Kitchen vent outside
 

Does anyone have experience with a contractor to run the kitchen vent outside and about how much it costs?

/What makes you think they don't vent outside? Pretty sure they do.

If you are talking about the Microwave "vent", mine goes to the attic (2013 vintage gardenia). I do have a concern about the eventual buildup of cooking fumes in the attic, however, venting through the roof could present staining problems there also.....

You could always run a vent line to the gable end of the roof then it goes through the wall instead of the roof. I don't know if the fan in the range hood/microwave is strong enough to really push the air that far but at least the cooking fumes wouldn't be in the attic if that is were they are going. I am currently renting a courtyard villa and I just went and looked. The microwave fan is cycling through a filter it doesn't vent anyplace. I will have to check it out when I get in my house.

Since your roof has ridge vents...
 

they'll be no build up of fumes...as to staining...we'll all be dead before it's even a hint of a concern...

That is interesting. My 2014 Gardenia vents outside through the roof.

I wouldn't think it vents into the attic. Look at your roof just above the wall were the fan is ,or even the outside wall

You should see two silver vents on the roof. One is for the kitchen fan and the other is for the dryer.

To all, I will look at the roof, but the house plans do not indicate a vent through the roof, so I could be mistaken, and if so, I am very sorry for any misinformation. Will check tomorrow.