Energy Cost-Efficient Rehabilitation Measures for the Portuguese Residential Buildings Constructed in the 1960–1990 Period

The Directive on the revised Energy Performance of Buildings (EPBD) 2010/31/EU required the Commission to establish, by means of a delegated act, a comparative methodology framework for calculating cost-optimal levels of minimum energy performance requirements for buildings and building elements. This chapter aims to contribute to the phasing proposed in the Directive mentioned. The results obtained from the thermal rehabilitation of the building envelope of a Portuguese residential reference building constructed in the 1960–1990 period make it possible to identify the best cost-efficient thermal rehabilitation measures. Conclusions on cost-efficient thermal rehabilitation are as follows: (i) the thermal rehabilitation of the roof produces the greatest variation in the primary energy building consumption (and the floor measures the smallest), (ii) the combination of thermal envelope rehabilitation measures creates synergy effects that lead to better results than single measures (regarding global costs and primary energy consumption), and (iii) it is more advantageous to proceed with a thermal rehabilitation package of measures rather than doing nothing.