ANSI ASHRAE Standard 90.4-2022 add c-2025 PDF

Full title and description

ANSI/ASHRAE Standard 90.4-2022 — Energy Standard for Data Centers — Addendum c (2025). This addendum modifies and clarifies selected energy-efficiency requirements and calculation procedures in the 2022 edition of Standard 90.4 and is published as part of ASHRAE’s continuous maintenance program; the changes are included in the consolidated 2025 revision of the standard.

Abstract

Addendum c to Standard 90.4-2022 provides targeted technical changes intended to improve accuracy and applicability of data-center energy metrics and compliance methods. The addendum refines electrical-loss and mechanical-load component calculations, updates performance breakpoints and crediting methods for on-site renewables and recovered heat, and clarifies how certain equipment (for example UPS and distribution components) is treated in the ELC/MLC methodologies. These changes are part of ASHRAE’s continuous maintenance process and are reflected in the consolidated 2025 edition.

General information

• Status: Addendum to ANSI/ASHRAE Standard 90.4-2022 (approved via ASHRAE continuous maintenance; consolidated in the 2025 revision).
• Publication date: Addendum C listed as effective June 30, 2025 (consolidated 90.4-2025 published as the updated ANSI/ASHRAE document).
• Publisher: American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE); ANSI-approved.
• ICS / categories: Relevant ICS areas include 91.140 (heating, ventilating and air-conditioning), and information-technology/data-centre classifications (ISO/IEC ICS 35.x series); the standard bridges HVAC, power distribution, and IT/data-center energy topics.
• Edition / version: Addendum c to ANSI/ASHRAE Standard 90.4-2022; changes incorporated into the consolidated ANSI/ASHRAE 90.4-2025 edition.
• Number of pages: ANSI/ASHRAE Standard 90.4-2022 (full standard) is listed at approximately 58 pages in vendor catalogs; individual addenda are typically short (a few pages). Users should consult the ASHRAE addenda PDF for the exact page count of Addendum C.

Scope

This addendum applies to the energy-efficiency requirements, calculation methods, and compliance paths defined by ANSI/ASHRAE Standard 90.4-2022 for data centers. The underlying standard (and therefore the addendum) addresses new data centers, additions to existing facilities, and alterations to systems and equipment where the energy-impacting elements are modified. The scope includes design, construction, planned operation and maintenance, and the use of on-site or off-site renewable energy resources where credits or adjustments are permitted.

Key topics and requirements

• Refinements to ELC (Electrical Load Component) and MLC (Mechanical Load Component) calculation procedures and breakpoints to better align segment calculations with design-load points.
• Clarified treatment and required accounting for UPS, transformers, and distribution losses within ELC totals (reduces ambiguity for compliance calculations).
• Updated credits and methodologies for on-site renewable energy and recovered heat, including how combined credits are applied against MLC/ELC totals.
• Adjustments supporting liquid-cooling classes and hotter allowable equipment inlet temperatures where applicable (alignment with modern data-center cooling strategies).
• Editorial clarifications, technical errata corrections, and small procedural changes that streamline compliance testing and documentation.

Typical use and users

Primary users are data-center design and commissioning teams, MEP engineers, energy managers, facility owners/operators, sustainability and compliance consultants, and code officials who adopt or reference ANSI/ASHRAE standards. The addendum is used to update design calculations, procurement specifications, and energy compliance documentation for projects subject to ASHRAE 90.4 requirements.

Related standards

Standard 90.4 cross-references and complements several other standards and guidance documents, most notably ANSI/ASHRAE Standard 90.1 (building energy efficiency requirements for building envelope, lighting, service water heating and related equipment) as well as industry data-center standards such as EN 50600 (data centre facilities), ISO/IEC guidance on data-center monitoring and sustainability, and other ASHRAE data-center guidance. Practitioners should consult these related documents when addressing envelope, systems outside data-center-specific scope, or detailed IT/DCIM interoperability requirements.

Keywords

Data center energy, ELC, MLC, ASHRAE 90.4, addendum, UPS losses, power distribution, liquid cooling, renewables credit, data-center compliance, commissioning, energy efficiency.

FAQ

Q: What is this standard?

A: ANSI/ASHRAE Standard 90.4 is the Energy Standard for Data Centers. It establishes minimum energy-efficiency requirements and methodologies tailored to data centers and related mission-critical facilities; Addendum C is a targeted update to the 2022 edition now captured in the 2025 consolidated release.

Q: What does it cover?

A: The standard (and this addendum) covers how to calculate and limit electrical and mechanical energy loads for data centers, how to document compliance, and how to apply credits for measures such as on-site renewables and heat recovery. It addresses design, construction, operation and maintenance elements that affect energy use.

Q: Who typically uses it?

A: Data-center architects and engineers, MEP designers, commissioning agents, energy and sustainability managers, facility owners/operators, and jurisdictional code officials who adopt or reference ASHRAE standards.

Q: Is it current or superseded?

A: Addendum C is part of ASHRAE’s continuous maintenance for the 2022 edition and is shown as an addendum effective June 30, 2025; its changes are incorporated into the consolidated ANSI/ASHRAE 90.4-2025 edition. Users should reference the most recent consolidated edition or the specific addendum PDFs for official requirements.

Q: Is it part of a series?

A: Yes. Standard 90.4 is part of ASHRAE’s family of energy standards (including Standard 90.1 and related documents) and is maintained via addenda under continuous maintenance; multiple addenda to 90.4-2022 are published as needed and a consolidated revision may be released (for example, 90.4-2025).

Q: What are the key keywords?

A: Data center energy, ELC, MLC, UPS losses, power distribution, liquid cooling, on-site renewables credit, ASHRAE 90.4, addendum C, energy compliance.