I'd start by bringing the problem to your dealer unless they have tried and failed to remedy the problem. If they can't help, Jeep Cares is a member on this site. You can send them a PM.
If Tripod is wrong, it could be that something is blocking your defroster from working. Leaves from autumn? Ice in the intake?
I notice that these little engines take awhile to warm up and when its below zero F, if I run my heater on high the engine actually loses temperature. Maybe if you backed the fan down a notch or two the air from the defroster would be warmer and do a better job.
If my windshield is frozen over I'll start my car and put the defroster on the warmest setting and lowest speed. I don't want to hit frozen glass with really hot air. Never happened to me, but I've heard of people cracking their windshields.