DEAR TIM: What can you tell me about gas fireplaces? Is it better to have a gas fireplace or a traditional wood-burning fireplace? Should I consider a ventless gas fireplace? If you say to burn gas, I am really interested in efficient gas fireplaces so I can turn my fuel dollars into heat in the house instead of going up the chimney. John McG., Buffalo, NY

DEAR JOHN: Gas fireplaces are very popular, and they keep getting better each year as manufacturers make improvements. Modern gas fireplaces are not only very efficient, but they are extremely realistic. Certain models are so well engineered, it takes a trained eye to realize gas is burning instead of wood.

Your final decision on which type of fireplace to buy or build needs to be well thought out. The first thing I would want to know is if the fireplace is purely decorative, or will it ever function as a heating source for your home. If the fireplace is decorative, then you have a much easier set of decisions to make.

But let me tell you a story that might influence your choice. Just after I moved into my current home, we had an unusual mid-fall snowstorm. The trees were still full of leaves, and the wet snow clung to the them like flies to flypaper. The weight of the snow cracked the branches and thousands of power lines around the city were pulled to the ground. The utility crews were overwhelmed with work.

This is a real wood-burning fireplace but the current fuel source is natural gas. It can be converted back to wood burning in less than five minutes. PHOTO CREDIT: Tim Carter

The power at my home was not restored for three and a half days. The first night my family thought it was a fun experience, but that laughter quickly went away as the power did not come back. The storm ushered in a wave of cold air that made the temperature drop inside my home. Fortunately, I had two fireplaces and plenty of wood to temper the inside air and keep the water pipes from freezing.

Yes, a portable generator would have allowed me to run my natural gas furnace. But I didn't have one, the stores quickly ran out and all of the tool rental shops had empty shelves. But because I had a fireplace that burned wood, I was able to survive. That storm taught me several valuable lessons.

Since that time, I remodeled one of the fireplaces. I kept it as a wood-burning fireplace, but I piped the firebox with natural gas. I currently have a gas fireplace with a set of realistic gas logs. With the flick of a switch, I have a warm, realistic instant fire.

But if for some reason I lose my natural gas supply, I can remove the log set, cap the natural gas line and be burning wood in a matter of minutes. This flexibility gives me enormous peace of mind. If you can find a gas fireplace that allows you to do a similar approved fuel-source switchover, give it serious consideration.

If you decide to purchase a ventless gas fireplace, be aware of a potentially harmful side effect. When you burn natural gas or liquified natural gas, water vapor is a byproduct. This is the vapor you often see streaming from chimneys on cold winter days. While seemingly harmless, this water vapor can and will condense on cool surfaces. If the vapor barriers in your walls are not good and/or your attic ventilation is poor, you can have serious condensation issues that can lead to mold or wood rot.

As for fuel efficiency, you should be able to obtain information from the gas fireplace manufacturers about rated fuel efficiencies. If you buy a quality gas fireplace that has the highest efficiency rating, you will be doing your pocketbook and the planet a big favor. Be sure you get the efficiency rating in writing. It is not a wise thing to trust verbal promises made by a salesperson.

Gas fireplaces can be installed very quickly. Traditional masonry fireplaces are almost always more expensive. But remember to weigh flexibility against cost. Direct-vent gas fireplaces offer fantastic placement opportunities as they can be placed in unusual places within a home. The exhaust gases from the direct-vent fireplaces can exit a wall instead of the roof of a home.

Be sure a qualified contractor installs your gas fireplace. Insist on a building permit, and try to be present when the building inspector looks at the work. Take as many photographs as possible during all phases of the installation. These photos may help you diagnose a problem at some later date.