According to the second law of thermodynamics, heat transfer between two systems always moves in the direction from higher to lower temperatures. The amount of thermal energy transferred by heat conduction, e.g., through a wall of a building, is influenced by the thermal resistances of the concrete wall and the insulation layer.
The thermal contact resistance between the individual layers also adds to the effective or total thermal resistance. It is mostly negligible in the case of building walls, but in the case of highly conducting materials (e.g., chip cooling), it has a huge impact on the cooling efficiency. Special pastes or thermal interface materials (TIMs) can be used to reduce the thermal contact resistance in electronic devices.
The NanoTR, PicoTR and all NETZSCH LFA systems are able to measure the thermal contact resistances in multi-layer systems.