Posts Tagged ‘gas fireplaces’

Gas Fireplaces – Vented or Ventless?

December 12th, 2017

Gas fireplaces vented or ventless are an ideal choice for anyone who wants to enjoy the warmth of a fire without the chores of hauling wood and cleaning ashes. Because gas fireplace options are growing in popularity every year, manufacturers have geared-up to offer us a wide selection of appliances. You’ll find gas logs, freestanding gas fireplaces, and contained fireplace units that are mounted on a wall.

Some gas log fixtures are vented so that gases produced during the burn travel outside, just as they move up and out of a chimney in a traditional wood burning fireplace.


Gallery of Gas Fireplaces by Connaughton Construction

Gas Fireplaces - Vented or Ventless?


Gas Fireplaces. Are They Safe?

Have your chimney cleaned by a professional chimney sweep before you fire up your gas logs for the first time. Although tests show that gas fireplaces do not increase carbon monoxide levels in your home, it’s safe to have the detectors if you use any gas appliances at home; including a furnace, a stove or a fireplace. Many gas fireplaces have safe technology. 

Can I convert a wood burning fireplace to gas?

Yes, you can purchase gas log inserts. However, you will have to have gas available at your location or have lines installed.

Vented gas logs can take the place of wood in a traditional hearth and chimney. You can choose a unit that burns either natural or propane gas. Be safe and always burn with the damper in a fixed open position.

  • Gas fireplaces are not a solution for a problem chimney. If the chimney has cracks, dirty, or doesn’t draw air well enough to burn wood, it is not suitable for gas logs.
  • Chimneys that are previously burning wood often times have a build up of creosote. Having a professional clean your fireplace chimney before installing and using gas logs will be safer.
  • Stainless steel liners in older chimneys is a good solution for those not having clay linings or those flue liners that are in bad condition.

 Are All Gas Fireplaces vented?

There are vented and ventless gas fireplaces. Vented or ventless refers to the gas logs. Vented gas logs require a fully functional wood burning fireplace. Ventless 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.

Gas Fireplaces Vented. Are they Efficient?

Positive Features of Vented Gas Logs

  1. Vented gas fireplaces have an extremely realistic flame pattern that looks like a wood fire.
  2. The flame is much taller than ventless logs
  3. The flame dances and wraps around logs like real wood.
  4. Vented gas fireplaces may require a CO2 detector – depending on local fire department requirements.
  5. Since the damper is fixed open, most of the smell will go up the chimney

Negative Features of Vented Gas Logs

  1. Vented gas logs produce less heat than ventless logs 
  2. Uses slightly more gas than ventless logs

Gas Fireplaces Ventless. Are they Safe?

The positive features of Ventless Gas Logs, they provide much better heat output than vented gas logs. They create less pollution. They use slightly less gas.

The Negative Features of Ventless Gas Logs

  1. 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 could result in mold or mildew.
  2. You must be careful not to burn your ventless logs for extended periods of time with windows closed as they can deplete the oxygen in your home.
  3. If you burn your ventless logs for more than an hour, 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.
  4. Ventless logs produce an odor that smells like kerosene, can cause eye irritation and coughing spells to those who are sensitive. They are legal in Massachusetts.
  5. Law requires Ventless logs to have an ODS (oxygen depletion system) as well as a CO2 detector.
  6. 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 less lofty.
  7. 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. 
  8. If there is a mantel above the fireplace, you may need to install a hood to divert heat away from it.
  9. There are also BTU limitations based on the cubic feet of air available to your room. Measure the maximum BTUs allowed using this formula: Room Width x Room Length x Ceiling Height x 20.
  10. Ventless gas logs are not legal in a bedroom or confined space. Only vented units are allowed in bedrooms.

 Gas Fireplace Building Codes

Building codes and local fire departments require the damper in your chimney to be permanently fixed open if you install gas logs. You can reduce drafts and heat loss by installing glass doors in front of the gas fireplace. But the doors must remain open while the fire is burning. Connaughton Construction knows the Boston codes for CHIMNEYS, FIREPLACES AND SOLID FUEL-BURNING APPLIANCES.

We recommend that you purchase a vented log gas fireplace, where possible. You will be happier with the flame that they produce and less likely to experience discomfort from odors or irritation. We recommend ventless logs when maximizing the heat output outweighs all of the other negative aspects.


Connaughton Construction, a construction management company, has over 30 experience implementing sustainable construction, energy efficiency, and smart technology. Gas fireplaces have become popular for every room. Installing vent-free gas logs is not a DIY job. Having a professional install. He/she can do the proper tests on the gas pressure, make sure the installation meets building codes and follows the specifications.

Request a Consultation with Connaughton Construction and let the new custom home project begin. Design your story with Connaughton Construction.


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If you prefer to talk to someone on the phone, please call John with Connaughton Construction at 781-899-1438 x 14 or  Ellen at x13.

About the Author. “Lover of all things digital – writing, SEO, websites – Carol Scalzo is the founder of Hit-the-Web Marketing where she helps businesses create significant, consistent, and valuable pieces of content. You can see more of her work at The Retail Factor, follow her on Twitter, or join her email list for businesses who want to turn their websites into lead generating machines.”

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