Basic Rainscreen Principles
At present most designers relate rain screen wall assembles to masonry veneer and or masonry cavity wall. These assemblies have been shown to work and over the years have been perfected to the point where no testing and or performance warranties are required, asked for or issued by the proponents of these systems namely the masonry industry. The main feature of a brick veneer wall assembly is the airspace (cavity) between the masonry and the back up system, weep holes, vent holes and flashing.
Current Acrylic Stucco Rain Screen Issues
The main factor contributing to the problems encountered with the acrylic stucco when applied on top of the insulation - known as Externally Insulating Finishing System (EIFS), is the inability of the assembly to dry through the EIFS making the performance of the system somewhat climate dependent. In a document prepared by the National Research of Canada (NRC) in September 2000 a number of deficiencies were identified, the most important one being failure of the system to drain and dry when water enters through the exterior causing softening of the drywall, delaminating of drywall sheathing, expansion and warping of OSB or plywood sheathing, corrosion of metal fasteners were some of the concerns raised by NRC in the above mentioned publication.
The problems encountered with this system in its current state are extensive and have resulted in the cancellation of liability insurance for professionals. Associations have notified their members about potential problems and issues warning in the form of identifying face sealed wall assemblies as systems with increased liability claims.
The OAA (Ontario Association of Architects) is quoted as saying the following: “The association will not cover you, pay damages, provide you with a defence or make supplementary payments for claims made against you, directly or indirectly arising out of, contributed by, caused by ingress of precipitation, resulting from, or in connection with your design or selection of an exterior above-grade wall which has no provision for drainage of precipitation that penetrates the wall system, or otherwise provided in the Practice Bulletins issued by the OAA.”
The NRC quoted document above is further stating that reduction of moisture is required for these systems to perform. For a system which can reduce the moisture load the NRC publication further states that no testing will be required. “Such a system could be achieved with rain screen principles for a mechanically attached EIFS that includes a vented, wide air cavity.” This system will also satisfy the requirement of the OAA by providing for drainage of precipitation that penetrates the wall system.
The Korax RainScreen Panel™ provides for all these requirements as it satisfies all existing code requirements as they relate to a vented rain screen wall.
Stucco RainScreen Panel™ is a trademark of Korax Technologies Inc.
Stucco RainScreen Panel™ Canadian patent #2249509 l US patent# 629862