I built one for a client, the electric heater came with a timer. A gap under the door is also recommended too, if I remember correctly. What an ordeal that was, ugh. Not the building the client. He had at least 30k into it, a near lawsuit from the neighbors, a timber framer from England, who was amazing, but still, and he called off the job twice before we broke ground. Lol. Called him, pull the plug Doug. People are funny, sometimes dealing with them is a harder than the work itself. Some people just want to hang out, it all pays the same.