What best describes thermal bridging in building envelopes, and which is a typical example?

• A. Thermal bridging occurs when high-R-value assemblies bypass or intersect low-R-value assemblies.
• B. Thermal bridging occurs when low-R-value assemblies bypass or intersect high-R-value assemblies; an example is corner studs in walls.
• C. Thermal bridging is simply insulation distributed to maximize R-value.
• D. Thermal bridging refers to radiant heat transfer only through windows.

Answer: (B)

Thermal bridging happens when a conductive element in the building envelope provides a heat path that bypasses or interrupts the higher-R insulation around it. In walls, the framing members (studs) are much more conductive than the insulation between them, so heat travels through these low-R-value elements and reduces the wall’s overall thermal performance. A classic example is corner studs in walls, which create continuous heat paths through the insulation at the corners. The other statements miss this conduction path: simply having insulation isn’t bridging, and thermal bridging isn’t about radiant transfer or windows.