Northern European nearly zero energy building concepts for apartment buildings using integrated solar technologies and dynamic occupancy profile: Focus on Finland and other Northern European countries

The European Union introduced the concept of nearly zero energy buildings with the recast of the European Building Directive, requiring Member States to define nearly zero energy building in their national plans indicating a threshold value for primary energy consumption. This study investigates nearly zero energy building apartment building concepts for Northern European countries, focusing on Finland and extending the analysis to Sweden, Norway and Estonia. Particularly, different building design principles and use of building integrated solar technologies have been considered. Differently from the available studies and in accordance with recent literature, which has demonstrated the significant role of occupants in building energy consumption, the Authors considered dynamic user behaviour in order to emulate more realistic home appliances’ electricity consumption and internal heat gains. Results emphasize that one turnkey nearly zero energy building solution does not exist. Indeed, many nearly zero energy building concepts can be achieved by adopting more energy performant building design principles and/or installing onsite solar technologies. The selection of the right building design principles, typology and size of solar technologies depends on the main building heating source; typically, district heating and ground source heat pumps in Nordic countries. In Finland, nearly zero energy building concepts can be achieved by adopting the Finnish passive design principles without installing renewable energy systems onsite. Energy efficient or passive design principles lead to nearly zero energy buildings both in Norway and Finland, if ground source heat pump is used as main heating source. With regard to Sweden and Estonia, depending on the adopted building design principle and main heating source, different sizes of solar technologies should be installed onsite in order to meet nearly zero energy building requirements. In any case, at northern latitudes the energy generated onsite with conventional solar technologies is not enough to reach the Net Zero Energy target and research should focus on innovative solutions, such as seasonal storage and advanced “building to urban energy networks” solutions to go even beyond the Net Zero Energy horizon and achieve positive energy buildings.