I know this is an old thread, but Im new and ran across this same problem and found the solution. The issue in my 2015 is that if you have the defroster on no mater what the temp is set at it blows hot air out of all the vents to include side vents to some extent even with the fan on low. We found it by accident. Switched it off of defrost and the car cooled off inside like it should.

I don't know about hot hot air but at least is going to be "filtered air" as in removing the humidity to the front windshield, that is why on humid/rainy days when you turn the a/c on you might develop humidity on the front windshield but once you turn it to defrost the windshield, the humidity disappears. When you turn the front defroster on it turns the compressor on, thus the "filtering effect" while the compressor off it will not defog your windshield (unless in cold climate or regions).
I normally don't want to drive around sucking everyone's else fumes and funny odors, so I keep my vents in recycling mode at all times with the compressor turned off (during winter and very cold days). A/C on while in recycle mode keeps the outside air out and the compressor works less by cooling air that has been previously cooled and it works less because it does not have to removed so much humidity since it was previously done.
Remember, the function (and main) of an a/c system is to remove the humidity of the air then is to cool it or to remove heat from it.
"An air conditioner was given its name for good reason. This is because it actually “conditions” the air by dehumidifying it. Humidity permeates moisture in the air which often results in heat being absorbed even more so. This is why when the humidity index is high, it can feel as if the temperature in the environment is even greater than it really is"
How Does an A/C Unit Work?