The Use of Light Walls in Buildings as a Consequence of the Most Recent European Regulations

Assuming the indoor air temperature to be constant, the thermal behaviour, under unsteady conditions, of an opaque external wall can be characterized by the following parameters: the decrement factor f, defined as the ratio between the wall dynamic thermal transmittance (UD) and the wall (static) thermal transmittance (U), and the time lag s, defined as the lag with which the external temperature oscillations are felt on the wall inner face. Such parameters depend on the wall thermal resistance and thermal capacity, on the period of the external temperature oscillations and on the stratigraphy of the wall. In a companion paper, after discussing the meaning of the parameters f and , the following problem is solved in a lumped-parameter schematization: to determine the stratigraphy of a wall, with given thermal resistance and capacity, minimizing f as well as the stratigraphy of a wall maximizing s. In this paper, after a brief discussion of the most recent Italian rules on the building energy performances, the possibility to realize multi-component light walls, characterized by better values of the parameters f and s, compared to those of heavy walls, is shown.