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Listed below are frequently asked questions regarding SUNREL software. This list will be updated periodically with more questions and answers.


Q: Can SUNREL run on computer platforms other than PCs running Windows?

A: The user interface, RunSUNREL is a Windows based program and can only run in Window 95 and higher. SUNREL is a written entirely in ANSI Fortran and can be compiled to run on any platform by command line. If you would like to run SUNREL on platforms other than Windows, please contact the Webmaster.

Q: Has SUNREL been through the BESTEST diagnostic process?

A: Yes, SUNREL has been successfully through the entire IEA BESTEST diagnostic process and through some of the HERS BESTEST process. Different versions of SERI-RES, which is the basis for SUNREL, were used as the baseline programs in the process of developing the BESTEST procedures.


Q: Where do I get weather files to use with SUNREL?

A: SUNREL can read TMY, TMY2, BLAST, and SUNREL weather files. TMY2 weather files for 239 locations in the U.S. are available online. SUNREL weather files are simple column delimited files that can be easily created with your own weather data. The SUNREL Technical Reference Manual contains the format of these files.

Technical Questions

Q: Does SUNREL model HVAC equipment performance?

A: No, the current version of SUNREL (anything below 2.0) does not model HVAC equipment performance. The program only calculates the loads that an HVAC system would see. However, work is under way to develop algorithms for modeling HVAC systems in SUNREL. These upgrades should be available by the end of August 2004. The algorithms have been developed to be very flexible and easy to use. The first release with HVAC algorithms will include models for fans, pumps, furnaces, direct expansion air-conditioning units, duct and piping losses, and simple economic calculations.

Q: What are the AMBIENT and GROUND zones?

A: AMBIENT and GROUND are SUNREL keywords that can be input for backside of Walls. AMBIENT tells SUNREL to model the exterior conditions of the wall using only the outdoor air temperature from the weather file (i.e. no solar or wind effects are modeled). This option is useful when modeling surfaces that do not see the sun such as an elevated floor. The GROUND keyword tells SUNREL to model the exterior conditions of this wall using the Ground Temperature specified in the RUNS input section.

Q: I am having a hard time understanding exactly how to use the leakage fraction % in the "wall" section... what is it, and what kind of number can you assign there? The same goes for the leakage fraction in the "exterior surfaces" section.

A: There are two methods of modeling infiltration: (1) with a fixed air change per hour, which can be scheduled; or (2) with an effective leakage area (ELA), which calculates the infiltration every time step. If you input an ELA, the leakage area can be divided among the walls of the zone by the user with the wall and surface leakage fractions or distributed evenly by the program if left blank. The wall leakage fraction is for interior walls and the surface leakage fraction is for exterior walls (This is a bit confusing). The leakage fraction is the fraction of the ELA for the zone that is in this wall or surface (roofs and floors are considered walls). The total of the leakage fractions for all the walls and surfaces in a zone must add up to 100 or if you leave one or more values blank, the program will assign the remaining fraction to these walls. Remember that exterior walls must be assigned to an exterior surface for solar calculations or to the SUNREL zone AMBIENT for no solar calculations. In the case of using the AMBIENT zone for the backside of an exterior wall, input the leakage fraction in the Walls section. The AMBIENT zone is useful for exterior walls that do no see the sun or have little effect from the sun.

Q: How are glazing data files generated using Window 4.1 or Window 5.X?

A: Window 4.1 and 5.1 and higher are window analysis programs developed by the Lawrence Berkeley National Laboratory. The latest version of the software is available online, free of charge. Note that Window 5.0 does not contain the proper glazing data report and cannot be used with SUNREL. In Window 5.1 and 5.2, the proper data file can be created from the Window library view or the Glazing System library view. Click on the "Report" button and select the detailed report. Only Window 5.1 and 5.2 have been tested with SUNREL, later versions may not have this feature or the report format may change.