Fireplaces that warm your home and wallet
Fireplaces rank among the top three features desired by new homeowners, according to the National Association of Home Builders, and it's easy to understand why — there's nothing quite like a fireplace to create the perfect ambience in a home. But your love affair with the fireplace would definitely cool if you knew how much of your energy dollars were going up in smoke.
According to the U.S. Department of Energy, the aesthetic appeal of a typical wood-burning fireplace with an open front is more than offset by its poor performance in terms of energy efficiency. A fireplace is only 10 percent efficient at converting wood to energy and delivering it to a room, and when it's operating, it actually increases the infiltration of cold air by creating a partial vacuum within the house. More surprising, convective (moving air) heat losses at the beginning and end of the burn are greater than the radiant heat provided by the fire.
The problems don't stop there. Most fireplaces are situated on exterior walls and are made up of large masses of masonry that are poor thermal insulators. As a result, they readily conduct inside heat outdoors. What's more, if you think a fireplace is a short-term solution to a power outage, you're wrong. A fireplace "can actually make your home colder than if you never built a fire in the first place," says Marni Rader, marketing director for Travis Industries, a Washington-based manufacturer of fireplaces, stoves and inserts.
All this is sure to send a chill down any fireplace owner's spine. Fortunately, there's good news for fireplace fans in the form of energy-efficient add-ons and improved models.
Upgrading existing fireplaces
Open fireplaces are designed to draw air from the room to send smoke and combustion gases up the chimney, but that air draw is what makes fireplaces inefficient — especially in the winter when they draw warm, conditioned air up the chimney and pull cold outside air into the room. Glass doors can slow the air draw (combustion air is provided by vents along the sides or bottom of the fireplace), but they also can reduce the amount of radiant heat provided to the room. As a result, they're limited in their ability to improve a fireplace's efficiency.
A better option is to install a fireplace insert, which is essentially a metal wood stove designed to fit into a conventional open fireplace. Inserts can be flush-mounted or extend onto the hearth, and they can burn wood, pellets or gas fuel. Best of all, thanks to an outer shell that circulates air, heating it and delivering it back to the room, they can make a significant difference in energy efficiency. "The average open 36-inch fireplace has about 400 cfm (cubic feet per minute) draw of air out of the house," Rader says. "Using a fireplace insert slows that air draw way down. It actually increases heating efficiency from 10 percent to 80 percent." Inserts must be certified by the EPA, which ensures their efficiency and effectiveness. In addition, the National Fire Protection Association requires that the insert be properly connected to the chimney's flue liner to prevent the buildup of creosote, which can be a fire hazard. A number of companies, including Regency, Jotul North America, Lennox, Rinnai, Quadra-Fire, Vermont Castings and Blaze King, make energy-efficient inserts.
Gas direct-vent inserts are extremely efficient because they use outside air for combustion, so no heat is drawn out of the home. Air intake and exhaust are provided by flexible metal tubes that run up the chimney. The tubes connect to the chimney cap to keep the two channels separate. Chad Hendrickson, product manager for Minnesota-based Heat & Glo, notes that direct-vent gas fireplace inserts have "a sealed combustion firebox, which provides superior heating efficiency while preventing spillage of combustion gases into the home. Add to these advantages the fact that chopping and hauling wood is (time-consuming), and you can see why they are growing in popularity."
New fireplace options
If you're planning to build a new fireplace, either in an existing home or a new one, there are several energy-efficient options, including traditional wood-burning units and direct-vent gas fireplaces, as well as cutting-edge developments like hydrogen-burning fireplaces.
If you long for a traditional wood-burning fireplace, consider an EPA-certified model, like the 7100 from Quadra-Fire. The 7100's efficient design includes an automatic combustion control system that provides maximum air at startup, and then automatically slows down the burn to a preset level after the fire is established.
This improves efficiency and extends burn time. It's paired with a massive firebox, so homeowners can burn a fire up to 16 hours with no poking, stoking or reloading. The air to the fire is supplied from the outside via a duct, which reduces negative pressure inside the home and prevents air infiltration through gaps in the building envelope. Because of its efficient design, the 7100 can heat a 3,500-square-foot home, via up to two remote heat-zone vents. This enables homeowners to change the fireplace from a zone heater to a whole-house heater by directing heat to other rooms, such as bedrooms or bathrooms. The Fireplace Xtrordinair Elite series by Travis Industries offers the look of a traditional masonry-style fireplace combined with the efficiency of a wood stove. "All of our wood-burning products are EPA-rated, which means they meet stringent combustion efficiency standards," Rader says. "(The design) reduces the amount of fuel consumed and the amount of pollutants produced."
