Remodelers know well how doing a poor job with moisture management on a project can lead to premature structural deterioration, shorten the life of claddings and paints, foster mold, rot and insect infestation — and lead to costly litigation. But given the plethora of products on the market, remodelers can be forgiven if they find themselves at a loss over which product makes sense for their project.
Fortunately, there’s a simple way to determine which type of product to use based on climate. Here’s a look at three climate based moisture management suggestions from the Building Enclosure Moisture Management Institute. BEMMI bases its guidelines on annual rainfall in the following way:
- 0 inches to 20 inches: Areas with 0 inches to 20 inches of rainfall may use a basic flat house wrap or such as something as simple as felt paper. These basic types of wraps are designed to protect against water intrusion, but they don’t offer any advance moisture management features.
- 20 inches to 40 inches: Areas with 20 inches to 40 inches should use enhanced moisture management — drainable wraps or drainage mats — especially if using absorptive cladding material such as engineered stone. Drainable wraps incorporate both a water resistive layer and drainage gap created by spacers. These gaps help water drain from behind the cladding at a faster rate. Manufacturers claim the newest drainable wraps can be as much as 100 times more effective at removing bulk water from the wall than traditional wraps.
- 40 inches or more: Areas with 40 inches or more of rainfall require water resistive barriers plus rain screens, which not only protect against water intrusion but also offer drying capabilities. Rain screens should be used regardless of cladding material. Rain screens are designed to work in conjunction with a housewrap, or water resistive barriers. They do so by creating a drainage and ventilation space between the cladding and the WRB. The larger the space created, the more drainage can occur. BEMMI recommends a 3/16” minimum airspace to create the combination of drainage, ventilation drying and a capillary break space to decouple the cladding from the WRB/sheathing. Anything less may provide some level of drainage within the wall assembly, but not ventilated drying and a capillary break, the organization warns.
For more on moisture management techniques and options go to http://www.tamlyn.com.