New ASHRAE standard defines ‘zero energy’ and ‘zero carbon’ buildings

ASHRAE has released a new standard that defines the terms "zero Energy" and "zero carbon" to describe buildings.

ANSI/ASHRAE Standard 228-2023, Standard Method of Evaluating Zero Net Energy and Zero Net Carbon Building Performance, sets requirements for evaluating whether a building or group of buildings meets a definition of “zero net energy” or a definition of “zero net carbon” during operation. The standard draws from other ASHRAE standards to address energy and carbon flows across a site boundary, their measurement, and their balance.

“Achieving a zero energy building has been viewed by many as a difficult goal to meet, with unforeseeable roadblocks and differing guidance,” said Keith Emerson, P.E., Life Member ASHRAE, chair of the Standards Project Committee 228. Standard 228 provides a consistent method for determining whether new and existing sites have reached zero energy. We hope this standard will become a helpful resource for building professionals in strategic decarbonization planning.”

Features of Standard 228 include:

• Allowances for sites that lack the means to produce adequate renewable energy, while placing additional requirements on the use of external carbon and renewable energy in the calculation.
• Defined calculation of energy in terms of source—a multiplier on the energy crossing the site boundary including energy used or lost in extraction, generation, and transit to the site.
• The main energy calculation made in terms of annual average factors. Allowance is made for the calculation of individual hours where data is available.