Our wood burning fireplace is covered by a glass door unit with a built in heat circulating grate. The air exchange is at the bottom- cold air drawn in and heated air blown out. Between the air intake/exhaust (and under the glass doors) is a vent. There is also a vent above the glass doors. We burn wood wth both vents open to draw in air to fuel the fire.

Does anyone know if we should (to be most energy efficient) leave both of these vents open. i.e. does leaving the bottom vent open simply allow the hot air to be sucked back in ? Obviously we have to let some air get in there.

thanks

Mike