Masonry Magazine November 2012 Page. 24
AIR BARRIERS
Both vapor permeable and vapor impermeable air barriers play critical roles in modern wall design; the choice of product is dependent on a wide range of factors, including climate, wall design and other building components. In addition, building materials continually are advancing, presenting architects with new choices, each with its own pros and cons. Working with a professional or manufacturer who has both the technical expertise and the modeling tools to fully evaluate your design against real-world conditions can save you time during the design phase and headaches down the road.
The prime choices for a firmly adhered air barrier are self-adhered membranes and fluid-applied membranes. Both are available in vapor permeable or impermeable variations, and both can deliver equivalent performance. Maintaining optimum dry film thickness of a fluid-applied membrane is critical to its performance. The thickness must be sufficient to cover all high and low points of the substrate. If the layer is too thin, voids can occur, creating leaks.
For this reason, using high-quality flashing systems at all openings is crucial to ensure a continuous air barrier throughout the building envelope. In addition, the air barrier should be firmly adhered to the wall surface. This is especially critical in wall designs with an air space between the air barrier and the exterior cladding. In these designs, wrap-type air barriers can "billow" to pump air back into buildings or at fastening points, causing it to stretch or potentially tear at anchor points when negative wind loads are strong enough, in effect "inflating" the air barrier envelope. Once breached, the air barrier loses its effectiveness.
Product Watch
DuPont Building Innovations has launched the DuPont Tyvek Fluid Applied Air and Water Weather Barrier System, which offers similar air and water protection of DuPont Tyvek CommercialWrap, but in a fluid-applied form. The system provides coverage and the combination of air and water hold-out and is ideal for application on concrete, concrete masonry unit, gypsum sheathing and complex high-rise buildings.
The complete DuPont Tyvek Fluid Applied Air and Water Weather Barrier system is comprised of Tyvek Fluid Applied Weather Barrier (WB), Tyvek Fluid Applied Flashing and Joint Compound, DuPont Sealant for Tyvek Fluid Applied System and Tyvek Fluid Applied Flashing - Brush Formulation. Applied in one coat by spraying or power rolling, DuPont Tyvek Fluid Applied WB saves time in the installation process. Additionally, combining low shrinkage with high elongation and elastic recovery allows DuPont Tyvek Fluid Applied products to stretch and move with the building, resulting in minimal cracking. Providing the ideal combination of air and water holdout, this fluid-applied product offers vapor permeability of 25 perms.
The DuPont Tyvek Fluid Applied system can play an important role in increasing the overall sustainability of commercial buildings by helping to control air leakage, which allows for more energy-efficient structures by reducing the amount of energy required for heating and cooling. The system also helps to improve indoor air quality by providing protection from water accumulation in the wall system, which can lead to the growth of mold and mildew, as well as wood rot and metal corrosion. Additionally, the system features low-VOC products.
The Tyvek Fluid Applied System can withstand nine months of UV exposure, can be applied to damp concrete and can be applied at temperatures as low as 25 degrees Fahrenheit, providing builders and contractors with more flexibility in their construction schedules. For more information, visit www.weatherization.tyvek.com.
Jane Wu is marketing manager, commercial air barrier products, at Grace Construction Products, chun jen.wu@grace.com. For more information, visit www.graceconstruction.com.
This article was previously published in the March 2012 issue of Metal Architecture magazine.