This paper is based on findings resulting from ASHRAE Research Project RP-1477.

In this paper, the results a series of sensitivity analyses are presented and discussed to assess the impact of the selection methodology to generate a typical weather year suitable for energy analysis of building systems. In particular, the impact of weighting factors associated with various weather variables was investigated. Moreover, the effect of the length of recorded data used to generate the typical year was evaluated. The analysis is carried out for 10 US sites for which measured weather data are reported for at least 30 years. The results indicate that using the TMY2 selection approach it was better to assign more weight to global solar radiation than to direct normal radiation and that 15 years of recorded data would be sufficient to generate a typical weather year.

Units: SI