Fireplace Flue Heat Recovery

Heat Extractors

• Heat extractors are located on chimney tops and draw extra heat from the flue, which is located at the top of the fireplace enclosure where the base of the chimney begins. They operate on different principles, including natural convection or radiation or with an electric blower, a process that pushes the heat from the flue gases downward from the flue and into the room. Heat extractors can reduce the force of the draft, which aids in starting the fire and keeping it going. To minimize this effect, install an extractor that has slightly more capacity than recommended for the size of the fireplace.

Flue Sealers

• Fireplace dampers are designed to open and close to keep debris, rain and snow from falling into the fireplace from the chimney as well as reduce the amount of cold air coming into the room. They are located below the flue of the chimney. Dampers frequently warp after the first exposure to hot fire, which lets cold air into the fireplace. Flue sealers are balloonlike devices inserted into open dampers and inflated to create a tight seal to prevent incoming air. They have a dangling handle to alert fire starters to remove them before building a fire. You can also fashion a homemade flue sealer by stuffing an old foam rubber pillow or cushion into heavy-duty trash bag and shoving it up the chimney. Whichever device you use, clean the flue first to ensure a tight seal and prevent soot falling on you when the sealer is removed.

Fireplace Inserts

• Although old-fashioned masonry fireplaces have charm, they are not particularly efficient at heating rooms. Installing a flue heat recovery device will improve their performance, but for maximum heat production, use a fireplace insert. Inserts fit inside the firebox or on the hearth, contain and circulate the fireplace heat and utilize a flue collar to prevent heat loss up the chimney, increasing their heating capacity to nearly as high as that of wood burning stoves.

Tips and Hints

• To prevent heat loss through flues when the fireplace is not being used on a regular basis, seal both the flue and the chimney top. Installing tempered glass doors on the front of the fireplace increases heat radiation, and heat-exchanger fans blow the hot fireplace air into the room. Once the fire is burning strong, crack a nearby window and lower the thermostat in the home to 50 or 55 degrees Fahrenheit to increase the heat flow from the fireplace.