FTIDOE is commercial version of the DOE-2 software that maintains 100% compatibility with the parent software project.  DOE-2 software has been validated by comparing its results with thermal and energy use measurements on actual buildings and with calculations.  Detailed information on some of the DOE-2 program validation efforts may be found in the following reports (available from the National Technical Information Service, 5285 Port Royal Road, Springfield, VA 22161):

• Comparison of DOE-2 with Measurements in the Pala Test Houses. Lawrence Berkeley National Laboratory, Report No. LBL-37979, 1995.
• DOE-2 Verification Project, Phase 1, Final Report. Los Alamos National Laboratory, Report No. LA-10649-MS, 1986.
• DOE-2 Verification Project, Phase 1, Interim Report. Los Alamos National Laboratory, Report No. LA-8295-MS, 1981

And from the Following reports from the Simulation Research Group at Lawrence Berkeley Laboratories.

• A Validation Suite for Fuel-Fired Furnace Models
  This e-mail address is being protected from spam bots, you need JavaScript enabled to view it and This e-mail address is being protected from spam bots, you need JavaScript enabled to view it , CANMET Energy Technology Center, NRC, Ottawa, Canada.
  Proc. Building Simulation 2003, 8th Int'l IBPSA Conference, Eindhoven, Netherlands, August 11-14, 2003.
• Validation Studies of the DOE-2 Building Engery Simulation Program -- Final Report
• Comparison of DOE-2 with Measurements in the PALA Test Houses
• Daylighting Simulation in DOE-2: Theory, Validation and Applications

 Additional validation reports and information can be found here.