With this new perspective, the nZEB concept could be not sufficient for reaching the new goals and it is important to design and refurbish buildings as Post-Carbon Buildings (PCB). PCB is represented by a building where the minimum energy performance is in line with national standard requirements but a great reduction of carbon emissions is expected.

However, it has been noted that focusing the attention only on buildings, considering each separately and analyzing the problem at single house level, is not sufficient to reduce the C02 emissions in the percentages established by COP 21 standards. For this reason, the EU has recommended to enlarge the content of the analysis promoting the concept of Post-Carbon City (PCC). PPC is defined as a city characterized by low-energy and low-emissions buildings provided with intelligent heating and cooling systems, electric and hybrid cars and better public trans-port. Moreover, when dealing with district scale and urban polices, it is also important including in the analysis aspects not strictly related to environmental impacts, but concerned social and economic sectors, such as the number of jobs created by the energy investments, the economic savings in energy bills, the people opinion upon different retrofit solutions, and so on.

Following these considerations, the thesis aims at exploring the carbon reduction potential of an existing district and the use of Multicriteria Decision Analysis (MCDA) supporting the selection of energy retrofit strategies.

In particular, the analysis is applied to an urban district located in the city of Turin (Northern Italy), which is composed of different residential apartment blocks built in different times. Starting from the existing buildings, different energy efficiency minimum requirement as imposed by Italian regulation and carbon reduction are combined for creating alternative strategies for the energy retrofit of the district. To do this, a dynamic simulation software (DesignBuilder) is used in order to obtain more precise results. Then, those strategies are evaluated using the PROMETHEE method (Preference Ranking Organization Method for Enrichment Evaluations) and a MCDA is applied. In particular, a family of environmental, social, technical and economic criteria has been defined with the aim of assessing the alternatives options and to select the best performing solution for the district under investigation.

Moreover, the thesis comprehends a comparison be-tween Mediterranean and Nordic climate studying the influence of the local climate upon similar technical solutions, investigating their efficiency in two existing district case studies, settled in Northern Italy and in Denmark.