This deep energy retrofit of a floor-apartment in Ano Komi-Kozani has as a goal to convert it into a zero-energy house. The interior spaces are redesigned in order to be more functional and with a focus on the exploitation of natural light and ventilation. “Fabric first” approach is followed. Emphasis is given on maximizing the performance of the components and materials that make up the building’s fabric itself, before considering the use of mechanical or electrical building services systems. Continuous super-insulation, thorough air tightness, triple-pane windows and passive solar gains, work together to yield a minimum heating demand. All active mechanical systems are extremely efficient: an air-water heat pump for heating, cooling and hot water, LED lighting, heat recovery ventilation (MHRV), and solar panels with net-metering on the roof. The result is a home with 80% decreased energy consumption.