Thermal Bridging: Observed Impacts and Proposed Improvement for Common Conditions

This investigation seeks to quantify the effects of thermal bridging in commercial facades and then propose alternative solutions to improve performance. Utilizing infrared images taken from targeted assemblies at 15 recently completed buildings; we have calculated the actual performance of a range of façade types and conditions. We have compared these R-values with the theoretical, design intended R-values from drawings and specifications to quantify the discrepancy between design and actual performance. These differences were seen to range from greater than 70% less than the design intended R-value to those with negligible differences. This range shows the unintended impact that design details can have on thermal performance. Based on thousands of images collected, we identified 16 common areas of thermal bridging that was commonly observed in the buildings surveyed. Broken into two broad categories of façade systems and transitions/penetrations, they range from such systems as curtain walls and existing wall renovations to conditions such as parapets and transitions to foundation. Using 2-D heat transfer simulations, models of these conditions were also developed. These models in conjunction with the infrared images were used to verify and understand the thermal bridges observed, as well as exploration of improved detailing. The study proposes alternatives to industry standards that can provide enhanced thermal performance.

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