Fulfillment of net-zero energy building (NZEB) with four metrics in a single family house with different heating alternatives

This study aims to investigate the fulfillment of four Net Zero Energy Building (NZEB) balances, NZEB-PE, NZEB-site, NZEB-emission and NZEB-cost, considering the four metrics of primary energy (PE), site energy, CO2-eqemissions and energy cost, respectively, using weighting factors based on Finnish and international reference data. The study analyzes five conventional energy systems and seven biomass-based standalone and shared combined heat and power (CHP) systems. These systems are connected to a single family house located in Helsinki, Finland, with two energy efficiency levels: a standard house and a passive house, simulated by Trnsys software. The annual balance of the import and export of the operational thermal and electrical energies is applied. The simulated results indicate that the NZEB-emission, NZEB-PE, NZEB-cost, and NZEB-site are arranged in that order according to the ease of fulfilling the annual balance. Making the house high in thermal energy efficiency (or adding solar thermal collectors) for all the studied systems is a step towards achieving NZEB-PE, NZEB-cost, and NZEB-site. On the contrary, achieving the NZEB-emission by the shared CHPs connected to the standard house is easier than the passive house. The NZEB balance is more attainable by the shared CHPs than the standalone CHPs. The NZEB-PE is easier to achieve using the international factors than using the Finnish PE factors.