Programs used to model the energy performance of buildings are complex, often containing 10,000 to over 100,000 lines of computer language. A single typo, error or bug in any one of those lines can have devastating consequences on the accuracy of the program. A new ASHRAE standard provides a standardized procedure to ensure that such simulation programs are accurate.

ANSI/ASHRAE Standard 140-2001, Standard Method of Test for the Evaluation of Building Energy Analysis Computer Programs, specifies test procedures for evaluating the technical capabilities and ranges of applicability of computer programs that calculate the thermal performance of buildings and their hvac systems. "Until development of Standard 140, there was no standardized procedure for ensuring any given computer program was accurate and appropriate for any given building energy modeling problems," Ron Judkoff, chairman of the standard committee, said. "Engineers and architects would simply have to take the word of the software vendor on faith."

Programs covered by the method of testing are used by engineers and architects to model the energy performance of buildings. Such programs can be used in the design of new buildings to make them more energy efficient and in the retrofit of existing buildings to determine what energy related improvements will deliver the "most bang for the buck," Judkoff said.

The standard provides a framework for adding all elements of an overall validation methodology including analytical, comparative and empirical tests, Judkoff said.