Direct Vent Fireplace Inserts are by far the most popular and most efficient type of fireplace insert.
With direct vent inserts, the insert is sealed. The air that is used to generate the flame (combustion air) is drawn from outside. The fumes that are a byproduct of the combustion are also vented to the outside. In this way, air contaminated with combustion byproducts and unused fuel does not circulate in the home, and household air is not used to fuel the combustion process.