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Using Housewrap for Masonry Applications:
According to the U.S. Department of Energy, weather-resistive barriers (WRB) such as housewrap – also known as building wrap – are recognized as an indispensable part of exterior wall systems, protecting building materials from exterior water penetration and keeping them dry. When used properly, the material improves a building’s durability, decreases maintenance costs, and reduces the risk of moisture-related problems such as mold and mildew. No matter what type of exterior cladding is used – and that includes stone and brick veneer and newer stucco systems – WRBs are essential to effective moisture management.
For some time now, building codes have required the use of WRBs like housewrap in the construction of frame buildings. That’s because any siding material, be it wood, masonry, vinyl or a combination of each, does not serve as a barrier to driving rain. Building science recognizes the need for such a barrier behind the siding to keep water from reaching the interior sheathing or framing.
This article will take a look at what constitutes a WRB, what types are available, what steps should be taken during installation, and how technological advances in housewrap in particular have made it the best choice in some construction projects. And, since masons regularly are tasked with installing housewrap during construction, it’s essential to be well versed in the product category and the proper installation techniques that will help them meet the latest building codes.
There are two main types of WRB. One is building paper, which is a traditional paper sheet or felt material that is asphalt coated or impregnated to increase its strength and resistance to water penetration. It does not have breathability and can trap moisture in the wall cavity. The other type of WRB is housewrap – sometimes called building wrap – which is made of a synthetic material, usually polymeric-based sheets of plastic. It has become the predominant WRB used in the construction industry today.
Housewrap has a number of advantages over building paper. It is lighter weight and produced in wider sheets, so that the material can be more quickly applied to the home’s shell. The product has three main performance criteria: blocks liquid water from entering the wall assembly, allows water vapor to escape from the wall cavity, and seals the building to reduce air infiltration.
Many different varieties of housewrap are on the market. Understanding the differences can be quite challenging. Some are woven and others non-woven. Some have perforations, others are low-perm micro-porous, and still others are non-perforated. The International Code Council-Evaluation Service (ICC-ES) is the U.S. leader in evaluating building products for compliance with residential and commercial codes. It has developed a list of WRB criteria to consider, which include:
Products for changing building codes
Manufacturers of housewrap products such as IPG (Intertape Polymer Group) NovaWrap ASPIRE Premium Building Wrap are educating customers in Georgia and elsewhere about how the ASPIRE product meets and exceeds the requirements of the tougher state energy code.
When NovaWrap ASPIRE was put on the market, it was created to address what IPG saw as the deficiencies in the housewrap technologies available, at that time, to builders and building owners. The product is 100 percent non-woven, polypropylene fabric that is designed to resist water penetration from the outside, while allowing the structure to “breathe,” thereby preventing moisture damage. Unlike other housewrap products that are manufactured with micro-perforations, NovaWrap ASPIRE is completely non-perforated to deliver better protection against water and air intrusion, better energy efficiency due to less air loss, and a balanced degree of water vapor transmission to avoid hot humid exterior air condensing on cooled interior walls.
The IPG Product Development team incorporated other features into the product to address drawbacks in competitive products on the market. Unlike some of the market-leading housewraps, NovaWrap ASPIRE stretches easily and conforms easily to building details. The translucent fabric allows for easy location of studs and overlaps, and the superior tear and puncture resistance saves on fasteners and creates less repairs and waste. It also can be left exposed to the elements for up to six months.
NovaWrap, like most of the better housewrap products on the market, can be installed under bricks, stone, stucco, EIFS, rigid foam, as well as wood and fiber cement siding. When working with stone veneers built over wood frame construction, the 2009 International Building Code (Section 1405.6) requires two layers of housewrap or other WRB. IPG recommends attaching one layer of its product to the sheathing and using an additional layer to the exterior side. In other words, the WRB should be separated from the stone and mortar by a second layer of WRB. The first layer, which was applied directly over sheathing or studs, serves as the wall system’s WRB and should be integrated with window and door flashings.
Brick facades require a ventilated air space – a minimum of one inch – between the housewrap and the cladding. It’s essential to follow the manufacturer’s guidelines regarding the use of an air space between the brick veneer and the sheathing.
As building science continues to evolve, product development specialists are working to create the right WRB products to better help reduce air infiltration, cut utility costs, improve indoor air quality, and increase comfort. The ultimate goal is to help system specifiers, designers, architects and contractors meet sustainability goals for the betterment of the environment.
|Last Updated on Wednesday, 05 December 2012 15:37|