Thermal Design

A major aim for new connector technology is to reduce thermal bridging, a phenomenon that drastically decreases the thermal efficiency of sandwich wall panels (SWP).  As put in the 2019 dissertation, Reducing Thermal Bridging and Understanding Second-Order Effects in Concrete Sandwich Wall Panels by Taylor J. Sorensen, “Thermal bridging can be thought of as a thermal short circuit for heat.”  In his study, Sorensen evaluated dozens of buildings using thermal cameras to show weak spots in panels where thermal bridging is most common.

(Left) A sandwich wall constructed with steel truss connectors and (Right) the thermal image showing significant thermal bridging.  Images courtesy of Taylor J. Sorensen (2019).

Sorensen’s dissertation suggests best practices to make SWP retain their insulative properties by reducing thermal bridging.  “Steel SWP connectors act as thermal bridges, allowing a significant amount of heat transfer to occur… Using thermally insulative connectors will save building owners thousands of dollars by decreasing costs to heat and cool their structure” (Sorensen, 2019, p. 77). 

The Impact on R-Value

A 1985 article called Thermal Properties of Sandwich Panels by Calvin McCall illustrated the effect of thermal bridging on the insulative properties of SWP by measuring the R-value reduction when using steel ties and solid sections.  His research showed a 38% reduction in the thermal resistance of the insulation layers when steel occupies just 0.08% of the layer.  Further, he described an example that illustrated “the effect a 6 in. solid block of concrete around the perimeter of the panel… [resulting in] a reduction of 77 percent from… the unpenetrated insulation” (McCall, 1985, p. 37).

The thermal resistance is reduced by 38% in a panel with steel occupying 0.08% of the area of the insulation layer when compared to a panel with no steel penetrating the insulation. 

A 6-inch solid perimeter reduces the thermal resistance by 77% compared to a section with unpenetrated edge-to-edge insulation.

Consequences of Thermal Bridging

“In a recent study done with the support of the Portland Cement Association, we compared the thermal bridging caused by steel ties and non-conductive connectors. We observed a reduction of only about 2% in the effective R-value in panels with non-conductive ties, whereas the panels with steel ties showed a significant decrease of approximately 30%. A large reduction in R-value not only leads to higher costs to heat and cool the building, but can also cause condensation, leading to corrosion, mold, and damage to interior features.” -Dr. Marc Maguire, associate professor at University of Nebraska.

The IconX System

The Icon System retained 99% of the R-value in a finite analysis heat transfer model performed on a 4-3-4 panel with one IconX Connector every 8 square feet. In comparison, if the IconX Connector was made out of steel rather than glass fibers and vinyl ester resins, the result would be a loss of 26% of the R-value in the same panel.

The IconX System is Code Compliant. Our connector is thermally non-conductive and designed to be used with edge-to-edge and top-to-bottom insulation.