Design and Parametric Analysis of a Solar-Driven Facade Active Layer System for Dynamic Insulation and Radiant Heating: A Renovation Solution for Residential Buildings

The constantly increasing energy demand in aged households of urban areas highlights the need for effective renovation solutions towards nZEB to meet the European Commission's energy reduction and decarbonization targets. To address these targets, a variety of retrofitting interventions are proposed that incorporate hydronic systems into the building envelope, minimizing heat loss through the external walls and occasionally heating or cooling adjacent thermal zones. The present study analyses a low-temperature solar-powered hydronic active wall layer attached to the skin of a residential building in combination with solar collectors for heat generation. A typical floor of a five-storey, post-war, poorly insulated multi-family building is modelled considering two different climatic conditions: Berlin (Germany) and Kastoria (Greece). The design parameters, such as the area of the collector, the temperature of the fluid entering the active layer, the volume of the buffer tank and insulation thickness have been determined in order to optimize the impact on the heating system. Techno-economic assessment-followed by sensitivity analysis-has been conducted to scrutinize the feasibility of such a renovation solution. Last but not least, the nZEB compliance for both cases is examined based on EU and national nZEB definitions. The results indicate that a reduction of heating demand by up to 93% can be achieved, highlighting that such a renovation solution can be profitable in both examined locations while at the same time reaching the nZEB state.