Here is a possible theory - When I start my car (2016 GTD) initially the heating and ventilation system doesn't do very much for about the first 5 seconds, as in next to sod all. After this initial time lapse, it all starts coming to life with the circulating fan cycling up and then the heating/ventilation process begins. I can only presume that the HVAC module has been setup to do this deliberately so as to ensure that the battery load is minimised as much as possible so as to ensure the maximum available capacity is there for the engine start up process and to allow the load on the electrics to settle before the ancillaries kick in properly? The downside is that in those 5 secs while sitting in the car (with doors and windows closed), is more than enough time (at this time of year) for the darned thing to mist up!! What I've started doing is unlock the car; hold my breath; open driver's door; get in; start car (still holding breath!) and count to five - circulating fan cycles up and then... b-r-e-a-t-h
I know, it is less than ideal. Wouldn't mind guessing that there is scope to adjust the HVAC module through VCDS or something similar...?