With a direct vent fireplace system, the burning area is sealed off with a glass screen. The enclosed area within the firebox prevents indoor, “conditioned room air” from being drawn up through the chimney. Instead, direct vent systems use double-walled air-cooled metal venting flues. These double-walled flues are specifically designed to draw in outside air, preheat it, and vent it back outside. Using the safe and efficient Isokern Maximus Traditional Series Fireplace means you are utilizing the finest materials known in building construction today.