From a recent conversation on load sizing here:
"1. Trace700 usually will run all 12 cooling design months and so it may happen that a zone does not peak in same month as the summer design OADB and this may be due to a higher solar component in the off month. So I always recommend, whether running Trace or E+, to run all 12 months for cooling design."
This seems to be a common reason for differences in cooling design sizing between Trace and OpenStudio/EnergyPlus.
The solution is to add in 'SummerDesignDay' 'SizingPeriod:DesignDay' objects for each month. From what I can tell, most .ddy files packaged with the TMY3 datasets include 'SizingPeriod:DesignDay' objects for only 1 month for heating and 1 month for cooling.
12 month design day data are available
So it's possible to do a 12-month cooling design load calc by taking the 12-month data, finding the appropriate 'SizingPeriod:DesignDay' objects for the site, copying them over to the .ddy file, and then reimporting that into OpenStudio.
It's a bit tedious.
Does anyone know if there is a .ddy dataset available online that includes 12-month 'SizingPeriod:DesignDay' objects for TMY3 locations?
