I have a packet of condensation information that I have gathered to answer this question. One question I would ask is do you have high performance Glass such a LOW E. If you have this type of glass then it is good. The Low E product is doing its job. I will take an excerpt from an article printed in the "Seattle Times - written by Darrell Hay". {But to have so very little heat loss as to allow dew on the exterior is very impressive.}
I hope this helps.