Another option is a heat-retaining soapstone fireplace, also known as a masonry heater. Widely used in Europe, these fireplaces have yet to find widespread acceptance in the United States, though sales have grown steadily. The efficiency of a soapstone fireplace, manufactured by companies such as Finland-based Tulikivi, is due to its ability to retain most of the thermal energy produced by a fire, instead of allowing it to escape up the chimney. The fireplace then radiates the heat evenly and steadily long after the fire has gone out.
The Tulikivi line includes radiant, energy-efficient soapstone fireplaces, bake ovens and cook stoves, available through U.S. distributors. Similarly, Biofire Kachelofen radiant-heat fireplaces, which are manufactured in Austria and available in the United States, offer a combustion efficiency in the 90 percent range, providing 12 hours of heat from one small fire that burns for about an hour, says Heinz Flurer, president of the company. The wood burns at a high temperature, resulting in a complete, environmentally friendly burn. The core of a Biofire Kachelofen consists of a refractory firebox and a network of refractory passageways that enable the fireplace to absorb the heat from the fire quickly and release it evenly during the next 12 hours. Each fireplace is individually engineered and designed to meet a chimney's draft capabilities and the homeowner's design requirements.
When it comes to choosing between traditional wood-burning and direct-vent gas fireplaces, the latter have several key advantages. They give off very few particulates, so in general they're more eco-friendly than wood-burning fireplaces. There's no need for a chimney to vent combustion byproducts, which means no heat loss up the stack. They're easy to use, since there's no need to buy, chop or stoke them with wood. There's also no need to scoop ashes, since these fireplaces produce none. They are fairly simple to install and inexpensive to operate, and they come in a number of styles and sizes. Direct-vent fireplaces are rated in BTUs per hour (1 BTU is defined as the amount of heat required to raise 1 pound of water 1 degree Fahrenheit). The Majestic Designer series of direct-vent gas fireplaces from Vermont Castings, for example, puts out between 30,000 and 38,000 BTUs per hour, which can efficiently heat an entire smaller home, or one or two spacious rooms. (The heat loss for a typical home ranges from 40,000 to 120,000 BTUs per hour, depending on the home's size and insulation, as well as the climate.) The company's Chateau series, which are reminiscent of open Rumford-style wood fireplaces, are rated at between 34,000 and 46,000 BTUs per hour.
Direct-vent gas fireplaces do not require a chimney to carry away combustion gases. Instead, they use outside air for combustion, and can vent relatively cool combustion gases either vertically (through the roof) or horizontally (through a wall) via piping and a specially designed termination cap, as well as up a standard chimney flue. Models are available for installation in just about any area of the home. The Infinity gas fireplace from Heat & Glo, for example, has a draft assist system that enables vent piping of up to 90 feet with up to eight elbows, so the fireplace can be installed in even the trickiest locations. The Soulstice model, meanwhile, is a compact unit, rated at 12,000 to 17,500 BTUs per hour, that's designed for installation in smaller rooms such as bedrooms. Another option for homeowners is Heatilator's FreshAir Fireplace, which operates in conjunction with a heat recovery ventilator to heat the home with fresh air while expelling stale air. It recovers more than 80 percent of the heat normally wasted through a fireplace's flue vent, Hendrickson notes, by transferring heat "from the exhaust gases to incoming fresh air, which can pick up another 100 degrees on its way to a home's living areas." Most direct-vent systems are easily controlled with either switches on the fireplace or via remote controls. Some can be set with automatic shutoff times, and some have more sophisticated management systems.
The dual challenge of improving fireplace energy efficiency while reducing pollution is on the front burner for industry experts, says Thomas Stroud, senior manager of codes and standards for the Hearth, Patio & Barbecue Association in Virginia. Upgrading fireplace efficiency should be on every homeowner's list of improvements as well. By being aware of your options and choosing wisely, you can ensure that your energy dollars aren't going up in smoke.