Does it seem like you’re hearing the terms “thermal bridging” and “thermal break” more frequently? You are, and there’s a good reason for it. Simply put, when it comes to façades, thermal bridging is the movement of heat from the inside to the outside or from the outside in. Helen Sanders with Technoform North America in Beachwood, Ohio, describes it as the thermal equivalent of an electrical short circuit, or the thermal equivalent of water flowing through holes in a dam.
“Heat will find the path of least resistance and will flow through the pathways that offer the best conduction path,” she says. “The leakage of heat can cause serious issues relating to condensation and mold, as well as occupant thermal discomfort and degraded energy performance,” she says, adding that this can be especially problematic when it occurs in the middle of the wall where condensation and mold cannot be seen.
Today, building and energy performance requirements are becoming increasingly stringent, and when it comes to the building envelope, much of that focus is on improving thermal performance. Many companies in the glass and metal industry are working to improve performance with thermal breaks. These breaks are used to stop the transfer of heat in and around fenestration. Sanders explains that without a barrier to heat flow in the frame or edge of glass—no matter how good the glass—the heat will flow around the edges.
“If we want to get a seat at the design table with the HVAC contractors, our industry needs to understand thermal performance of façade systems inside and out and be able to offer practical and aesthetically pleasing solutions to the design team,” says Sanders.
Bridging the Gap
Thermal bridging can be a concern on several different areas of the façade. These areas can include the window frame and edge of glass connections between the perimeter of the fenestration and the adjacent wall; within spandrel panels and between the spandrel areas of curtainwall and the transparent areas; connections of opaque panels to the building structure; floor slab edges/balcony edges; parapets; and at attachments, such as sunshades.
“The thermal performance of the façade is the linchpin of building performance. While it can be traded off with higher efficiency HVAC and lighting systems to achieve the same overall energy performance, this trade off negatively impacts building resilience and thermal comfort, especially next to the envelope,” says Sanders. “If the glazing industry wants to ensure investments are made in the façade and that glazed areas continue to be maintained, we need to understand thermal performance of every aspect of the façade, from the individual components, to the thermal impact of how they interface to each other and the building structure, and strive to improve them all.”
Michael Smalley, director of business development at IWR North America in St. Louis, adds that with increased efforts of sustainability within the built environment, there is a heightened awareness of thermal bridging and how to mitigate it.
“The increasingly popular use of façade features and elements, such as sunshades, fins and decorative elements, has led to more opportunities for thermal bridging as these features can increase susceptibility for thermal transfer.”
Sanders also notes that spandrel is a key area to focus on.
“We need to deliver high performance solutions here in order to improve curtainwall performance and keep up with building performance requirements.”
The information is excerpted from the feature titled, “Breaking Bridges.” To read the full article, which originally appeared in the September 2020 issue of USGlass magazine, click here. To sign up to receive USGlass magazine free of charge, click here.