What are the Pros and Cons of Vented and Ventless Gas Fireplaces?


Last night I was at a stylish CWE condo that had a nice ventless fireplace in the Living Room. I thought it looked great…and I started wondering….”How can a gas fireplace be Ventless?”.  Well read below to find out more!

(The picture is of my Vented fireplace…..I have to work on it a little bit to get the flames more even.)

Basic Overview

Vented Gas Logs Require a Fully Functional Wood Burning Fireplace, Ventless (or Vent Free) Gas Logs can be installed in either a wood burning fireplace, or a ventless fireplace that is rated for aftermarket ventless logs. Ventless gas logs will produce more heat, while vented gas logs will look much more realistic. Read the Pros and Cons of each below:

Vented Gas Logs:

“Fully Vented” gas logs must be burned in a fireplace that is capable of burning real wood and must be burned with the damper open. The reason for this is that they do not burn the gas cleanly and create exhaust that is very similar to burning a real wood fire. This exhaust needs to be able to go up the chimney. The real beauty of vented gas logs is that they produce substantially more yellow flame than ventless logs which makes them look far more realistic. The downside is that most of the heat goes right up the chimney.
However, In most cases, you can offset this heat loss by slightly closing the damper…but you must be careful that the exhaust from your logs is not coming into the room because, just like burning real wood, it contains Carbon Monoxide. A good way to test this is to turn on your gas logs with the damper slightly closed. Hold a lighter or candle in front of the fireplace opening near the top. If the flame from the lighter (candle) is being drawn in toward the fireplace, then you are OK. If the flame is standing still or pushed out toward the room, then your fireplace is not drafting enough and you must open the damper more.

Positive Features of Vented Gas Logs:

-Extremely realistic flame pattern that looks like a wood fire.
-Flame is much taller than ventless logs
-Flame dances and wraps around logs like real wood.
-Does not require a CO2 detector
-Since the damper is open, most of the smell will go up the chimney
Negative Features of Vented Gas Logs:

Do’s and Dont’s for Vented Gas Logs
(Additional information you should read before buying Ventless Gas Logs)

-Less heat than ventless logs (probably won’t heat your room)
-Uses slightly more gas than ventless logs
-Check out some Vented Gas Log Installation Manuals Here before you purchase.

Ventless Gas Logs:

Ventless gas logs (often referred to as “Vent Free” gas logs) have specially designed burners that burn the gas cleanly and produce almost no exhaust…somewhat like the way a gas range in a kitchen works. Since there is little or no exhaust, they can be burned with the damper closed.
The beauty of this type of system is that 99.9% of the heat produced by the gas logs goes into the room, so they produce substantially more heat than their vented counter-parts. However, there are many negative features commonly associated with ventless logs that you must be aware of before you decide to purchase them:

Positive Features of Ventless Gas Logs:

-Much better heat output than vented gas logs
-Less pollution
-Slightly less gas consumption
Negative Features of Ventless Gas Logs:

Do’s and Dont’s for Ventless Gas Logs
(Additional information you should read before buying Ventless Gas Logs)

-The main byproducts of burning gas cleanly are Carbon Dioxide and Water Vapor. Because of this, ventless gas logs will introduce excess moisture into your home which can result in mold or mildew.
-You must be careful not to burn your ventless logs for extended periods of time with windows closed, otherwise they can potentially deplete the oxygen in your home.
-If you burn your ventless logs for more than an hour or so, you must crack open a window to allow air into your home to replace the oxygen burned by the ventless logs. This will introduce cold air into the room and offset some of the heating benefits that ventless logs claim to have.
-Ventless logs produce an odor that many people equate to the smell of burning kerosene. So if you have a sensitive nose, you may not be able to handle the smell and will be greatly dissatisfied with ventless logs. On the other hand, we’ve heard some people who like the smell because it reminds them of their childhood days at Grandma’s house. (Read Why Ventless Gas Logs Smell)
-Ventless logs can cause eye irritation and coughing spells to those who are sensitive.
-Ventless logs are required to have an ODS (oxygen depletion system) as well as a CO2 detector…which might tell you that there are some risks involved in operating them if these systems fail.
-The flame pattern with ventless logs is not nearly as realistic in comparison to vented logs. Because the gas must burn cleanly, the flame height is very low, it is more blue than yellow and appears to be more nerveous and less lofty.
-Also, you will find that the flame does not dance around like a real wood fire and very little of the flame actually touches the logs. The reason for this is that when the flame touches the logs, it gets cooled off and does not burn cleanly and starts to produce soot and exhaust gases.
-Installing vent-free gas logs is not a DIY job. Installation must be performed by a professional who can do the proper tests on your gas pressure and make sure that the installation meets building codes and follows the specifications required.
-Clearances to combustables is different than that of wood buring fires or vented gas logs. If there is a mantel above the fireplace, you may need to install a hood to divert heat away from it. You should check the Installation Manual for the Ventless Logs for clearance requirements before you order them.
-There are also BTU limitations based on the cubic feet of air available to your room. The maximum BTUs allowed is calculated using this formula: Room Width x Room Length x Ceiling Height x 20.
-Ventless gas logs may not be legal in a bedroom or confined space (differs with local building codes).
-Other restrictions apply with each of the various burner systems available, so again, you should read the installation manual pertaining to the ventless logs you are considering “Before You Purchase”.
Bottom Line: We highly recommend that you purchase vented gas logs. You will be much happier with flame that they produce and less likely to experience discomfort from odors or irritation. We only recommend ventless logs when maximizing the heat output outweighs all of the other negative aspects.

This article was pulled from the Hansen Wholesale website.  They seemed to do the best job of explaining this question.

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