A novel technique for unlocking wall elements’ thermal sensitivity under dynamic conditions and shedding light on the processes until convergence to a steady-periodic state

In an effort to rationalise the building envelope's energy efficiency, emphasis has been recently placed on highlighting the transient thermal behaviour of construction elements. In this regard, special focus has been given towards the evaluation of dynamic thermal parameters, under a stabilized periodic regime. However, despite the fact that these indicators outline a suitable technique to evaluate the significance of thermal inertia, they fall short of divulging the thermal performance of building structures to an unsteady state and more specifically a heat flux forcing function. On this ground, this study proposes a distinct technique to clarify the thermal responsiveness of multilayered building configurations with a constant internal surface heat flux as the boundary condition. The justification for this novel approach as opposed to the established practice is rather insightful. Using this methodological framework, one may assess the time needed for a heating system's ability to achieve a certain balance in terms of attaining a gradual convergence of temperatures to a steady-periodic state. From a different vantage point, it is feasible to isolate and reveal the impact of shortwave radiant sources striking on various types of internal surfaces. The study's objectives are met by numerical simulations of wall configurations in response to a range of constant heat flux values applied to the surface facing the inside. Particularly, the generic installations of the opaque elements under analysis correspond to concrete wall assemblies, with a thermal insulation layer that varies in thickness and placement. In line with this notion, the results reflect the potential benefits of decrypting the thermal sensitivity of these elements by implementing an equivalent electrical circuit model. In a nutshell, numerical findings exploring the transition from instability to steady-periodic conditions might enable us to improve our decisions regarding the thermal mass allocation in the planning of buildings.