A direct-vent wall furnace is a self-contained sealed combustion heating appliance that warms inside air by recirculating it around a sealed chamber, and discharges combustion byproducts outside the home via direct-vent. They are permanently attached to the structure of a building, and are not connected to ductwork.

Direct-vent technology describes a gas-burning appliance that uses two pipes - often one smaller pipe within another larger pipe - to both exhaust the flue gases and bring in fresh air for combustion. They are one of the safest, most convenient, and most popular ways of adding a gas fireplace to your home.

Direct-Vent systems mount on an outside wall and have a vent-within-a-vent system to draw in outdoor air to support combustion and exhaust flue products to the outdoors. The vent cap installs on the outside wall of the home.

Through-the-wall venting simply means removing furnace exhaust gases through the wall. Typically, you bore a hole in an exterior wall and connect the vent pipe from the furnace through it. That way, exhaust gases from the furnace can head out through the wall.