A must read ...even though you are only surveying, but this seemed like a informative article.
Gas fireplaces are popular and they get better each year as manufacturers make improvements. Not only are modern gas fireplaces efficient, but certain models are so well engineered that it takes a trained eye to detect that gas is burning instead of wood.
Deciding which type of fireplace to buy or build requires careful thought. First, will the fireplace be decorative, or will it function as a heating source for your home? If it's intended only to be decorative, then you have a much easier set of decisions to make.
Let me tell you a story that might influence your choice. Just after I moved into my home, we had an unusual mid-fall snowstorm. The trees were still full of leaves, and the wet snow clung to 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.
The power at my home was not restored for 3 1/2 days. The first night, my family thought it was fun, but that feeling quickly went away. Fortunately, I had two fireplaces and plenty of wood to temper the inside air and keep the water pipes from freezing.
A portable generator would have allowed me to run my natural gas furnace, but I didn't have one and the stores quickly ran out. I survived because I had a fireplace that burned wood.
The storm taught me several valuable lessons. Since then, I have remodeled one of the fireplaces. I kept it as a wood-burning fireplace, but I piped the firebox with natural gas. I have a gas fireplace with a set of realistic gas logs -- with the flick of a switch, I have a warm, realistic fire. If for some reason I lose my natural gas supply, I can remove the log set, cap the gas line and burn wood in a matter of minutes. This flexibility gives me peace of mind. If you can find a gas fireplace that allows you to do a similar approved fuel-source switch, give it serious consideration.
If you decide to buy a ventless gas fireplace, be aware of a potentially harmful side effect. When you burn natural gas or liquefied 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 or if 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 makers about that. 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. Don't trust oral promises made by a salesperson.