Point your script directly to the C:\REFPROP directory to call the DLL files.

Some older installers trigger false positives in modern antivirus software (e.g., Windows Defender, McAfee). The installer uses self-extracting archives that may be flagged as suspicious. Disable real-time protection just for the installation duration, then re-enable it afterward.

Before beginning the installation, ensure your system meets these basic requirements: Operating System

Approximately 10–20 MB of available hard disk space. 2. Core Installation Steps

The system prompted for the Fortran runtime — a companion expected to be present. It installed silently, like a hand sliding a key into a lock. A moment later, a dialog requested permission to set environment variables. Yes: add REFPROP to the PATH. The thought of invoking thermodynamic properties from any terminal felt like granting the software the freedom to be called wherever curiosity led.

If you have REFPROP 10 installed, you can still use the 9.1 interface for backward compatibility. NIST provides a specific REFPRP91.XLA patch to help version 10 users run older spreadsheets without changing formula syntax.

To prevent Excel from blocking the DLL, you must add the REFPROP folder as a via File > Options > Trust Center > Trust Center Settings .

The setup wizard will guide you through the license agreement and destination folder selection. The default installation path is usually C:\Program Files\REFPROP or C:\Program Files (x86)\REFPROP .

Windows 7, 8, 10, or 11 (32-bit or 64-bit). Storage: Approximately 50 MB of free disk space.