A direct-vent gas fireplace uses a single exterior opening to expel combustion gas and draw clean air in. Unlike natural-vent fireplaces, direct-vent fireplaces can be vented horizontally as well ...

Gas fireplaces, including inserts, can be direct-vent or ventless. Direct-vent systems are usually more expensive and less energy-efficient since heat escapes up the chimney. Unvented or vent-free ...