What are NZEBs?
Net or nearly zero energy buildings (NZEB) are highly efficient buildings with extremely low energy demand, which is met by renewable energy sources. Such buildings produce as much energy as they consume, accounted for annually. In order to achieve their net zero energy goals, NZEBs must first sharply reduce energy demand using energy efficient technologies, and then utilize  renewable energy sources (RES) to meet the residual demand. In such buildings, efficiency gains enable the balance of energy needs to be supplied with renewable energy technologies. This is the most logical approach to reach NZEB goal.

However, this broad definition leaves plenty of room for  interpretations—and for misunderstandings among owners, architects, and other stakeholders in the NZEB project. Agreeing to a common definition of NZEB boundaries and metrics is essential to developing design goals and strategies.

Beyond this very general definition, a number of more specific definitions and terms have been put forth to better capture the specifics of how NZEB performance is achieved and measured. These specific definitions reflect the differences in priorities and perspectives among the diverse set of parties interested in NZEB buildings—for example, emphasis on demand-side versus supply-side technologies or a focus on onsite energy use versus carbon emissions—and can have an impact on design decisions (Torcellini et al. 2006).

The varying definitions of net-zero energy buildings also put forth different metrics for measuring NZEB performance and different boundaries within which the net zero balance must be maintained. This section defines the boundaries and metrics accepted globally.

Definitions of NZEB are critical in determining the path to zero energy goals, and significantly influence design choices of architects and building owners. Appropriateness of definitions to a project vary according to project goals and values of the designer and building owner, making it essential for them to understand which definition will suit their purpose best.