I am glad this came up too, my solution was a little different. We all know if you run the re-circulate option, you save energy on heat/AC but not having to heat/AC the outside, but as mentioned here, if you do that, the windows fog up quickly.
The best solution I've found is to put a manual block in front of the vent that brings in outside air so that when you vent fresh air, you really don't get but a tiny fraction of it. It is enough to defrost the window, but not so much that you burn a lot of extra energy trying to heat freezing outside air constantly. You can defrost a fogged window with just air ram mode (no heat or AC) but you don't want to freeze in the winter time (or melt in the summer time), so you need the HVAC to remove the moisture and control temperature.
When you press the defrost button, you'll notice it goes into an "auto" mode where it blast all the air on the front window and then does the AC or Heat based on your temperature settings. So if it is cold outside, the AC runs to remove moisture and the electric heat runs to warm up the cool air. When it is hot outside, you just get AC to remove moisture and keep the temperature down to what you set it for.
Moisture removal actually has a separate drain path, you don't have to technically be venting outside air into the cabin for this to work. Venting outside air just helps to speed up the process, but unfortunately, the Leaf can't re-circulate while on defrost. The air block mod fixes that issue, so you keep the inside car temperature to your liking, use a lot less energy, and the windows remain fog free without the need to clean, chemicals, layers, etc. The leaf has a dual defrost + floor air direction but you can't re-circulate in this mode, so you still waste extra energy when the outside temperature is very cold/hot. Another reason why I did the air dam on my system to limit how much "outside" air actually comes in.
I should probably write up a DIY for this with pictures, it would make much more sense. :mrgreen:
