The 90 series began in 1975 and has been updated twice since then. The current version presently used was modified and released in 1989. ASHRAE/IES 90.1 standards have been required for new buildings in the United States since 1994 but have been incorporated into Toronto and Vancouver designs since 1991.

90.1 is organized into 13 sections:

The document begins with "Basic Requirements" and then breaks into two pathways:

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