The fireplace damper, or flue, is designed to help you use the warm air in your home as efficiently as possible. The lack of a chimney flue or damper sometimes causes the "chimney effect" in your home, which pulls outside up to half of the warm air in a room. The draft from having no damper or an open damper is almost like having an open window or an open door nearby. Being able to effectively use this type of fireplace is important to keeping your energy bills lower.
Use a draft eliminator or a chimney balloon. These inflatable products plug up the chimney so no drafts get in or warm air escapes when you do not have a fire in the fireplace. Insert it and inflate it with a few breaths of air. Let the air out and remove the balloon when you want to light a fire.
Add doors to your fireplace. Fireplace doors keep the soot more contained and also cut down on drafts from outside air. These can be used either with or without grate heaters, which blow the warm air from the fire back out into the room. Grate heaters can also be used without fireplace doors to increase your fireplace's energy efficiency.
Install an outdoor air intake near your fireplace. The chimney draws air from the room to fuel the combustion process, which can pull cold air through window drafts and doors in other rooms. An outdoor air intake draws the air from outside but closer to the fireplace, leaving alone the warm air already in your home.