PH-79-08-1 -- The Representatitveness of TRY Data in Predicting Mean Annual Heating and Cooling Requirements

Building designers must accurately compute the average annual energy requirements of buildings in order to optimize energy conserving measures. The Test Reference Year (TRY) hourly climate data tapes provided by National Oceanic and Atmospheric Administration (NOAA) are being used by engineers for computing building energy requirements in a large number of U.S. locations. The tapes were originally selected to avoid extreme months rather than to represent average, or long-term, climate; the appropriateness of using TRY tapes for the latter purpose should be determined and possible errors quantified. The magnitude of these errors would determine whether or not building energy usage predictions based on analyses using the TRY tapes can be expected to reflect long-term performance, and whether such analyses can be used for making economic decisions on energy conservation options.

The report describes in detail the Test Reference Year data tapes for computerized building energy calculations. The TRY tapes accuracy in representing the average long-term climate is tested by comparing the degree days and average temperatures calculated from the TRY tapes themselves to the National Weather Services long-term records for these parameters. Degree days to a wide range of different base temperatures have also been investigated for each TRY tape.

Heating and cooling requirements calculated from the TRY tapes may be adjusted to more closely represent those of the long-term climate at each location. The percent difference between TRY calculated degree days and long-term degree days is used to adjust the energy values. The degree-day bases used in this report are applicable to a single family ranchstyle house designed to be representative of current construction.

Citation: ASHRAE Transactions, Volume 85, Part 1, Philadelphia, PA



Product Code(s): D-PH-79-09-1