Did you have this problem with your old furnace. if not, any chance your old furnace was either an 80% efficient furnace, or if it was a 90%plus, did it get its combustion air from inside the house.
Next time you open the door, and there is ice on the storm door. Scrape as much of the ice off as possible, and weigh it. Is it just a few grams of ice, or is it a pound or more. Just a few grams. Your door is sealed okay. A pound, your door leaks a lot of air, whether you see daylight or not.
You need an HRV.
At 20.9°C and 57% RH. The moisuture will condense on any surface at a temp of 12.1°C.
When posting in certain forums, knowing your location will help others give better feedback/advice/solutions to your questions.