On a cold winter day, there's nothing quite like snuggling by a cozy, wood-burning fireplace -- right? It's comforting and when you go to resell your home it can add value depending on how your particular fireplace is set up.

If it's a traditional, wood-burning fireplace like the kind you'd find in a living room, den and some bedrooms, then it could be costing you money. Your fireplace could simply be posing as an effective way to warm your home, when in reality it may be robbing your home of its heat by sucking the warm air up the chimney and causing you to have to run your heater as well. It's also polluting the air!

"The number one pollutant in the winter time is wood-burning fireplaces," says Kaye Thornton of Brower Mechanical, Inc in Rockland, California.

Some states are beginning to regulate what days you can use wood-burning fireplaces because of the Particulate Matter 10 (PM10) that is given off from them. PM10 is a mixture of materials such as smoke, dust, salt, soot, metals, and acids. It is considered to be among the most harmful of all air pollutants because, once inhaled, the particles get lodged deep in the lungs. Health problems start occurring as the body begins to react to the foreign particles.

Homeowners who still want to have the charm of fires burning but not the pollutants are converting to gas fireplace inserts that use ceramic wood-like pieces to create the illusion of a real fire.

"They have fireplace inserts that you can slide right into your existing masonry fireplace. Most of them are in sealed-combustion chambers so they don't rob the air in the house in order to keep the fire burning. The venting system is such that it expels the bad gasses and brings in the fresh air to keep the fire burning," explains Thornton.

A layer of air surrounds the inner firebox and a second metal layer contains the air that is warmed by the inner firebox. Once the fire is lit, the fireplace insert works to draw in fresh air, warm it up between the layers and then, as hot air rises, it's sent up through the top and out into the room. The inserts can be designed to look like the surrounding fireplace. They can be made to resemble real brick and also act as extremely good insulating material. Adding a fan to this type of unit can also help to generate more warmth into the room. But the fans aren't always necessary. One of the greatest features of a glass-front fireplace is warmth that permeates the room from these decorative logs and jets that are contained in the metal firebox.

"The heat just radiates out into the room," says Thornton.

These aren't new devices but they are gaining in popularity as homeowners realize what a drain on the wallet a real wood-burning fire can be. So, converting your existing fireplace to a gas-unit type can be more cost-effective, much cleaner, and easier to use.

If you install a wood-burning fireplace insert to improve your fireplaces heat efficiency, it must meet the Environmental Protection Agency certification requirements to ensure that it is clean-burning and highly efficient. These devices are basically a wood-stove design that fits into a conventional open fireplace.

If you don't have a chimney then you might opt for a direct vent fireplace. This is a sealed gas fireplace that takes fresh air and pulls it into the house through a pipe in the flue and then burns it in the combustion chamber. The bad gasses are taken from the home through an outside wall or the roof. These are often used in bedrooms and bathrooms because no combustion by-products spill out and there is no backdraft that escapes into the house.

Vent-free fireplaces operate without the need to vent to the outside. These are installed against a wall that has access to a gas line. They can also be recessed into a wall. For combustion, they draw room air and then convert it to warm air that is delivered into the room. There are no drafts which is why these types are considered to burn at an efficiency rate of more than 90 percent. However, there is an ongoing debate about the quality of indoor air that's associated with these models. Some argue that, since fresh air must be exchanged in order to compensate for the room air that is used during combustion, the air quality is compromised.

Converting your fireplace can be a bit costly (maybe thousands of dollars depending on your needs) but experts say in the long run it is worth the money spent. So, if warming your feet by the fire sounds appealing, make sure that you're burning a fire in a highly-efficient fireplace; otherwise it may end up burning a hole in your wallet too.