Thermal Bridging from Cladding Attachment Strategies Through Exterior Insulation

Passive House standards call for highly insulated wall assemblies with effective insulation values in the range of R-40 to R-60 or higher. Recent shifts in construction have resulted in a more common use of continuous exterior insulation installed outside the primary structure and behind the cladding. The use of exterior insulation can result in more efficient wall assemblies that have less thermal bridging caused by the structural elements; however, the cladding attachment systems connecting the cladding back to the structure through the insulation have a wide range of thermal bridging effects and can significantly affect effective R-values.

This paper presents the results of three dimensional thermal modeling which quantifies the actual impact of thermal bridging in typical exterior insulated wall assemblies. Results are presented for several different types of cladding attachment strategies through exterior insulation, with a focus on discrete clips and fasteners that aim to reduce the thermal bridging through the insulation. This paper is intended to provide guidance on efficiently insulated wall assemblies and will be useful to help designers select more thermally efficient cladding attachment strategies as they aim to achieve Passive House standards.

This paper was presented at the 2014 North American Passive House Conference.