Net-zero energy buildings: The influence of definition on greenhouse gas emissions

摘要

Since the Net-Zero Energy Building (NZEB) concept was introduced, four widely-accepted definitions have been proposed: net-zero site-energy buildings, net-zero source-energy buildings, net-zero energy-cost buildings, and net-zero emission buildings. This study compares the effectiveness of these four NZEB definitions in reducing the operational emissions of a building. As the context of comparison, a simple geometry located in two different cities, i.e. Toronto and Miami, with four different energy behaviours is considered. We find, for both locations, that requiring a net-zero energy cost balance leads to the lowest emissions, 102-145% reduction for Toronto and 99-117% for Miami. Net-zero site-energy building, in the second place, reduces the emission levels in the building by 92-108% in Toronto and 97-110% in Miami and results in negative or close-to-zero emission levels, ranging from -1.26 to 1.35 kgCO2e/m(2) in Toronto and -7.05 to 1.95 kgCO2e/m(2) in Miami. Net-zero source-energy building definition, in the third place, reduces the emissions by 74-108% in Toronto and by 97-103% in Miami. Finally, the net-zero emission building definition (according to the CaGBC Zero Carbon Building standard), contrary to its designation, is the least effective definition in reducing greenhouse gas emissions (49-86% reduction for Toronto and 89-94% reduction for Miami), as it permits notable non-zero net-emission levels in the building (2.44 to 7.69 kgCO2e/m(2) in Toronto and 3.77 and 8.19 kgCO2e/m(2) in Miami). (C) 2021 Elsevier B.V. All rights reserved.