Thermal bridge: definition and weak points of a floor

What is a thermal bridge?

A thermal bridge is an area of a building's envelope where insulation is interrupted or weakened. Heat passes through these areas more easily than elsewhere, creating localized energy loss and, often, a cold surface on the interior side.

Flemish regulations refer to this as a "constructive node" (bouwknoop), a broader term than thermal bridge, which has been in use for permit applications since 2011 according to the Flemish Region's EPB-pedia.

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Where are floor thermal bridges located?

In floors, they are concentrated at the edges and where the insulation layer is interrupted:

• the junction between the slab and exterior walls, when the floor insulation does not meet the wall insulation;
• door thresholds, where the available thickness is reduced;
• ducts and pipes laid on the slab, where gaps are left between cut insulation panels;
• open joints between poorly fitted insulation panels.

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Thermal bridge or simple insulation defect: what is the difference?

A thermal bridge is structural: it stems from the design, such as a slab passing through wall insulation. An insulation defect stems from installation, such as an open joint. Both produce the same effect, but the former is addressed in the plans, while the latter is addressed on-site.

This is one of the arguments for sprayed PUR : applied as a single piece, it conforms to ducts and irregularities without any joints. The perimeter strip, meanwhile, decouples the screed from the walls but does not provide edge thermal insulation.

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How Davide Chape limits floor thermal bridges

Before installation, we identify the points where the insulation layer is at risk of being interrupted: thresholds, wall bases, and floor networks. Our choice of technique follows from this. See our floor insulation solutions.