Fireplaces are an often overlooked source for reducing heating and cooling cost. Fireplaces are vented to the outside by the chimney. This is an opening of several square feed for flue gases and smoke to escape. This is necessary for the fireplace to operate safely and effectively. Unfortunately this is also potentially one of the largest openings in your house to loose your expensive heated and air conditioned air.
The chimney was originally installed with a door to reduce this air flow when not in use. This chimney damper is a heavy steel door that you should close when the fireplace isn't in use to prevent drafts through the chimney. At best the damper will act as a small window opening to the outside. In many cases it will act as a door wide open to the outside. Over time these dampers can break, warp or otherwise not close properly. This can be detected by smoke or other odors coming in throught the chimney, and cold drafts in the winter. When you fell cold drafts through the chimney in the winter you are also loosing expensive heat up the chimney.
There are a couple of options to fix this. If the fireplace is no longer being used, consider having a professional cap the chimney. This will permanently close the window to the outside. Many houses built with fireplaces have never been used or are no longer being used.
Another cheaper and less permanent option is an inflatable chimney plug. These chimney plugs (also known as Chimney Balloon (tm) or Chimney Pillows (tm)) act like a large, heavy duty inflatable fireplace damper. When not in use, these plugs are installed in the top of the chimney and plug off the chimney opening like a cork. When the fireplace is going to be used, the plug is deflated, removed and set aside for later.
Chimney plugs or balloons are durable, effective and inexpensive. These plugs can easily pay for themselves in one heating season.