The impact of retrofitting in southern European residential buildings with intermittent or continuous heating

Renovating the existing building stock is important for the building sector to reach the carbon neutral level. However, in addition to evaluating energy conservation and emission reduction potential brought about by renovation, it is also important to pay much attention to the change in the indoor climate after retrofit since people spend approximately 90% of their time indoors. This study aims to compare building energy consumption and the indoor climate after implementing several novel renovation technologies and their packages in southern European residential buildings through building-level simulations. The novel technologies include bio-aerogel thermal insulation, photovoltaic vacuum window, phase change material, insulating breath membrane, room specific air handling unit with heat recovery, a 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 with an intermittent or continuous heating schedule in IDA ICE and used as the reference cases for renovation technologies simulations. The novel renovation technologies were classified into the passive package, ventilation package and generation package, and then integrated into the building models to evaluate their impact on building energy consumption and indoor climate. The novelty of this study was to assess energy consumption and indoor climate change brought by the combinations of retrofit technologies in different southern European countries. It also revealed the impact of intermittent or continuous heating schedules on the energy conservation potential of retrofit technologies. The impact of retrofit technologies on building energy consumption and indoor climate was significantly affected by heating schedules. The energy consumption reduction acquired by thermal insulation improvement under intermittent heating schedules was much lower than that under continuous heating schedules in all demo buildings since thermal insulation improvement resulted in an indoor air temperature increase when intermittently heated. Besides, when the intermittent heating schedule was switched to the continuous heating schedule, although the absolute energy consumption reduction brought by generation technologies increased, the relative reduction in percentage was diminished due to the increased backup energy demand for space heating.