I purchased my house about 3 years ago and there is an over the range microwave that is set to recirculate. I am purchasing a new over the range microwave and would like to run duct work. the wall that the microwave on is shared with the drywalled/insulated but unheated garage. I really don't want to build a soffit in the kitchen to run it to an exterior wall. The only other option is to run it into the garage into loft of the garage and out the roof or run it along the wall of the garage and out the wall of the garage. A few questions:

1) I am concerned that if I run it in the garage that condensation would form in the pipe.

2) If I run it along the garage wall and out the the wall I would use a down pointing vent cap about 16" below the soffit vent. The concern I have with this scenario is the vent would be right outside of the back
door of my house. Is there any code issues with this?

Thanks for the feeback.

 

The path of least resistance would be to go straight up and thru the roof.

 

Termination must be ten feet from an opening.