What is ASHRAE 90.4?
ASHRAE 90.4 is the ASHRAE Energy Standard for Data Centers. It sets minimum energy efficiency requirements for the design, construction and operation planning of data centers, using a mechanical load component and an electrical loss component to assess cooling and power distribution efficiency. It works alongside ASHRAE 90.1 for the rest of the building.
What it is
ASHRAE 90.4 was created because general building energy codes did not fit data centers well. Their loads are dominated by IT equipment, and efficiency depends mostly on cooling and power distribution.
The standard uses two main metrics. The mechanical load component, or MLC, captures cooling system efficiency. The electrical loss component, or ELC, captures losses in power distribution from the utility to the IT equipment. Designs must meet maximum values that depend on climate zone and design.
Where codes adopt ASHRAE 90.1, they often reference 90.4 for data centers. Adoption and editions vary by jurisdiction.
Who it applies to
Designers, owners and operators of new data centers and major renovations in jurisdictions that adopt it. Check which edition your code references.
Operators also use its metrics to compare actual performance with design intent, since a design that meets the standard can still drift in operation as loads, setpoints and equipment condition change.
How it is measured
Compliance is shown in design calculations, but operation shows whether design intent holds.
- Mechanical system energy against design MLC
- Electrical losses from utility input to IT load
- Design and actual IT load
- Operating trends across seasons
How Aqueduct helps
Aqueduct supplies measured mechanical and electrical performance against design values.
- aQ EnergySmart metering of cooling plant and power distribution
- Measured losses across UPS and distribution compared with design
- Fault detection on chillers, CRAHs and economizers
- Verified results after corrective work