Report by RDH Building Science
To summarize the thermal performance of the various cladding attachment strategies presented, the range of thermal effectiveness of the exterior insulation is shown below. These percentages can be multiplied by the R-value of the exterior insulation and added to the back-up wall R-value to determine an approximate overall effective R-value for the wall assembly.
There are many cladding attachment systems that can be used to support claddings of all types through exterior insulation. Energy codes including ASHRAE Standard 90.1 and NECB consider thermal bridging and insulation effectiveness, making an efficient cladding attachment strategy an important component of the enclosure design. Important to consider are systems that provide the required structural support, meet the fire performance requirements, minimize thermal bridging, are easy to install, and are cost effective. As this is an emerging industry, cladding attachment systems are constantly evolving and being developed.
In the end there are many things to consider before you decide on which method may be right for you. Does the additional performance provided from fiberglass clips with no through screws allow you to avoid wrapping another 2" of insulation around the building? Do the savings in insulation and time to install outweigh the added costs of the clips? These are sound discussions to have with your Passive House Designer and should help highlight the pros and cons of each method.