: Designers must ensure their calculated MLC and ELC values are below the maximum allowable thresholds defined for specific climate zones.

The ASHRAE Digital Collections offer online access with automatic updates to ensure you are always using the latest version. 💡 2025 Edition Update

Always check the "Standards Addenda" section on the ASHRAE website. These free PDF downloads contain the most recent corrections and updates published between major edition releases. Conclusion

ASHRAE provides a Free Standards Read-Only Preview on their website. You cannot download or print this version, but you can read the full text.

There is no ASHRAE 904 . If a PDF claims to be “ASHRAE 904,” it is either a mislabeled 90.4 or a fake document.

In the past, building owners often chose the cheapest air conditioner or boiler upfront, only to pay triple the cost in energy bills over ten years. ASHRAE 904 provides the legal and engineering framework to prove that a high-efficiency variable refrigerant flow (VRF) system or a geothermal heat pump is actually cheaper in the long run than a standard packaged unit.