Second law analysis of periodic heat conduction through a wall

Periodic heat conduction through a wall is a simple model for the behaviour of a building wall submitted to climatic temperature changes. Beyond the well-known definition of heat transfer, the present concern is thermodynamics, through two quantities. The first quantity is the total entropy generation (total over time period and wall thickness). Formal derivation shows that from this point of view also, the phenomenon is the superposition of stationary linear heat-conduction plus periodic heat-diffusion around a uniform temperature. The second quantity is defined by considering ideal Carnot cycles that would maintain the inner space at a prescribed temperature. Parameters that influence either quantities are explored, evidencing values of the wall thickness beyond which there does not seem to be any interest in increasing the wall thickness.