Geothermal retrofitting of buildings is one solution to help address climate change and to meet renewable energy generation goals and sustainability targets. At the building level, it is possible to attain: – 40-70% savings on heating – 20-50% savings on cooling Overall, geothermal energy is: – Renewable: Ground energy is available endlessly, 24 hours a day for heating and cooling. – Environmentally friendly: Any usage of ground energy reduces the emissions of greenhouse gas. – Safe and controllable: Ground energy is technically mature and has been used for heating and cooling for more than 50 years. – High performance: a response to all energy demands such as heating, cooling, hot water and energy storage. – Versatile: applicable in combination with other energy sources. – Economically sustainable: regionally usable, independent of external suppliers and changes in currency exchange rates. However, the cost and efficiency of existing geothermal systems, mostly based on vertical wells, to provide heating and cooling in buildings being retrofitted or renovated are not very competitive in particular when digging is difficult. As such, there is the need to develop easy to install and efficient underground coupling systems for retrofitting existing types of buildings, including historical buildings, to make geothermal energy a standard source of heat and cold in building renovation. Improved and more cost-efficient heat pumps to optimize the use of the energy generated by geothermal systems can also be an important contribution to improving the overall performance and cost effectiveness of geothermal retrofits. If these challenges are successfully addressed and exploitation pathways developed, the benefits of geothermal energy can be attained by an increased number of buildings.