Need to use the air con and screen defroster button more, by the sound of it - see the handbbook - (page 4.28 for 2011 models)
And yes, silca sachets will help to remove excess buildup of mositure that should be overcome by regular use of the a/c
Oh, and make sure the two cabin sensors are not covered over.
If the problem still persists the a/c may need recharging - again that may be down to lack of use throughout the year,