Regarding OpenStudio, I have found that the defaults for the Output Control Reporting Tolerances for heating and cooling are very low, 0.2K if you open an empty OpenStudio model. AHSRAE 90.1-2007 Addendum cr defines If I'm not mistaken, ASHRAE specifies the reporting tolerance as is to be set to half of the throttling range, or the room temperature difference between full heating and no heating or full cooling and no cooling. For many models, this would be closer to the 1-3K range depending on the system. Of course this doesn't solve any modeling issues that may be causing hours to be unmet but it is important to understand how the unmet hours are determined and that they are being reported correctly.