There is some evidence they got in through a window vent
They don't get it in. Typically they live in the wall of your home and go outside to get food. In the spring and fall, especially with the unusually warm weather. They should be going dormant, but it is too warm. So they can't find food outside, instead they look inside and that is when you find them. Once winter comes they will go away. The challenge is finding their nest. These are really amazing insects. In the summer you should be able to find one or more spots where they are leaving the house to get food. You can watch them stream out in a single file line across a phone line or some other feature of the house.
To get rid of them, the trick used is to blow powered boric acid into the cavity between the outside siding and the wall. Like this the ants must pass through it to get outside, this eventually kills the nest. I had my house treated a few years back, it took a while to take full effect but I haven't seen them inside for a while now.
You need to find an exterminator that has proper knowledge of ants. Because what often happens is the exterminator comes in spray a bit around the floor boards charges you a few hundred dollars and leaves. You find a few dead ants, then winter comes, ants are gone, because of winter not the spraying. So you're happy until the spring when the ants come back because the exterminator was useless.
Good luck it is a real pain in "the you know what" to deal with.
I played an upscale Malibu wedding (lots of celebs) with an electric viola player a few years ago; just keys & viola.
We played several Bach & Scarlatti fugues. The electric harpsichord parts played a minor, or major 3rd respectively, above/below the electric viola sounded so fantastic I couldn't stop laughing the whole time.