Gas Log Buyer's Guide

Can’t decide between vented or ventless? Here are the pros and cons of both vented and ventless gas logs all in one convenient place for you.

The different styles of gas fireplace logs available are vented gas logs and ventless gas logs. There are pros and cons to both models but the main difference is vented gas logs require a chimney or flue and an open damper to be safely operated. Ventless, or vent-free, gas logs can be installed without the need for a chimney allowing for more customization into where you want your gas log installation.

Vented Gas Logs

Vented gas logs produce a byproduct of carbon monoxide that needs to be allowed to escape to the outside through a chimney or flue. Every time these appliances are used, the damper must be opened, just as with a wood-burning fireplace.

The good news is these gas logs are much more realistic looking than ventless gas logs. The flames are much taller and will flicker around much like a wood-burning fire. It is for this reason that vented gas logs are a good choice for people thinking of making the switch from a wood-burning fireplace to a gas fireplace. The type of logs is customizable as well, whether you feel a sturdy oak or a beautiful birch will match the aesthetic of your room better.

Because vented gas logs need a chimney, a fair amount of heat will escape through the chimney. For this reason, vented gas logs are less efficient than ventless gas logs, as they use more fuel and produce less heat in the room. But these gas logs are still more efficient and more convenient to use than a wood-burning fireplace.

Pros of Vented Gas Logs

More efficient than a wood-burning fireplace
More realistic looking than ventless gas logs
Taller flames
Logs can be customized and rearranged for a pleasing display
No BTU limit
Flames can touch logs

Cons of Vented Gas Logs

Less efficient
Costs more
Emit more pollution
The damper must stay open
Heat loss through the chimney

Ventless Gas Logs

Ventless gas logs (or vent-free gas logs). don’t need a chimney. Don’t be mistaken, these gas logs can still be installed in a house or fireplace with a chimney. The damper can remain closed while the fire is burning.

Because of the lack of chimney needed for the functioning of these gas logs, the heat will not escape outside through the chimney or flue, and will instead stay inside your home. Therefore ventless gas logs will heat up a room much quicker and effectively than the vented gas logs. Another side effect of this phenomenon is less fuel is needed to fuel the flame creating a more efficient system. And finally, ventless gas logs will emit a significantly less amount of pollution, in the form of carbon monoxide that is released into the atmosphere through the chimney.

Ventless gas logs are less realistic looking than their vented counterparts. The flames are smaller and more stagnant because they lack the airflow from an open damper, and often will burn in a pre-programmed pattern.

Ventless gas logs also come with oxygen depletion sensors. Because this design uses air from the room for combustion there will be an attached oxygen depletion sensor to shut off the logs if the oxygen gets to a low level. It is not recommended to let ventless gas logs stay on continuously for extended periods of time. The other byproduct of ventless gas logs is water vapor. This will create a bit of humidity in the room the fireplace is located in and can be counteracted by cracking open a window. Finally, this design will not allow any odors produced by the gas-burning to escape through the chimney and will release a smell the longer it burns, this is why ventless gas logs are not recommended for people with asthma or allergies.

Pros of Ventless Gas Logs

Heats your home faster and more efficiently
Less expensive
Chimney not required, leading to easier installation
Less pollution emitted
Less gas consumed
Comes with an oxygen sensor

Cons of Ventless Gas Logs

Not as realistic display
Not recommended to run for extended periods of time.
Adds humidity into the home
Not legal in some states such as California and Massachusetts
6,000-40,000 BTU limit
Produces odors that cannot escape through the chimney
Not recommended for people with allergies

What are Gas Logs Made of?

Gas logs are made from either ceramic fiber or a refractory cement mixture—materials that can handle high temperatures for extended periods of time. Sometimes steel bars are added to the inside for reinforcement, to prevent cracking after being heated many times over.

