Airflow And Drainage In Your Exterior Walls

Technology | Moisture Control

An Austin, Texas apartment uses Driwall™ Rainscreen 020-1 to help keep exterior walls from molding by creating ventilation and drainage.

By Jim O’Neill
All photos courtesy of Keene Building Products

Airflow And Drainage In Your Exterior Walls

Airflow And Drainage In Your Exterior Walls Located in Austin, Texas, this complex offers luxury one-bedroom and two-bedroom apartments. Each of the 13 unique floor plans feature hardwood or stained concrete flooring, granite or quartz countertops, stainless steel appliances, spacious walk-in closets, and private balconies. Residents can enjoy the vast amount of amenities, including the high-quality athletic center, the resort-style swimming pool, or the outdoor grilling area. Take a short drive and explore the Austin Music Hall, hit some golf balls at Austin Top Golf, have a shopping day at Arbor Walk, or grab a bite to eat at the various restaurants. Everything you desire in multi-family living is provided right here.

Airflow And Drainage In Your Exterior WallsIn order to provide extended life of the apartment complex and peace of mind for the tenants and owners of this building, it is important to make sure that it does not mold and decay, ruining the profitability of the project. Eliminating as many concerns as possible about moisture issues is important to everyone. With the increase in building thermal protection, moisture problems are on the rise throughout all new construction. Creating a greater need for hydrostatic pressure release and a ventilation method is significant. Adding a rainscreen product is the answer to these problems. Let’s learn more about rainscreens.

Airflow And Drainage In Your Exterior Walls

The three-dimensional mat is heat-laminated to a nonwoven lightweight, breathable fabric in order to provide a separation from cementitious sidings.

The three-dimensional mat is heat-laminated to a nonwoven lightweight, breathable fabric in order to provide a separation from cementitious sidings.

Driwall Rainscreen 020-1 installation

Driwall Rainscreen 020-1 installation

There are multiple reasons why adding rainscreen to your wall cavity is beneficial. For thin veneer stone, stucco and other masonry veneers when it rains, large quantities of that moisture will be stored in the wall system. When it is cooler and dryer inside and it stops raining outside, water-driven moisture will be forced through the weather-resistant barrier. This process is called solar-driven moisture. The best way to reduce this is to add an air space that can act like a chimney to relieve the pressure on the weather-resistant barrier.

One of the most common places for moisture issues is when you see transitions between dissimilar materials. For example, where stucco goes into a window, or when brick goes into fiber cement board siding. This is because there is too much reliance on flashing details, and flashing details often is installed incorrectly, resulting in moisture issues. If you can create an air space outside of those flashing areas, it can help overcome any errors that occur by introducing airflow and drainage.

 

Driwall Rainscreen is allowing the walls to breath and stay dry.

Driwall Rainscreen is allowing the walls to breath and stay dry.

A great resource from 2008 is the National Association of Home Builders (NAHB)1 article: “Improving Drainage and Drying Features in Certain Conditions: Rain Screen Designs for Absorptive Claddings.” In this guide, the author discusses how a typical water-resistive barrier or housewrap is not the best drainage material for exterior walls, and that there is a need for rainscreen designs.

 

You may be familiar with the study done in 2007 by the Building Research Association of New Zealand (BRANZ)2 where the drying rates were measured in a series of wall panels over a period of three years. The biggest conclusion discovered in this study was that the rate of drying is significantly different back inside the wall then it is behind the exterior wall veneer. Another discovery is that and open rainscreen wall dries significantly faster than walls without air space.

Driwall Rainscreen 020-1 is a nominal quarter-inch, randomly oriented, geometric patterned drainage and ventilation mat. It is designed to eliminate moisture and moisture vapor in masonry and other siding. The three-dimensional mat is heat-laminated to a nonwoven lightweight, breathable fabric in order to provide a separation from cementitious sidings. The monofilaments are heat-welded at the junctions to form a structure that spaces exterior veneer away from the inner sheathing.

When Driwall Rainscreen is used, no mortar or other debris can enter the cavity, which ensures proper drainage and ventilation.

When Driwall Rainscreen is used, no mortar or other debris can enter the cavity, which ensures proper drainage and ventilation.

The product is useful in cavity wall designs and rainscreen systems in which air space is needed for drainage and ventilation. By increasing energy efficiency without introducing a ventilation and drainage method, siding applications see an increase in moisture issues. It is essential to have a means of drainage and circulation of air to help prolong the life and look of the stone, stucco, and fiber cement used on this apartment complex. When Driwall Rainscreen is used, no mortar or other debris can enter the cavity, which ensures proper drainage and ventilation.

The full-wall DriwalI Rainscreen 020-1 product rolls over the weather-resistant barrier to separate it from the exterior veneers. The air space that is provided will assure that any moisture that penetrates the siding can drain to the exterior.

Airflow And Drainage In Your Exterior Walls For this particular Austin apartment complex, Keene Building Products’ Driwall Rainscreen 020-1 was incorporated to alleviate any future concerns related to moisture behind the variety of exterior veneers including: stone, stucco, and fiber cement. Proper airflow and ventilation are essential for quality construction. By applying Driwall Rainscreen, this Austin, Texas apartment complex is allowing the walls to breath and stay dry, prolonging the life and durability of the whole structure.


Jim O’Neill is division manager for Building Envelope Products at Keene Building Products. He can be reached at jmo@keenebuidling.com.

References:

  1. National Association of Home Builders (NAHB), “Improving Drainage and Drying Features in Certain Conditions: Rain Screen Designs for Absorptive Claddings.” 2008. Available from: https://www.nahb.org/en/research/legal-issues/~/media/04DFC0575FBB4EE48669520B85DC9C28.ashx
  2. Bassett, M. “Examining Drying Rates In Walls,” Build #100, June/July 2007 (Building Research Association of New Zealand), at pages 66-67. Available from: http://www.buildmagazine.org.nz/assets/PDF/B100-66-DryRateWalls.pdf

 

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