Paper Conference

Proceedings of BSA Conference 2013: 1st Conference of IBPSA-Italy


The admittance method for calculating the internal temperature swings in free running buildings

Luigi Marletta, Gianpiero Evola, Maria Giuga, Fabio Sicurella

Abstract: In order to describe the dynamic thermal response of buildings, the dynamic transfer properties, such as the thermal admittance and the decrement factor, can be used. These parameters, firstly introduced in the Seventies by some British researchers, allow us to quantify the response of the building fabric to sinusoidal temperature variations occurring on both sides of the fabric. Their use has been recently suggested in some international standards, such as the EN ISO 13786:2007. However, little reference is made in the scientific literature to a further dynamic transfer property, the surface factor, that describes the response of the opaque components of a building to sinusoidal radiant heat fluxes occurring on their internal surface. The surface factor is worth being exploited, since the effect of wall inertia on the radiant heat gains is relevant in the study of the thermal behaviour of a building, especially in summer. In this paper, an operational formulation of the surface factor is firstly provided starting from its conceptual definition. Afterwards, based on all the previously mentioned dynamic transfer properties, a comprehensive procedure for the assessment of the cyclic temperature swings in an enclosed space is introduced. Thanks to the use of the Fourier analysis, this procedure allows tackling any periodic driving force, and not only sinusoidal ones. The reliability of the procedure is validated against the test cases proposed in the Standards EN ISO 13791:2012 and EN ISO 13792:2012. Finally, the results shown in the paper enable us to realize the size of the approximation introduced by calculating the dynamic transfer properties only with the first harmonic, i.e. based on sinusoidal driving forces with a period P = 24 hours, as suggested by the simplified approach proposed in the EN ISO 13792:2012 standard.
Pages: 59 - 68