A cold bridge, also known as a thermal bridge, is a term used in building construction and insulation to describe a location where a gap or discontinuity in the insulation allows heat to flow through more easily than in the surrounding materials. In the context of insulating a foundation, a cold bridge refers to a section of the foundation where there is a break in the insulation, allowing heat to escape more easily and leading to increased heat loss.

Cold bridges can occur in a variety of ways, such as where there is a break in the continuity of the insulation, where two different materials meet, or where there are penetrations through the insulation such as pipes or ducts. In the case of a foundation, cold bridges can occur where the insulation is interrupted by elements such as footings, columns, or wall ties, or where the insulation is not installed properly or is compressed.

Cold bridges can lead to increased heat loss, energy waste, and potential condensation and mold issues. To minimize the impact of cold bridges in a foundation, it is important to properly design and install the insulation, paying attention to details such as ensuring continuity of the insulation, avoiding compressions or gaps in the insulation, and providing thermal breaks around penetrations or structural elements.