Gas Fireplaces, Inserts & Log Sets

Many people often confuse gas fireplaces, gas inserts and gas logs sets. Each one is different and serves a different need, and below we discuss the three different appliance types.



Gas log sets are the most simple and basic appliances among the three. A gas log set consists of a gas burner and a log set or some other media, such as stones, glass or geometrically formed stones, often referred to as “geoshapes.”  To install a gas log set, you must already have a working wood burning fireplace, and we can help you select the right one for you in that case. You cannot put gas log sets into existing gas fireplaces. Gas logs come in two main varieties, vented and vent-free.

  • Vented gas log sets require that you either remove the fireplace damper or clamp it into a partially open position. To install a vented gas log set, by code, you’re not allowed to close the damper.
  • Vent-free or Ventless gas log sets require that you seal the damper shut. The advantage to a vented gas log set is that they can run for longer periods of time and the fumes will vent into the outside atmosphere.

Since water vapor is a byproduct of propane or natural gas combustion, you also avoid moisture issue, so that is a pro with vented gas log sets. One drawback to vented gas log sets is that they are very inefficient sources of heat, and they are most decorative in nature. Both vented and ventless gas log sets can be operated without electricity. There are a number of other code considerations with vented and ventless gas log sets to consider, and we can help you choose the right set for you to make sure that you are installing the correct appliance compliant with code and manufacturer specifications.

Gas Fireplace Inserts are appliances that also must be installed into existing, approved wood burning fireplaces. Gas fireplace inserts are almost always sealed, direct vent appliances that draw their combustion air from outside via an aluminum liner and exhaust the fumes through a separate aluminum liner. There are some B-Vent fireplaces and fireplace inserts that draw their combustion air from inside the room and exhaust through a steel or aluminum liner, but they are quite uncommon. Most gas fireplace inserts are “heater rated”, which means they are of a considerably more efficient than decorative gas fireplaces and gas log sets (usually over 75% efficient) and they can be set to a thermostat. Since gas fireplace inserts go into existing fireplaces, it’s important to properly measure your existing fireplace to make sure it will fit. Moreover, there are also clearance issues (such as clearance to any wooden mantel, trim, wall or floor) to take into consideration. We always recommend that we send an installer out to measure your fireplace first to ensure that it can be installed according to code and manufacturer specifications and to give you a price quote to deliver, install and vent the fireplace. Gas fireplace inserts are always sold with a shroud or backer that goes around the appliance and covers the fireplace opening. It’s important that this is measured as well as some fireplace insert manufacturers only sell standard sizes and do not make custom-made surrounds.

Gas Fireplace are appliances that are framed into a wall. This is commonly done after the house is built by boxing in a cabinet for the fireplace to sit in. The material around the fireplace can be drywall, wood, stone or just about any material; just make sure that your builder follows the installation instructions as some fireplaces require non-combustible boards above or around the fireplace, or they may require non-combustible steel studs, though this is less common. Gas fireplaces are almost always direct vent, so they take their combustion air from the outside using co-axial direct vent pipe (pipe inside of a pipe). The inner pipe exhausts the combustion byproducts, and the space around the pipe serves as the conduit for the fresh combustion air. Direct vent appliances can terminate horizontally, meaning you’d have a steel vent cap on the side of your house, or vertically, meaning you’d have a steel chimney cap popping up through the roof. Some companies make gas fireplaces, but they don’t make gas fireplace inserts or gas log sets.