Why junctions behave differently
A thermal bridge occurs where geometry or materials change the heat-flow path, such as at a corner, balcony, floor edge or window junction. Two-dimensional geometry can affect heat flow even when insulation appears continuous. Resistance through a flat wall area therefore cannot describe a junction. Assessment needs the actual dimensions and materials of the connected elements.
Heat loss and surface temperature
Linear thermal transmittance, ψ, is expressed in W/(m·K). It describes additional heat transfer per unit length within an adopted accounting convention. Internal surface temperature answers a different question: how cold a particular location becomes. Moisture risk also depends on indoor humidity. A small contribution to total heat loss does not automatically establish an acceptable surface temperature at the coldest point.
A model must become a buildable detail
A component's good rating cannot eliminate poor connections. Show insulation, supports, fixings and seals on the junction drawing, together with relevant tolerances. Changes in floor levels can interrupt insulation at a threshold or plinth. Resolve these locations before ordering windows, doors and façade accessories, when the arrangement can still be changed without discarding completed work.
Specify the assessment clearly
For a critical junction, request the drawing, model boundary conditions and dimensional convention used to calculate ψ. A coloured temperature plot without inputs does not support a comparison between alternatives. Thermography can help locate irregularities under suitable conditions, but it cannot replace a numerical junction model. Start by listing repeated junction types and their lengths in the house, then prioritise details that combine substantial exposure with difficult construction interfaces.