ASHRAE 90.4 is a code-intended standard that provides a framework for the energy-efficient design and operation of data centers, acknowledging their unique and intensive power and cooling loads compared to other commercial buildings. It was developed as a "sister standard" to the well-known ASHRAE 90.1, which covers energy efficiency for all buildings except low-rise residential. Importantly, Standard 90.4 is not meant to replace 90.1 entirely but serves as an alternative compliance path specifically for data centers. It references Standard 90.1 for conventional building elements like the building envelope, lighting, and service water heating, while providing its own specialized requirements for mechanical cooling and electrical power systems.
This article explores the key provisions, technical updates, and compliance pathways in the 2022 version of ASHRAE 90.4 — a document often mistakenly referred to as "ASHRAE 904."
: Calculations must now account for UPS redundant capacity , meaning efficiency is judged based on total available capacity, not just the active load. ashrae 904 pdf upd
: Recent updates often refine the maximum allowable values for MLC to reflect improvements in cooling technology and higher efficiency expectations in modern facility design. Accessing the PDF
A data center is considered compliant if its calculated MLC and ELC values are lower than the maximum allowable values specified in the standard. Section 11 of the standard provides an alternative compliance path that allows some trade-offs between the MLC and ELC, giving designers flexibility in their approach. ASHRAE 90
A common point of confusion is the relationship between ASHRAE 90.4 and Power Usage Effectiveness (PUE), the industry’s most familiar efficiency metric.
In the rapidly evolving landscape of digital infrastructure, data centers have become the backbone of modern society. Yet, their energy consumption continues to rise sharply. In response, , Energy Standard for Data Centers and Telecommunications Facilities , has emerged as the definitive benchmark for designing energy-efficient, high-availability facilities. The latest update (2022) introduces critical changes that align with real-world operational data, climate-adaptive metrics, and the growing need for decarbonization. It references Standard 90
The definitive source for purchasing the most up-to-date, legal PDF or printed version of Standard 90.4 is the official ASHRAE website.
Standard 90.4 works in tandem with Standard 90.1. While 90.4 governs the data center baseline, building envelope, lighting, and service water heating systems still defer to 90.1 requirements.
With the rise of high-density AI chips, traditional air cooling is often insufficient. Recent updates have integrated specific compliance pathways for direct-to-chip liquid cooling and immersion cooling systems.
A: ASHRAE is a non-profit, but it sells standards to fund research. There is no legal, "free" official copy except for students through university libraries (as noted above). Beware of torrent links—they are almost always obsolete.