Background In the past few decades, the housing construction industry and sector has developed by maximising economical benefits and minimising costs, often due to urban pressure and speculation (especially in Spain). Such pressures have led to the construction of houses with very low energy efficiency and with significant direct and indirect impacts on natural resources and human health. The European construction industry is responsible for 40% of all waste and it consumes 40% of materials and 40% of primary energy. However, new legislation and certification systems call for the application of the latest knowledge on material, design and energy efficiency at ‘real-population’ level by making efficient bio-climatic houses available and affordable to low/medium income citizens. Objectives The EDEA project aimed to develop an efficient methodology for the design and construction of social housing in the region of Extremadura. The goal was to construct sustainable buildings that are more energy and resource efficient, while also being of better quality. The project aimed to demonstrate that with appropriate designs and the suitable application/use of existing products on the market it is possible to improve considerably the environmental performance of buildings. The challenge was to achieve this aim, while keeping the costs down to a reasonable level so that it would present a viable alternative for social house construction. To achieve these goals, EDEA planned to practice, test, evaluate and disseminate methodologies and technologies – some new, others already existing – that efficiently help to reduce CO2 emissions, optimise the energy consumption process, and constitute best practices in the field of ‘bio-climatic architecture’ and construction. The project would focus on the use of renewable energies, intelligent home technologies (domotics) for the optimisation of passive energy systems, production and sustainable consumption models, sustainable use of natural resources and materials, and the recovery and recycling of waste, among other aspects of construction. The project planned to cover the overall building life cycle including deconstruction. Results The EDEA project focused on the development of an efficient methodology for designing and constructing social housings in the region of Extremadura. To achieve this goal, twin ‘demonstration’ houses were built in Cáceres on the same plot, with the same geographical orientation (North-South), the same structural system and subject to the same weather conditions. The construction features, surfaces and materials are similar to those currently used in social housing in the region of Extremadura. One of the houses was called the ‘Pattern house’ and would serve as a reference for the project, remaining unchanged during its duration. In the other one, the ‘Experimental house’, a range of improvement measures (‘strategies’) were tested and demonstrated. It was the first time that such a full-scale demonstration had been carried out in a ‘hot’ country. Several installations were implemented in the houses: a biomass heating system, a geothermal system for heating and cooling, a heat pump, a condensing boiler, a ground-to-air geothermal exchanger, and a solar thermal, solar photovoltaic and wind energy system for generating electricity. In addition, external weather conditions were measured on site (i.e. temperature, relative humidity, solar radiation and wind speed and direction). Around 300 sensors were placed on each house for monitoring and control (remote management), and a total of 15 different passive and 70 active strategies were studied. The passive strategies are those that improve the construction and design of the building. The active strategies improve the efficiency and CO2 emissions of energy installations. More than 5 000 energy simulations were performed using different software and nine strategies were tested in the houses to assess their performance. The tests compared the two houses by measuring the real improvement generated by each strategy in order to know which passive strategies generate the best results for the reduction of energy consumption and which active strategies are the most sustainable. The results make it possible to compare several options and evaluate whether investment would be cost-effective, affordable and sustainable for people on a low income. Furthermore, the environmental sustainability of all the 400 construction materials used in the houses was also assessed. More than 50 companies in the building and energy sectors were involved in the project. The monitoring system is online and accessible to interested parties on the project's website. Moreover, the project also helped shape the ‘Special Housing Plan’ that aims to improve the comfort and image of social houses that are constructed by the regional government of Extremadura. The project methodology is now being used to inform housing policy at the regional level, particularly in the design of current and future social housing in Extremadura and in the evaluation of energy efficiency subsidies in housing. Contacts were also established with the national housing ministry in order to spread the project results to other Spanish regions and to improve national regulations. The publication of a Methodological Guide on Sustainability could also help to transfer the methodology to other regions with similar conditions. Positive economical results are also to be expected regarding the houses construction and maintenance costs. The project produced a cost-effective/affordable model of bio-climatic/sustainable housing to people with low income, as well as social benefits such as quality improvement of social households in Spain (comfort/human health considerations), education and awareness raising of citizens and users of this type of housing, and training provided to stakeholders (construction, engineering, acoustics and energy fields). The project comprises strong economical and social aspects as it is included within the "Special Housing Plan" seeking to improve also comfort and image of social houses, constructed by the regional Government of Extremadura. Finally, several European projects focused on energy-efficient buildings have used many of the results of the project. These include E4R-Evaluation of energy efficiency in buildings, Retrofitting SUDOE space (SUDOE Programme) and EnEf-Promotion of training in energy efficiency in the building sector (Lifelong Learning Programme, Leonardo da Vinci). Further information on the project can be found in the project's layman report and After-LIFE Communication Plan (see "Read more" section).