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Building Tip
Weather Resistive Barriers are more than a code requirement. These materials prevent the intrusion of water into our homes, allow harmful water vapor to escape, and improve energy efficiency.
Improvements on traditional Weather Resistive Barriers have been struggling to make waves in our building community. At one point, the standard was such that, the general term for weather resistive barriers used in the field was the name of the brand most builders were using.
Now, builders have more options with other manufacturers in the market. The new products available are upgrades to the standard of two layers of 60-minute paper behind stucco. These products promote greater drainage of the incidental moisture found behind the stucco. Additionally, variations in the ability of the weather resistive barrier to withstand moisture intrusion and vapor permeability, allow for the product to be prescribed with consideration of the local climate of the project.
Furthermore, these products act as air barriers. To a certain degree, they limit the amount of unconditioned air to infiltrate the building. Properly installed, the weather resistive barrier reduces heating costs by preventing wind washing through insulation.
Simply including an off-the-shelf weather resistive barrier in the building envelope is no longer adequate. Care must be taken in the selection of the product, and greater care must be taken in the installation. Proper installation requires careful attention to detail, and an understanding of building sciences. Improper installation may result in leaks and higher energy bills.
The use of these products, in conjunction with a rain screen system, is highly recommended in close proximity to the ocean, and locations with high levels of rain and moisture.
Here are some samples of weather resistive barriers:
HardieWrap
http://www.jameshardie.com/builder/weatherbarrier.shtml
Dupont Tyvek
http://www2.dupont.com/Tyvek_Weatherization/en_US/index.html
VaproShield
http://www.vaproshield.com/products/wallshield
Typar
http://www.typar.com/builder/products/index.html?bl=main-products&it=main-products
By Micah Rodler, Inspector/Consultant
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