This research develops a bottom-up procedure to assess the potential of food-energy-water (FEW) systems on the rooftops of buildings in an urban district in Spain considering the urban morphology of the built environment and obtains accurate assessments of production and developmental patterns. A multicriteria decision-making technique implemented in a geographical information system (GIS) environment was used to extract suitable rooftop areas. To implement this method, the slope (tilt), aspect (azimuth), shading, and solar radiation of the rooftops were calculated using LiDAR (Light Detection and Ranging) data and building footprints. The potential of FEW system implementation was analysed at the building and morphology levels. The results showed several differences between residential and non-residential urban morphologies. Industrial areas contained the highest productivity for FEW systems. The production was 2.51 kg of tomatoes/m², 48 kWh of photovoltaic energy/m², and 0.16 l of rainwater/m². Regarding the residential urban morphologies, the more compact tents resulted in better performance. Among the FEW systems, although water could best benefit from the features of the entire roof surface, the best production results were achieved by energy. The food system is less efficient in the built environment since it requires flat roofs. The methodology presented can be applied in any city, and it is considered optimal in the European context for the development of self-production strategies for urban environments.

Urban Building Energy Models (UBEMs) are useful instruments to know the energy consumption of building stocks at urban and national levels. UBEMs can be classified into different types and subtypes. The current detailed physics-based bottom-up UBEMs at a national scale play a crucial role in assessing the energy efficiency of national building stocks and defining improvement strategies. These models heavily rely on archetypes and energy simulations, demanding significant computational resources. We propose here a new type of national-scale detailed physics-based UBEM based on Energy Performance Certificates (EPCs), and other open big data, which has the advantage that it can be automatically updated, in a short time, and with standard computer means. In this paper, we define the methodology to build this new type of national-scale EPC-based UBEM. We have checked that the model for the case of Spain can be automatically generated and updated in less than 6 h with a standard computer, and it generates results that match official data in more than 98 % for four indicators. The generated model contains information about 10,939,801 buildings in Spain, out of which 1,202,708 have EPCs. The model allows us to map and analyse the buildings in the country by integrating multiple variables of different nature, such as geographical (Autonomous Community, municipality, type of municipality), physical (area, number of floors, date of construction), use-related (main use of the building and use of each of its building units), and energy-related (climate zone, energy class, energy consumption, CO₂ emissions). In this paper, we have proven that the model allows for the development of some indicators to measure the progress of decarbonisation trajectories whose development will become mandatory for European Member States soon.

The COVID-19 crisis has changed daily habits and the time that people spend at home. It is expected that this change may have environmental implications because of buildings’ heating energy demand. This paper studies the energy and environmental implications, from a Life Cycle Assessment (LCA) approach, due to these new daily habits in residential buildings at their current level of thermal insulation, and in different scenarios of thermal retrofit of their envelope. This study has a building-to-building approach by using Geographical Information Systems (GIS) for the residential housing stock in the case of Barcelona, Spain. The results show that a change in daily habits derived from the pandemic can increase the heating energy consumption and carbon dioxide emission in residential buildings by 182%. Retrofitting all buildings of Barcelona, according to conventional energy renovation instead of nearly Zero Energy Buildings (nZEB), will produce between 2.25 × 10⁷ and 2.57 × 10⁷ tons of carbon dioxide. Retrofitting the building stock using energy recovery is the option with better energy and emission savings, but also is the option with higher payback time for buildings built until 2007. The methodology presented can be applied in any city with sufficient cadastral data, and is considered optimal in the European context, as it goes for calculating the heating energy consumption.