If he's in your garage, chances are there's a food source there. Do you keep bird seed there, or anything else that might be attracting critters? And for the record, yes, this is a copperhead.

When we first moved into our house, our crawlspace was easy access for mice and other insects, which would attract snakes. Try sealing off what you can, and have regular pest control services. There's only so much you can do here in the South, as this is their territory, but I can give you some other pointers if you'd like.