Warming yourself by a fire is one of life’s simple pleasures. Unfortunately, traditional fireplaces are notoriously inefficient. They draw huge amounts of air from rooms they’re supposed to be heating to fuel the fire with oxygen and sometimes lose more heat than they produce. At best, an open fireplace is only 10 percent efficient. Far better options are wood stoves, pellet stoves and fireplace inserts. Or if you’re building a new home, a simple masonry heater can carry you through the winter months.
Wood heat may seem old-fashioned, but it offers many benefits over conventional home-heating fuels. First, wood is renewable and abundant in many locations-even in cities, where mountains of wood pallets, shipping crates, construction-site scrap lumber (make sure it’s chemical free) and tree trimmings are readily available.
Wood is sometimes viewed as the black sheep of the renewable energy family because it produces the most air pollution of the many types of renewable energy. However, improvements in wood-burning technology have made it a much better choice today than in the past. Burning wood in the new generation of clean, efficient stoves can help reduce emissions of carbon dioxide, the principal greenhouse gas that leads to global warming. And, when sustainably harvested wood replaces fossil fuels, we can reduce our reliance on foreign oil.
Wood stove wisdom
Wood stoves come in many shapes, sizes, styles and colors. Those designed for serious home heating fall into two categories: radiant and circulating. Radiant woodstoves are made from welded steel or cast iron. These stoves’ walls absorb the fire’s heat and radiate it into the room.
Circulating stoves consist of a welded-steel or cast-iron shell surrounded by an air space and a second layer of metal. The fire heats the inner shell, warming the air space. Heated air flows from this space either passively (by convection) or actively (by a fan).
Both radiant and circulating stoves achieve rather impressive combustion efficiencies-from 60 to 80 percent. (A stove’s combustion efficiency is the percentage of the fuel’s potential energy it releases.) Radiant and circulating stoves achieve their high efficiencies, in part, by specially designed openings in the stove that introduce air into the combustion chamber at strategic locations. The more air-and hence oxygen-that’s available, the more efficient combustion becomes.
To further boost efficiency, some wood stoves pass exhaust gases through ceramic honeycomb devices called catalytic burners. The catalytic burner ignites the unburned hydrocarbons the wood gives off, thereby producing a significant amount of energy that would otherwise be wasted. This improves overall heat production, but catalytic burners add several hundred dollars to the stove’s cost and must be replaced every three to six years.
A less expensive efficiency enhancement is an internal baffle, which directs exhaust gases back over the fire, where they ignite, wringing more heat from the wood. Both baffles and catalytic burners increase combustion efficiency and result in cleaner burning stoves-which means less air pollution and less creosote buildup on the flue pipe. (Creosote is a mixture of organic compounds that deposits inside the flue pipe and can catch fire.)
Pellets: The “other” wood
Those who want to avoid cutting or hauling wood might consider a pellet stove, which burns pellets made of corn or compressed sawdust from lumber-mill waste. You can purchase the pellets from local hardware or discount stores. Then, simply pour the pellets into the stove’s hopper, where they’re fed into the fire as needed by an electric auger.
Updating your old fireplace
If you live in a home with an old fireplace, consider a fireplace insert-a steel or cast-iron box that fits neatly into the opening. Most models achieve combustion efficiencies around 70 percent.
A fireplace insert costs as much as a wood stove, but because it utilizes the existing chimney-provided the chimney’s in good shape-it costs less to install. Select a model that comes with a blower (fan) that circulates warm air around the fireplace combustion chamber and moves it quickly into the adjoining room.
Hot stones at home
Ideal for new home construction, a masonry heater is a super-efficient, wood-burning stove that extracts more energy from wood than conventional wood stoves. Hot exhaust gases exit via a serpentine flue that snakes through the high-mass body of the stove, which is made from brick, stone, cement block or adobe.
As the exhaust gases make their way through the flue, the mass absorbs heat and slowly radiates it into the room. Masonry heaters produce a more comfortable heat than wood stoves. Plus, heat from a single burn radiates into a room much longer-from 6 to 24 hours.
When shopping for a woodstove, check the manufacturers’ stickers that indicate efficiency and emissions. These provide a great way to compare models and select the most efficient and clean-burning stove.
Also consider buying a stove fan that’s powered by the stove’s heat. It sits atop the stove and circulates air more quickly around the room. Look for the Heat Wave (www.ThermalEngines.com) or EcoFan (www.Caframo.com) brands.
From Field to Fuel: Burning Biomass
One of the most exciting home-heating developments in recent years is the biomass stove, a combustion device much like a pellet stove. Biomass stoves burn unconventional organic fuels, including corn, cherry pits, olive pits, wheat and other cereal grains. Users feed seeds and grains into a hopper that delivers a slow, steady stream of fuel to the combustion chamber.
Available in bulk in many rural locations, relatively inexpensive cereal grains could provide a substantial amount of heat to homes, offices or workshops. These fuel sources contain a huge amount of energy and burn cleanly. They’re also renewable and provide a potentially lucrative market for farmers’ crops.
Feeling Hot, Hot, Hot
Wood-Burning Stoves and Fireplace Inserts
• Renewable, widely available fuel
• Nearly carbon-neutral (releases almost no net greenhouse gas emissions)
• Many models to choose from
• Widely available in most locations
• Fairly efficient
• Produce more pollution than natural gas and a lot more than solar heating systems
• Heat unevenly; hotter in immediate vicinity
• Produce a fairly dry heat
• Pose a fire hazard if not properly installed and operated
• Require frequent refueling and cleaning
• Considerable handling of wood
• All of the benefits of a wood stove plus automatic fueling
• Burn cleaner than woodstoves (less pollution and ash)
• Some models can be integrated with existing forced-air heating systems
• Requires electricity, so will not heat during power outages
• Pellets stored in plastic packaging; not likely to be locally sourced
• Usually burn only pellets