Two pipe system, uses outside air for combustion and exhausts to the outside. Does not require vertical roof penetration, but can be installed vertically.
a furnace or boiler design where all the air for combustion is taken from the outdoors and all exhaust products are released to the outdoors, also known as sealed combustion. Direct Vent is also known as balanced flue venting in oil furnaces and boilers.
Method of venting appliance whereby all air for combustion is derived directly from the outside atmosphere and all flue gases are discharged directly to the outside atmosphere.