I spent 6.5 hrs yesterday in low 20' temps, no sun, and about a 10 MPH breeze, what you could call "brisk". Just sitting there, not moving other the hand controls. My first extended cold weather job since the cabn and it was GREAT! The door still is not finished as per the gap in the rear and bottom, I am figuring ways to do that while still letting it slide easy (next time I'g go with a bi-fold/school bus type door, easier to fab and seal) but I found with the Espar heater it didn't matter much. It is easily big enough, and if and when the last two big gaps are sealed up, I will be able to wear just a t-shirt if I really want to piss off the guys I'm working with (they be wearing Carharts....)!
No issue with the windshield fogging either, a little at first, then none. I still have not decided on the final positioning of the heater outlet, so just have the 4' flex line I can aim wherever. I will never go back to a out in the open cab (much less a standup), sitting down, in the heat and out of the wind, just like a real crane operator, is where it's at!