The current industry standards for building energy efficiency have led to a significant trend toward placing exterior insulation within the cavity behind anchored masonry veneers. To comply with ever changing energy standards, building designers need to consider the impact of thermal bridging caused by masonry connectors and shelf angles that penetrate this exterior insulation. This paper examines the need to address thermal bridging in the context of masonry tie and shelf angle support design and selection to achieve compliance with the International Energy Conservation Code (IECC), ASHRAE Standard 90.1, or the National Energy Code for Buildings (NECB).
After discussing the different energy code requirements for walls, this paper presents the results of threedimensional thermal modelling that quantifies the impact of thermal bridging in typical exterior masonry veneer wall assemblies. Modelling was completed for a variety of masonry tie products with common backup wall assemblies and a variety of masonry shelf angle attachment options. The modelling included generic masonry tie and shelf angle attachment options in addition to proprietary FERO Thermal Tie™ Masonry Connectors (i.e., FERO Thermal Ties) and FERO FAST Thermal Bracket™ Offset Shelf Angle Supports − Standard (i.e., FAST Thermal Bracket Supports). Physical thermal performance testing was also completed to validate the model results for the Fast Thermal Bracket Support using a modified ASTM C177 large-scale guarded hot plate apparatus. The results demonstrate that masonry tie and shelf angle design can have a significant impact on thermal performance. This paper also presents the results of a comparative study to illustrate the impact of thermal bridging caused by comparable non-masonry cladding assemblies supported by continuous/intermittent metal Z-girts, clips, or screws.
The information presented in this paper will be of interest to design professionals who are responsible for assessing overall building energy efficiency and code compliance and selecting cladding support materials for masonry veneer wall assemblies.