Simulating the Thermal Impact of Masonry Ties

Abstract

In masonry veneer wall assemblies, lateral ties are a structural requirement. Traditionally they are fabricated from steel, which has a high conductivity. Building codes require that ties be tightly spaced and, in most climate zones, it requires continuous insulation in the majority of wall assemblies. Continuous insulation in the cavity space results in the ties penetrating the insulation layer. The combination of material, required spacing, and location of insulation result in most masonry veneer walls being constructed with a significant amount of thermal bridges causing a loss in thermal performance. At present, the building industry typically does not account for these thermal bridges and their effect on the exterior enclosure. We speculate that the reasoning for this is primarily due to a lack of industry accepted information relative to the thermal reduction of the masonry wall system from the inclusion of ties. The purpose of this paper is to begin providing this missing information. Using three dimensional Finite Element Modeling software (thermal modeling), common masonry wall assemblies are studied by simulating them with and without masonry ties. This comparative analysis quantifies the impact of masonry ties on the thermal performance of each wall assembly studied. In recent history, large steps, such as continuous insulation requirements, thermally broken fenestration systems, low-e coatings, and air barrier technologies have been introduced to increase the performance of exterior enclosures and thus the overall efficiency of the built environment. The industry now must focus its attention on the details of wall systems to take the next steps in incrementally increasing building efficiency. Data obtained through three dimensional thermal modelling is used to address the impact masonry ties have on the thermal performance of wall systems. Finally, alternate materials are evaluated and considered as a means to improve thermal performance of the masonry veneer wall assemblies.