A traditional fireplace may look cozy, but it can let as much as 90 percent of the fire’s heat escape up the chimney. Install a wood fireplace insert and suddenly your fireplace does a lot more than just get by on looks alone.

In fact, depending on the model and installation, a wood fireplace insert can deliver as much as 80 percent of the fire’s heat into the room.

A wood fireplace insert is like a firebox, or wood stove, that sits inside the fireplace opening. Inserts are usually made from steel or cast iron and have glass doors so you still have the view of a roaring fire. Most inserts come equipped with a recirculating fan to gently, and quietly, blow the heated air into the room. Others even have a thermostat to control the temperature.

The heat efficiency of a wood fireplace insert comes from its design. Inserts have an inner and outer box with airspace between them that opens to the room. The unit works like a combustion chamber when a fire is lit, with cold air being drawn in and warmed between the two boxes before it is carried back out into the room. As the heated air goes out more air is drawn in to replace it, and so on. The recirculating fan, or blower as it is sometimes called, helps to make this process even more efficient.

Proper installation of the fireplace insert ensures maximum efficiency and safety. The National Fire Protection Association requires that inserts be installed with a positive connection between the appliance outlet and the flue liner of the chimney. All wood fireplace inserts must also comply with the Environmental Protection Act Phase II Clean Air Regulations. Each unit is tested for particulate emissions and to ensure it produces fewer than 7.6 grams per hour. An EPA-certified wood burning fireplace insert can reduce emissions from burning wood to almost nothing.

As with all fireplaces, a wood fireplace insert needs to be inspected regularly by a professional chimney sweep certified by the Chimney Safety Institute of America.