scope:

ASHRAE Research project 1273-RP recalculated and expanded the tables of climatic design conditions in the ASHRAE Handbook-Fundamentals. These tables provide values of dry-bulb, wet-bulb, and dew-point temperature, enthalpy, and wind speed at various frequencies of occurrence over annual and monthlyperiods and for some of these, mean coincident values of other variables of interest. Compared to the previous edition of the Handbook, the new tables include additional elements and are calculated for a much greater number of stations over a longerperiod of record. This paper explains the procedure used to compute the design conditions, the data sources used, the techniques employed to screen out erroneous data, and the completeness criteria required by the calculation. It also provides a summary of the stations included in the 2005 Handbook and a brief description of how the new values compare to thosepublishedin the 2001 edition. Finally, thepaperprovides an overview of the capability of the Weather Data Viewer, a companion CD-ROM that gives full access to the frequency information used to compile the tables of climatic design conditions.