While thermal bridging is widely acknowledged to exist in modern commercial building envelopes, little is known on the significance of its impact. Back in November at the annual Architecture Boston Expo (ABX), Andrea Love and Charles Klee spoke about the Thermal Performance of Facades. Based on Payette’s analysis of the observed performance of existing facades and the model performance of proposed alternatives, the presentation focuses on seven conditions in the building envelope where thermal bridges were observed.
A team of Payette employees set out and visited eight past projects to see what could be learned regarding the actual thermal performance. Using a thermal imaging camera and some basic information about the interior, exterior and radiant temperatures, the team was able to calculate the R-value from the images. Using the traditional one-dimensional R-value calculation as a baseline and the design intent for the thermal performance, we compared them to the thermal image R-values. Many of the R-values seen in the facades of the existing buildings were 40-60% less than what had been intended in design. However there was a big range, with R-values varying from showing little impact of thermal bridges to more than 75% less than the anticipated R-value.
Payette identified a number of common conditions with thermal bridges, such as rainscreen support connections or the transition from foundation to above grade walls. Seven of these areas were then modeled using the heat flow simulation program THERM, and alternative options to minimize thermal bridging were explored.
While much can be done to better understand the thermal performance of our building envelopes, the process developed provides a way to understand the performance of past work, as well as a method for analyzing future projects. We look forwards to exploring this more as we continue this research with our Upjohn Research Grant.
Research also conducted by:
Daniel Gonzalez Brenes