ASHRAE Standard 90.4-2019 provides a specialized energy-efficiency framework for data centers, focusing on the mechanical load component (MLC) for cooling and the electrical loss component (ELC) for power systems to meet specific PUE targets. The standard emphasizes a performance-based approach to design, aligning with thermal guidelines to ensure efficiency while maintaining equipment reliability. The official, copyrighted document for the standard can be acquired directly through the ASHRAE Bookstore.
Standard 90.4 acts as a "sister" or companion standard to 90.1. While 90.4 governs the technical "computer room" spaces, 90.1 still applies to the rest of the facility, including: Building Envelope: Insulation and window performance. Lighting: Efficiency of lamps and control systems. Service Water Heating: Systems for domestic hot water use. Recent Evolution (90.4-2022)
Unlike the widely known Power Usage Effectiveness (PUE) metric, which measures total facility efficiency, ASHRAE 90.4 focuses on the design of individual infrastructure components. Compliance is achieved by meeting specific maximum values for two key components: ashrae 90.4 pdf
This limits electrical losses from power distribution gear:
ASHRAE 90.4 uses the same climate zones as 90.1 (0 through 8). But unlike 90.1, the MLC allowance varies significantly. You must look up your location in the PDF’s annex tables. ASHRAE Standard 90
Disclaimer: This article is for informational purposes only. Always consult a licensed professional engineer and the official ASHRAE standard for actual compliance requirements.
Even with the PDF in hand, engineers struggle with these issues: Standard 90
Standard 90.4 uses a performance-based approach, focusing on two primary components that must be calculated and compared against maximum allowable values based on climate zones: Data Center Knowledge Mechanical Load Component (MLC):
By following the guidelines and requirements outlined in ASHRAE 90.4, data center designers and operators can create more energy-efficient, reliable, and sustainable facilities that support the growing demands of the digital economy.