Ventless Gas Fireplaces: What to Know Before You Buy

Napoleon Grandville VF Series 37" Vent Free Natural Gas Fireplace

Courtesy of Amazon

Even though few homes today rely on fireplaces as their primary heating source, many homeowners still enjoy the ambiance of a warm fireplace. Ventless gas fireplaces in particular are popular because they're clean and easy to use.

What Is a Ventless Gas Fireplace?

Alternatively called unvented or vent-free, a ventless gas fireplace pipes natural gas or propane into a gas unit; the flames run through gaps in artificial ceramic fiber logs.

Installing a fireplace can often be complicated due to venting, especially with retroactive installations. The number of homes being built with traditional masonry chimneys for wood-burning fireplaces has plummeted in recent years. Even an alternative to the wood-burning fireplace, the vented gas fireplace, is being installed in fewer numbers due to the rise of air-tight homes, which save energy by closing off all possible thermal passages.

With that in mind, a ventless gas fireplace might be the solution. Easier to install than vented wood or gas fireplaces and capable of warming small rooms, gas fireplaces that have no vents passing to the exterior are becoming more popular for remodeling work and even in new-construction homes.

How Ventless Gas Fireplaces Work

The gas unit for a ventless gas fireplace has its own control panel to control the pilot light and the flames. Holes in the noncombustible artificial logs help them fit onto each other in a precise manner.

Instead of venting through a chimney or tube to the outside, a ventless gas fireplace sends the spent gasses back into the room. Traveling in a U-shaped path, oxygen enters the bottom of the ventless gas fireplace from the room and vents back into the room through the top.

Ventless vs. Vented Gas Fireplaces

Ventless gas fireplaces differ from vented gas fireplaces in terms of the logs, flame pattern, and method of venting. With vented fireplaces, the flames can run through, around, and over the logs, creating a more chaotic and realistic appearance. But with ventless units, the flames must run through prescribed holes (called posts), which makes them look more artificial.

Combustion occurs whenever there is a flame, and spent gasses and debris from that combustion must vent somewhere. Ventless gas fireplaces are deemed to operate within the range of safety for cycling these combusted gasses back into the home's interior. By contrast, vented gas fireplaces create a dangerously high amount of combustion and must vent to the outside.

Are Ventless Gas Fireplaces Safe?

The safety of ventless gas fireplaces is a subject of debate. According to industry group Vent-Free Gas Products Association, a patchwork of regulations across the United States controls the legality of ventless fireplaces. Roughly a third of states allows these units with no restrictions. California is the only state that outright bans all ventless fireplaces. In the remaining states, a welter of regulations controls ventless fireplaces based on factors such as areas of the house, population of the city, and altitudes.

Ventless gas fireplaces have a feature called an oxygen detection system, which automatically turns off the unit if oxygen levels in the room fall below a certain level. Low oxygen levels can be a concern with well-insulated homes that have a slow exchange of indoor and outdoor air.

Cost of Ventless Gas Fireplaces vs. Other Options

Ventless and vented gas fireplace inserts, gas units, and log assemblies are competitively priced with each other. Both require the same type of natural gas or propane connection, so there is no cost difference in terms of plumbing.

The major price difference between the two types of fireplaces is with venting. Direct-vent gas fireplaces require two vents in the back: one that expels gasses and another that draws in fresh air from the outside. Many direct-vent fireplaces are vented with a single two-chamber vent pipe.

The cheapest way to have a ventless fireplace in your home is with gel-based units. No plumbing is required, as the unit uses alcohol-based gel fuel canisters that burn up to three hours.

Pros
  • Ventless fireplaces require no flues or chimneys. This saves wall and floor space. Plus, it limits the number of penetrations into the home, which is valuable for saving energy.

  • Ventless gas fireplaces produce enough heat that they could conceivably serve as a secondary heat source for a small space.

  • Unlike wood-burning fireplaces, ventless models produce no ash and no airborne debris, making them an eco-friendly option. Because some communities even ban wood-burning fireplaces, a ventless fireplace might be the only option.

Cons
  • Ventless models can emit odors because combustion stays in the room.

  • The flames of ventless models look less real than vented gas or wood-burning fireplaces. Vented models tend to have a better flame pattern.

  • While ventless fireplaces do create heat, there is very little radiant heat. The heat immediately leaves the firebox. The logs don't heat up much and thus don't retain heat.