An oil filled heater is a safe way to go. They don't use all that much power once they're warmed up, and give you safe convective heat. Make sure you have decent circulation and you'll be fine. Depending on how cold it is and how well insulated the attic is, you might need two of them. Last winter it was cold(for here) down to about 14 at night and only in the 35-45 degree range during the day for a week. I had no problem maintaining a constant 65@ night and 70-75 in the day.