Stucco with continuous insulation, or CI Stucco, can provide a means to comply with energy code and prescriptive CI requirements for exterior walls on residential and commercial construction. Regardless of the CI material type selected, adding CI behind traditional or proprietary stucco systems can bring new considerations in terms of system application and performance. Below are five items to know and consider with CI Stucco systems:
Energy code definition of continuous insulation (CI)
Codes define CI as an insulating material that is continuous without thermal bridges other than fasteners and service openings. Stucco systems sometimes add or use insulation sandwiched between girts, hat channels, Z furring, etc. outboard of the water resistive barrier and supporting assembly. While improving thermal performance, these systems do not meet the definition of continuous insulation because of discontinuities caused by the girts, Z furring, or hat channels.
Practical thicknesses of CI
While there may be exceptions, CI thicknesses typically do not exceed 2 or possibly 3” due to practical limitations. Common factors that can influence and possibly limit CI thicknesses include stucco weight, stud type/spacing, fasteners/means of attachment, stucco accessory availability, and project specific details or conditions.
CI can impact detailing and stucco accessories
Traditional and proprietary stucco systems typically finish into an accessory such as a casing bead, weep screed, etc. that has grounds to match the stucco thickness. Accessories such as these serve multiple purposes including closure or termination of stucco at conditions such as openings, tops of walls, foundations, etc.
Adding CI behind stucco changes the exterior wall thickness, plane/geometry, and impacts stucco detailing particularly in terms of system terminations. CI stucco will typically incorporate specialized accessories or standard accessories with larger/deeper grounds to accommodate and close or terminate added thicknesses associated with CI Stucco systems. Figure 1 is an example of a specialized accessory with an extended flange weep screed that can provide closure for CI Stucco at a foundation.
System attachment
Manufacturers of proprietary CI stucco systems commonly provide or specify system attachment methods. Additionally, IBC Chapter 26 and IRC Chapter 703 includes tables for attachment of cladding systems over continuous insulation for a variety of applications based on cladding weight, fastener spacing, framing type/spacing, Ci thickness, etc.
Fire Testing
Several types of continuous insulation are commonly used with CI stucco systems. Depending in part on the type of CI material and construction, CI Stucco systems may be subject to compliance with fire test requirements such as NFPA 285 and ASTM E 119 respectively for non combustible and fire resistive construction.
Feel free to contact the Bill Egan Group for more detailed or additional information.
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