Using the dynamic thermal properties to assess the internal temperture swings in free running buidlings. A general model and its validation according to ISO 13792

The dynamic thermal behaviour of opaque building components can be studied through the well-known dynamic thermal properties, i.e. thermal admittance, decrement factor and surface factor. These parameters, firstly introduced in the 70s, make it possible to quantify the response of the building fabric to sinusoidal temperature swings; their use has been recently recommended in some international Standards, such as the ISO 13786:2007. This paper shows that, based on the previously mentioned properties, it is possible to build up a general analytical model for the simulation of the dynamic response of a whole room. In comparison with other similar approaches available in the literature, the proposed model is more rigorous and comprehensive. Indeed, thanks to the use of the Fourier analysis, one can tackle any periodic driving force, and not only sinusoidal ones. Moreover, the model facilitates the identification of each single heat flux released by the opaque envelope as a response to each different forcing condition. The reliability of the model is checked against the procedure outlined in the Standard ISO 13792:2012. The results also clarify to which extent a higher order of harmonics may affect the shape of the indoor air temperature profile and the reliability of the model.