Thermo-Active Foundation Walls for the Energy Efficiency of Near-Zero Energy Residential Buildings

Energy savings in buildings and the focus on efficiency in energy uses become key elements in trying to improve future living conditions. Starting from this point, low-enthalpy geothermal energy is an efficient renewable resource when coupled with a Geothermal Heat Pump (GHP). The study of geothermal heat exchangers through energy geostructures define its interest in terms of reducing consumption, environmental impacts and costs. This paper investigates the technological system of energy foundations, delv- ing into the case of a geothermal exchanger integrated into foundation walls because they represent under-studied systems and because they are interesting from a performance and construction standpoint. The preliminary step was to evaluate the performances of different kind of foundation walls as geothermal exchanger coupled with a geothermal heat pump using dynamic modelling in the TRNSYS suite. The configuration under study was hypothesised by carrying out preliminary tests and varying the boundary conditions of the retaining walls. The final optimised configuration was subsequently applied and sized on two case studies for two common building types, such as an in-line building and a terraced building. The dimensioning of the geothermal system is based on residential build- ings and near-Zero Energy standard. The simulation was performed in an Italian Mediterranean location to evaluate its performance, and then the consumption of these systems was extrapolated and compared to air source heat pumps. In conclusion, this technology could generate favourable impacts on energy consumption and emissions, proving to be suitable for both the construction of ex novo buildings and the energy refurbishment of existing ones.