Agreed it is the heater core also. It would be in your best interest to replace the EVAP core while you pull the dash for the heater core anyways because with the EVAP it's only a matter of time before that starts leaking.

 

If the windows are fogging up and there is a mildew smell coming from the hvac system, but the core is not leaking,(i checked it by removing the dash and hvac system and no leak) what else could cause this problem? Bad motors in the hvac system which does not give me outside air?

 

most likely the A/C drain is plugged up and causing the condesation to sit in the pan until it backs up into the hvac box, check to see if the drain through the firewall is open (a wire coathanger unbent will usually make short work of it)

 

I know this is an old forum, but I'm responding to this comment in case it helps someone currently. There is a cabin air filter in the Durangos. I have a 2015 and it's located behind the glove box. I take off my glove box door to access the filter.

 

Yours is a Third Gen, this is the first Gen forum. So far as I know, none of the first gens got a filter.