Thermal Bridging: The Final Frontier of High-Performance Buildings
Minimizing use of energy and natural resources are vital components of the global strategy to protect our environment. The US has responded to this awareness with a tightening of building energy and performance standards. ASHRAE 90.1, for instance, has significantly reduced the energy that can be consumed by a building. One significant aspect of energy loss from a building is conductive heat transfer through the building envelope. Common improvement strategies to minimize conductive heat loss--include reducing the window-to-wall ratio, using high-performance window systems and improving façade insulation--are largely responsible for the overall thermal performance of an exterior wall. The focus has turned to a long-overlooked aspect of the design—thermal loss through structural components. Traditionally, not a lot of attention has been paid to the various thermal bridges that are integral to these larger envelope assemblies because they were thought to represent a relatively small percentage of the overall energy loss. As we improve the thermal performance of our overall wall systems, however, the heat loss through thermal bridges becomes a much greater percentage of energy loss and, thus, more important to consider and control. This article explores identifying thermal bridges and employing off-the-shelf, manufactured structural thermal breaks (MSTBs) as a solution.