Fipronil is in Termidor which is about the most popular product used in the structural pest control industry. Also in Frontline. It is a very good ingredient for most ants.
Carpenter ants do prefer rotting wood and will definitely start there. They are not above attacking unrotted wood (ie, your house) once they get going. They are worse on houses than termites in the Pacific NW. I've seen them chew into a stack of plywood burrowing into each board.
But for sure, get under your house if you can and see if there is any wet wood touching the ground or poking through the vapor barrier. Or under porch/deck. As mentioned firewood is a great attractor for them. I cringe every time I see someone stack their winter wood up against the house.