sink vent into attic only and not through the roof

I have to run a new vent from the kitchen sink because of a remodel. Is there any reason why I can't just terminate the pipe in the attic of the house and not go through the roof? There are plenty of roof vents so no problem with air.

Sewer gas from the main sewer line comes up the vent pipes. The sewer gas smell will migrate back into the house from the attic, regardless of attic ventilation.

Getting it to the attic is usually the hard part. Once you get to that point, just take it through the roof. It needs to go above the roof to meet code and it is a better option than using an AAV. An AAV could work on your vent in the attic, but taking the vent through the roof is a better solution. If it is just a matter that you don't want to go on the roof, get a roofing guy out there and he can install what you need (and the cost shouldn't be much either).

A AAV can only be used if there is a vent through the roof somewhere in the system to let sewer gas out of the home, and to allow for positive and negative pressures in the system.
An AAV only deals with negative.
You still need a pipe through the roof.

Correct. I assume that he already has a vent through the roof for the rest of his system. Anyway, that can be another option: tie into an existing VTR inside the attic assuming you already have adequate venting for the rest of your system.

We don't know your layout and you didn't mention why you were trying to avoid going through the roof, but these are your options:

1. new vent through the roof for the sink
2. tie into an existing vent
3. use an AAV (assuming there is already a vent(s) for your system)

Options 1 and 2 are the better options. In fact, to make option 3 work, you could just as easily do option 2 instead.

I once had a customer with a terrible sewer gas problem. I discovered that a vent had not been extended through the roof when the roof had been changed years ago. Under certain conditions the house created a "negative" air flow and sucked air from the attic down the walls and out through any openings, such as electrical outlets.