Table of Contents—2025 ASHRAE Handbook—Fundamentals
The 2025 ASHRAE Handbook—Fundamentals covers basic principles and data used in the HVAC&R industry. It's more than 1,100 pages have been extensively updated and cover foundational concepts such as thermodynamics, psychrometrics, and heat transfer, and provide practical guidance on building envelopes, indoor environmental quality, load calculations, duct and piping system design, refrigerants, energy resources, sustainability, climate change, and more.
The ASHRAE Technical Committees that prepare these chapters provide new information, clarify existing content, delete obsolete materials, and reorganize chapters to make the Handbook more understandable and easier to use. The Handbook is available in hard copy, downloadable PDF, and as access to all four current volumes (plus extra features and an archive of discontinued chapters) via Handbook Online.
Updates have been made throughout the volume, but just a few of the highlights include the following.
- Chapter 5, Two-Phase Flow: expanded explanations of the latest research and extensive table updates.
- Chapter 14, Climatic Design Information: greatly expanded cli-mate data tables (available via download with the PDF version of this chapter at technologyportal.ashrae.org, and with a subscription to Handbook Online). The Handbook Online version also includes access to the updated 2025 Weather Data Viewer.
- Chapters 25, 26, and 27, addressing various aspects of heat, air, and moisture control: extensive updates and new examples.
- Chapter 30, Thermophysical Properties of Refrigerants: new data and graphs for R-448A, RE-449A, and R-454B.
- Chapter 31, Physical Properties of Secondary Refrigerants (Brines): all graphs and tables have been updated.
- Chapter 35, Sustainability: heavily rewritten to address the latest data and approaches.
- Chapter 36, Global Climate Change: extensive updates to reflect the most up-to-date climate knowledge and forecasts.
- Chapter 38, Measurement and Instruments: updated to the latest practices.
- Chapter 40, Units and Conversions: new explanatory text and examples to help readers navigate a dual-unit world.
Future corrections for this volume will be listed in subsequent volumes and on the ASHRAE website. Any extensive out-of-sequence updates in future will be posted to ASHRAE Handbook Online as a supplemental feature.
Reader comments are welcomed. To suggest improvements for a chapter, please write to Handbook Editor, ASHRAE, 180 Technology Parkway, Peachtree Corners, GA 30092, fax 678-539-2168, or e-mail hkennedy@ashrae.org.
Moli (Heather) Kennedy
Editor