Buildings are the key factor to transform cities and to contribute to recent European energy efficiency objectives for 2030 and long-term 2050. New buildings account to only 1–2% annually. Yet, ninety percent of the existing building stock in Europe was built before 1990, it is therefore necessary to promote their energy renovation to achieve the set objectives. Renovation solutions are available on the market, yet a wrong implementation and integration due to a lack of knowledge neither maximizes the energy performance of the post-retrofitting nor the financial optimisation and viability of the projects. This paper presents research on a plug & play, modular, easy installable façade and ICT decision making technologies to provide affordable solutions in order to overcome those deep renovation barriers. The paper sets out by defining a value framework that can be applied by real estate investors for making better retrofitting decisions for residential buildings, through mapping targeted building typologies and investigating new building revalorisation strategies, new renovation concepts and KPIs for evaluation. Thereafter the paper presents the modular and easy-to-install façade system that is replicable and scalable at European level.

The nearly Zero Energy building (nZEB) renovation market is currently the key feature in the construction sector. RenoZEB aims to develop a systematic approach for retrofitting by assembling different technologies in a plug and play building envelope. This paper presents the methodology used to transform the RenoZEB concept in the design system. A multi-criteria decision matrix is used for the selection of the best façade technologies within the market while the analysis of the existing building conditions allows to develop a replicable approach for designing deep retrofitting intervention through a plug&play façade. The methodology appears to be a valuable support for the selection of technologies and allows to define a design guideline for the envelope.

In this paper, the application of demand-side flexibility to residential users and energy communities is discussed. From the H2020 project HOLISDER, it appears that selected Key Exploitable Results are not commercially interesting on their own as flexibility services but certainly are an add-on by cross-value stacking to regular energy services. For groups of prosumers, such as energy communities, cross-stacking can enlarge the awareness and commitment within the communities and, therefore, play an important role in the uptake of citizen communities as promoted by the EU Green Energy Package.

The retrofitting of the existing building stock is one of the most important goals to be pursued to meet European targets. In this context, the RenoZEB project has developed a modular methodology for the deep retrofitting of buildings, which is enabled by a prefabricated plug-and-play façade that integrates different on-market technologies to achieve nZEB standards. This article reports on the activities conducted in the study and design of the RenoZEB prefabricated envelope system, providing insights on the tests conducted and the results achieved for the façade system, with a specific focus on the use of technology laboratory facilities for real-environment validation, which revealed the system to be in line with the project objectives.