Towards the implementation of periodic thermal transmittance in Spanish building energy regulation

Abstract The recent development of the calculation methodology for dynamic thermal properties of buildings has opened new possibilities for reducing their energy demand; however, building codes still rely on the traditional static approach. This research aims at filling in this gap by exploring how periodic thermal properties can be implemented in the Spanish regulatory framework. For this purpose, 2,413 wall typologies were analysed in the two extreme climate zones as per the Spanish regulation pertaining to energy efficiency. Results show that the static U-value itself is not sufficient to optimize the energy demand of buildings, as for a single value of U variations of 4,000 kWh in the energy demand are expected. Regarding periodic variables, decrement factor and time shift were the most effective to minimize the energy demand, along with flexible limitations for the periodic thermal transmittance and the time shift. In warm climates, the former can be disregarded if the latter is greater than 15 h. The findings from this study disscuss the applicability of the static thermal transmittance and propose a methodology to select and limit periodic variables for the two most extreme climates in Spain.