What direct vent means
A direct vent appliance takes all its combustion air from outside and sends all its exhaust outside through a sealed vent, so it does not use or affect the air in the house.
Also called sealed combustion.
Where it matters on a HVAC job
Direct vent furnaces, water heaters and fireplaces can go in tight houses and small rooms where an atmospheric unit could backdraft. The vent termination has clearance rules, so plan where it exits the wall before you quote.
What the model code says
- The code defines a direct vent appliance as one with sealed combustion that draws all its air from outside and sends all flue gases outside. (IRC 2021, Chapter 2)
Check which code edition your building department enforces for direct vent before you quote.
What it costs
Jobs that involve direct vent are priced in the gas fireplace installation cost guide: about $3,700 typical, usually $2,300 to $8,000. The guide shows its sources and what moves the price.
Work it out
- Cost guide: Gas fireplace installation cost
- Licensing: HVAC license rules by state
- Tools, templates and guides: Free HVAC resources
Sources: 2021 International Residential Code, Chapter 2, Definitions (ICC). Checked October 9, 2026.