NEED4B aims to develop an open and easily replicable methodology for designing, constructing, and operating new low energy buildings, aiming to a large market uptake. The NEED4B methodology will be validated and refined by a strong demonstration programme, envisaging the construction of 27.000 square meters, spread among five different climatic zones, buildings types and uses.The weighted average of energy consumption in the demo sites, on primary energy, is 43 kWh/m2•year, representing a 65% of reduction compared with the current regulation and regular practice. The weighed average of CO2 emissions is 1,91 kg/m2•year, corresponding to a of 94% reduction compared to the current national regulations and regular practices. The total emissions avoided by the five demo sites are 831,9 tCO2/year.The proposed methodology will integrate tools and procedures that already exist or are under development, like Integrated Project Delivery, Building Information Modelling, Life Cycle Assessment, Life Cycle Cost and simulation softwares, providing recommendations and guidelines, adapted to the different type of stakeholders (investors, promoters, owner, users, architects, contractors, public authorities, SMEs, etc.) for the whole construction process.NEED4B will be part of an ambitious initiative that will totally invest 191 M€ and involve around 46.000 person months for the design, construction and monitoring of the demo sites. The requested EC contribution (5,7 M€ grant and 590 persons months) will help to leverage these resources, obtaining an exemplary coordinated EU low energy buildings demonstration, with high replication potential due to the associated methodology, and a relevant visibility. The weighted average energy savings are 60 kWh/m2•year, resulting in reduction of the bill of 9,6 €/m2•year. The weighted average cost for each kWh reduced is 0,81 €/ m2•year, and the weighted average cost for each kgCO2 avoided is of 3,5 €/ m2•year.