Despite their undeniable aesthetic appeal, fireplaces are not desirable in terms of energy efficiency. Only about ten percent of the woods energy is transferred to the room as heat, the rest escapes up the chimney. When in use, the fireplace also pulls cold air into your home through cracks and leaks, and when not in use the brick and stone mass of most fireplaces readily conducts heat from your home to the outside. To minimize energy waste from the fireplace in your home, make sure the damper or flue is shut tightly when the fireplace is not in use. Consider the benefits of things like tempered glass doors, fireplace inserts that seal dormant openings, and heat exchangers that recover some of the energy that would otherwise be lost.