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HVACSIM+ User's Guide Update



Cheol D. Park


The first version of HVACSIM+, which stands for “HVAC SIMulation PLUS other systems”, as introduced by National Institute of Standards and Technology (NIST) in 1985 as a computer simulation tool to simulate entire building systems [1]. Since then, the HVACSIM+ computer program package and manuals have been distributed to researchers, students, and consultants in more than 40 countries around the world. Since the first distribution of the program to public, a number of modifications have been made. Because some of statements in the Fortran 77 computer code of the HVACSIM+ used more than 20 years have become obsolete in the context of today’s Fortran 90/95 standards, an upgrade to Fortran 90/95 standards was deemed necessary. This conversion task was recently completed by NIST. During the conversion, the logic flows were maintained as close to the original as possible. This update manual is a condensed guide to running the programs in the HVACSIM+ package. Much of the substance of this manual is extracted directly from the previous manuals. This manual is intended to update and supplement the previous manuals, not to replace them. To confirm correct operation of the new code and illustrate its use, some of examples of system and building shell simulations were chosen from the previous documents. Simulation runs were made in the command line interface of a popular operating system in step-by-step manner. The input and output information of those runs is listed in this manual.
NIST Interagency/Internal Report (NISTIR) - 7514
Report Number


building simulation, building system modeling, computer simulation program, HVAC system simulations, HVACSIM+


Park, C. (2008), HVACSIM+ User's Guide Update, NIST Interagency/Internal Report (NISTIR), National Institute of Standards and Technology, Gaithersburg, MD, [online], (Accessed April 17, 2024)
Created July 1, 2008, Updated November 10, 2018