20 Jan Thermal Bridging: When Heat Finds a Way Around Insulation
Insulation plays a vital role in controlling heat flow, but it doesn’t work in isolation. If heat can travel through the building structure itself, it can bypass insulated areas entirely. This effect, known as thermal bridging, is a major contributor to unexpected heat loss and reduced energy efficiency.
Thermal bridges form when conductive materials create alternative paths for heat to move through the building envelope. While a lower U-Value always indicates better thermal performance, these pathways increase the overall U-Value of walls and roofs, leading to higher energy consumption and reduced thermal comfort.
Thermal bridging commonly occurs at:
- steel or aluminium framing
- slab edges and floor junctions
- roof-to-wall connections
- penetrations for pipes, ducts, and cables
- window and door interfaces
When these areas are not properly addressed, parts of the building envelope effectively become “heat highways,” allowing heat to move freely through the structure. In lightweight steel-framed walls, the impact can be significant. Depending on the design, thermal bridging may reduce the effective R-Value by up to 50%, even when insulation is present.
The effects of thermal bridging can be limited by fitting insulation closely around framing members, services, and irregular shapes. By fully filling cavities and reducing gaps, insulation continuity is improved and unwanted heat flow is minimized. However, as mentioned above, insulation alone cannot eliminate all thermal bridges.
To achieve reliable, real-world thermal performance, additional strategies should be considered, including:
- installing thermal breaks to interrupt heat flow
- adding continuous external insulation layers
- using non-conductive components at critical junctions
- ensuring insulation is installed fully and consistently across the building envelope
Understanding thermal bridging is essential for translating high R-Value materials into actual building performance. With careful detailing and accurate U-Value calculations, designers and builders can significantly reduce heat loss and deliver buildings that perform as intended — not just in theory, but in everyday use.