A couple of feet in our upstairs hallway wall is adjacent to the chimney and is 6-7 degrees warmer than the rest of the upstairs when the pellet stove is running. Is it acceptable to cut a hole and put a wall register in to allow some of the chimney heat to radiate into the upstairs? I know some people that have vents like this but wasnt sure about them being to code. Tried searching quite a bit but not sure the terms I should use. I would want to tightly seal it when the stove isn't used.