Abstract
Several different definitions of ‘net-zero’ or ‘climate-neutral’ buildings have arisen and are causing confusion. Different approaches quantify the greenhouse gas (GHG) emissions of buildings over their life-cycle. A typology is proposed based on distinctions between absolute and net-zero-emission buildings in relation to operational and full life-cycle approaches. Besides the absolute zero-emission approach, three different net-zero-emission approaches are: (1) a net-balance approach, which includes credits caused by potentially avoided emissions beyond the system boundary provided by exported energy; (2) an offsetting approach, based on the purchase of CO2 certificates; and (3) a technical approach, based on negative-emission technologies. The declaration of the approach chosen will provide clarity when discussing (net/absolute)-zero emission or climate-neutral buildings.
Policy relevance
The use of suitable terms, definitions, system boundaries as well as calculation and assessment rules is a prerequisite for credibility and transparency. Legal requirements for limiting GHG emissions from buildings and their fulfilment should therefore be formulated in a way that is understandable by both industry professionals and stakeholders with clear rules for documentation and the provision of evidence. This is particularly important for the proof of the political goal to create a climate-neutral building stock. A typology of (net-) zero building approaches is presented that explains their level of ambition, fosters transparency, and reduces misperceptions and misunderstandings.