The nZEB concept and its requirements for residential buildings renovation in Southern Europe: The case of multi-family buildings from 1961 to 1980 in Portugal and Spain

Southern Europe has an old housing stock and has the challenge, as the rest of European Union Member States, to transform it into a decarbonized one, by means of transforming the existing buildings into Nearly Zero Energy Buildings (nZEB). Member States have a large margin of discretion when defining the requirements for nZEB. In this paper, the nZEB requirements for the renovation of residential buildings in Portugal and Spain are studied in detail (unlike the usual more general comparative studies) for a specific building typology with poor energy performance. This is done by checking whether an existing residential building, renovated with different combinations of improvements of the envelope and active systems in two comparable cities in each of these two countries, fulfills the requirements or not, and by comparing the results of CO2 emissions reductions. One of the improvements of the envelope considered are those necessary to fulfill the compulsory major renovation requirements in both countries to check how much we are already approaching to the decarbonization of the residential sector. The results show that nZEB standards applied to the renovation of typical multi-family buildings of 1961-1980 in both countries will significantly contribute to the descarbonization of the building stock for this type of building typology, with reductions of 80-96% of CO2 emissions for Portugal and 71-94% for Spain, if they are applied. However, some aspects of the regulations could possibly be improved such as more restrictive requirements for the current regulations for major renovations in Portugal or the way energy from renewable sources is ensured in Spain, among others.

Automated summary

Southern European countries, like Portugal and Spain, are facing the challenge of transforming their old housing stock into decarbonized buildings. Research shows that applying nZEB standards to the renovation of typical multi-family buildings can significantly reduce CO2 emissions, but some aspects of regulations may need improvement.