How Do Direct Vent Fireplaces Work?

Direct vent is by far the most common venting method and is the newest form of venting, invented by the founders of Heat & Glo in the 1980s. It remains a popular choice because of its efficiency, safety, flexibility and the fact that it does not require an existing chimney.

But how, exactly, does it work? In direct vent fireplaces, a pair of rigid flues that nestle inside one another is installed in sections ranging from 4" to 48" in length, with 90°- and 45°- angled elbows that allow for flexibility with placement. A 4" inner flue is surrounded by an outer flue that is either 6 5/8" or 8" in diameter.

When the gas fireplace starts up, exhaust passes through the inner pipe to the outdoors, while the outer pipe brings in fresh air for combustion, transmitting it directly to the bottom of the sealed firebox, where it ignites the unit. The outer pipe also helps insulate surrounding combustible components from heat traveling through the system.

The direct vent fireplace unit is sealed off from the home’s interior with a high-temperature glass panel and protective screen, so any flames or combustion byproducts are completely separated from the air in your home. This illustration shows how a direct vent can be routed from the firebox directly through the wall to the outdoors, and also the optional side and top venting routes.

Direct vent gas fireplaces and inserts come in a broad range of sizes, efficiently producing heat almost anywhere in the home. Given the venting flexibility, wide range of styles and the fact that a chimney is not required for installation, direct vent appliances are well-suited to just about any type of home and room. Still have questions about fireplace venting? Review this article about Venting Explained or connect with a local authorized dealer for personalized help.