Newer models of gas logs have each log individually molded from a cast of real tree branch samples, and carved to match the unique details found in natural tree wood. This is to create to most realistic logs possible. Vented gas logs typically have orange and yellow flames. Ventless gas logs, with their smaller flames, usually have a blue-ish tint.

There are ways to decorate your fireplace around your gas logs. Before you put anything in or around your gas logs check the owner’s manual to ensure you aren’t compromising the safety of the log burner.

Lava rocks can be added to the floor around the gas log burner to give the effect of a coal bed surrounding your flames. Lava rocks also retain and emit heat as a bonus.
Embers are small clumps that increase the glowing effect of the gas logs to recreate the ambiance of a wood fire.
Pine cones or acorns crafted from ceramic or cement can be scattered around the gas log installation to add a cozy decorative feeling to your fireplace.

Control Options for your Gas Logs

There are various options to control how your gas logs are lit depending on if you want the ability to use a switch, or a remote, balanced against the price point.

Match-lit

This is the most basic control option for your gas logs. It is also the cheapest option. This can only be used for vented log sets fueled by natural gas. To light, a match or lighter is placed near the log burner as the gas is turned on. Once the gas is lit, the fireplace gas valve can be adjusted to control the flame height. A safety precaution is to watch your fingers whilst lighting and make sure the valve has been completely shut off when the gas logs are not in use.

Manual Safety Pilot

Also called a Safety Pilot Kit (SPK) this control option has a built-in safety system. A flame-sensing thermocouple (a type of small thermal generator) will shut off the gas flow if it doesn’t detect a flame.

This option also sometimes includes a push-button igniter that will produce a spark to ignite the flame rather than using a match or lighter. Some Manual Safety Pilots also have the option of a standing pilot light, a burner that is continuously lit at a low level, so the fire can be turned on and off with the knob and without the need to hold a match to the burner every time

Modified Safety Pilot Kits

A modified Safety Pilot kit is an SPK with a motor. This allows the connection of remote control.

Millivolt Valve

A millivolt Valve lacks the thermocouple the SPK contains. Instead, it has a thermopile, another type of small thermal generator. This appliance generates a larger millivolt current. This larger current is strong enough for the valve to be connected to a hand-held remote, a wall switch, a timer, or a thermostat. The Millivolt Valve also uses a standing pilot flame.

Electronic Valve

An electronic Valve is controlled with a switch directly on the gas valve, a switch on the wall, or remote control. This valve can be connected to the house power or battery operated.

Components of a Gas Log Set:

Gas valve: Controls the release of gas to fuel the flame.

Pilot assembly: Where a small flame is kept lit and will light the fire. This is often where the oxygen depletion senor in ventless gas logs is located.

Burner: Where the flame is produced.

Steel Grate: Holds the logs in place and creates a raised platform for the burner, gas supply line to rest under.

Logs: the ceramic tree branches the flame appears around.

Sand or Vermiculite: Facilitates the distribution of gas in the burner pan of vented gas logs.

Glowing Embers: Give the flame a more realistic appearance.

Damper clamp: keeps the chimney’s damper from closing, making sure no dangerous gases leak out of the firebox.

Getting the Correct Size Logs for your Fireplace

Gas logs come in a range of different sizes and arrangements. It is important to get the correct size for your firebox because getting a set that is too large will overheat your firebox and gas valves and cause permanent damage to your logs, your fireplace, or your home.

It’s easy to measure your firebox, take the measurements of the front width, the rear width, the depth, and the height. Then it is always a good idea to check the manufacturer's size requirements and combustion clearance for a better idea of the ideal size for your logs.

We're Here to Help!

We are here to help! Fireplace Deals’ inventory has dozens of design options for your perfect installation—whether you’re focused on a more efficient burn or having the most inviting centerpiece for your next family get-together. Changing up your home’s fireplace can be a daunting task, but our Learning Center has dozens of articles to educate you on the process, and if you have any more questions send an email or call 866-848-3473 to speak with an NFI-certified expert.