. Fluid-applied weather-resistive and air-resistive barriers may not be new, but there is a new trend toward using these products, according to Cullivan.
“It’s our opinion that loose layers or wraps, as they are referred to, have inherent weaknesses; in that when they’re installed, they’re installed with nails or stapled or their seams are taped—all of which create passages for air, for water, or just opportunities for system failure,” he says.
Tremco Barrier Solutions manufactures the fluid-applied Enviro-Dri, which can be rolled, sprayed, or brushed onto the sheathing system. Cullivan also notes that builders do not have to worry about tearing or blow-offs in high winds with fluid-applied products.
Other manufacturers, however, do not think there is a growing trend toward fluid-applied weather-resistant barriers on homes.
“In residential, we’re not seeing a great pull for the fluid-applied products, mainly because they are a higher-performing product,” says Alan Hubbell, marketing manager at DuPont, which manufactures Tyvek products. “Maybe if somebody wants to build a high-end, custom, residential home, you may see them use a fluid-applied [product], but you’re in a different price range than you are with wraps.”
The 2009 International Residential Code (IRC) not only requires a water-resistant barrier, but also a means of draining bulk water that enters the system so it does not reach the interior. Codes like this are driving many manufacturers to create new draining solutions.
“Drainable housewraps is an emerging category,” says Caruso. “As homes are getting tighter, you hear a lot about energy efficiency and the need for better moisture management because walls and roofs and the entire building envelope [are] less forgiving.”
HydroGap combines a drainage system and housewrap by adding 1-millimeter dimensional spacers that create a drainage gap.
“The drainable housewrap category doesn’t offer the same amount of performance characteristics as a true rainscreen, but it offers more than just a standard housewrap without impacting any trim details, without impacting any insulation, and basically it goes up the same way as a housewrap,” says Caruso.
DuPont also has a combination drainage and weather-resistant barrier system with its Tyvek DrainWrap. The DrainWrap includes vertical grooves on the surface to help channel bulk water out of the system.
“These products help provide greater drainage efficiency, especially when siding is hard up against the housewrap,” says Hubbell. “With vinyl, there are some spaces, and they want the vinyl to lay flat, so it’s not always needed.”
Hubbell says the way he can tell that drainage housewraps are a growing trend is by the amount of competitors entering the field.
Kirn says CertainTeed would think of making a drainage wrap in the future, but the company currently does not have one.
“We do see the need for drainage to continue to grow, especially as codes change from out West to the East,” says Kirn. “To the installer, they want to do it as easily as possible, and to have one piece that does it all would certainly be to their benefit even if it is a little bit more expensive.”
Along with water-resistant and air-resistant qualities, vapor permeability is another key component of most housewraps and weather-resistant barriers today.
“You want [the housewrap] to be strong enough to block water but also permeable so any vapors from inside the house actually breathe through the wall, don’t get trapped in the wall, and can actually escape through the wrap,” says Kirn. “It’s a very delicate balance because the more permeable you make it, the less water-resistant you make it.”
There is much discussion about how permeable the barrier should be. The 2009 IRC classifies anything with a rating of 5 perms or greater as vapor permeable, when tested using ASTM International’s Method A standard. Many building scientists and manufacturers, however, say the ideal perm rating is between 10 and 20, while other manufacturers say that a higher perm rating is better.
“Probably too much is made of the perm rating. I think it’s more important you have good water resistance and a means for the water to get out of the wall assembly,” said Caruso. HydroGap has a perm rating of 16.
At 56 perms, the Tyvek HomeWrap is on the higher end when it comes to vapor permeability.
A quality highlighted by many manufacturers of weather-resistant barriers is surfactant resistance.
“The issue with some wraps is you won’t know there’s a problem with surfactants until five-to-10 years down the line,” says Kirn. “Soups, oils, tannins, different types of woods such as your OSB substrate or even your wood siding will have these surfactants in them.”
He uses the term “cornflaking” to describe what happens when surfactants break down water molecules, allowing them to pass through a housewrap that is not surfactant resistant.
“Instead of having one sheet, the entire wall becomes crinkled like little cornflakes, and it’ll start breaking up,” says Kirn.
“You basically just add soap to water and see if it affects the water-resistance performance of the product; so for us, it doesn’t,” says Caruso. “But even more important than surfactant resistance, when you have a spacer built into the housewrap, it’ll reduce the amount and duration of exposure to surfactants.”
Hubbel, however, says surfactants puzzle him, and he doesn’t see them as a problem because Tyvek doesn’t get calls about issues with surfactants.
Surfactant resistance is just one piece of the puzzle when it comes to weather-resistant barriers aimed at better energy efficiency.
“Energy efficiency is already more important, and it’s only going to increase,” says Barrett. “I’m finding my applicators much more educated and much more interested in learning the correct way to do things.”
Eliminating uncapped fasteners, increasing drainage options, and trying different materials are coming together in new ways to keep water and air out of homes while allowing vapor to escape. PR
Advancements in weather-resistant barriers keep things tight yet ventilated to save energy.