Evaluating European directives impacts on residential buildings' energy performance: a case study of Spanish detached houses

Spain has a high level of energy consumption and CO2 emissions in detached houses, being the lack of an adequate insulation level and efficient energy systems the main causes. The Spanish Government has been performing modifications on its Building Technical Code (BTC) to address this issue, following European Directives. An assessment of the development of the Spanish BTC from its first 2006 version has been conducted in this work. A standard Spanish detached house was placed in the different Spanish climatic zones, designed with the minimum requirements of the 2006 and 2013 BTCs, and was then analyzed using the software Cerma. The results show that energy demand is reduced and the energy rating is improved with the stricter requirements introduced in the 2013 BTC. Although energy demand and CO2 emissions vary significantly among the 13 different climatic zones studied, the BTC modifications allow to reach a minimum energy rating independently of the climatic zone where the house is located. Opaque enclosures and internal loads were found to be the main contributors to building-related emissions. Additionally, possible actions to improve energy rating in detached houses are evaluated, finding that a moderate insulation thickness increase and the installation of heat pumps allow to reach the highest energy rating, being the improvement more apparent in northern and central regions. The results of this work may be extrapolated to other countries with similar climatic conditions to the studied zones, providing guidelines to fulfill energy saving regulations, evaluate emission sources and improve building energy efficiency.