As the building sector is the largest single contributor for energy consumption and greenhouse gas (GHG) emissions in the EU, improving building energy efficiency plays a key role in achieving the ambitious goal of carbon neutrality. In addition to constructing new buildings with energy efficiency regulation, it is also important to renovate the existing building stock for lower energy consumption and GHG emissions. This study aims at verifying the building level performance of several novel retrofit technologies and their combinations under southern European climate conditions. The novel retrofit technologies include bio-aerogel thermal insulation, photovoltaic vacuum window, phase change material, insulating breath membrane, room specific air handling unit with heat recovery, photovoltaic/thermal system and solar assisted heat pump. Three representative residential buildings in different southern European countries were chosen as the demo buildings to implement energy renovation in this study. These existing demo building models were simulated in IDA Indoor Climate and Energy simulation software (IDA ICE) and used as the reference cases for retrofit technology simulations. The retrofit technologies were classified into the passive package, ventilation package and generation package, and then integrated into the building models to examine their impact on primary energy and CO2 emissions. Finally, different final combinations of retrofit technologies were simulated to achieve the lowest building energy consumption and CO2 emissions after renovation. According to the simulation results, the novel retrofit technologies all had a certain impact on primary energy and CO2 emissions, while the impact of the same technology varied significantly in different demo buildings based on building type, climate conditions, heating schedules, etc. Regarding the performance of the final combinations, the maximum primary energy reduction after renovation was 48%, 58% and 64% in the Greek, Portuguese and Spanish demo buildings; the corresponding CO2 emissions reduction was 48%, 58% and 66%, respectively. The lower reduction in the Greek and Portuguese demo building was caused by their heating schedules since energy renovation led to indoor air temperature level increase when the demo buildings were intermittently heated.