As the saying goes, “April showers bring May flowers. While there are certainly good thoughts about the emergence of abundant greenery, for the commercial and residential construction segment, rain and moisture can deliver immediate and future troubles. One of those concerns is keeping the sheathing dry behind the selected natural or synthetic cladding system.
Enter the importance of a properly installed rainscreen. In very basic terms, rainscreens can vary in design but their primary job is to effectively drain rain and developing moisture from behind the cladding. At the same time, rainscreens control the building wetting forces of gravity, capillary action, and wind pressure differences.
A rainscreen creates an air gap between the decorative façade and the sheathing of the building. This space allows for the circulation of air across a weather resistant barrier such as TYPAR and is critical to removing potential condensation or direct water infiltration. The all important weather resistant barrier helps to prevent water molecules from entering the insulated cavity which can create an ideal environment for damaging mold conditions to develop. By themselves, weather resistant barriers are not always adequate in keeping the complete wall cavity dry.
There are two major rainscreen design types that are usually used—a field built drainage plane or a drainage mat. The drainage plane and drainage mat products attempt to fill the same role which is the elimination of entrapped moisture from the building envelope through the creation of a permanent, predictable space between the veneer and the backup wall. Unlike our neighbor to the north, Canada, most US state and local building codes do not mandate the use of best practices which always incorporates a rainscreen system. In those instances where a rainscreen is used in residential construction, the method of choice in the Northeast US appears to be the drainage mat.
The benefits of using a rainscreen drainage mat are many:
• They provide drainage of excess moisture and ventilation all in one product
• They help keep the siding and entire wall cavity dry
• Rainscreen drainage mates are lightweight and easy to handle
• Most drainage mats are made from a polymer core that are resistant to most known corrosive chemicals, including solvents
• They do not absorb or release moisture
• Rainscreens are not a source for the promotion of mold, mildew or bacteria.
Recently Boston Cedar was named as the exclusive Northeast distributor for Keene Building Products which is an Ohio based manufacturer of 3-dimensional building envelope products for moisture control. Boston Cedar has two of the most popular drainage mats in stock and ready for immediate delivery:
Driwall™ Rainscreen 020-1 Thickness 0.25 Inches / 6 mm DriwalI™ Rainscreen is a drainage mat for exterior wall systems. The entangled net product eliminates incidental moisture problems in most exterior veneer applications, including stucco, manufactured stone, and plank siding.
Driwall™ CDR Vent (Complete Drained Roof) Thickness 0.30 Inches / 7.6 mm Driwall™ CDR Vent is drainage and ventilation mat designed to eliminate moisture and moisture vapor in roofing and siding applications. It is useful in cedar shingle/shake roofing and siding where a clean airspace is desired for ventilation and drainage.
The building shown in the photo has a severely damaged wall cavity system due to lack of best practices being used during the cladding installation.