August 25, 2011 Leave a comment
Staying Dry at the Beach
By Keith Lolley, Vice President of Sales at Advanced Building Products
As a father to two young boys I learned early on that a trip to the beach means planning ahead and bringing extra clothes knowing inevitably…they will eventually get wet. The same can be said for building in coastal areas, or any other geographical location that experiences significant amounts of wind and water. Builders and homeowners can hope for the best, or they can plan ahead and be prepared for potentially wet and detrimental conditions.
The term rainscreen technology has increasingly made its way into print and conference rooms across the United States and Canada over the last few years. So what exactly is rainscreen technology? When you hear this term remember this phrase, “allowing moisture to drain, not remain.” The concept is that simple. When builders use rainscreen technology they are creating a pressure equalized air-space within a wall system to reduce the forces that draw moisture into the wall assembly. This capillary break, often between 6mm and 10mm, allows for proper drainage and accelerated drying of water vapor that accumulates within the interior of the wall assembly. Without this capillary break, moisture will remain trapped within the wall system eventually leading to structural failure and potential mold issues.
Commercial construction experts have been designing and building cavity/drainage walls dating back over 100 years. The cavity acts as the airspace collecting moisture that gets past the exterior veneer giving moisture the ability to drain down and out of the wall via a system of thru-wall flashings, mortar diverters, and drainage devices. This proven concept is an effective way to control moisture; however, cavity wall construction is a little costly for residential applications. By using a rainscreen drainage mat, residential applications create the benefits of a cavity wall design without the cavity wall costs.
Tim Powers Construction is a high end homebuilder in New England who builds many homes along the coast of Maine and New Hampshire. Tim sees the added benefits to building with rainscreen drainage mats and states “here on the coast, moisture is always a concern. There is no such thing as a waterproof cladding, so moisture intrusion needs to be addressed early on. There are a few drainage mats available in New England, but we find some products easier to work with than others. We have been very happy with the Mortairvent® rainscreen product from Advanced Building Products.” Mortairvent® creates a continuous capillary break which allows moisture to drain quickly. The material is resistant to most known corrosive chemicals and doesn’t supply a food source for mold. With a Class A fire rating, builders and home owners are confident in the quality being installed on their home.
The United States version of Mortairvent® consists of rolls covering 200 square feet each, which makes them a good size to work with on site and the built in filter fabric gives added stability when building with cedar and fiber cement. The product is packaged in poly bags, which means less clean up on jobsites and the integral bug screen is very beneficial. The best thing about Mortairvent®, it is difficult to install incorrectly. Exterior walls are very angular with multiple penetrations, windows, and doorways as part of their design. Rainscreen drainage mats sometimes need to be cut on site to account for these angles. Some rainscreen products can only be installed one way, which leaves a lot of waste. The open weave design of Mortairvent® allows builders to cut the product to fit any sidewall design because the drainage plane is cross directional.
Rainscreen technology is required by code in most of the Canadian Provinces, and we are seeing more and more demand for these products here in the United States. Building science experts recommend a rainscreen for geographic areas that experience an average rainfall in excess of 20 inches per year. The 2006 version of the International Building Code states in section 703.1 that “the exterior wall envelope shall be designed and constructed in a manner that prevents the accumulation of water within the wall assembly by providing a water-resistant barrier behind the exterior veneer…and a means of draining water that enters the assembly to the exterior.”
Other states, such as Oregon, are starting to introduce rainscreen technology into their building codes as well requiring a 3mm minimum capillary break. This minimum airspace cannot be accomplished by using two layers of felt paper. A rainscreen drainage mat is the preferred method.
Whether building with commercial cavity wall components, or weather resistant barriers and rainscreen drainage mats for residential applications, the all-wall approach to drainage and ventilation is the best way to protect wall systems from moisture related damage. So the next time you bid a project, remember to include a rainscreen drainage mat in your bid.