Had a 2013 CX-5, no problems getting and keeping windows clear. Got a "new" used 2016 and I can't keep the windows clear, not just the windshield. It's Houston, so it's hot and humid. I've tried using the defroster (makes the problem worse), raising the interior temp, switching to outside air and nothing seems to work. HELP

 

defroster is pointless as it doesn't have a pre heater and due to the efficient running of the engine it doesn't produce enough natural heat to defrost from the engine at start up.
try cleaning your windows first with some autoglym glass cleaner and if it still has the issue use something like an anti fogger like rainx

 

Hmmm, mines a 2016 GT. It’s also very humid and hot (102 deg yesterday) here in Charlotte and I’m not having that issue. I leave the HVAC set on auto year round.

 

I think the key words are "new used " could be a product the dealer has used on the internal glass or they have never been cleaned throughly enough
I'm in the UK and that tends to be the only reasons I get issues with all fogging in my cars and vans
Normally traffic and people's breath putting a film on the inside of glass.