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• A model for the optimization of energy renovation of districts is presented. • The model covers both energy supply systems and envelope design. • The model is applied to a case study district located in Northern Spain. • The designs are limited by the roof availability and economic feasibility. • The model can be used for fast design and policy making. The nearly Zero Energy Building concept should be adopted in the renovation of existing buildings and actions upscaled and applied to larger and larger urban areas. In this context, this paper presents an optimization methodology for drafting integral renovation actions at district level. The methodology is based on a MILP model that allows selecting energy saving measures, as well as the design and operation of energy supply systems amongst a very large set of potential permutations. For its application, the concept of District Equivalent Building is introduced, defined as a virtual building with a set of energy loads equal to the addition of all the individual load vectors of each building. The methodology was applied to a real residential district located in Bilbao (northern Spain). For this case study, the optimal renovation plan was obtained, considering for that three different optimization objectives: (i) Optimal-Cost, (ii) Zero Energy District (ZED) and (iii) Zero Energy District including domestic electricity consumption in the calculation of the non-renewable primary energy consumption (ZED'). Although similar solutions were adopted for each of these cases, significant differences were get attending the hourly operation of the solutions. These cases were economically assessed and the optimal-cost curve was obtained. [ABSTRACT FROM AUTHOR]

• Different renovation intervention levels are evaluated. • The technoeconomic feasibility by itself does not explain the actual renovation rates. • Existing social, material and legal barriers are key for a comprehensive analysis. • Measures should be taken to boost district/building level interventions. Building is one of the main sectors in which significant energy savings can be achieved with a consequent reduction in emissions. This paper assesses the large-scale renovation of buildings, exploring the quantitative and qualitative factors that determine their replicability potential from three different perspectives, namely dwelling, building and district intervention level. Different passive and active measures are assessed, covering energy saving measures, the improvement of energy supply systems and the integration of renewable energy sources. Different scenarios are defined for each intervention level, which are evaluated using the methodology developed in the IEA-EBC Annex 75 project. The methodology is applied to a residential district located in Bilbao (Northern Spain). The analysis is based on the results obtained from the simulation of 41 combinations of different renovation options, obtained by simulation in the Design Builder software. The assessment is carried out from the evaluation of different key performance factors, including annualised cost and annual primary energy consumption, as well as the CAPEX and OPEX requirements. The results show that energy renovation of buildings offers a great opportunity for energy reduction at affordable investment costs, obtaining the cost optimal values when the intervention focus on the energy system and reaching net NRPE values close to zero when the intervention is carried out in a comprehensive way, considering energy systems and thermal improvement of the envelope. Additionally, the different energy reduction scenarios show that, while interventions at district level offer the greatest potential for minimising annual costs and primary energy consumption levels, intervening at building level offers only slightly worse results. However, there are other issues which can better explain the current low rate of renovation works in the urban environment. Thus, if the additional existing social, material and legal barriers and constraints are included in the analysis, it becomes clear why renovation from a district perspective is not actually leading the race. Given this situation, some measures and policies are proposed to realise the true potential of large-scale building renovation. [ABSTRACT FROM AUTHOR]