The original standard, ASHRAE 90, was published in 1975. There have been multiple editions to it since. In 1999, the Board of Directors ashrae 90.1 2016 pdf ASHRAE voted to place the standard on continuous maintenance, based on rapid changes in energy technology and energy prices. This allows it to be updated multiple times in a year.
The standard was renamed ASHRAE 90. It has since been updated in 2004, 2007, 2010, 2013 and 2016 to reflect newer and more efficient technologies.
In general, there are two means, or paths for building designers to comply with ASHRAE 90. Prescriptive path: All components of the building meet the minimum standards specified by ASHRAE 90. This now has three paths. For code compliance there is Chapter 11, which compares an energy model for your building to an energy model for a barely compliant building with the same HVAC system and in the 2016 edition an Appendix G path was added that compares an energy model of your building against a baseline model based on the 2004 edition of Standard 90.
1 and requires lower energy consumption that varies depending on the building type. Within the sections of the standard, there are some variations to this. Some sections have mandatory provisions, simplified approaches, or trade-off opportunities. This baseline ECB is established using building energy simulation to model a building with the same size and program as the project building, built according to the prescriptive requirements of ASHRAE 90.
The ECB is expressed in units of dollars. A building energy simulation is then performed on the proposed building design. The proposed energy cost budget must be less than or equal to the baseline energy cost budget to achieve compliance.