The most important thing to understand in the ASHRAE 90.4 PDF is the concept of (Mechanical Load Component) and EEL (Electrical Loss Component).
Historically, data centres fell under ASHRAE Standard 90.1 ( Energy Standard for Buildings Except Low-Rise Residential Buildings ). This created friction because Standard 90.1 focuses on human comfort, using metrics like Energy Efficiency Ratio (EER) for baseline equipment.
: This calculates the sum of all power required for cooling, fans, pumps, and heat rejection equipment, divided by the total IT equipment power. Compliance factors vary by ASHRAE Climate Zone .
: Recognizing that technology spaces scale incrementally, 90.4 provides realistic exemptions for minor modifications and expansions that would otherwise stall under standard building permits. Evolution of the Standard: 2016 to the Present ashrae 90.4 pdf
Crucial for compliance. Terms like "Computer Room Air Handler (CRAH)," "Uninterruptible Power Supply (UPS) efficiency," and "Economizer" are strictly defined.
The standard is evolving. The 2022 version introduced stricter ELC limits for transformers (moving towards NEMA TP-1 efficiency). The next revision (expected 2025) may include:
Hot-aisle and cold-aisle containment systems have become standard practice to prevent air mixing and optimize cooling efficiency. The most important thing to understand in the ASHRAE 90
Are you designing a or retrofitting an existing facility ?
This limits losses from the utility feed all the way to the server rack. This includes UPS losses, transformers, and PDU inefficiencies. If your UPS is 5+ years old, you might already be failing this requirement.
You can download a PDF of ASHRAE 90.4 from the ASHRAE website: : This calculates the sum of all power
This covers an enormous range of facilities, from small "Edge" rooms to large "Hyperscale" cloud facilities, of which there are hundreds of thousands in the U.S. alone.
Transformers and main switchgear.