Recently at a customer’s home my service technician encountered a question that we get quite frequently: “Does it matter what type of fireplace I install my vented gas logs in?” Sometimes when I have to explain to a customer that they can not burn wood in their fireplace until it is relined due to vertical cracks in the flue tiles, missing mortar joints, etc., they sometimes inquire as to whether or not they can install a gas log set instead. What type of fireplaces can vented gas logs be installed in?
Masonry Fireplace (Clay flue liners)
You may install a vented gas log set in a masonry fireplace as long as it is not damaged. A masonry fireplace typically consists of a brick exterior with a cement crown and chimney cap on the outside with clay flue tiles lining the inside. It has a damper down near the smoke chamber which can be opened and closed with chain pulleys (typically) and is generally designed to burn wood. Generally a vented gas log set can be installed in a masonry chimney so long as the gas logs will fit in the existing firebox. Have your chimney swept prior to installing gas logs if you previously used the chimney for burning wood.
Prefabs (Woodburning)
Prefabricated fireplaces have gained and lost popularity over time, but is basically a factory manufactured fireplace. It consists of a large metal box that is the firebox with a round metal chimney pipe attached to it for venting the byproducts of combustion. The firebox is lined with refractory plates. The pipe vents up out of the home and is usually surrounded by siding to aesthetic purposes. Your chimney’s flue liner should be at least 8″ in diameter if you wish to use it for burning wood, and the damper must be open when using your gas logs. Some manufacturers have specific instructions regarding gas logs in their products, so contact your manufacturer before making a gas log set purchase.
Although there are other types of fireplace approved for venting gas logs, these are by and far the most frequent types of chimneys we get questions about regarding the installation of gas logs. If you have specific questions regarding your chimney system, feel free to give me the details in the comments section or on the Askthechimneysweep forum. Always follow local building codes and remember that some manufacturers have specifications regarding gas log installation that must be followed.