An ASHRAE Standard Method of Test is being developed for systematically testing whole-building energy simulation models and diagnosing the sources of predictive disagreement. The procedure, ASHRAE Proposed Standard 140P, Standard Method of Test for the Evaluation of Building Energy Analysis Computer Programs, uses the"comparative testing" approach. In this method, a set of test cases is carefully defined so that equivalent input files can be developed for a variety of detailed and simplified whole building energy simulation programs. Results are then generated and compared using a variety of detailed simulation programs and/or different versions of one simulation program.

In the proposed ASHRAE Standard 140P, the tests progress systematically from extremely simple to relatively realistic. The more realistic cases, while geometrically simple, test the ability of the programs to model such combined effects as thermal mass, direct solar gain windows, window shading devices, internally generated heat, infiltration, sunspaces, and dead-band and set-back thermostat control. The more simplified cases facilitate diagnosis by allowing excitation of particular heat transfer mechanisms. Output values for the cases, such as annual loads, annual maximum and minimum temperatures, peak loads, and some hourly data, are compared and used in conjunction with diagnostic logic to determine the algorithms responsible for prediction differences.

Field trials of the method were conducted with a number of detailed, state-of-the-art programs by researchers from nations participating in International Energy Agency (IEA) Solar Heating and Cooling (SHC) Programme Task 12b and Buildings and Community Systems (BCS) Annex 21c. The procedure was very effective at revealing bugs, faulty algorithms, and input errors in a group of building energy simulation programs that may be considered among the world's best. The final output data from the simulation programs used for the field trials can be used as reference ranges for comparing and diagnosing other detailed or simplified design tools.

ASHRAE Standard Project Committee 140P adopted IEA BESTEST, International Energy Agency Building Energy Simulation Test and Diagnostic Method (Judkoff and Neymark 1995a). IEA BESTEST, which is in the public domain, was developed in cooperation with the IEA SHC Task 12b and BCS Annex 21c. Also included is a description of changes to IEA BESTEST by SPC 140P so that it could be adopted into Standard 140P.

Units: SI