Energy retrofitting of existing building stock has significant potential for the reduction of energy consumption and greenhouse gas emissions. Roughly half of the CO2 emissions from Czech building stock are estimated to be allocated to residential buildings. Approximately one-third of the Czech residential building stock have already been retrofitted, but retrofitting mostly takes place in large cities due to greater income. A favourable concept for the mass retrofitting of residential building stock, affordable even in low-income regions, was of interest. For a reference building, multi-criteria assessment of numerous retrofitting measures was performed. The calculation involved different building elements, materials, solutions, and energy-efficiency levels in combination with various heating systems. The assessment comprised environmental impact, represented by operational and embodied primary energy consumption and greenhouse gas emissions, and investment and operational costs using the annuity method. Analysis resulted in the identification of favourable retrofitting measures and showed that complex building retrofitting is advantageous from both a cost and an environmental point of view. The environmental burden could be decreased by approximately 10–30% even without photovoltaic installation, and costs per year could be decreased by around 40%.

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Buildings are responsible for a significant share of EU energy consumption. To improve energy efficiency of the building stock, it is needed to significantly increase renovation rates. To overcome actual barriers related to this problem, such as partial and non-systematic renovations, lasting unrest during renovation or time-consuming wet processes, an industrialized construction system using prefabricated modular elements seems to be a possible way. Such system for mass energy retrofitting of residential buildings in Central Europe was developed in H2020 project MORE-CONNECT. The work presented in this article aimed to roughly estimate potential yearly energy savings by applying this new modular retrofitting system on one typology segment of the Czech residential building stock: non-renovated multifamily residential buildings built between 1946 and 1960 with total gross floor area covering over 7 million square meters. The main objective of the research presented in this paper was to make a hypothetic rough estimation of potential yearly energy savings by applying the new modular retrofitting system on a target typology of the Czech residential building stock. According to the calculations, application of proposed retrofitting system on the chosen building type would reduce the total energy consumption in Czech residential buildings by 2.9 % and by 1.8 % compared to energy consumption in all Czech buildings.

In order to significantly reduce energy consumption of its building stock, Europe has to focus on energy retrofitting of existing buildings. A usual building retrofitting process is very labour intensive and time consuming. It usually takes several weeks or even months to replace old windows by new, install new thermal insulation layers on the external walls and roofs of buildings and renew the heat distribution systems or to attach renewable energy sources on the building’s envelope. To make refurbishment more efficient and allow its scaling up, a European project Development and Advanced Prefabrication of Innovative, Multifunctional Building Envelope Elements for Modular Retrofitting and Connections (MORE-CONNECT) has been initiated under H2020 program. This project developed a system of prefabricated retrofitting modules, that enable to cut primary energy consumption of a typical residential building by 80 %, reduce on-site installation time bellow two weeks and improve the indoor environmental quality. At the same moment, the project aimed on implementation of systemic quality control over the whole design, pre-production, production and installation process in order to significantly reduce the number of warranty claims by the clients. The paper describes the design process of the modular retrofitting system and a pilot installation made on a mock-up building to test the concept, and presents the experience made.

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