What relative humidity % should be used for an interior space to determine if condensation is a risk?

[Scott]

What relative humidity % should be used for an interior space to determine if condensation is a risk?  Should I is use an online dew point calculator and play around with various % at the outer edges of the comfort zone, say 35% and 65%, as worst case scenarios?  

I have modeled a roof / wall in THERM 7.8.8 and used the standard exterior boundary condition temperature of 14 deg F, and interior boundary condition temperature of 68 deg F.  

Therm model attached - any insight would be appreciated.  Thanks

Scott