HEATING BASICS   Choose The Heating Technology That’s Right For You.   Gas heating systems come in three burner varieties, each with unique advantages:   Vent-Free: Beauty And Great Savings Vanguard vent-free gas products deliver up to 33,000 Btu of clean, quiet, odorless heat — enough to warm up to 1,100 square feet for just pennies an hour. Because there’s no venting, there’s no heat loss. That’s why vent-free products deliver 99% heating efficiency to dramatically lower your energy bills.   Direct-Vent: Stylish And Clean-Burning Direct-vent products feature a sealed combustion firebox, so room air doesn’t come into contact with the flames. Direct-vent designs draw outside air to the burners through an outer pipe, while exhaust gases are expelled through a smaller inner pipe. Room air gets heated as it circulates through the passageways around the burner system. Direct-vent products provide about 75% to 80% heating efficiency.   B-Vent: Economical Alternative To Wood Burning B-vent burner systems use room air to sustain the flame, while exhaust gases are vented outside your home. Room air is heated as it circulates in and around the enclosed burner system. Most B-vent products offer up to 75% heating efficiency.