Paradoxically, a basic fireplace is a poor way to heat a home: Most of the heat goes up the flue, a lot of toxic and corrosive gases are released in combustion, and without the proper setup the furnace-heated air in the house is also drawn right up the flue.
Fortunately, these concerns have been addressed by the fireplace and stove industry, making many of today's models as efficient as they are attractive.
Direct-vent and vent-free gas-fueled fireplaces have much greater efficiency than a vented gas fireplace.
Direct vent appliances exhaust connect to the outdoors with a short pipe, and use a single vent to exhaust combustion gases; often, the same vent contains an inner sleeve that draws in fresh air for combustion.
Vent-free appliances are designed to produce such a low amount of carbon monoxide that they can be used safely without a vent to the outside. Some states restrict the installation of vent-less fireplaces, so check with your local building department to find out where you can use this kind of fireplace.
Wood-burning fireplace efficiency is often determined at installation. That means making changes to improve efficiency can be both difficult and expensive.
One additional way to improve the efficiency is to install a wood-burning stove insert (see page 4 of this story). While the fireplace will run much more efficiently, the appearance will change drastically.
If you have an older fireplace, be sure to maintain it well, burn only well-seasoned hardwoods, and use the glass doors, if the fireplace has them.
Browse these tips for smart fireplace installation from the the Hearth, Patio & Barbeque Association:
- Install the fireplace and chimney inside the building envelope rather than creating a bump-out to house them.
- Install the chimney so it exits the roof at or near the highest point on the house. That shortens the amount of flue exposed to the weather.
- Use straight chimney systems. Every bend in the chimney, even a slight one, slows airflow and reduces efficiency.
- Install and use glass doors. Along with an outside air source, glass doors confine the combustion to the firebox, drawing in less air from the room.
- Avoid very short chimney systems. Fireplaces need a flue of the right length to maximize the draw (the ability of a fireplace to pull air, heat, and smoke up the chimney and vent them to the outside).
Ultra-efficient fireplaces with the heat output of a furnace are an option for those truly committed to using a fireplace to heat a home. Because of the intense heat these fireplaces generate, correct installation is crucial.
Outside the Firebox
Some of the heat from a fireplace simply dissipates through the sides of the firebox. Many pre-fabricated fireplaces, both gas- and wood-fueled, enclose the firebox with a secondary box and a venting system. Air circulates air around the firebox, capturing that heat and releasing it back into the room; adding a fan increases the air circulation.
EPA-certified fireplaces and fireplace inserts burn the wood at maximum efficiency and recover as much heat as possible.
This certification is relatively new, so older fireplaces, both masonry and prefabricated, were not designed to meet these specifications; if the fireplace in your home is more than 20 years old, a newer fireplace may be a good choice. Have your fireplace evaluated by a qualified fireplace professional.
Masonry HeatersMassive stone fireplaces like this are good choices in cold climates. Image courtesy of Tulikivi.
First, the physics: Metal heats quickly and loses that heat rapidly. Masonry warms up slowly and releases heat gradually. That's an important consideration if you're planning to use a fireplace or stove to heat your home.
A wood-burning stove surrounded by masonry will produce a nice, even heat for hours, even with a small fire. This choice can't be taken lightly: masonry heaters are heavy and expensive. In northern states, however, this kind of stove can be a wise, even economical, choice. After all, most of these heaters were developed in Scandinavia.
One way to improve the efficiency of an existing fireplace is to install a fireplace insert. An insert is, essentially, a mini-stove that slips into the existing space.
Fuel options run the gamut -- wood, gas, pellets, electricity -- so you can readily change the fuel source to suit your needs. Wood-, gas-, or pellet-fueled inserts may require that the flue be adapted, but an electric insert requires that you simply close off the flue.
Inserts are generally designed to operate at maximum fuel efficiency, that means you could see dramatic improvement in heat generation and fuel consumption, especially if you choose an EPA-Certified insert.
Another popular choice is to simply put an efficient wood-burning stove in a fireplace opening. This choice does affect the flue, so a little extra work may be required. But the end result can be a quaint and attractive fireplace that warms the room.