ASHRAE 90.1 is the US reference energy standard for commercial building design, published jointly by ASHRAE and IES. It sets minimum efficiency for envelope, HVAC, service water heating, power, lighting and controls, and most US commercial energy codes point to an edition of it. More detail sits on the ASHRAE 90.1 compliance page.

Is ASHRAE 90.1 the same as the IECC?

No. The International Energy Conservation Code is a model code from the International Code Council, and its commercial provisions accept ASHRAE 90.1 as an alternative way to comply. A design team picks one path per project, and the local building department confirms which edition of each it enforces.

Does ASHRAE 90.1 reach a building that is not being renovated?

Generally not. Its requirements attach to new construction, additions and alterations, although a city building performance standard can still apply to that building. Owners of existing stock usually meet operating limits through programs like building performance standards, which judge measured use rather than design.

Which ASHRAE 90.1 rules depend on operating data?

The controls and metering provisions. ASHRAE 90.1 calls for scheduling, setback and economizer controls, and section 8.4.3.1 of the 2013 edition sets energy metering requirements. Aqueduct reads that metering and the HVAC points afterward, so fault detection and diagnostics shows whether the designed sequences still run.

Glossary

Energy standards and regulation

What is ASHRAE 90.1?

Definition

ANSI/ASHRAE/IES Standard 90.1 sets minimum energy efficiency requirements for the design of sites and buildings, except low-rise residential, covering envelope, HVAC, water heating, power, lighting and controls.

Where 90.1 carries weight

Architects, MEP engineers and code officials apply it to new buildings, additions and major alterations. It becomes enforceable only where a state or city adopts it, usually through its commercial energy code, and the adopted edition differs from place to place. Green building rating systems and federal building rules also reference it, so one project can meet more than one edition.

The current edition

ASHRAE lists 90.1-2025 as current, titled Energy Standard for Sites and Buildings Except Low-Rise Residential Buildings, and its bookstore page says the edition incorporates 105 addenda. Design teams show compliance through mandatory provisions plus either a prescriptive or a performance path.

Catching control drift after handover

Design compliance says nothing about whether schedules and setpoints still hold years later. Aqueduct reads BMS points over BACnet or Modbus through a field device network controller, and the RTU digital twin reports setpoint attainment, sequence exceptions and economizer state, so drift from the designed sequence surfaces as a fault. Where control is enabled, with owner approval, each schedule change is logged in command history.

What is ASHRAE 90.1?

Where 90.1 carries weight

The current edition

Catching control drift after handover

ASHRAE 90.1: common questions

See Aqueduct on your own facility.