How to Tell the Difference Between Vented and Unvented Gas Logs

Gas Fireplaces 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.

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 three basic types:

  • Vented Logs – For use in Fireplaces with the damper open Price Range $250 to $550
  • Unvented Logs – For converting existing wood burning fireplaces – damper can be left fully closed. Price Range $350 to $500
  • Partially Vented Logs – A newer type which combines some of the features of Vented and Unvented Gas Logs.

Vented Logs

how to tell the difference between vented and unvented gas 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.

But this realistic beauty comes at a price; vented logs are also the least efficient of the three types. They consume for 50,000 to 90,000 BTU/HR of Gas which costs 40 cents to 80 cents per hour (Natural Gas) and 60 cents to $1.00 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.

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.

Unvented Logs (Ventless and Vent-Free Logs)

direct vent gas fireplace

In the past three years, 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 99%. 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 30,000 BTU/HR which costs from 6 cents to 30 cents per hour (Natural Gas) to 10 cents to 50 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.

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 safety 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!

Partially Vented Logs

These Logs allow you to close your fireplace damper most of the way, leaving it only 10% open. The result is plenty of heat in the room, while most of the combustion by-products go up the chimney.

Although not as effective as Unvented Logs, and not as realistic as Vented Logs, these logs provide the ever-so-important middle ground and are probably a good option for many. They use less BTU’s than fully Vented types (30,000 to 50,000 BTU/HR) and are available in a few different styles and colors.

Installing your Gas Logs

It is highly recommended that your new fireplace logs be installed by a qualified plumber or heating contractor. This is not the right job for a DIY’s. Most jobs are installed with a 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 an ongoing basis, consider the Gas Fireplace Inserts or Gas Stoves.

Best Gas Logs to Buy

If you have a wood burning fireplace and are tired of the mess of wood it is easy to convert to burning gas logs.  There is natural and propane gas available. Logs are obtainable as vented for a natural looking fire or vent free for clean burning, heat producing Gas Logs

Outdoor Gas Logs

Intended to take the high BTU production of an out-of-doors fireplace without degrading, gas logs are crafted to look and burn just like real firewood.   With the ceramic fiber being developed, the look of glowing embers is blazing.

Ventless Gas Logs

Vent-free gas logs make up for their lack of flash with more heat and less air pollution but they don’t burn as high as vented logs. Ventless gas logs don’t need an open chimney and it uses less gas, saving you money.

Vented Gas Logs

They are designed to operate with an open chimney, most of the heat that they generate breaks out the chimney hole.   They are more decorative than actually heat efficient.  Vented gas logs are confirmed to offer the most realistic flame of an artificial fire.

Advantages of vented artificial fireplace gas logs over the burning of wood

Fireplace gas logs work with natural or propane (lp) gas. Instantly on and easy off, hence — no energy wasted– no more hauling — no more stacking — no more carrying into the house — no more splinters, cuts and scratches– no more falls on hard ground — no more litter on carpet — no more flying sparks or rolling coals — with log Sets, not much carpet damage or fire risk — no more worry when you sleep — no more stoking and stirring — no more scooping, sweeping and hauling ashes — no screen needed, it hides the beauty of the fireplace logs

And especially — no more CRITTERS AND VERMIN in your fireplace logs woodpile.

See-Thru Gas Logs

It can be difficult to choose gas logs for a see-through fireplace.  It must be installed in a fireplace with a fully functional chimney, to outline the smoke and combustion gases from your home. See thru gas logs are a great way to welcome the cold of winter or chill of fall. These sets give you the beauty and warmth of a fire without all of the hassle.

Pine Gas Logs

Pine wood offers long lasting embers on the fireplace.  They are cast from real trees selected for their realism and beauty.   It is tough and reliable and is styled accordingly to your fireplace accessories

Empire Gas Logs

Empire gas logs are ventless and they produce considerably more heat at about half the energy cost.  The feature is captured in each one and reproduced in quality ceramics and fiber. Realistic and natural, they will keep their true form even after years of use.

Contemporary Ventless Gas Sets

The contemporary ventless gas sets are an alternative solution to traditional log sets.  It can change the way your fireplace sets the mood in your home.  It can turn modern heating into a new definition of what a fireplace looks like.

Oak Gas Logs

Oaks are known for their health, strength and courage and an oak wood can bring a delicate attraction and warmth to your home.  Every log set comes complete with the fireplace accessories easy for installing.

Campfire Gas Logs

It recreates the natural look of a conventional campfire, importing it to your fireplace.  The campfire gas logs are carefree and wild as they were intended to be.

Coal Basket Gas Logs

This is the perfect answer for small fireplaces where gas logs can’t fit.   They are placed the same way but use less gas and offer a more attractive appeal for historic homes, it will redefine the way you approach in-home heating.  It comes with the usual fireplace accessories for ease of installation.



Jay Green
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