• Active since 1995, is THE place on the internet for free information and advice about wood stoves, pellet stoves and other energy saving equipment.

    We strive to provide opinions, articles, discussions and history related to Hearth Products and in a more general sense, energy issues.

    We promote the EFFICIENT, RESPONSIBLE, CLEAN and SAFE use of all fuels, whether renewable or fossil.
Not open for further replies.

webfish LLC
Staff member
Oct 18, 2013
Gas Fireplace Logs have become very popular in the last few years. With this new popularity, however, has come the usual barrage of questions regarding these products and their uses.

Gas Logs

Gas Fireplaces Logs have become very popular in the last decade. With this new popularity, however, has come the usual barrage of questions regarding these products and their uses. First, some information common to all these types. They are all available set up for Natural Gas or LP (Propane). They all require that you have an existing wood burning fireplace with a decent chimney system installed (have a chimney sweep check your chimney and fireplace). They are all available (or standard) with multi-function safety controls to assure that unlit gas cannot be sent into the living area.

Gas Logs are available in two basic types:

Vented Logs - For use in Fireplaces with the damper open. Price Range typically from $300 to $600

Unvented Logs - For converting existing wood burning fireplaces - damper can be left fully closed or open. Price Range typically from $350 to $650

Installing your Gas Logs

Heating Your Home

Vented Logs

Millions of vented logs are in use in fireplaces across the US. These tried and true log sets have been sold for 20 years or more, and are still the most popular type. They are available in lengths from 12” to over 60” (that’s a big fireplace !). Vented logs are the most realistic wood fire substitute made, and are available in different styles and finishes which resemble oak, birch, hickory and many other wood species. This realistic beauty comes at a price; vented logs are also the least efficient of the three types. They consume from 50,000 to 90,000 BTU/HR of Gas which costs 60 cents to $1.50 per hour (Natural Gas) and 75 cents to $1.75 per hour (LP). The efficiency is rather low, meaning that only 10% of this heat is returned to the home. The rest goes up the chimney, much like your old wood fire did.


Typical Vented Gas Logs - Monesson Duzy

Technically speaking, the reason Vented Logs look so good is they intentionally burn the Gas “dirty”. A dirty gas flame is a yellow flame…which simulates wood very well. The glowing embers found on most of these sets add to the charm and realism. The Vented Log Sets are also the most flexible - logs can be moved around and repositioned, remote controls and wall switches are available and additional logs, embers, branches and pine cones can be added. If you are looking for the most realistic fire, and don’t have a heating problem in the room or in your home, then the Vented Logs may be a good option for you.

Some newer vented gas log sets have been upgraded to use less gas than the standard models and certain brands actually produce noticeable radiant heat into the home.

Unvented Logs (Ventless and Vent-Free Logs)

In the past decade, unvented log sets have become extremely popular, and the sales volume is approaching that of the Vented logs. The real revolution occurred when engineers figured out a way to produce a yellow flame with these sets, while still achieving a clean burn. Many folks are curious how you can burn a fuel in the home and have little on no effect on the air quality in the home. The easiest way to understand is to use your Kitchen Gas Range as an example. A range uses a special burner design to achieve a clean, smokeless flame. Unvented gas logs use a similar technology.

Because the damper can remain closed, a high degree of efficiency is achieved—over 95%. The small amount of carbon dioxide and water vapor released into the home (as a by-product of the gas combustion) is well under the current Federal guidelines. Unvented logs are also economical to use. They burn a rates from 10,000 BTU/Hr to 40,000 BTU/HR which costs from 15 cents to 75 cents per hour (Natural Gas) to 20 cents to 85 cents per hour (LP). These logs do have yellow flames and glowing embers, but they do not look as real as the Vented Logs. This is due to the smaller BTU rating and the clean burning design.


Unvented (Vent-Free)Gas Logs - Monesson
There is some controversy over unvented logs. Some states (Mass., Ca. and a few others) do not allow the use of any unvented gas appliance. People with asthma, or other respiratory sensitivities may find the slight odor and small decrease in room oxygen levels uncomfortable. This may be a bigger concern in newer, tightly constructed homes. Rest assured, however, that these logs are equipped with a modern safety device called an ODS (oxygen depletion sensor), which would shut the flame off if the oxygen content of the air dropped below a safe level. In my extensive experience, I’ve never heard of one of these sensors failing or even going off. Unvented logs do not allow for the repositioning or adding of additional logs or branches. Remote controls, wall thermostats and other options are not as prevalent as with the Vented logs. It is not a good idea to use these logs for full time heating or to use them while you are not in the area or sleeping. They are, in effect, an “open fire” and the normal precautions should be considered. Since these logs produce so much heat, wood surfaces (mantels, shelves, etc.) above the fireplace should be protected or removed - see installation instructions or ask your hearth retailer for these specs.

If your intention is to replace your wood fire, supply some space heating (attended) and provide a backup emergency heat source for your home (yes, they work during power failures), then an Unvented Log Set could have your name on it !

Measuring for your Gas Logs

What size will fit? This depends on the exact type of gas log and control (valve, remote, etc.) you are considering. A good guide to measuring - and some video guides are located at this site.

Installing your Gas Logs

It is highly recommended that your new fireplace logs be installed by a qualified plumber or HVAC services company. This is not the right job for a DIY’s. Most jobs are installed with threaded pipe, which must be cut and threaded on the job. In addition, technical knowledge and certain instruments are required to set up and adjust the gas logs. Installation prices can vary, usually running from $200 to $350 for a basic job. It’s well worth it for the peace of mind—support your local contractor !

Heating your Home

Gas logs are a convenient way to convert your fireplace from wood. You didn’t use your open fireplace to heat your home on a full time basis, and your new Gas Logs are not designed for that purpose either. If you are looking to convert your fireplace to help heat an area on a ongoing basis, consider the Direct Vented or B-Vented Gas Fireplace Inserts or Gas Stoves.
Last edited:
Not open for further replies.