Thermal bridging is one of the most overlooked causes of energy loss in modern buildings. When heat finds a faster path through structural members like steel studs or concrete slabs, it bypasses your insulation entirely. This can reduce your wall's effective R-value by 30% or more, according to building science research. Old Mill Building Products offers insulation wall systems that help architects and builders address this challenge head-on.
In this article, you'll learn what thermal bridging is, where it typically occurs in exterior wall assemblies, and how selecting the right insulation strategy can improve your building's energy performance while simplifying architectural detailing decisions.
Thermal bridging happens when a material with higher thermal conductivity creates a pathway for heat to bypass insulation. In wall assemblies, this typically occurs where steel studs, concrete slabs, or metal fasteners extend through the building envelope. Heat naturally follows the path of least resistance, flowing through these conductive elements instead of the insulation around them.
The result is significant energy loss. Research from building science experts shows that thermal bridging can account for up to 30% of heat loss in insulated buildings. For steel-framed walls, cavity insulation may be only 45% to 55% effective when thermal bridging is not addressed.
Understanding where thermal bridges occur is the first step toward designing wall assemblies that deliver the R-values you specify.
Thermal bridges appear at several key locations in commercial and residential wall construction. Identifying these areas helps you make informed decisions during the design phase.
Steel shelf angles support masonry veneer loads and transfer weight back to the building's structural frame. These angles interrupt the insulation layer and create direct thermal pathways from interior conditioned space to the exterior environment.
Cantilevered steel or concrete balconies often extend from interior slab edges through the building envelope. Without thermal breaks, these connections conduct heat directly through the wall assembly, causing localized cold spots and potential condensation issues.
Steel clips, Z-girts, and other cladding supports frequently penetrate exterior insulation. Each metal connection reduces the insulation's overall effectiveness. According to the Continuous Insulation Coalition, using non-metallic cladding supports can improve wall insulation effectiveness by over 90%.
Equipment supports, anchors, and structural penetrations at rooflines and foundation walls also create thermal bridges. These often-overlooked details can reduce the building envelope's effective R-value by 20% to 70% if not properly addressed.
R-value measures thermal resistance, but the number printed on insulation packaging tells only part of the story. Your wall assembly's actual performance depends on how well the insulation layer remains uninterrupted.
Building scientists distinguish between "nominal" R-value (the rating of the insulation material itself) and "effective" or "whole-wall" R-value (the actual thermal resistance of the complete assembly). When steel studs spaced 16 inches on center interrupt fiberglass batts, the effective R-value drops dramatically compared to the nominal rating.
For example, a 2x6 wood-framed wall with R-19 cavity insulation delivers roughly 85% of its nominal R-value due to wood framing. The same wall with steel studs might deliver only 45% to 55% of the insulation's rated value. This gap highlights why exterior insulation strategies have become increasingly important.
Placing insulation on the outside of structural framing creates an uninterrupted thermal barrier. This approach, often called "outsulation" or exterior insulation, wraps the building in a thermal blanket that prevents framing members from conducting heat through the envelope.
Modern energy codes recognize this advantage. The U.S. Department of Energy notes that foam board insulation can deliver up to twice the thermal resistance of other insulating materials at the same thickness when installed correctly.
The Panel+ wall system from Old Mill Building Products exemplifies this approach by combining EPS foam panels (delivering R-4.2 to R-4.8 per inch) with integrated air and water barriers. This single-system approach reduces thermal bridging while simplifying the installation process.
Energy codes have evolved to require exterior insulation in most commercial construction. ASHRAE 90.1 and the International Energy Conservation Code (IECC) define requirements that increasingly favor exterior insulation strategies.
According to code definitions, insulation qualifies as "continuous" when it is "uncompressed and continuous across all structural members without thermal bridges other than fasteners and service openings." This means that only minimal penetrations like screws or nails may interrupt the insulation layer.
Climate zones across the United States now require varying amounts of exterior insulation for both residential and commercial buildings. Meeting these requirements helps ensure your building performs as designed and keeps operating costs predictable for owners over time.
Specifiers and installers can prevent thermal bridging problems by following these guidelines during design and construction:
Thermal bridging undermines even well-intentioned insulation strategies when building assemblies allow heat to bypass insulated areas. By understanding where thermal bridges occur—at shelf angles, balcony connections, cladding attachments, and penetrations—you can specify wall systems that deliver their rated R-values.
Exterior insulation approaches place a thermal blanket around the entire structure, preventing framing members from conducting heat through the envelope. Old Mill Building Products simplifies this approach with the Panel+ wall system, combining insulation, air and water protection, and veneer alignment in one code-compliant solution backed by a 15-year warranty.
For your next project, consider how addressing thermal bridging can improve energy performance, reduce operating costs, and simplify code compliance.
Thermal bridging occurs when materials with higher thermal conductivity—like steel studs, concrete slabs, or metal fasteners—create pathways for heat to bypass insulation. Heat flows through these conductive materials faster than through surrounding insulation, reducing the wall's overall thermal resistance.
Thermal bridging can account for up to 30% of heat loss in insulated buildings. For steel-framed walls with only cavity insulation, the effective R-value may be just 45% to 55% of the insulation's nominal rating. Addressing thermal bridges at assembly intersections can improve this performance dramatically.
Exterior insulation significantly reduces thermal bridging by wrapping the structure in an uninterrupted thermal layer. Old Mill Building Products' Panel+ wall system delivers R-4.2 to R-4.8 per inch of EPS foam while integrating air and water protection, addressing multiple building envelope needs in one system.
ASHRAE 90.1 and the IECC define continuous insulation as "insulation that is uncompressed and continuous across all structural members without thermal bridges other than fasteners and service openings." Only minimal penetrations like screws may interrupt the insulation to meet this definition.
Common thermal bridge locations include masonry shelf angles, balcony and canopy connections, cladding attachment systems, and roof or foundation penetrations. Old Mill Building Products addresses these concerns with Panel+, which features integrated drainage channels and NFPA 285 compliance for commercial applications.